// Trim / Extend — ribbon definitions + full command implementations.
//
// TRIM  (TR): Click the segment you want to remove. The command finds all
//             intersections of that entity with every other entity and trims
//             out the clicked interval. Stays active — click more segments,
//             press Enter to finish.
//
// EXTEND (EX): Click near one end of an entity.  The command extends that
//              endpoint to the nearest intersecting boundary. Stays active.

use std::f64::consts::TAU;

// The plane geometry these commands run on lives in opencadkernel; `geom` adapts
// its call shapes to the loose scalars and f32 render vertices used here.
use super::geom;
use super::geom::{
    arc_parameter as arc_t, arc_points as arc_pts, ellipse_closest_parameter,
    ellipse_points as ellipse_pts, lerp as lerp2, normalize_angle as norm,
};

use crate::modules::draw::fence::{crossing_box_preview, FencePick};

use codec::entities::{
    Arc as ArcEnt, Circle as CircleEnt, Ellipse as EllipseEnt, Line as LineEnt, LwPolyline,
    LwVertex, Ray as RayEnt, Spline as SplineEnt, XLine as XLineEnt,
};
use codec::types::Vector3;
use codec::{EntityType, Handle};
use glam::DVec3;
use kernel::geom2d::nurbs::clamped_uniform_knots;
use kernel::geom2d::{
    intersect as kernel_intersect, trim_spans as kernel_trim_spans, Arc as KernelArc, BulgeArc,
    Circle as KernelCircle, Curve, Ellipse as KernelEllipse, EllipseArc as KernelEllipseArc,
    Extent as KernelExtent, Line as KernelLine, NurbsCurve, Ray as KernelRay,
    Tolerance as KernelTolerance, XLine as KernelXLine,
};

use crate::entities::curve::{entity_curve_xy, entity_with_lwpolyline_world_xy};

use crate::command::{CadCommand, CmdResult};
use crate::modules::draw::modify::spline_ops::{
    spline_cut, spline_nearest_t, spline_pts_wire, spline_range, spline_to_nurbs, t_to_rel,
};
use crate::modules::IconKind;
use crate::scene::model::wire_model::WireModel;
use crate::t;

use super::entity_index::ModifyEntityIndex;

// ── Dropdown constants ─────────────────────────────────────────────────────

pub const DROPDOWN_ID: &str = "trim_extend";
pub const ICON: IconKind = IconKind::Svg(include_bytes!("../../../../assets/icons/trim.svg"));

pub const DROPDOWN_ITEMS: &[(&str, &str, IconKind)] = &[
    (
        "TRIM",
        "Trim",
        IconKind::Svg(include_bytes!("../../../../assets/icons/trim.svg")),
    ),
    (
        "EXTEND",
        "Extend",
        IconKind::Svg(include_bytes!("../../../../assets/icons/extend.svg")),
    ),
];

// ══════════════════════════════════════════════════════════════════════════
// Geometry helpers
// ══════════════════════════════════════════════════════════════════════════

// ── Boundary geometry ─────────────────────────────────────────────────────

/// Virtual extent used to represent infinite ends of Ray / XLine.
const TRIM_EXTENT: f64 = 1_000_000.0;

/// Sampling density for the plan-view point lists the fence and preview
/// passes walk. The renderer's own figure, so a preview cut lands where the
/// drawn geometry is rather than a chord away from it.
const SAMPLE_SEGMENTS_PER_RADIAN: f64 = kernel::geom2d::DEFAULT_SEGMENTS_PER_RADIAN;
/// If a trim interval endpoint is beyond this threshold it is treated as "infinite".

#[derive(Clone)]
enum Geo {
    Line {
        handle: Handle,
        p1: [f64; 2],
        p2: [f64; 2],
    },
    Arc {
        handle: Handle,
        cx: f64,
        cy: f64,
        r: f64,
        a0: f64,
        a1: f64,
    },
    Circle {
        handle: Handle,
        cx: f64,
        cy: f64,
        r: f64,
    },
    /// Semi-infinite line from base in +direction.
    Ray {
        handle: Handle,
        bx: f64,
        by: f64,
        dx: f64,
        dy: f64,
    },
    /// Fully-infinite line through base along direction.
    InfLine {
        handle: Handle,
        bx: f64,
        by: f64,
        dx: f64,
        dy: f64,
    },
    /// Ellipse arc: center, semi-axes, unit major-axis direction, parameter range [t0,t1].
    Ellipse {
        handle: Handle,
        cx: f64,
        cy: f64,
        a: f64,  // semi-major
        b: f64,  // semi-minor
        nx: f64, // unit major-axis X
        ny: f64, // unit major-axis Y
        t0: f64, // start parameter
        t1: f64, // end parameter (may be > 2π if wrapped)
    },
    /// A NURBS boundary, carried exactly.
    Spline {
        handle: Handle,
        curve: Box<NurbsCurve>,
    },
}

impl Geo {
    fn handle(&self) -> Handle {
        match self {
            Self::Line { handle, .. }
            | Self::Arc { handle, .. }
            | Self::Circle { handle, .. }
            | Self::Ray { handle, .. }
            | Self::InfLine { handle, .. }
            | Self::Ellipse { handle, .. }
            | Self::Spline { handle, .. } => *handle,
        }
    }

    fn endpoints(&self) -> Vec<[f64; 2]> {
        match self {
            Self::Line { p1, p2, .. } => vec![*p1, *p2],
            Self::Arc {
                cx, cy, r, a0, a1, ..
            } => vec![
                [cx + r * a0.cos(), cy + r * a0.sin()],
                [cx + r * a1.cos(), cy + r * a1.sin()],
            ],
            Self::Ray { bx, by, .. } => vec![[*bx, *by]],
            Self::Ellipse {
                cx,
                cy,
                a,
                b,
                nx,
                ny,
                t0,
                t1,
                ..
            } => {
                if (t1 - t0).abs() < TAU - 1e-6 {
                    let pt_at = |t: f64| {
                        let ct = t.cos();
                        let st = t.sin();
                        [
                            cx + nx * a * ct - ny * b * st,
                            cy + ny * a * ct + nx * b * st,
                        ]
                    };
                    vec![pt_at(*t0), pt_at(*t1)]
                } else {
                    vec![]
                }
            }
            Self::Spline { curve, .. } => vec![curve.point_at(0.0), curve.point_at(1.0)],
            Self::Circle { .. } | Self::InfLine { .. } => vec![],
        }
    }
}
pub fn is_trim_boundary_entity(entity: &EntityType) -> bool {
    matches!(
        entity,
        EntityType::Line(_)
            | EntityType::Arc(_)
            | EntityType::Circle(_)
            | EntityType::Ellipse(_)
            | EntityType::Ray(_)
            | EntityType::XLine(_)
            | EntityType::Spline(_)
            | EntityType::LwPolyline(_)
            | EntityType::Polyline(_)
            | EntityType::Polyline2D(_)
            | EntityType::Polyline3D(_)
    )
}
fn build_geos(entities: &[EntityType]) -> Vec<Geo> {
    let mut out = Vec::new();
    for e in entities {
        let h = e.common().handle;
        match e {
            // A polyline acts as a boundary through its constituent edges, so
            // a Line/Arc/… can be trimmed against it. Explode into Line + Arc
            // segments and tag each with the polyline's own handle (so trim
            // still excludes it as the click target).
            EntityType::LwPolyline(_)
            | EntityType::Polyline(_)
            | EntityType::Polyline2D(_)
            | EntityType::Polyline3D(_) => {
                for seg in crate::modules::draw::modify::explode::explode_polyline_segments(e) {
                    if let Some(g) = geo_from_entity(h, &seg) {
                        out.push(g);
                    }
                }
            }
            _ => {
                if let Some(g) = geo_from_entity(h, e) {
                    out.push(g);
                }
            }
        }
    }
    out
}

/// Convert a simple boundary entity (Line / Arc / Circle / Ray / XLine /
/// Ellipse / Spline) into a `Geo`, tagged with `h`. Returns `None` for types
/// that do not act as trim boundaries.
fn geo_from_entity(h: Handle, e: &EntityType) -> Option<Geo> {
    // The geometry itself comes from the one converter, in plan-view
    // coordinates. What is left here is only the shape of the boundary
    // record, which the edit options need to mutate — `imply_edge_geos` turns
    // a segment into an infinite line and opens an arc into a full circle,
    // neither of which a bare curve says.
    match entity_curve_xy(e)? {
        Curve::Line(line) => Some(Geo::Line {
            handle: h,
            p1: line.start,
            p2: line.end,
        }),
        Curve::Arc(arc) => Some(Geo::Arc {
            handle: h,
            cx: arc.centre[0],
            cy: arc.centre[1],
            r: arc.radius,
            a0: arc.start_angle,
            a1: arc.end_angle,
        }),
        Curve::Circle(circle) => Some(Geo::Circle {
            handle: h,
            cx: circle.centre[0],
            cy: circle.centre[1],
            r: circle.radius,
        }),
        Curve::Ray(ray) => Some(Geo::Ray {
            handle: h,
            bx: ray.origin[0],
            by: ray.origin[1],
            dx: ray.direction[0],
            dy: ray.direction[1],
        }),
        Curve::XLine(line) => Some(Geo::InfLine {
            handle: h,
            bx: line.base[0],
            by: line.base[1],
            dx: line.direction[0],
            dy: line.direction[1],
        }),
        Curve::Ellipse(arc) => {
            let ellipse = arc.ellipse;
            if ellipse.major_radius < 1e-9 {
                return None;
            }
            let t0 = arc.start_parameter;
            let mut t1 = arc.end_parameter;
            if t1 <= t0 {
                t1 += TAU;
            }
            Some(Geo::Ellipse {
                handle: h,
                cx: ellipse.centre[0],
                cy: ellipse.centre[1],
                a: ellipse.major_radius,
                b: ellipse.minor_radius,
                nx: ellipse.major_axis[0],
                ny: ellipse.major_axis[1],
                t0,
                t1,
            })
        }
        Curve::Nurbs(curve) => Some(Geo::Spline {
            handle: h,
            curve: Box::new(curve),
        }),
        // A polyline reaches here already taken apart into its segments.
        Curve::Polyline(_) => None,
    }
}

// ── Intersection helpers ──────────────────────────────────────────────────

// ── Boundary crossings ────────────────────────────────────────────────────
//
// Every cut a trim or extend makes comes from one question: where does the
// entity being edited meet the boundaries picked as cutting edges. The kernel
// answers it for any pair of curves, so these four just describe the target as
// a `Curve` and hand it over.

/// The entity a boundary came from, so a curve is never cut by itself.
fn geo_handle(geo: &Geo) -> Handle {
    match geo {
        Geo::Line { handle, .. }
        | Geo::Arc { handle, .. }
        | Geo::Circle { handle, .. }
        | Geo::Ray { handle, .. }
        | Geo::InfLine { handle, .. }
        | Geo::Ellipse { handle, .. }
        | Geo::Spline { handle, .. } => *handle,
    }
}

/// A boundary as a kernel curve.
fn geo_to_curve(geo: &Geo) -> Option<Curve> {
    Some(match geo {
        Geo::Line { p1, p2, .. } => Curve::Line(KernelLine {
            start: *p1,
            end: *p2,
        }),
        Geo::Arc {
            cx, cy, r, a0, a1, ..
        } => Curve::Arc(KernelArc {
            centre: [*cx, *cy],
            radius: *r,
            start_angle: *a0,
            end_angle: *a1,
        }),
        Geo::Circle { cx, cy, r, .. } => Curve::Circle(KernelCircle {
            centre: [*cx, *cy],
            radius: *r,
        }),
        Geo::Ray { bx, by, dx, dy, .. } => Curve::Ray(KernelRay {
            origin: [*bx, *by],
            direction: [*dx, *dy],
        }),
        Geo::InfLine { bx, by, dx, dy, .. } => Curve::XLine(KernelXLine {
            base: [*bx, *by],
            direction: [*dx, *dy],
        }),
        Geo::Ellipse {
            cx,
            cy,
            a,
            b,
            nx,
            ny,
            t0,
            t1,
            ..
        } => Curve::Ellipse(KernelEllipseArc {
            ellipse: KernelEllipse {
                centre: [*cx, *cy],
                major_radius: *a,
                minor_radius: *b,
                major_axis: [*nx, *ny],
            },
            start_parameter: *t0,
            end_parameter: *t1,
        }),
        // Exactly, not through its sampling. The kernel intersects a NURBS by
        // subdivision against a bounding box, so a boundary spline cuts where
        // it actually runs rather than where a 64-chord approximation of it
        // does.
        Geo::Spline { curve, .. } => Curve::Nurbs((**curve).clone()),
    })
}

/// Where `target` is cut by every boundary except its own entity, as
/// parameters along it in `0..=1`.
fn cut_params(target: &Curve, handle: Handle, geos: &[Geo]) -> Vec<f64> {
    let tolerance = KernelTolerance::new(CUT_TOLERANCE);
    // A bounded target's parameters are pinned to its own span, as every
    // caller here expects. An unbounded one — a ray shot out to find the
    // nearest boundary — has to keep whatever it comes back with, since the
    // whole point is how far away the crossing is.
    let bounded = matches!(target.extent(), KernelExtent::Bounded);
    let mut ts: Vec<f64> = geos
        .iter()
        .filter(|geo| geo_handle(geo) != handle)
        .filter_map(geo_to_curve)
        .flat_map(|boundary| {
            kernel_intersect(target, &boundary, tolerance)
                .into_iter()
                .map(|hit| {
                    if bounded {
                        hit.t_a.clamp(0.0, 1.0)
                    } else {
                        hit.t_a
                    }
                })
                .collect::<Vec<_>>()
        })
        .collect();

    // ── Endpoint contact detection ──
    // When a boundary entity terminates on (or within snap tolerance of) the
    // target curve, register that contact point as a cut parameter.
    const ENDPOINT_TOLERANCE: f64 = CUT_TOLERANCE;
    let mut contacts = Vec::new();

    for geo in geos.iter().filter(|g| geo_handle(g) != handle) {
        // 1. Boundary endpoints touching target
        for pt in geo.endpoints() {
            let t = target.parameter_at(pt);
            let valid_t = if bounded {
                let slack = CUT_TOLERANCE;
                if (-slack..=1.0 + slack).contains(&t) {
                    Some(t.clamp(0.0, 1.0))
                } else {
                    None
                }
            } else {
                Some(t)
            };

            if let Some(t_cand) = valid_t {
                let proj = target.point_at(t_cand);
                let dx = pt[0] - proj[0];
                let dy = pt[1] - proj[1];
                if (dx * dx + dy * dy) <= ENDPOINT_TOLERANCE * ENDPOINT_TOLERANCE {
                    contacts.push(t_cand);
                }
            }
        }

        // 2. Target endpoints touching boundary
        if bounded && !target.is_closed() {
            if let Some(boundary_curve) = geo_to_curve(geo) {
                let boundary_bounded = matches!(boundary_curve.extent(), KernelExtent::Bounded);
                for &t_end in &[0.0, 1.0] {
                    let pt = target.point_at(t_end);
                    let u = boundary_curve.parameter_at(pt);
                    let valid_u = if boundary_bounded {
                        let slack = CUT_TOLERANCE;
                        if (-slack..=1.0 + slack).contains(&u) {
                            Some(u.clamp(0.0, 1.0))
                        } else {
                            None
                        }
                    } else {
                        Some(u)
                    };
                    if let Some(u_cand) = valid_u {
                        let proj = boundary_curve.point_at(u_cand);
                        let dx = pt[0] - proj[0];
                        let dy = pt[1] - proj[1];
                        if (dx * dx + dy * dy) <= ENDPOINT_TOLERANCE * ENDPOINT_TOLERANCE {
                            contacts.push(t_end);
                        }
                    }
                }
            }
        }
    }

    // Prioritize exact endpoint contact parameters over raw ray intersections,
    // ensuring trimmed endpoints match boundary endpoints down to machine precision.
    let is_closed = target.is_closed();
    for t_contact in contacts {
        if let Some(pos) = ts.iter().position(|&t| {
            let diff = (t - t_contact).abs();
            let cyclic = if is_closed {
                diff.min(1.0 - diff)
            } else {
                diff
            };
            cyclic < 1e-6
        }) {
            ts[pos] = t_contact;
        } else {
            ts.push(t_contact);
        }
    }

    ts.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
    ts.dedup_by(|a, b| {
        let diff = (*a - *b).abs();
        let cyclic = if is_closed {
            diff.min(1.0 - diff)
        } else {
            diff
        };
        cyclic < 1e-6
    });

    // For closed curves, ensure the first and last cuts don't duplicate across the 0/1 seam
    if is_closed && ts.len() >= 2 {
        let seam_diff = (ts[ts.len() - 1] - (ts[0] + 1.0)).abs();
        if seam_diff < 1e-6 {
            ts.pop();
        }
    }

    ts
}

/// A Ray entity as the kernel curve it is, so its parameter is the ray's own
/// rather than a fraction of some invented length.
fn ray_curve(r: &RayEnt) -> Curve {
    Curve::Ray(KernelRay {
        origin: [r.base_point.x, r.base_point.y],
        direction: [r.direction.x, r.direction.y],
    })
}

/// An XLine entity as the kernel curve it is.
fn xline_curve(x: &XLineEnt) -> Curve {
    Curve::XLine(KernelXLine {
        base: [x.base_point.x, x.base_point.y],
        direction: [x.direction.x, x.direction.y],
    })
}

/// How close two points have to be to count as a crossing.
///
/// Loose enough that a boundary drawn to meet an entity still registers when
/// its endpoint is a rounding step away, which is the usual case in a drawing
/// that was snapped together rather than computed.
const CUT_TOLERANCE: f64 = 1e-7;

fn line_seg_ts(ax: f64, ay: f64, bx: f64, by: f64, target: Handle, geos: &[Geo]) -> Vec<f64> {
    cut_params(
        &Curve::Line(KernelLine {
            start: [ax, ay],
            end: [bx, by],
        }),
        target,
        geos,
    )
}

fn polyline_seg_ts(
    p0: [f64; 2],
    p1: [f64; 2],
    bulge: f64,
    target: Handle,
    geos: &[Geo],
) -> Vec<f64> {
    if let Some(ba) = BulgeArc::from_bulge(p0, p1, bulge) {
        let (from, to) = if ba.sweep >= 0.0 {
            (ba.start_angle, ba.start_angle + ba.sweep)
        } else {
            (ba.end_angle, ba.end_angle - ba.sweep)
        };
        let arc_curve = Curve::Arc(KernelArc {
            centre: ba.center,
            radius: ba.radius,
            start_angle: from,
            end_angle: to,
        });
        let ts = cut_params(&arc_curve, target, geos);
        let mut u_ts: Vec<f64> = if ba.sweep >= 0.0 {
            ts
        } else {
            ts.into_iter().map(|t| (1.0 - t).clamp(0.0, 1.0)).collect()
        };
        u_ts.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
        u_ts.dedup_by(|a, b| (*a - *b).abs() < 1e-6);
        u_ts
    } else {
        line_seg_ts(p0[0], p0[1], p1[0], p1[1], target, geos)
    }
}

fn arc_seg_ts(
    cx: f64,
    cy: f64,
    r: f64,
    a0: f64,
    a1: f64,
    target: Handle,
    geos: &[Geo],
) -> Vec<f64> {
    cut_params(
        &Curve::Arc(KernelArc {
            centre: [cx, cy],
            radius: r,
            start_angle: a0,
            end_angle: a1,
        }),
        target,
        geos,
    )
}

#[allow(clippy::too_many_arguments)]
fn ellipse_seg_ts(
    cx: f64,
    cy: f64,
    a: f64,
    b: f64,
    nx: f64,
    ny: f64,
    t0: f64,
    t1: f64,
    target: Handle,
    geos: &[Geo],
) -> Vec<f64> {
    cut_params(
        &Curve::Ellipse(KernelEllipseArc {
            ellipse: KernelEllipse {
                centre: [cx, cy],
                major_radius: a,
                minor_radius: b,
                major_axis: [nx, ny],
            },
            start_parameter: t0,
            end_parameter: t1,
        }),
        target,
        geos,
    )
}

/// Cuts on a spline, solved against the true curve rather than a sampling of
/// it. The kernel subdivides and converges, so a cut lands where the boundary
/// actually crosses instead of where a fixed number of samples said it did.
fn spline_seg_ts(spl: &SplineEnt, target: Handle, geos: &[Geo]) -> Vec<f64> {
    let Some(curve) = spline_to_nurbs(spl) else {
        return vec![];
    };
    cut_params(&Curve::Nurbs(curve), target, geos)
}

/// Trim an Ellipse entity. Returns the surviving ellipse-arc segments.
fn trim_ellipse(orig: &EllipseEnt, ts: &[f64], t_click: f64) -> Vec<EntityType> {
    let t0 = orig.start_parameter;
    let mut t1 = orig.end_parameter;
    if t1 <= t0 {
        t1 += TAU;
    }
    let span = t1 - t0;
    let angle_at = |t: f64| t0 + span * t;

    // A closed ellipse has no ends for `trim_intervals` to anchor on. Handing
    // it one makes it invent cuts at the parameter seam, so the survivor comes
    // back as two arcs either side of the seam instead of one joined across
    // it — and if the click lands in the wrapping piece, the wrong side goes.
    // Circles avoid this by treating the cuts cyclically; see `trim_circle`.
    if (span - TAU).abs() < 1e-9 {
        if ts.len() < 2 {
            return vec![];
        }
        let click = t_click.rem_euclid(1.0);
        // The gap holding the click, with the last one wrapping past 1.0 back
        // to the first cut.
        let gap = (0..ts.len()).find_map(|i| {
            let from = ts[i];
            let to = if i + 1 < ts.len() {
                ts[i + 1]
            } else {
                ts[0] + 1.0
            };
            let holds = |t: f64| t >= from && t < to;
            (holds(click) || holds(click + 1.0)).then_some((from, to))
        });
        let Some((from, to)) = gap else {
            return vec![];
        };
        // The survivor runs from the far edge of the removed gap all the way
        // round to its near edge. Leaving the end below the start is what
        // signals the wrap to everything downstream.
        let mut e = orig.clone();
        e.common.handle = Handle::NULL;
        e.start_parameter = angle_at(to % 1.0);
        e.end_parameter = angle_at(from % 1.0);
        return vec![EntityType::Ellipse(e)];
    }

    let major_radius = orig.major_axis.x.hypot(orig.major_axis.y);
    if major_radius < 1e-9 {
        return vec![];
    }
    let curve = Curve::Ellipse(KernelEllipseArc {
        ellipse: KernelEllipse {
            centre: [orig.center.x, orig.center.y],
            major_radius,
            minor_radius: major_radius * orig.minor_axis_ratio,
            major_axis: [
                orig.major_axis.x / major_radius,
                orig.major_axis.y / major_radius,
            ],
        },
        start_parameter: t0,
        end_parameter: t1,
    });
    trim_intervals(&curve, ts, t_click)
        .into_iter()
        .filter_map(|(ta, tb)| {
            if (tb - ta).abs() < 1e-6 {
                return None;
            }
            let mut e = orig.clone();
            e.common.handle = Handle::NULL;
            e.start_parameter = angle_at(ta);
            e.end_parameter = angle_at(tb);
            Some(EntityType::Ellipse(e))
        })
        .collect()
}

/// Extend an Ellipse arc to the nearest boundary (along the arc direction).
fn extend_ellipse(orig: &EllipseEnt, t_click: f64, geos: &[Geo]) -> Option<EntityType> {
    let t0 = orig.start_parameter;
    let mut t1 = orig.end_parameter;
    if t1 <= t0 {
        t1 += TAU;
    }
    let span = t1 - t0;
    let a = (orig.major_axis.x.powi(2) + orig.major_axis.y.powi(2)).sqrt();
    if a < 1e-9 {
        return None;
    }
    let b = a * orig.minor_axis_ratio;
    let (nx, ny) = (orig.major_axis.x / a, orig.major_axis.y / a);
    let cx = orig.center.x;
    let cy = orig.center.y;
    let ts = ellipse_seg_ts(cx, cy, a, b, nx, ny, t0, t1, orig.common.handle, geos);
    let extend_end = t_click >= 0.5;

    let best = if extend_end {
        ts.into_iter()
            .filter(|&t| t > 1.0 + 1e-6)
            .min_by(|x, y| x.partial_cmp(y).unwrap())
    } else {
        ts.into_iter()
            .filter(|&t| t < -1e-6)
            .max_by(|x, y| x.partial_cmp(y).unwrap())
    };

    let best_t = best?;
    let new_param = t0 + span * best_t;
    let mut e = orig.clone();
    e.common.handle = Handle::NULL;
    if extend_end {
        e.end_parameter = new_param;
    } else {
        e.start_parameter = new_param;
    }
    Some(EntityType::Ellipse(e))
}

// ── Spline trim / extend ──────────────────────────────────────────────────

/// Trim a Spline entity. Returns surviving spline pieces (one or two).
fn trim_spline(spl: &SplineEnt, ts: &[f64], t_click: f64) -> Vec<EntityType> {
    let Some(curve) = spline_to_nurbs(spl) else {
        return vec![];
    };
    let (t0, t1) = curve.domain();
    let curve = Curve::Nurbs(curve);

    trim_intervals(&curve, ts, t_click)
        .into_iter()
        .filter_map(|(ta, tb)| {
            let t_lo = t0 + ta * (t1 - t0);
            let t_hi = t0 + tb * (t1 - t0);
            if t_hi - t_lo < 1e-9 {
                return None;
            }
            // Cut away everything before the interval, then everything after
            // it, leaving [t_lo, t_hi]. Either cut is a no-op when the
            // interval already reaches that end of the curve — dropping the
            // piece there would delete the half the user meant to keep.
            let after_low = match spline_cut(spl, t_lo) {
                Some((_, right)) => right,
                None => spl.clone(),
            };
            let kept = match spline_cut(&after_low, t_hi) {
                Some((middle, _)) => middle,
                // The interval reaches the far end, so nothing is left to cut.
                None => after_low,
            };
            Some(EntityType::Spline(kept))
        })
        .collect()
}

/// Extend a Spline toward the nearest boundary (nearest endpoint to pick).
fn extend_spline(spl: &SplineEnt, t_click: f64, geos: &[Geo]) -> Option<EntityType> {
    // Sample spline and treat it like a polyline; look for intersections beyond
    // the current start (t<0 virtual) or end (t>1 virtual).
    // For splines we simply find whether the start (t=0) or end (t=1) is closer
    // to the click, then walk along that tangent direction to the nearest boundary.
    let curve = spline_to_nurbs(spl)?;
    let (t0, t1) = curve.domain();
    let extend_end = t_click >= 0.5;

    // Tangent at the endpoint (numerical, Δ = 1e-4 of range)
    let delta = (t1 - t0) * 1e-4;
    let (ep_t, tang_dir) = if extend_end {
        let p0 = curve.point_at_knot(t1 - delta);
        let p1 = curve.point_at_knot(t1);
        (t1, [p1[0] - p0[0], p1[1] - p0[1]])
    } else {
        let p0 = curve.point_at_knot(t0);
        let p1 = curve.point_at_knot(t0 + delta);
        (t0, [p0[0] - p1[0], p0[1] - p1[1]]) // reverse for "before start"
    };
    let ep = curve.point_at_knot(ep_t);
    let (dx, dy) = (tang_dir[0], tang_dir[1]);
    let len = (dx * dx + dy * dy).sqrt();
    if len < 1e-12 {
        return None;
    }
    let (dx, dy) = (dx / len, dy / len);

    // Shoot a real ray from the endpoint along the tangent. The direction is a
    // unit vector, so the parameter that comes back is the distance to the
    // boundary — no stand-in length to pick, and nothing beyond it to miss.
    let shot = Curve::Ray(KernelRay {
        origin: ep,
        direction: [dx, dy],
    });
    let best_t = cut_params(&shot, spl.common.handle, geos)
        .into_iter()
        .filter(|&t| t > 1e-6)
        .reduce(f64::min)?;

    let hit_x = ep[0] + best_t * dx;
    let hit_y = ep[1] + best_t * dy;

    // Add a new control point at the hit location by appending/prepending.
    let z = spl.control_points.first().map(|v| v.z).unwrap_or(0.0);
    let mut new_spl = spl.clone();
    new_spl.common.handle = Handle::NULL;
    new_spl.fit_points.clear();
    if extend_end {
        new_spl
            .control_points
            .push(codec::types::Vector3::new(hit_x, hit_y, z));
    } else {
        new_spl
            .control_points
            .insert(0, codec::types::Vector3::new(hit_x, hit_y, z));
    }
    // Rebuild knots (uniform) for the extended control polygon.
    let degree = new_spl.degree as usize;
    let n = new_spl.control_points.len();
    new_spl.knots = clamped_uniform_knots(degree, n);
    Some(EntityType::Spline(new_spl))
}

// ── Trim helpers ──────────────────────────────────────────────────────────

fn trim_intervals(curve: &Curve, ts: &[f64], t_click: f64) -> Vec<(f64, f64)> {
    kernel_trim_spans(curve, ts, t_click, KernelTolerance::new(CUT_TOLERANCE))
        .into_iter()
        .map(|span| (span[0], span[1]))
        .collect()
}

/// Trim a Line entity. Returns the surviving line segments.
fn trim_line(orig: &LineEnt, ts: &[f64], t_click: f64) -> Vec<EntityType> {
    let p1 = [orig.start.x, orig.start.y];
    let p2 = [orig.end.x, orig.end.y];
    let z = orig.start.z;
    let curve = Curve::Line(KernelLine { start: p1, end: p2 });
    trim_intervals(&curve, ts, t_click)
        .into_iter()
        .filter_map(|(ta, tb)| {
            let a = lerp2(p1, p2, ta);
            let b = lerp2(p1, p2, tb);
            if (b[0] - a[0]).hypot(b[1] - a[1]) < 1e-6 {
                return None;
            }
            let mut l = orig.clone();
            l.common.handle = Handle::NULL;
            l.start = Vector3::new(a[0], a[1], z);
            l.end = Vector3::new(b[0], b[1], z);
            Some(EntityType::Line(l))
        })
        .collect()
}

/// Extend a clicked Arc end along its circle to the nearest boundary
/// crossing (#409). `t_click` ∈ [0,1] within the current span picks the end:
/// ≥ 0.5 extends the end angle CCW, < 0.5 extends the start angle CW.
fn extend_arc(orig: &ArcEnt, t_click: f64, geos: &[Geo]) -> Option<EntityType> {
    let cx = orig.center.x;
    let cy = orig.center.y;
    let r = orig.radius;
    if r < 1e-9 {
        return None;
    }
    let a0 = orig.start_angle;
    let a1 = orig.end_angle;
    let span = {
        let s = norm(a1) - norm(a0);
        if s <= 0.0 {
            s + TAU
        } else {
            s
        }
    };
    if span >= TAU - 1e-9 {
        return None; // already a full circle
    }
    // Boundary crossings around the FULL circle, then re-expressed relative
    // to the arc's own span: t ∈ [0,1] lies on the arc, t > 1 walks CCW past
    // the end and wraps around toward the start.
    let ts: Vec<f64> = arc_seg_ts(cx, cy, r, a0, a0 + TAU, orig.common.handle, geos)
        .into_iter()
        .map(|t| t * TAU / span)
        .collect();
    let extend_end = t_click >= 0.5;
    let best = if extend_end {
        // First crossing CCW past the end.
        ts.iter()
            .copied()
            .filter(|&t| t > 1.0 + 1e-6)
            .min_by(|x, y| x.partial_cmp(y).unwrap())
    } else {
        // First crossing CW before the start — in wrapped span-relative
        // coordinates that is the LARGEST t outside the arc.
        ts.iter()
            .copied()
            .filter(|&t| t > 1.0 + 1e-6)
            .max_by(|x, y| x.partial_cmp(y).unwrap())
    }?;
    let ang = norm(a0) + span * best;
    let mut a = orig.clone();
    a.common.handle = Handle::NULL;
    if extend_end {
        a.end_angle = ang;
    } else {
        a.start_angle = ang;
    }
    Some(EntityType::Arc(a))
}

/// Trim an Arc entity. Returns the surviving arc segments.
fn trim_arc(orig: &ArcEnt, ts: &[f64], t_click: f64) -> Vec<EntityType> {
    let a0 = orig.start_angle;
    let a1 = orig.end_angle;
    let span = {
        let s = norm(a1) - norm(a0);
        if s <= 0.0 {
            s + TAU
        } else {
            s
        }
    };
    let angle_at = |t: f64| norm(a0) + span * t;
    let curve = Curve::Arc(KernelArc {
        centre: [orig.center.x, orig.center.y],
        radius: orig.radius,
        start_angle: a0,
        end_angle: a1,
    });

    trim_intervals(&curve, ts, t_click)
        .into_iter()
        .filter_map(|(ta, tb)| {
            if (tb - ta).abs() < 1e-6 {
                return None;
            }
            let mut a = orig.clone();
            a.common.handle = Handle::NULL;
            a.start_angle = angle_at(ta);
            a.end_angle = angle_at(tb);
            Some(EntityType::Arc(a))
        })
        .collect()
}

/// Trim a clicked Circle. A full circle has no endpoints, so it needs ≥2
/// boundary crossings: the arc segment containing the click is removed and the
/// circle becomes a single Arc spanning the rest. With fewer than two crossings
/// there is nothing to cut, so an empty result leaves the circle unchanged.
///
/// `ts` are the cut parameters in [0,1) around the circle (angle / TAU), sorted.
fn trim_circle(orig: &CircleEnt, ts: &[f64], t_click: f64) -> Vec<EntityType> {
    if ts.len() < 2 {
        return vec![];
    }
    let tc = t_click.rem_euclid(1.0);
    // Find the cyclic gap (ta, tb) between adjacent cuts that holds the click;
    // the last gap wraps past 1.0 back to the first cut.
    let n = ts.len();
    let mut removed: Option<(f64, f64)> = None;
    for i in 0..n {
        let ta = ts[i];
        let tb = if i + 1 < n { ts[i + 1] } else { ts[0] + 1.0 };
        if (tc >= ta && tc < tb) || (tc + 1.0 >= ta && tc + 1.0 < tb) {
            removed = Some((ta, tb));
            break;
        }
    }
    let (ta, tb) = match removed {
        Some(g) => g,
        None => return vec![],
    };

    // Surviving arc runs CCW from the far edge of the removed gap all the way
    // around to its near edge.
    let mut arc = ArcEnt::new();
    arc.common = orig.common.clone();
    arc.common.handle = Handle::NULL;
    arc.center = orig.center;
    arc.radius = orig.radius;
    arc.thickness = orig.thickness;
    arc.normal = orig.normal;
    arc.start_angle = (tb % 1.0) * TAU;
    arc.end_angle = (ta % 1.0) * TAU;
    vec![EntityType::Arc(arc)]
}

/// Extract a sub-polyline between parameter `s0` and `s1` (`s0 < s1`).
/// Preserves and proportionally scales arc bulges on partial segments.
fn extract_sub_polyline(poly: &LwPolyline, s0: f64, s1: f64) -> Option<LwPolyline> {
    if s1 <= s0 + 1e-9 {
        return None;
    }
    let n = poly.vertices.len();
    if n < 2 {
        return None;
    }
    let closed = poly.is_closed;
    let seg_count = if closed { n } else { n - 1 };
    if seg_count == 0 {
        return None;
    }

    let vx = |i: usize| -> [f64; 2] {
        let v = &poly.vertices[i % n];
        [v.location.x, v.location.y]
    };
    let seg_bulge = |i: usize| -> f64 { poly.vertices[i % n].bulge };

    let mut raw_verts: Vec<(f64, f64, f64)> = Vec::new();
    let mut curr = s0;
    while curr < s1 - 1e-9 {
        let seg_idx_unwrapped = curr.floor() as usize;
        let next_int = (seg_idx_unwrapped + 1) as f64;
        let end_curr = s1.min(next_int);
        let seg = seg_idx_unwrapped % seg_count;
        let u_a = (curr - seg_idx_unwrapped as f64).clamp(0.0, 1.0);
        let u_b = (end_curr - seg_idx_unwrapped as f64).clamp(0.0, 1.0);
        if u_b > u_a + 1e-9 {
            let p0 = vx(seg);
            let p1 = vx(seg + 1);
            let b = seg_bulge(seg);
            let (start_pt, sub_bulge) = if let Some(ba) = BulgeArc::from_bulge(p0, p1, b) {
                let sp = ba.sample(u_a);
                let sub_b = if (u_a - 0.0).abs() < 1e-9 && (u_b - 1.0).abs() < 1e-9 {
                    b
                } else {
                    let sweep = ba.sweep * (u_b - u_a);
                    (sweep * 0.25).tan()
                };
                (sp, sub_b)
            } else {
                let sp = [p0[0] + u_a * (p1[0] - p0[0]), p0[1] + u_a * (p1[1] - p0[1])];
                (sp, 0.0)
            };
            raw_verts.push((start_pt[0], start_pt[1], sub_bulge));
        }
        curr = end_curr;
    }

    // End point of the last sub-segment
    let end_pt = {
        let seg_idx_unwrapped = (s1 - 1e-9).floor() as usize;
        let seg = seg_idx_unwrapped % seg_count;
        let u = (s1 - seg_idx_unwrapped as f64).clamp(0.0, 1.0);
        let p0 = vx(seg);
        let p1 = vx(seg + 1);
        let b = seg_bulge(seg);
        if let Some(ba) = BulgeArc::from_bulge(p0, p1, b) {
            ba.sample(u)
        } else {
            [p0[0] + u * (p1[0] - p0[0]), p0[1] + u * (p1[1] - p0[1])]
        }
    };
    raw_verts.push((end_pt[0], end_pt[1], 0.0));

    // Filter out coincident consecutive points to prevent degenerate zero-length segments
    let mut clean_verts: Vec<(f64, f64, f64)> = Vec::new();
    for (x, y, b) in raw_verts {
        if let Some(last) = clean_verts.last_mut() {
            if (last.0 - x).hypot(last.1 - y) < 1e-6 {
                if last.2 == 0.0 {
                    last.2 = b;
                }
                continue;
            }
        }
        clean_verts.push((x, y, b));
    }

    if let Some(last) = clean_verts.last_mut() {
        last.2 = 0.0;
    }

    if clean_verts.len() < 2 {
        return None;
    }

    let mut new_poly = poly.clone();
    new_poly.common.handle = Handle::NULL;
    new_poly.is_closed = false;
    new_poly.vertices = clean_verts
        .into_iter()
        .map(|(x, y, b)| {
            let mut v = LwVertex::from_coords(x, y);
            v.bulge = b;
            v
        })
        .collect();
    Some(new_poly)
}

/// Kernel curve for one LwPolyline segment.
///
/// The boolean tells whether the kernel curve runs opposite to the polyline's
/// own segment direction. Negative-bulge arcs are represented by the kernel as
/// a positive-sweep arc, so their intersection parameter has to be reversed
/// back to the polyline's local 0..1 parameter.
fn lwpoly_segment_curve(poly: &LwPolyline, segment: usize) -> Option<(Curve, bool)> {
    let n = poly.vertices.len();
    if n < 2 {
        return None;
    }

    let a = &poly.vertices[segment % n];
    let b = &poly.vertices[(segment + 1) % n];

    let p0 = [a.location.x, a.location.y];
    let p1 = [b.location.x, b.location.y];

    if (p1[0] - p0[0]).hypot(p1[1] - p0[1]) < 1e-12 {
        return None;
    }

    if let Some(arc) = BulgeArc::from_bulge(p0, p1, a.bulge) {
        if arc.sweep >= 0.0 {
            Some((
                Curve::Arc(KernelArc {
                    centre: arc.center,
                    radius: arc.radius,
                    start_angle: arc.start_angle,
                    end_angle: arc.start_angle + arc.sweep,
                }),
                false,
            ))
        } else {
            Some((
                Curve::Arc(KernelArc {
                    centre: arc.center,
                    radius: arc.radius,
                    start_angle: arc.end_angle,
                    end_angle: arc.end_angle - arc.sweep,
                }),
                true,
            ))
        }
    } else {
        Some((Curve::Line(KernelLine { start: p0, end: p1 }), false))
    }
}

/// Global polyline parameters at which non-adjacent segments of the same
/// polyline intersect.
///
/// Segment neighbours are deliberately excluded: their common vertex is a
/// normal polyline vertex, not a self-intersection. A polyline cuts itself
/// only when it is one of the cutting edges.
fn lwpoly_self_cut_params(poly: &LwPolyline, geos: &[Geo]) -> Vec<f64> {
    let n = poly.vertices.len();
    if n < 3 || !geos.iter().any(|geo| geo.handle() == poly.common.handle) {
        return Vec::new();
    }

    let closed = poly.is_closed;
    let segment_count = if closed { n } else { n - 1 };
    let total = segment_count as f64;

    let mut cuts = Vec::new();

    for i in 0..segment_count {
        let Some((curve_a, reverse_a)) = lwpoly_segment_curve(poly, i) else {
            continue;
        };

        for j in (i + 1)..segment_count {
            // Ordinary neighbouring segments meet at their common vertex.
            let adjacent = j == i + 1 || (closed && i == 0 && j + 1 == segment_count);

            if adjacent {
                continue;
            }

            let Some((curve_b, reverse_b)) = lwpoly_segment_curve(poly, j) else {
                continue;
            };

            let hits = kernel_intersect(&curve_a, &curve_b, KernelTolerance::new(CUT_TOLERANCE));

            for hit in hits {
                let mut ua = hit.t_a;
                let mut ub = hit.t_b;

                if reverse_a {
                    ua = 1.0 - ua;
                }
                if reverse_b {
                    ub = 1.0 - ub;
                }

                if !ua.is_finite()
                    || !ub.is_finite()
                    || ua < -1e-7
                    || ua > 1.0 + 1e-7
                    || ub < -1e-7
                    || ub > 1.0 + 1e-7
                {
                    continue;
                }

                ua = ua.clamp(0.0, 1.0);
                ub = ub.clamp(0.0, 1.0);

                // If both sides only touch at existing vertices, those
                // vertices already act as trim limits below.
                let a_endpoint = ua <= 1e-7 || ua >= 1.0 - 1e-7;
                let b_endpoint = ub <= 1e-7 || ub >= 1.0 - 1e-7;

                if a_endpoint && b_endpoint {
                    continue;
                }

                let pa = i as f64 + ua;
                let pb = j as f64 + ub;

                cuts.push(if closed { pa.rem_euclid(total) } else { pa });

                cuts.push(if closed { pb.rem_euclid(total) } else { pb });
            }
        }
    }

    cuts.sort_by(f64::total_cmp);
    cuts.dedup_by(|a, b| (*a - *b).abs() < 1e-6);
    cuts
}

/// Trim a clicked LwPolyline: remove the portion containing the click, bounded
/// by the nearest boundary intersections on each side. A closed polyline needs
/// ≥2 cuts and becomes an open polyline (the surviving arc); an open one yields
/// the surviving piece(s). Bulges on surviving arc segments are preserved
/// with proportionally scaled curvature.
fn trim_lwpolyline(poly: &LwPolyline, cx: f64, cy: f64, geos: &[Geo]) -> Option<Vec<EntityType>> {
    let handle = poly.common.handle;
    let n = poly.vertices.len();
    if n < 2 {
        return None;
    }
    let closed = poly.is_closed;
    let seg_count = if closed { n } else { n - 1 };
    let total = seg_count as f64;

    let vx = |i: usize| -> [f64; 2] {
        let v = &poly.vertices[i % n];
        [v.location.x, v.location.y]
    };
    let seg_bulge = |i: usize| -> f64 { poly.vertices[i % n].bulge };

    // External boundary cuts as global params (segment index + local u).
    let mut cuts: Vec<f64> = Vec::new();

    for i in 0..seg_count {
        let p0 = vx(i);
        let p1 = vx(i + 1);
        let b = seg_bulge(i);

        for u in polyline_seg_ts(p0, p1, b, handle, geos) {
            let param = i as f64 + u.clamp(0.0, 1.0);

            cuts.push(if closed {
                param.rem_euclid(total)
            } else {
                param
            });
        }
    }

    // A polyline can also cut itself. These are intersections between
    // non-adjacent segments belonging to this same LwPolyline. Its vertices
    // are not cuts: the trimmed piece runs on past corners to the next
    // cutting edge, and a polyline no edge crosses is left alone.
    cuts.extend(lwpoly_self_cut_params(poly, geos));

    cuts.sort_by(f64::total_cmp);
    cuts.dedup_by(|a, b| (*a - *b).abs() < 1e-6);
    if cuts.is_empty() {
        return None;
    }

    // Click param: nearest point on the polyline.
    let mut best = (f64::INFINITY, 0.0_f64);
    for i in 0..seg_count {
        let p0 = vx(i);
        let p1 = vx(i + 1);
        let b = seg_bulge(i);
        let (d, u) = if let Some(ba) = BulgeArc::from_bulge(p0, p1, b) {
            let angle = (cy - ba.center[1]).atan2(cx - ba.center[0]);
            let (travelled, sweep) = if ba.sweep >= 0.0 {
                ((angle - ba.start_angle).rem_euclid(TAU), ba.sweep)
            } else {
                ((ba.start_angle - angle).rem_euclid(TAU), -ba.sweep)
            };
            let u = if sweep < 1e-12 {
                0.0
            } else if travelled <= sweep {
                (travelled / sweep).clamp(0.0, 1.0)
            } else {
                let gap = TAU - sweep;
                let past_end = travelled - sweep;
                if past_end <= gap * 0.5 {
                    1.0
                } else {
                    0.0
                }
            };
            let pt = ba.sample(u);
            let dist2 = (pt[0] - cx).powi(2) + (pt[1] - cy).powi(2);
            (dist2, u)
        } else {
            let (dx, dy) = (p1[0] - p0[0], p1[1] - p0[1]);
            let len2 = dx * dx + dy * dy;
            let u = if len2 > 1e-12 {
                (((cx - p0[0]) * dx + (cy - p0[1]) * dy) / len2).clamp(0.0, 1.0)
            } else {
                0.0
            };
            let px = p0[0] + u * dx;
            let py = p0[1] + u * dy;
            let dist2 = (px - cx).powi(2) + (py - cy).powi(2);
            (dist2, u)
        };
        if d < best.0 {
            best = (d, i as f64 + u);
        }
    }
    let t_click = best.1;

    let mut out: Vec<EntityType> = Vec::new();
    if closed {
        if cuts.len() < 2 {
            return None;
        }
        let n = cuts.len();
        let mut removed = None;
        for i in 0..n {
            let a = cuts[i];
            let b = if i + 1 < n {
                cuts[i + 1]
            } else {
                cuts[0] + total
            };
            if (t_click >= a && t_click < b) || (t_click + total >= a && t_click + total < b) {
                removed = Some((a, b));
                break;
            }
        }
        let Some((lo, hi)) = removed else {
            return None;
        };
        let mut s1 = lo;
        while s1 <= hi {
            s1 += total;
        }
        if let Some(piece) = extract_sub_polyline(poly, hi, s1) {
            out.push(EntityType::LwPolyline(piece));
        }
    } else {
        let mut bounds = vec![0.0];
        bounds.extend(cuts.iter().copied());
        bounds.push(total);
        bounds.dedup_by(|a, b| (*a - *b).abs() < 1e-6);
        let n = bounds.len();
        let mut removed = None;
        for i in 0..n - 1 {
            let a = bounds[i];
            let b = bounds[i + 1];
            if (t_click >= a && t_click < b) || (i + 2 == n && t_click <= b) {
                removed = Some((a, b));
                break;
            }
        }
        let Some((lo, hi)) = removed else {
            return None;
        };
        if lo > 1e-6 {
            if let Some(piece) = extract_sub_polyline(poly, 0.0, lo) {
                out.push(EntityType::LwPolyline(piece));
            }
        }
        if hi < total - 1e-6 {
            if let Some(piece) = extract_sub_polyline(poly, hi, total) {
                out.push(EntityType::LwPolyline(piece));
            }
        }
    }

    if out.is_empty() {
        None
    } else {
        Some(out)
    }
}

// ── Extend helpers ────────────────────────────────────────────────────────

/// Extend the first or last segment of an LwPolyline to the nearest boundary.
/// Click point (DXF XY) determines which end to extend.
/// The nearest boundary crossing past one end of a segment.
///
/// `t` runs on the infinite line through `from` → `to`: zero at `from`, one
/// at `to`. Extending the far end wants the smallest `t` above one; extending
/// the near end wants the largest `t` below zero. `None` when nothing lies
/// that way.
///
/// The crossings come from `cut_params`, which is the same kernel call every
/// other cut in this file uses. What was here instead was a match over every
/// `Geo` variant with its own line-line, line-circle and line-ellipse test —
/// twice, once for a line and once for a polyline's terminal segment — and a
/// boundary spline was walked as sixty-four chords rather than intersected.
fn extension_hit(
    from: [f64; 2],
    to: [f64; 2],
    handle: Handle,
    geos: &[Geo],
    beyond_end: bool,
) -> Option<f64> {
    let direction = [to[0] - from[0], to[1] - from[1]];
    if direction[0].hypot(direction[1]) < 1e-9 {
        return None;
    }
    // An infinite line rather than the segment: the crossing being looked for
    // is by definition off the end of the drawn part.
    let ray = Curve::XLine(KernelXLine {
        base: from,
        direction,
    });
    let hits = cut_params(&ray, handle, geos);
    if beyond_end {
        hits.into_iter()
            .filter(|t| *t > 1.0 + 1e-6)
            .min_by(f64::total_cmp)
    } else {
        hits.into_iter()
            .filter(|t| *t < -1e-6)
            .max_by(f64::total_cmp)
    }
}

fn extend_lwpoly(
    poly: &LwPolyline,
    click_x: f64,
    click_y: f64,
    geos: &[Geo],
) -> Option<EntityType> {
    let n = poly.vertices.len();
    if n < 2 {
        return None;
    }

    let first = &poly.vertices[0];
    let second = &poly.vertices[1];
    let last = &poly.vertices[n - 1];
    let prev = &poly.vertices[n - 2];

    let d_first = (first.location.x - click_x).hypot(first.location.y - click_y);
    let d_last = (last.location.x - click_x).hypot(last.location.y - click_y);
    let extend_end = d_last <= d_first;

    // Extract the terminal segment as a virtual line.
    let (ax, ay, bx, by) = if extend_end {
        (
            prev.location.x,
            prev.location.y,
            last.location.x,
            last.location.y,
        )
    } else {
        (
            second.location.x,
            second.location.y,
            first.location.x,
            first.location.y,
        )
    };

    let (dx, dy) = (bx - ax, by - ay);
    let len2 = dx * dx + dy * dy;
    if len2 < 1e-12 {
        return None;
    }

    let best_t = extension_hit([ax, ay], [bx, by], poly.common.handle, geos, true)?;

    let new_x = ax + best_t * dx;
    let new_y = ay + best_t * dy;
    let mut new_poly = poly.clone();
    new_poly.common.handle = Handle::NULL;
    if extend_end {
        let last_v = new_poly.vertices.last_mut()?;
        last_v.location.x = new_x;
        last_v.location.y = new_y;
    } else {
        let first_v = new_poly.vertices.first_mut()?;
        first_v.location.x = new_x;
        first_v.location.y = new_y;
    }
    Some(EntityType::LwPolyline(new_poly))
}

/// Extend a Line to the nearest boundary on the extended side.
/// t_click < 0.5 → extend start (look for t < 0); t_click ≥ 0.5 → extend end (t > 1).
fn extend_line(orig: &LineEnt, t_click: f64, geos: &[Geo]) -> Option<EntityType> {
    let ax = orig.start.x;
    let ay = orig.start.y;
    let bx = orig.end.x;
    let by = orig.end.y;
    let (dx, dy) = (bx - ax, by - ay);
    let extend_end = t_click >= 0.5;
    let best_t = extension_hit([ax, ay], [bx, by], orig.common.handle, geos, extend_end)?;

    let mut line = orig.clone();
    line.common.handle = Handle::NULL;
    let new_x = ax + best_t * dx;
    let new_y = ay + best_t * dy;
    if extend_end {
        line.end = Vector3::new(new_x, new_y, orig.end.z);
    } else {
        line.start = Vector3::new(new_x, new_y, orig.start.z);
    }
    Some(EntityType::Line(line))
}

/// Trim a Ray entity.
///
/// The parameter is the ray's own: `t = 0` at the base and advancing by one
/// `direction` per unit, unbounded above. A surviving piece that reaches
/// infinity stays a Ray; one with two ends becomes a Line.
fn trim_ray(orig: &RayEnt, ts: &[f64], t_click: f64) -> Vec<EntityType> {
    let bx = orig.base_point.x;
    let by = orig.base_point.y;
    let bz = orig.base_point.z;
    let dx = orig.direction.x;
    let dy = orig.direction.y;
    let dz = orig.direction.z;
    let pt = |t: f64| [bx + t * dx, by + t * dy, bz + t * dz];

    let curve = ray_curve(orig);
    trim_intervals(&curve, ts, t_click)
        .into_iter()
        .filter_map(|(ta, tb)| {
            let pa = pt(ta);
            let pb = pt(tb);
            if tb.is_finite() && (pb[0] - pa[0]).hypot(pb[1] - pa[1]) < 1e-6 {
                return None;
            }

            if tb.is_infinite() {
                // Still extends to infinity → remains a Ray with new base
                let r = RayEnt::new(Vector3::new(pa[0], pa[1], pa[2]), Vector3::new(dx, dy, dz));
                let mut r = r;
                r.common = orig.common.clone();
                r.common.handle = Handle::NULL;
                Some(EntityType::Ray(r))
            } else {
                // Finite segment → Line
                let mut l = LineEnt {
                    common: orig.common.clone(),
                    ..LineEnt::new()
                };
                l.common.handle = Handle::NULL;
                l.start = Vector3::new(pa[0], pa[1], pa[2]);
                l.end = Vector3::new(pb[0], pb[1], pb[2]);
                Some(EntityType::Line(l))
            }
        })
        .collect()
}

/// Trim an XLine entity.
///
/// The parameter is the line's own: `t = 0` at the base point, advancing by
/// one `direction` per unit and running both ways without limit. A surviving
/// piece keeps whichever ends reach infinity — both, and it is still an XLine;
/// one, and it is a Ray; neither, and it is a Line.
fn trim_xline(orig: &XLineEnt, ts: &[f64], t_click: f64) -> Vec<EntityType> {
    let bx = orig.base_point.x;
    let by = orig.base_point.y;
    let bz = orig.base_point.z;
    let dx = orig.direction.x;
    let dy = orig.direction.y;
    let dz = orig.direction.z;
    let pt = |t: f64| [bx + t * dx, by + t * dy, bz + t * dz];

    let curve = xline_curve(orig);
    trim_intervals(&curve, ts, t_click)
        .into_iter()
        .filter_map(|(ta, tb)| {
            let pa = pt(ta);
            let pb = pt(tb);
            let ext_neg = ta.is_infinite();
            let ext_pos = tb.is_infinite();

            match (ext_neg, ext_pos) {
                (true, true) => {
                    // Whole XLine survived (shouldn't happen after a real trim)
                    let mut x = orig.clone();
                    x.common.handle = Handle::NULL;
                    Some(EntityType::XLine(x))
                }
                (true, false) => {
                    // Extends toward -infinity: Ray at pb pointing in -dir
                    let r = RayEnt::new(
                        Vector3::new(pb[0], pb[1], pb[2]),
                        Vector3::new(-dx, -dy, -dz),
                    );
                    let mut r = r;
                    r.common = orig.common.clone();
                    r.common.handle = Handle::NULL;
                    Some(EntityType::Ray(r))
                }
                (false, true) => {
                    // Extends toward +infinity: Ray at pa pointing in +dir
                    let r =
                        RayEnt::new(Vector3::new(pa[0], pa[1], pa[2]), Vector3::new(dx, dy, dz));
                    let mut r = r;
                    r.common = orig.common.clone();
                    r.common.handle = Handle::NULL;
                    Some(EntityType::Ray(r))
                }
                (false, false) => {
                    // Finite segment
                    let mut l = LineEnt {
                        common: orig.common.clone(),
                        ..LineEnt::new()
                    };
                    l.common.handle = Handle::NULL;
                    l.start = Vector3::new(pa[0], pa[1], pa[2]);
                    l.end = Vector3::new(pb[0], pb[1], pb[2]);
                    Some(EntityType::Line(l))
                }
            }
        })
        .collect()
}

// ── Point-generation helpers ──────────────────────────────────────────────

const DIM_RED: [f32; 4] = [1.0, 0.3, 0.3, 0.6];

fn line_pts(l: &LineEnt) -> Vec<[f32; 3]> {
    geom::line_points(
        [l.start.x, l.start.y, l.start.z],
        [l.end.x, l.end.y, l.end.z],
    )
}

fn entity_pts(e: &EntityType) -> Vec<[f32; 3]> {
    match e {
        EntityType::Line(l) => line_pts(l),
        EntityType::Arc(a) => arc_pts(
            a.center.x,
            a.center.y,
            a.radius,
            a.start_angle,
            a.end_angle,
            a.center.z,
        ),
        EntityType::Ellipse(e) => {
            let a = (e.major_axis.x.powi(2) + e.major_axis.y.powi(2)).sqrt();
            if a < 1e-9 {
                return vec![];
            }
            let b = a * e.minor_axis_ratio;
            let (nx, ny) = (e.major_axis.x / a, e.major_axis.y / a);
            let t0 = e.start_parameter;
            let mut t1 = e.end_parameter;
            if t1 <= t0 {
                t1 += TAU;
            }
            ellipse_pts(e.center.x, e.center.y, a, b, nx, ny, t0, t1, e.center.z)
        }
        EntityType::Spline(s) => spline_pts_wire(s),
        EntityType::LwPolyline(p) => {
            let elev = p.elevation as f32;
            let xy_pts = preview_sample_xy(e);
            xy_pts
                .into_iter()
                .map(|pt| [pt[0] as f32, pt[1] as f32, elev])
                .collect()
        }
        // For preview, show a 20-unit section of semi-infinite results
        EntityType::Ray(r) => {
            let bx = r.base_point.x;
            let by = r.base_point.y;
            let bz = r.base_point.z;
            let far_x = bx + r.direction.x * 20.0;
            let far_y = by + r.direction.y * 20.0;
            let far_z = bz + r.direction.z * 20.0;
            vec![
                [bx as f32, bz as f32, by as f32],
                [far_x as f32, far_z as f32, far_y as f32],
            ]
        }
        _ => vec![],
    }
}

// ══════════════════════════════════════════════════════════════════════════
// TrimCommand
// ══════════════════════════════════════════════════════════════════════════

// ── TRIM / EXTEND option machinery (#336) ─────────────────────────────────

/// Sub-mode of the TRIM / EXTEND commands (#336). `Pick` is the quick mode;
/// the others are entered through the option keywords.
enum TrimMode {
    Pick,
    /// Collecting cutting/boundary edges; Enter returns to Pick.
    SelectEdges,
    /// Collecting fence points; Enter runs the fence pass.
    Fence(FencePick),
    /// Crossing: waiting for the first rectangle corner.
    CrossFirst,
    /// Crossing: first corner picked, waiting for the second.
    CrossSecond([f64; 2]),
    /// Erase mode: each pick deletes the object; Enter returns to Pick.
    Erase,
}

#[derive(Clone, Copy)]
struct CrossingWindow {
    min: [f64; 2],
    max: [f64; 2],
}

fn segment_window_range(p1: [f64; 2], p2: [f64; 2], window: CrossingWindow) -> Option<(f64, f64)> {
    let mut lo: f64 = 0.0;
    let mut hi: f64 = 1.0;
    for axis in 0..2 {
        let d = p2[axis] - p1[axis];
        if d.abs() < 1e-12 {
            if p1[axis] < window.min[axis] - 1e-9 || p1[axis] > window.max[axis] + 1e-9 {
                return None;
            }
            continue;
        }
        let mut a = (window.min[axis] - p1[axis]) / d;
        let mut b = (window.max[axis] - p1[axis]) / d;
        if a > b {
            std::mem::swap(&mut a, &mut b);
        }
        lo = lo.max(a);
        hi = hi.min(b);
        if lo > hi + 1e-9 {
            return None;
        }
    }
    Some((lo.clamp(0.0, 1.0), hi.clamp(0.0, 1.0)))
}

/// Crossing selection trims LwPolyline segments independently. A segment that
/// lies inside the selection rectangle but never meets a cutting edge must
/// survive; otherwise a rectangle loses its far vertical edge (#588).
fn crossing_trim_lwpolyline(
    poly: &LwPolyline,
    geos: &[Geo],
    window: CrossingWindow,
) -> Option<Vec<EntityType>> {
    let handle = poly.common.handle;
    let n = poly.vertices.len();
    if n < 2 {
        return None;
    }
    let closed = poly.is_closed;
    let seg_count = if closed { n } else { n - 1 };
    let total = seg_count as f64;
    let vertex_xy = |i: usize| {
        let v = &poly.vertices[i % n];
        [v.location.x, v.location.y]
    };
    let seg_bulge = |i: usize| -> f64 { poly.vertices[i % n].bulge };

    let mut removed = Vec::<(f64, f64)>::new();

    // Compute the polyline's own non-adjacent segment intersections once.
    // These global parameters will later be mapped back into each source segment.
    let self_cuts = lwpoly_self_cut_params(poly, geos);

    for i in 0..seg_count {
        let a = vertex_xy(i);
        let b = vertex_xy(i + 1);
        let bulge = seg_bulge(i);
        let window_range = if let Some(ba) = BulgeArc::from_bulge(a, b, bulge) {
            let steps = 32usize;
            let mut min_t: Option<f64> = None;
            let mut max_t: Option<f64> = None;
            for s in 0..=steps {
                let t = s as f64 / steps as f64;
                let pt = ba.sample(t);
                if pt[0] >= window.min[0] - 1e-9
                    && pt[0] <= window.max[0] + 1e-9
                    && pt[1] >= window.min[1] - 1e-9
                    && pt[1] <= window.max[1] + 1e-9
                {
                    min_t = Some(min_t.map_or(t, |m: f64| m.min(t)));
                    max_t = Some(max_t.map_or(t, |m: f64| m.max(t)));
                }
            }
            match (min_t, max_t) {
                (Some(lo), Some(hi)) => Some((lo, hi)),
                _ => None,
            }
        } else {
            segment_window_range(a, b, window)
        };
        let Some((inside_lo, inside_hi)) = window_range else {
            continue;
        };
        // External intersections on this segment.
        let mut cuts = polyline_seg_ts(a, b, bulge, handle, geos);

        // Also include self-intersections belonging to this source segment.
        // `lwpoly_self_cut_params()` stores them as global polyline parameters:
        //     segment_index + local_parameter
        //
        // Convert the ones belonging to segment `i` back to local 0..1.
        let seg_start = i as f64;
        let seg_end = seg_start + 1.0;

        for global_t in self_cuts.iter().copied() {
            if global_t > seg_start + 1e-6 && global_t < seg_end - 1e-6 {
                cuts.push(global_t - seg_start);
            }
        }

        // The source segment endpoints are also valid trim limits.
        cuts.push(0.0);
        cuts.push(1.0);

        cuts.sort_by(f64::total_cmp);
        cuts.dedup_by(|a, b| (*a - *b).abs() < 1e-6);

        // Remove every trim span that is actually touched by the selection box.
        //
        // A single source segment may contain several sub-spans when external
        // boundaries cross it. Only the sub-spans overlapping the window are removed.
        for span in cuts.windows(2) {
            let lo = span[0].clamp(0.0, 1.0);
            let hi = span[1].clamp(0.0, 1.0);

            if hi - lo <= 1e-6 {
                continue;
            }

            // This trim span participates when its parameter interval overlaps the
            // portion of the source segment lying inside the crossing rectangle.
            let overlaps_window = hi >= inside_lo - 1e-6 && lo <= inside_hi + 1e-6;

            if overlaps_window {
                removed.push((i as f64 + lo, i as f64 + hi));
            }
        }
    }
    if removed.is_empty() {
        return None;
    }

    removed.sort_by(|a, b| a.0.partial_cmp(&b.0).unwrap_or(std::cmp::Ordering::Equal));
    let mut merged = Vec::<(f64, f64)>::new();
    for span in removed {
        if let Some(last) = merged.last_mut() {
            if span.0 <= last.1 + 1e-6 {
                last.1 = last.1.max(span.1);
                continue;
            }
        }
        merged.push(span);
    }

    let mut kept = Vec::<(f64, f64)>::new();
    if closed {
        for i in 0..merged.len() {
            let start = merged[i].1;
            let mut end = merged[(i + 1) % merged.len()].0;
            if i + 1 == merged.len() {
                end += total;
            }
            if end - start > 1e-6 {
                kept.push((start, end));
            }
        }
    } else {
        let mut cursor = 0.0;
        for &(start, end) in &merged {
            if start - cursor > 1e-6 {
                kept.push((cursor, start));
            }
            cursor = cursor.max(end);
        }
        if total - cursor > 1e-6 {
            kept.push((cursor, total));
        }
    }

    Some(
        kept.into_iter()
            .filter_map(|(start, end)| {
                extract_sub_polyline(poly, start, end).map(EntityType::LwPolyline)
            })
            .collect(),
    )
}

/// Quick-mode trim at a click/crossing point: the surviving pieces, or `None`
/// when the pick doesn't intersect any boundary (or the type is unsupported).
fn pick_trim_at(
    all: &[EntityType],
    geos: &[Geo],
    handle: Handle,
    px: f64,
    py: f64,
) -> Option<Vec<EntityType>> {
    let entity = all.iter().find(|e| e.common().handle == handle);
    let result: Option<Vec<EntityType>> = match entity {
        Some(EntityType::Line(l)) => {
            let ax = l.start.x;
            let ay = l.start.y;
            let bx = l.end.x;
            let by = l.end.y;
            let ts = line_seg_ts(ax, ay, bx, by, handle, geos);
            if ts.is_empty() {
                return None;
            }
            let dx = bx - ax;
            let dy = by - ay;
            let len2 = dx * dx + dy * dy;
            let t_click = if len2 > 1e-12 {
                ((px - ax) * dx + (py - ay) * dy) / len2
            } else {
                0.5
            };
            Some(trim_line(l, &ts, t_click))
        }
        Some(EntityType::Arc(a)) => {
            let cx = a.center.x;
            let cy = a.center.y;
            let a0 = a.start_angle;
            let a1 = a.end_angle;
            let ts = arc_seg_ts(cx, cy, a.radius, a0, a1, handle, geos);
            if ts.is_empty() {
                return None;
            }
            let click_angle = (py - cy).atan2(px - cx);
            let t_click = arc_t(click_angle, a0, a1);
            Some(trim_arc(a, &ts, t_click))
        }
        Some(EntityType::Circle(c)) => {
            let cx = c.center.x;
            let cy = c.center.y;
            let ts = arc_seg_ts(cx, cy, c.radius, 0.0, TAU, handle, geos);
            if ts.len() < 2 {
                return None;
            }
            let click_angle = (py - cy).atan2(px - cx);
            let t_click = arc_t(click_angle, 0.0, TAU);
            let survivors = trim_circle(c, &ts, t_click);
            if survivors.is_empty() {
                return None;
            }
            Some(survivors)
        }
        Some(EntityType::Ray(r)) => {
            let curve = ray_curve(r);
            let ts = cut_params(&curve, handle, geos);
            if ts.is_empty() {
                return None;
            }
            let t_click = curve.parameter_at([px, py]);
            Some(trim_ray(r, &ts, t_click))
        }
        Some(EntityType::XLine(x)) => {
            let curve = xline_curve(x);
            let ts = cut_params(&curve, handle, geos);
            if ts.is_empty() {
                return None;
            }
            let t_click = curve.parameter_at([px, py]);
            Some(trim_xline(x, &ts, t_click))
        }
        Some(EntityType::Ellipse(e)) => {
            let a = (e.major_axis.x.powi(2) + e.major_axis.y.powi(2)).sqrt();
            if a < 1e-9 {
                return None;
            }
            let b = a * e.minor_axis_ratio;
            if b < 1e-9 {
                return None;
            }
            let (nx, ny) = (e.major_axis.x / a, e.major_axis.y / a);
            let t0 = e.start_parameter;
            let mut t1 = e.end_parameter;
            if t1 <= t0 {
                t1 += TAU;
            }
            let ts = ellipse_seg_ts(e.center.x, e.center.y, a, b, nx, ny, t0, t1, handle, geos);
            if ts.is_empty() {
                return None;
            }
            // t_click: project mouse onto ellipse local param
            let rx = px - e.center.x;
            let ry = py - e.center.y;
            let xl = rx * nx + ry * ny;
            let yl = -rx * ny + ry * nx;
            let t_ell = ellipse_closest_parameter(a, b, xl, yl);
            let t_click = arc_t(t_ell, t0, t1);
            Some(trim_ellipse(e, &ts, t_click))
        }
        Some(EntityType::Spline(s)) => {
            let ts = spline_seg_ts(s, handle, geos);
            if ts.is_empty() {
                return None;
            }
            let t_click = spline_nearest_t(s, px, py)
                .and_then(|t_actual| {
                    let (t0, t1) = spline_range(s)?;
                    Some(t_to_rel(t_actual, t0, t1))
                })
                .unwrap_or(0.5);
            Some(trim_spline(s, &ts, t_click))
        }
        Some(EntityType::LwPolyline(p)) => trim_lwpolyline(p, px, py, geos),
        _ => None,
    };
    result
}

/// Quick-mode extend at a click/crossing point: the lengthened entity, or
/// `None` when no boundary lies beyond that end (or the type is unsupported).
fn pick_extend_at(
    all: &[EntityType],
    geos: &[Geo],
    handle: Handle,
    px: f64,
    py: f64,
) -> Option<EntityType> {
    let entity = all.iter().find(|e| e.common().handle == handle);
    let result: Option<EntityType> = match entity {
        Some(EntityType::Line(l)) => {
            let ax = l.start.x;
            let ay = l.start.y;
            let bx = l.end.x;
            let by = l.end.y;
            let dx = bx - ax;
            let dy = by - ay;
            let len2 = dx * dx + dy * dy;
            let t_click = if len2 > 1e-12 {
                ((px - ax) * dx + (py - ay) * dy) / len2
            } else {
                0.5
            };
            extend_line(l, t_click, geos)
        }
        Some(EntityType::Arc(a)) => {
            let ang = (py - a.center.y).atan2(px - a.center.x);
            let t_click = arc_t(ang, a.start_angle, a.end_angle);
            extend_arc(a, t_click, geos)
        }
        Some(EntityType::Ellipse(e)) => {
            let t0 = e.start_parameter;
            let mut t1 = e.end_parameter;
            if t1 <= t0 {
                t1 += TAU;
            }
            let span = t1 - t0;
            let a = (e.major_axis.x.powi(2) + e.major_axis.y.powi(2)).sqrt();
            if a < 1e-9 {
                return None;
            }
            let b = a * e.minor_axis_ratio;
            if b < 1e-9 {
                return None;
            }
            let (nx, ny) = (e.major_axis.x / a, e.major_axis.y / a);
            let rx = px - e.center.x;
            let ry = py - e.center.y;
            let xl = rx * nx + ry * ny;
            let yl = -rx * ny + ry * nx;
            let t_ell = ellipse_closest_parameter(a, b, xl, yl);
            let t_click = arc_t(t_ell, t0, t1);
            let _ = span;
            extend_ellipse(e, t_click, geos)
        }
        Some(EntityType::LwPolyline(p)) => extend_lwpoly(p, px, py, geos),
        Some(EntityType::Spline(s)) => {
            let t_click = spline_nearest_t(s, px, py)
                .and_then(|t_actual| {
                    let (t0, t1) = spline_range(s)?;
                    Some(t_to_rel(t_actual, t0, t1))
                })
                .unwrap_or(0.5);
            extend_spline(s, t_click, geos)
        }
        _ => None,
    };
    result
}

/// Edge option (#336): treat boundary edges as implied — straight edges run
/// on past their endpoints and arcs close to full circles, so objects trim /
/// extend to the boundary's extrapolation, not only its drawn extent.
fn imply_edge_geos(geos: &mut [Geo]) {
    for g in geos.iter_mut() {
        match g {
            Geo::Line { handle, p1, p2 } => {
                let (dx, dy) = (p2[0] - p1[0], p2[1] - p1[1]);
                if dx.hypot(dy) > 1e-9 {
                    // An implied edge cuts wherever the boundary's line would
                    // reach, which is what an infinite line is. Stretching the
                    // segment to a stand-in length instead both invents a
                    // limit and, at survey coordinates, is no larger than the
                    // coordinates themselves.
                    *g = Geo::InfLine {
                        handle: *handle,
                        bx: p1[0],
                        by: p1[1],
                        dx,
                        dy,
                    };
                }
            }
            Geo::Arc { a0, a1, .. } => {
                *a0 = 0.0;
                *a1 = TAU;
            }
            _ => {}
        }
    }
}

/// Dense XY sampling for the fence pass — covers the types the quick pick
/// supports (adds Circle / Ray / XLine over `sample_entity_xy`).
fn fence_sample_xy(e: &EntityType) -> Vec<[f64; 2]> {
    match e {
        // The two unbounded kinds, which `sample_entity_xy` declines to
        // guess a length for. Here there is one: as far as a trim reaches.
        EntityType::Ray(r) => vec![
            [r.base_point.x, r.base_point.y],
            [
                r.base_point.x + r.direction.x * TRIM_EXTENT,
                r.base_point.y + r.direction.y * TRIM_EXTENT,
            ],
        ],
        EntityType::XLine(x) => vec![
            [
                x.base_point.x - x.direction.x * TRIM_EXTENT,
                x.base_point.y - x.direction.y * TRIM_EXTENT,
            ],
            [
                x.base_point.x + x.direction.x * TRIM_EXTENT,
                x.base_point.y + x.direction.y * TRIM_EXTENT,
            ],
        ],
        _ => sample_entity_xy(e),
    }
}

/// Every crossing point of `e` with the fence polyline, in traversal order.
/// Each drives the same per-type pick as a direct click, so the actual cuts
/// happen at the exact boundary intersections.
fn fence_cross_points(e: &EntityType, fence_geos: &[Geo]) -> Vec<[f64; 2]> {
    let pts = fence_sample_xy(e);
    let mut out = Vec::new();
    for w in pts.windows(2) {
        // NOTE: the exclusion handle must differ from the fence geos' own —
        // passing NULL against NULL-handle geos excluded the whole fence.
        let mut ts = line_seg_ts(
            w[0][0],
            w[0][1],
            w[1][0],
            w[1][1],
            Handle::new(FENCE_PROBE),
            fence_geos,
        );
        ts.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
        for t in ts {
            out.push(lerp2(w[0], w[1], t));
        }
    }
    out
}

/// Trim/extend one entity at EVERY fence crossing: the pick is re-applied to
/// the surviving pieces until no crossing bites (a fence across both
/// overhanging ends of one line clears both). Returns `None` when nothing
/// changed. Pieces carry NULL handles for the ReplaceMany placeholder flow.
fn fence_pieces(
    e: &EntityType,
    geos: &[Geo],
    fence_geos: &[Geo],
    window: Option<CrossingWindow>,
    extend: bool,
) -> Option<Vec<EntityType>> {
    if !extend {
        if let (EntityType::LwPolyline(poly), Some(window)) = (e, window) {
            return crossing_trim_lwpolyline(poly, geos, window);
        }
    }

    let target = e.common().handle;
    let mut pieces = vec![e.clone()];
    let mut changed = false;
    for _round in 0..8 {
        let mut next: Vec<EntityType> = Vec::new();
        let mut any = false;
        for piece in &pieces {
            let mut tmp = piece.clone();
            tmp.as_entity_mut().set_handle(target);
            let tmp_all = [tmp];
            let mut consumed = false;
            let mut cps = fence_cross_points(&tmp_all[0], fence_geos);
            // Crossing works like a crossing SELECTION: an object wholly
            // inside the window is picked too — synthesize the click at a
            // sampled point inside it.
            if cps.is_empty() {
                if let Some(window) = window {
                    if let Some(p) = fence_sample_xy(&tmp_all[0]).into_iter().find(|p| {
                        p[0] >= window.min[0]
                            && p[0] <= window.max[0]
                            && p[1] >= window.min[1]
                            && p[1] <= window.max[1]
                    }) {
                        cps.push(p);
                    }
                }
            }
            for cp in cps {
                let res = if extend {
                    pick_extend_at(&tmp_all, geos, target, cp[0], cp[1]).map(|x| vec![x])
                } else {
                    pick_trim_at(&tmp_all, geos, target, cp[0], cp[1])
                };
                if let Some(mut sub) = res {
                    for sp in &mut sub {
                        sp.as_entity_mut().set_handle(Handle::NULL);
                    }
                    next.extend(sub);
                    any = true;
                    changed = true;
                    consumed = true;
                    break;
                }
            }
            if !consumed {
                next.push(piece.clone());
            }
        }
        pieces = next;
        if !any || pieces.len() > 64 {
            break;
        }
    }
    if changed {
        Some(pieces)
    } else {
        None
    }
}

/// Fence / Crossing pass (#336): every object crossing the fence polyline is
/// trimmed (or extended) at each of its crossing points; the cuts land on the
/// boundary-edge intersections, the fence only selects.
/// Boundary/edge-selection highlight colour (the EXTRIM boundary yellow).
const OPT_YELLOW: [f32; 4] = [1.0, 0.90, 0.15, 1.0];

/// Sentinel handles for the fence pass: the fence's own geos and the probe
/// handle used against them must never collide with a real entity handle (or
/// with each other — `line_seg_ts` drops geos matching the probe handle).
const FENCE_GEO: u64 = u64::MAX - 8;
const FENCE_PROBE: u64 = u64::MAX - 9;

fn build_fence_geos(fence: &[[f64; 2]]) -> Vec<Geo> {
    fence
        .windows(2)
        .map(|w| Geo::Line {
            handle: Handle::new(FENCE_GEO),
            p1: w[0],
            p2: w[1],
        })
        .collect()
}

/// Live result preview of a fence / crossing pass: each affected original in
/// red, its surviving pieces in cyan — the same convention as the pick hover.
fn fence_result_preview(
    all: &[EntityType],
    geos: &[Geo],
    fence: &[[f64; 2]],
    window: Option<CrossingWindow>,
    extend: bool,
    implied_edges: bool,
) -> Vec<WireModel> {
    let fence_geos = build_fence_geos(fence);
    let mut out = Vec::new();
    for e in all {
        if e.common().handle.is_null() {
            continue;
        }
        if let Some(pieces) = fence_pieces(e, geos, &fence_geos, window, extend) {
            out.push(WireModel::solid(
                "trim_rm".into(),
                entity_pts(e),
                DIM_RED,
                false,
            ));
            for (i, pe) in pieces.iter().enumerate() {
                out.push(WireModel::solid(
                    format!("trim_keep_{i}"),
                    entity_pts(pe),
                    WireModel::CYAN,
                    false,
                ));
                if extend {
                    if let Some(t) = extend_tail_preview(e, pe, "extend_tail") {
                        out.push(t);
                    }
                }
            }
            if implied_edges {
                let cuts = piece_cut_points(e, &pieces);
                out.extend(implied_cut_guides(all, e.common().handle, &cuts));
            }
        }
    }
    out
}

fn fence_pass(
    all: &[EntityType],
    geos: &[Geo],
    fence: &[[f64; 2]],
    window: Option<CrossingWindow>,
    extend: bool,
) -> Vec<(Handle, Vec<EntityType>)> {
    let fence_geos: Vec<Geo> = build_fence_geos(fence);
    let mut out = Vec::new();
    for e in all {
        let h = e.common().handle;
        if h.is_null() {
            continue;
        }
        if let Some(pieces) = fence_pieces(e, geos, &fence_geos, window, extend) {
            out.push((h, pieces));
        }
    }
    out
}

/// The ADDED tail of an extend result, dashed — the slice of the extended
/// curve beyond the original endpoint, so the preview shows the extension
/// itself rather than only a recolored whole (#336). Generic over entity
/// type via the sampled points.
fn extend_tail_preview(orig: &EntityType, ext: &EntityType, name: &str) -> Option<WireModel> {
    let op = entity_pts(orig);
    let ep = entity_pts(ext);
    if op.len() < 2 || ep.len() < 2 {
        return None;
    }
    let d2 = |a: &[f32; 3], b: &[f32; 3]| {
        let dx = a[0] - b[0];
        let dy = a[1] - b[1];
        dx * dx + dy * dy
    };
    let nearest_idx = |pts: &[[f32; 3]], q: &[f32; 3]| {
        let mut best = 0usize;
        let mut bd = f32::MAX;
        for (i, p) in pts.iter().enumerate() {
            let d = d2(p, q);
            if d < bd {
                bd = d;
                best = i;
            }
        }
        best
    };
    let of = op.first().unwrap();
    let ol = op.last().unwrap();
    let ef = ep.first().unwrap();
    let el = ep.last().unwrap();
    let tail: Vec<[f32; 3]> = if d2(ol, el) > 1e-10 {
        let i = nearest_idx(&ep, ol);
        ep[i..].to_vec()
    } else if d2(of, ef) > 1e-10 {
        let i = nearest_idx(&ep, of);
        ep[..=i].to_vec()
    } else {
        return None;
    };
    if tail.len() < 2 {
        return None;
    }
    let mut w = WireModel::solid(name.into(), tail, [0.3, 1.0, 1.0, 1.0], false);
    w.pattern_length = 0.8;
    w.pattern = [0.5, -0.3, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0];
    w.line_weight_px = 1.6;
    Some(w)
}

/// Distance from `q` to the drawn (sampled) body of `e`.
fn dist_to_drawn(e: &EntityType, q: [f64; 2]) -> f64 {
    let pts = fence_sample_xy(e);
    let mut best = f64::MAX;
    for w in pts.windows(2) {
        let (a, b) = (w[0], w[1]);
        let (dx, dy) = (b[0] - a[0], b[1] - a[1]);
        let len2 = dx * dx + dy * dy;
        let t = if len2 > 1e-12 {
            (((q[0] - a[0]) * dx + (q[1] - a[1]) * dy) / len2).clamp(0.0, 1.0)
        } else {
            0.0
        };
        let px = a[0] + dx * t;
        let py = a[1] + dy * t;
        best = best.min((q[0] - px).hypot(q[1] - py));
    }
    best
}

/// Endpoints of the surviving pieces that are NOT endpoints of the original —
/// i.e. the actual cut points of a trim result.
fn piece_cut_points(orig: &EntityType, pieces: &[EntityType]) -> Vec<[f64; 2]> {
    let op = entity_pts(orig);
    if op.len() < 2 {
        return vec![];
    }
    let f = op.first().unwrap();
    let l = op.last().unwrap();
    let closed = (f[0] - l[0]).abs() < 1e-6 && (f[1] - l[1]).abs() < 1e-6;
    let ends: Vec<[f32; 3]> = if closed { vec![] } else { vec![*f, *l] };
    let mut out = Vec::new();
    for pe in pieces {
        let pp = entity_pts(pe);
        if pp.len() < 2 {
            continue;
        }
        for q in [pp.first().unwrap(), pp.last().unwrap()] {
            let is_orig_end = ends.iter().any(|e| {
                let dx = e[0] - q[0];
                let dy = e[1] - q[1];
                dx * dx + dy * dy < 1e-6
            });
            if !is_orig_end {
                out.push([q[0] as f64, q[1] as f64]);
            }
        }
    }
    out
}

/// Edge: Extend guides (#336): for every cut point that does NOT lie on a
/// boundary's drawn body, draw a dashed guide along the boundary's implied
/// extension — from its drawn end to the cut — so the user sees WHICH edge
/// causes the cut there. Lines get a straight guide, arcs follow the circle.
fn implied_cut_guides(all: &[EntityType], target: Handle, cuts: &[[f64; 2]]) -> Vec<WireModel> {
    let mut out = Vec::new();
    'cuts: for (ci, cp) in cuts.iter().enumerate() {
        let tol = 1e-6 * (1.0 + cp[0].abs() + cp[1].abs());
        // Attributed to a drawn body → nothing implied to explain.
        for e in all {
            let h = e.common().handle;
            if h.is_null() || h == target {
                continue;
            }
            if dist_to_drawn(e, *cp) < tol {
                continue 'cuts;
            }
        }
        // Find the boundary whose extrapolation passes through the cut.
        for e in all {
            let h = e.common().handle;
            if h.is_null() || h == target {
                continue;
            }
            match e {
                EntityType::Line(l) => {
                    let (ax, ay) = (l.start.x, l.start.y);
                    let (dx, dy) = (l.end.x - ax, l.end.y - ay);
                    let len = dx.hypot(dy);
                    if len < 1e-9 {
                        continue;
                    }
                    // Perpendicular distance to the infinite line.
                    let d = ((cp[0] - ax) * dy - (cp[1] - ay) * dx).abs() / len;
                    if d < tol {
                        let d_start = (cp[0] - ax).hypot(cp[1] - ay);
                        let d_end = (cp[0] - l.end.x).hypot(cp[1] - l.end.y);
                        let from = if d_start < d_end {
                            [ax as f32, ay as f32, 0.0]
                        } else {
                            [l.end.x as f32, l.end.y as f32, 0.0]
                        };
                        let mut w = WireModel::solid(
                            format!("edge_guide_{ci}"),
                            vec![from, [cp[0] as f32, cp[1] as f32, 0.0]],
                            OPT_YELLOW,
                            false,
                        );
                        w.pattern_length = 0.8;
                        w.pattern = [0.5, -0.3, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0];
                        out.push(w);
                        continue 'cuts;
                    }
                }
                EntityType::Arc(a) => {
                    let r = (cp[0] - a.center.x).hypot(cp[1] - a.center.y);
                    if (r - a.radius).abs() < tol {
                        // Follow the circle from the nearer drawn end to the
                        // cut, going the short way outside the drawn span.
                        let theta = (cp[1] - a.center.y).atan2(cp[0] - a.center.x);
                        let a0 = norm(a.start_angle);
                        let a1 = norm(a.end_angle);
                        let ccw_from_end = (theta - a1).rem_euclid(TAU);
                        let cw_from_start = (a0 - theta).rem_euclid(TAU);
                        let (base, sweep) = if ccw_from_end <= cw_from_start {
                            (a1, ccw_from_end)
                        } else {
                            (a0, -cw_from_start)
                        };
                        let steps = ((sweep.abs() * 16.0).ceil() as usize).max(2);
                        let pts: Vec<[f32; 3]> = (0..=steps)
                            .map(|i| {
                                let ang = base + sweep * (i as f64 / steps as f64);
                                [
                                    (a.center.x + a.radius * ang.cos()) as f32,
                                    (a.center.y + a.radius * ang.sin()) as f32,
                                    0.0,
                                ]
                            })
                            .collect();
                        let mut w =
                            WireModel::solid(format!("edge_guide_{ci}"), pts, OPT_YELLOW, false);
                        w.pattern_length = 0.8;
                        w.pattern = [0.5, -0.3, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0];
                        out.push(w);
                        continue 'cuts;
                    }
                }
                _ => {}
            }
        }
    }
    out
}

/// Extend hover preview: the whole result in cyan, the added tail dashed and
/// — with Edge: Extend on — a guide along the implied boundary that the new
/// endpoint lands on.
fn extend_hover_wires(
    orig: &EntityType,
    ext: &EntityType,
    all: &[EntityType],
    target: Handle,
    implied_edges: bool,
) -> Vec<WireModel> {
    let mut out = vec![WireModel::solid(
        "extend_prev".into(),
        entity_pts(ext),
        WireModel::CYAN,
        false,
    )];
    if let Some(t) = extend_tail_preview(orig, ext, "extend_tail") {
        out.push(t);
    }
    if implied_edges {
        // The moved endpoint is the cut against the (implied) boundary.
        let cuts = piece_cut_points(orig, std::slice::from_ref(ext));
        out.extend(implied_cut_guides(all, target, &cuts));
    }
    out
}

pub struct TrimCommand {
    all_entities: Vec<EntityType>,
    entity_index: ModifyEntityIndex,
    geos: Vec<Geo>,
    mode: TrimMode,
    /// Cutting-edge selection; empty = every object cuts (quick mode).
    edge_set: Vec<Handle>,
    /// Edge option: boundaries extrapolate past their drawn extent.
    implied_edges: bool,
    /// Live Shift state — Shift+click extends instead of trims (#336).
    shift: bool,
}

impl TrimCommand {
    pub fn new(all_entities: Vec<EntityType>) -> Self {
        Self::with_cutting_edges(all_entities, Vec::new())
    }

    pub fn with_cutting_edges(all_entities: Vec<EntityType>, initial_edges: Vec<Handle>) -> Self {
        let all_entities: Vec<EntityType> = all_entities
            .iter()
            .map(entity_with_lwpolyline_world_xy)
            .collect();

        let entity_index = ModifyEntityIndex::build(&all_entities);

        let mut cmd = Self {
            all_entities,
            entity_index,
            geos: Vec::new(),
            mode: TrimMode::Pick,
            edge_set: initial_edges,
            implied_edges: false,
            shift: false,
        };

        cmd.rebuild_geos();

        cmd
    }

    /// Boundary geometry from the edge selection (or everything when none),
    /// with the Edge option's implied extrapolation applied on top.
    fn rebuild_geos(&mut self) {
        self.entity_index = ModifyEntityIndex::build(&self.all_entities);
        self.geos = if self.edge_set.is_empty() {
            build_geos(&self.all_entities)
        } else {
            let picked: Vec<EntityType> = self
                .all_entities
                .iter()
                .filter(|e| self.edge_set.contains(&e.common().handle))
                .cloned()
                .collect();
            build_geos(&picked)
        };
        if self.implied_edges {
            imply_edge_geos(&mut self.geos);
        }
    }

    /// Exact analytic boundaries whose boxes overlap the picked entity. The
    /// host already narrowed the cursor pick; this second broad phase keeps
    /// TRIM preview/intersection work local on dense drawings.
    fn nearby_geos(&self, handle: Handle) -> Vec<Geo> {
        if self.implied_edges {
            return self.geos.clone();
        }
        let Some(handles) = self.entity_index.nearby_handles(&self.all_entities, handle) else {
            return self.geos.clone();
        };
        self.geos
            .iter()
            .filter(|geo| handles.contains(&geo.handle()))
            .cloned()
            .collect()
    }

    fn fence_run(&mut self, fence: &[[f64; 2]], window: Option<CrossingWindow>) -> CmdResult {
        let repl = fence_pass(&self.all_entities, &self.geos, fence, window, self.shift);
        if repl.is_empty() {
            return CmdResult::NeedPoint;
        }
        CmdResult::ReplaceMany(repl, Vec::new())
    }

    fn stage_replacements(&mut self, replacements: &[(Handle, Vec<EntityType>)]) {
        for (handle, _) in replacements {
            if let Some(index) = self
                .all_entities
                .iter()
                .position(|entity| entity.common().handle == *handle)
            {
                self.all_entities.remove(index);
            }
            self.edge_set.retain(|edge| edge != handle);
        }
        for (_, entities) in replacements {
            self.all_entities.extend(entities.iter().cloned());
        }
        self.rebuild_geos();
    }
}

impl CadCommand for TrimCommand {
    fn name(&self) -> &'static str {
        "TRIM"
    }

    fn prompt(&self) -> String {
        let edge = if self.implied_edges {
            t!(" [Edge: Extend]")
        } else {
            std::borrow::Cow::Borrowed("")
        };
        match &self.mode {
            TrimMode::Pick => {
                crate::tf!("TRIM{edge}  Click segment to remove (Shift+click extends):")
                    .into_owned()
            }
            TrimMode::SelectEdges => crate::tf!(
                "TRIM  Select cutting edges [{} picked, Enter = done]:",
                self.edge_set.len()
            )
            .into_owned(),
            TrimMode::Fence(pick) => crate::tf!(
                "TRIM{edge}  Fence: pick points [{} placed, Enter = trim crossed]:",
                pick.len()
            )
            .into_owned(),
            TrimMode::CrossFirst => crate::tf!("TRIM{edge}  Crossing: first corner:").into_owned(),
            TrimMode::CrossSecond(_) => {
                crate::tf!("TRIM{edge}  Crossing: opposite corner:").into_owned()
            }
            TrimMode::Erase => {
                t!("TRIM  Erase: click objects to delete [Enter = done]:").into_owned()
            }
        }
    }

    fn options(&self) -> Vec<crate::command::CmdOption> {
        use crate::command::CmdOption;
        match self.mode {
            TrimMode::Pick => vec![
                CmdOption::new("Cutting edges", "T"),
                CmdOption::new("Fence", "F"),
                CmdOption::new("Crossing", "C"),
                CmdOption::new(
                    if self.implied_edges {
                        "Edge: Extend"
                    } else {
                        "Edge: No extend"
                    },
                    "E",
                ),
                CmdOption::new("Erase", "R"),
                CmdOption::enter("Done"),
            ],
            _ => vec![CmdOption::enter("Done")],
        }
    }

    fn wants_text_input(&self) -> bool {
        true
    }

    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
        // Consumed inputs return Some(NeedPoint) — None would be offered to
        // the command a second time by the driver.
        match text.trim().to_uppercase().as_str() {
            "T" | "CUTTING" | "B" | "BOUNDARY" => {
                self.edge_set.clear();
                self.mode = TrimMode::SelectEdges;
                Some(CmdResult::NeedPoint)
            }
            "F" | "FENCE" => {
                self.mode = TrimMode::Fence(FencePick::fence());
                Some(CmdResult::NeedPoint)
            }
            "C" | "CROSSING" => {
                self.mode = TrimMode::CrossFirst;
                Some(CmdResult::NeedPoint)
            }
            "E" | "EDGE" => {
                self.implied_edges = !self.implied_edges;
                self.rebuild_geos();
                Some(CmdResult::NeedPoint)
            }
            "R" | "ERASE" => {
                self.mode = TrimMode::Erase;
                Some(CmdResult::NeedPoint)
            }
            _ => None,
        }
    }

    fn set_shift(&mut self, shift: bool) {
        self.shift = shift;
    }

    fn needs_entity_pick(&self) -> bool {
        matches!(
            self.mode,
            TrimMode::Pick | TrimMode::SelectEdges | TrimMode::Erase
        )
    }

    fn on_entity_pick(&mut self, handle: Handle, pt: DVec3) -> CmdResult {
        if handle.is_null() {
            return CmdResult::NeedPoint;
        }
        match self.mode {
            TrimMode::SelectEdges => {
                // Toggle membership; the boundary rebuilds on Enter.
                if let Some(pos) = self.edge_set.iter().position(|h| *h == handle) {
                    self.edge_set.remove(pos);
                } else {
                    self.edge_set.push(handle);
                }
                CmdResult::NeedPoint
            }
            TrimMode::Erase => {
                // Erase option: delete without needing an intersection.
                if let Some(pos) = self
                    .all_entities
                    .iter()
                    .position(|e| e.common().handle == handle)
                {
                    self.all_entities.remove(pos);
                }
                self.edge_set.retain(|h| *h != handle);
                self.rebuild_geos();
                CmdResult::ReplaceEntity(handle, vec![])
            }
            _ => {
                let (px, py) = (pt.x, pt.y);
                let new_entities = if self.shift {
                    // Shift+click swaps to Extend for this pick (#336).
                    pick_extend_at(&self.all_entities, &self.geos, handle, px, py).map(|e| vec![e])
                } else {
                    let geos = self.nearby_geos(handle);
                    pick_trim_at(&self.all_entities, &geos, handle, px, py)
                };
                if let Some(new_entities) = new_entities {
                    // Snapshot is updated in on_entity_replaced once we know
                    // the real handles. Pre-stage: remove the old entry now so
                    // geos exclude it immediately.
                    if let Some(pos) = self
                        .all_entities
                        .iter()
                        .position(|e| e.common().handle == handle)
                    {
                        self.all_entities.remove(pos);
                        // Pieces join with NULL handles as geometry-only placeholders.
                        self.all_entities.extend(new_entities.clone());
                        self.edge_set.retain(|h| *h != handle);
                        self.rebuild_geos();
                    }
                    CmdResult::ReplaceEntity(handle, new_entities)
                } else {
                    CmdResult::NeedPoint
                }
            }
        }
    }

    fn on_entity_replaced(&mut self, _old: Handle, new_handles: &[codec::Handle]) {
        // Batch gestures stage several NULL-handle replacement groups before
        // the document assigns real handles. The host applies them in the same
        // order, so fill the first remaining placeholders on each callback.
        let mut handles = new_handles.iter().copied();
        for entity in self
            .all_entities
            .iter_mut()
            .filter(|entity| entity.common().handle.is_null())
        {
            let Some(handle) = handles.next() else {
                break;
            };
            entity.as_entity_mut().set_handle(handle);
        }
        self.rebuild_geos();
    }

    fn on_drag_selection(
        &mut self,
        fence: &[[f64; 2]],
        window: Option<([f64; 2], [f64; 2])>,
    ) -> Option<CmdResult> {
        if !matches!(self.mode, TrimMode::Pick) || fence.len() < 2 {
            return None;
        }
        let window = window.map(|(min, max)| CrossingWindow { min, max });
        let replacements = fence_pass(&self.all_entities, &self.geos, fence, window, self.shift);
        if replacements.is_empty() {
            return Some(CmdResult::NeedPoint);
        }
        self.stage_replacements(&replacements);
        Some(CmdResult::ReplaceManyContinue(replacements))
    }

    fn accepts_drag_selection(&self) -> bool {
        matches!(self.mode, TrimMode::Pick)
    }

    fn on_hover_entity(&mut self, handle: Handle, pt: DVec3) -> Vec<WireModel> {
        match self.mode {
            TrimMode::SelectEdges => {
                // Picked cutting edges stay highlighted; the hovered candidate
                // joins them at half strength.
                let mut out: Vec<WireModel> = self
                    .edge_set
                    .iter()
                    .filter_map(|h| self.all_entities.iter().find(|e| e.common().handle == *h))
                    .map(|e| WireModel::solid("edge_sel".into(), entity_pts(e), OPT_YELLOW, false))
                    .collect();
                if !handle.is_null() && !self.edge_set.contains(&handle) {
                    if let Some(e) = self
                        .all_entities
                        .iter()
                        .find(|e| e.common().handle == handle)
                    {
                        let mut c = OPT_YELLOW;
                        c[3] = 0.45;
                        out.push(WireModel::solid(
                            "edge_cand".into(),
                            entity_pts(e),
                            c,
                            false,
                        ));
                    }
                }
                return out;
            }
            TrimMode::Erase => {
                // Erase mode: the hovered object previews fully red.
                if let Some(e) = self
                    .all_entities
                    .iter()
                    .find(|e| e.common().handle == handle)
                {
                    return vec![WireModel::solid(
                        "erase_prev".into(),
                        entity_pts(e),
                        DIM_RED,
                        false,
                    )];
                }
                return vec![];
            }
            TrimMode::Pick => {}
            _ => return vec![],
        }
        if self.shift {
            // Shift held: preview the extend result instead.
            if let Some(ext) = pick_extend_at(&self.all_entities, &self.geos, handle, pt.x, pt.y) {
                if let Some(orig) = self
                    .all_entities
                    .iter()
                    .find(|e| e.common().handle == handle)
                {
                    return extend_hover_wires(
                        orig,
                        &ext,
                        &self.all_entities,
                        handle,
                        self.implied_edges,
                    );
                }
                return vec![WireModel::solid(
                    "extend_prev".into(),
                    entity_pts(&ext),
                    WireModel::CYAN,
                    false,
                )];
            }
            return vec![];
        }
        if handle.is_null() {
            return vec![];
        }

        let nearby_geos = self.nearby_geos(handle);
        let geos = nearby_geos.as_slice();
        let entity = self.entity_index.get(&self.all_entities, handle);

        let mut hover_wires = match entity {
            Some(EntityType::Line(l)) => {
                let ax = l.start.x;
                let ay = l.start.y;
                let bx = l.end.x;
                let by = l.end.y;
                let ts = line_seg_ts(ax, ay, bx, by, handle, geos);
                if ts.is_empty() {
                    return vec![];
                }
                let dx = bx - ax;
                let dy = by - ay;
                let len2 = dx * dx + dy * dy;
                let t_click = if len2 > 1e-12 {
                    ((pt.x as f64 - ax) * dx + (pt.y as f64 - ay) * dy) / len2
                } else {
                    0.5
                };
                let survivors = trim_line(l, &ts, t_click);
                let p1 = [l.start.x as f32, l.start.y as f32, l.start.y as f32];
                let p2 = [l.end.x as f32, l.end.y as f32, l.end.y as f32];
                let removed = WireModel::solid("trim_rm".into(), vec![p1, p2], DIM_RED, false);
                let mut out = vec![removed];
                for (i, e) in survivors.iter().enumerate() {
                    let pts = entity_pts(e);
                    out.push(WireModel::solid(
                        format!("trim_keep_{i}"),
                        pts,
                        WireModel::CYAN,
                        false,
                    ));
                }
                out
            }
            Some(EntityType::Arc(a)) => {
                let cx = a.center.x;
                let cy = a.center.y;
                let a0 = a.start_angle;
                let a1 = a.end_angle;
                let ts = arc_seg_ts(cx, cy, a.radius, a0, a1, handle, geos);
                if ts.is_empty() {
                    return vec![];
                }
                let click_angle = (pt.y as f64 - cy).atan2(pt.x as f64 - cx);
                let t_click = arc_t(click_angle, a0, a1);
                let survivors = trim_arc(a, &ts, t_click);
                let orig_pts = arc_pts(cx, cy, a.radius, a0, a1, a.center.z);
                let removed = WireModel::solid("trim_rm".into(), orig_pts, DIM_RED, false);
                let mut out = vec![removed];
                for (i, e) in survivors.iter().enumerate() {
                    let pts = entity_pts(e);
                    out.push(WireModel::solid(
                        format!("trim_keep_{i}"),
                        pts,
                        WireModel::CYAN,
                        false,
                    ));
                }
                out
            }
            Some(EntityType::Circle(c)) => {
                let cx = c.center.x;
                let cy = c.center.y;
                let ts = arc_seg_ts(cx, cy, c.radius, 0.0, TAU, handle, geos);
                if ts.len() < 2 {
                    return vec![];
                }
                let click_angle = (pt.y as f64 - cy).atan2(pt.x as f64 - cx);
                let t_click = arc_t(click_angle, 0.0, TAU);
                let survivors = trim_circle(c, &ts, t_click);
                if survivors.is_empty() {
                    return vec![];
                }
                let orig_pts = arc_pts(cx, cy, c.radius, 0.0, TAU, c.center.z);
                let removed = WireModel::solid("trim_rm".into(), orig_pts, DIM_RED, false);
                let mut out = vec![removed];
                for (i, e) in survivors.iter().enumerate() {
                    let pts = entity_pts(e);
                    out.push(WireModel::solid(
                        format!("trim_keep_{i}"),
                        pts,
                        WireModel::CYAN,
                        false,
                    ));
                }
                out
            }
            Some(EntityType::Ray(r)) => {
                let bx = r.base_point.x;
                let by = r.base_point.y;
                let curve = ray_curve(r);
                let ts = cut_params(&curve, handle, geos);
                if ts.is_empty() {
                    return vec![];
                }
                let t_click = curve.parameter_at([pt.x as f64, pt.y as f64]);
                let survivors = trim_ray(r, &ts, t_click);
                // Show a finite preview section (20 units) for the original ray
                let far = [
                    (bx + r.direction.x * 20.0) as f32,
                    (by + r.direction.y * 20.0) as f32,
                    r.base_point.z as f32,
                ];
                let base = [bx as f32, by as f32, r.base_point.z as f32];
                let removed = WireModel::solid("trim_rm".into(), vec![base, far], DIM_RED, false);
                let mut out = vec![removed];
                for (i, e) in survivors.iter().enumerate() {
                    let pts = entity_pts(e);
                    out.push(WireModel::solid(
                        format!("trim_keep_{i}"),
                        pts,
                        WireModel::CYAN,
                        false,
                    ));
                }
                out
            }
            Some(EntityType::XLine(x)) => {
                let bx = x.base_point.x;
                let by = x.base_point.y;
                let curve = xline_curve(x);
                let ts = cut_params(&curve, handle, geos);
                if ts.is_empty() {
                    return vec![];
                }
                let t_click = curve.parameter_at([pt.x as f64, pt.y as f64]);
                let survivors = trim_xline(x, &ts, t_click);
                let neg = [
                    (bx - x.direction.x * 20.0) as f32,
                    (by - x.direction.y * 20.0) as f32,
                    x.base_point.z as f32,
                ];
                let pos_pt = [
                    (bx + x.direction.x * 20.0) as f32,
                    (by + x.direction.y * 20.0) as f32,
                    x.base_point.z as f32,
                ];
                let removed = WireModel::solid("trim_rm".into(), vec![neg, pos_pt], DIM_RED, false);
                let mut out = vec![removed];
                for (i, e) in survivors.iter().enumerate() {
                    let pts = entity_pts(e);
                    out.push(WireModel::solid(
                        format!("trim_keep_{i}"),
                        pts,
                        WireModel::CYAN,
                        false,
                    ));
                }
                out
            }
            Some(EntityType::Ellipse(e)) => {
                let a = (e.major_axis.x.powi(2) + e.major_axis.y.powi(2)).sqrt();
                if a < 1e-9 {
                    return vec![];
                }
                let b = a * e.minor_axis_ratio;
                if b < 1e-9 {
                    return vec![];
                }
                let (nx, ny) = (e.major_axis.x / a, e.major_axis.y / a);
                let t0 = e.start_parameter;
                let mut t1 = e.end_parameter;
                if t1 <= t0 {
                    t1 += TAU;
                }
                let ts = ellipse_seg_ts(e.center.x, e.center.y, a, b, nx, ny, t0, t1, handle, geos);
                if ts.is_empty() {
                    return vec![];
                }
                let rx = pt.x as f64 - e.center.x;
                let ry = pt.y as f64 - e.center.y;
                let xl = rx * nx + ry * ny;
                let yl = -rx * ny + ry * nx;
                let t_ell = ellipse_closest_parameter(a, b, xl, yl);
                let t_click = arc_t(t_ell, t0, t1);
                let survivors = trim_ellipse(e, &ts, t_click);
                let orig_pts =
                    ellipse_pts(e.center.x, e.center.y, a, b, nx, ny, t0, t1, e.center.z);
                let removed = WireModel::solid("trim_rm".into(), orig_pts, DIM_RED, false);
                let mut out = vec![removed];
                for (i, ent) in survivors.iter().enumerate() {
                    let pts = entity_pts(ent);
                    out.push(WireModel::solid(
                        format!("trim_keep_{i}"),
                        pts,
                        WireModel::CYAN,
                        false,
                    ));
                }
                out
            }
            Some(EntityType::Spline(s)) => {
                let ts = spline_seg_ts(s, handle, geos);
                if ts.is_empty() {
                    return vec![];
                }
                let t_click = spline_nearest_t(s, pt.x as f64, pt.y as f64)
                    .and_then(|t_actual| {
                        let (t0, t1) = spline_range(s)?;
                        Some(t_to_rel(t_actual, t0, t1))
                    })
                    .unwrap_or(0.5);
                let orig_pts = spline_pts_wire(s);
                let removed = WireModel::solid("trim_rm".into(), orig_pts, DIM_RED, false);
                let survivors = trim_spline(s, &ts, t_click);
                let mut out = vec![removed];
                for (i, ent) in survivors.iter().enumerate() {
                    let pts = entity_pts(ent);
                    out.push(WireModel::solid(
                        format!("trim_keep_{i}"),
                        pts,
                        WireModel::CYAN,
                        false,
                    ));
                }
                out
            }
            Some(EntityType::LwPolyline(p)) => {
                let Some(survivors) = trim_lwpolyline(p, pt.x as f64, pt.y as f64, geos) else {
                    return vec![];
                };
                let orig = WireModel::solid(
                    "trim_rm".into(),
                    entity_pts(entity.unwrap()),
                    DIM_RED,
                    false,
                );
                let mut out = vec![orig];
                for (i, ent) in survivors.iter().enumerate() {
                    out.push(WireModel::solid(
                        format!("trim_keep_{i}"),
                        entity_pts(ent),
                        WireModel::CYAN,
                        false,
                    ));
                }
                out
            }
            _ => vec![],
        };
        // Edge: Extend — explain cuts landing on an IMPLIED boundary with a
        // dashed guide from that boundary's drawn end to the cut point (#336).
        if self.implied_edges && !hover_wires.is_empty() {
            if let (Some(orig), Some(pieces)) = (
                entity,
                pick_trim_at(&self.all_entities, geos, handle, pt.x, pt.y),
            ) {
                let cuts = piece_cut_points(orig, &pieces);
                hover_wires.extend(implied_cut_guides(&self.all_entities, handle, &cuts));
            }
        }
        hover_wires
    }

    fn on_point(&mut self, pt: DVec3) -> CmdResult {
        match &mut self.mode {
            TrimMode::Fence(pick) => {
                pick.push([pt.x, pt.y]);
                CmdResult::NeedPoint
            }
            TrimMode::CrossFirst => {
                self.mode = TrimMode::CrossSecond([pt.x, pt.y]);
                CmdResult::NeedPoint
            }
            TrimMode::CrossSecond(p1) => {
                // The rectangle's edges act as a 4-segment fence, and objects
                // wholly inside the window are picked too (crossing-selection
                // semantics).
                let p1 = *p1;
                let p2 = [pt.x, pt.y];
                self.mode = TrimMode::Pick;
                let rect = [p1, [p1[0], p2[1]], p2, [p2[0], p1[1]], p1];
                let window = CrossingWindow {
                    min: [p1[0].min(p2[0]), p1[1].min(p2[1])],
                    max: [p1[0].max(p2[0]), p1[1].max(p2[1])],
                };
                self.fence_run(&rect, Some(window))
            }
            _ => CmdResult::NeedPoint,
        }
    }

    fn on_preview_wires(&mut self, pt: DVec3) -> Vec<WireModel> {
        match &self.mode {
            TrimMode::Fence(pick) if !pick.is_empty() => {
                let mut out = vec![pick.preview([pt.x, pt.y], "trim_fence")];
                let mut fpts = pick.path();
                fpts.push([pt.x, pt.y]);
                out.extend(fence_result_preview(
                    &self.all_entities,
                    &self.geos,
                    &fpts,
                    None,
                    self.shift,
                    self.implied_edges,
                ));
                out
            }
            TrimMode::CrossSecond(p1) => {
                let p1 = *p1;
                let p2 = [pt.x, pt.y];
                let mut out = vec![crossing_box_preview(p1, p2, "trim_cross")];
                let rect = [p1, [p1[0], p2[1]], p2, [p2[0], p1[1]], p1];
                let window = CrossingWindow {
                    min: [p1[0].min(p2[0]), p1[1].min(p2[1])],
                    max: [p1[0].max(p2[0]), p1[1].max(p2[1])],
                };
                out.extend(fence_result_preview(
                    &self.all_entities,
                    &self.geos,
                    &rect,
                    Some(window),
                    self.shift,
                    self.implied_edges,
                ));
                out
            }
            _ => Vec::new(),
        }
    }

    fn on_enter(&mut self) -> CmdResult {
        match std::mem::replace(&mut self.mode, TrimMode::Pick) {
            TrimMode::SelectEdges => {
                self.rebuild_geos();
                CmdResult::NeedPoint
            }
            TrimMode::Fence(pick) if pick.is_usable() => self.fence_run(&pick.path(), None),
            TrimMode::Fence(_)
            | TrimMode::CrossFirst
            | TrimMode::CrossSecond(_)
            | TrimMode::Erase => CmdResult::NeedPoint,
            TrimMode::Pick => CmdResult::Cancel,
        }
    }
    fn on_escape(&mut self) -> CmdResult {
        // Esc leaves a sub-mode first; a second Esc ends the command.
        if !matches!(self.mode, TrimMode::Pick) {
            self.mode = TrimMode::Pick;
            return CmdResult::NeedPoint;
        }
        CmdResult::Cancel
    }
}

// ══════════════════════════════════════════════════════════════════════════
// ExtendCommand
// ══════════════════════════════════════════════════════════════════════════

pub struct ExtendCommand {
    all_entities: Vec<EntityType>,
    entity_index: ModifyEntityIndex,
    geos: Vec<Geo>,
    mode: TrimMode,
    /// Boundary-edge selection; empty = every object is a boundary.
    edge_set: Vec<Handle>,
    /// Edge option: boundaries extrapolate past their drawn extent.
    implied_edges: bool,
    /// Live Shift state — Shift+click trims instead of extends (#336).
    shift: bool,
}

impl ExtendCommand {
    pub fn new(all_entities: Vec<EntityType>) -> Self {
        let all_entities: Vec<EntityType> = all_entities
            .iter()
            .map(entity_with_lwpolyline_world_xy)
            .collect();
        let entity_index = ModifyEntityIndex::build(&all_entities);
        let geos = build_geos(&all_entities);
        Self {
            all_entities,
            entity_index,
            geos,
            mode: TrimMode::Pick,
            edge_set: Vec::new(),
            implied_edges: false,
            shift: false,
        }
    }

    fn rebuild_geos(&mut self) {
        self.entity_index = ModifyEntityIndex::build(&self.all_entities);
        self.geos = if self.edge_set.is_empty() {
            build_geos(&self.all_entities)
        } else {
            let picked: Vec<EntityType> = self
                .all_entities
                .iter()
                .filter(|e| self.edge_set.contains(&e.common().handle))
                .cloned()
                .collect();
            build_geos(&picked)
        };
        if self.implied_edges {
            imply_edge_geos(&mut self.geos);
        }
    }

    fn fence_run(&mut self, fence: &[[f64; 2]], window: Option<CrossingWindow>) -> CmdResult {
        // EXTEND's fence extends; Shift held at Enter swaps it to trim.
        let repl = fence_pass(&self.all_entities, &self.geos, fence, window, !self.shift);
        if repl.is_empty() {
            return CmdResult::NeedPoint;
        }
        CmdResult::ReplaceMany(repl, Vec::new())
    }
}

impl CadCommand for ExtendCommand {
    fn name(&self) -> &'static str {
        "EXTEND"
    }

    fn prompt(&self) -> String {
        let edge = if self.implied_edges {
            t!(" [Edge: Extend]")
        } else {
            std::borrow::Cow::Borrowed("")
        };
        match &self.mode {
            TrimMode::Pick => {
                crate::tf!("EXTEND{edge}  Click near end of object to extend (Shift+click trims):")
                    .into_owned()
            }
            TrimMode::SelectEdges => crate::tf!(
                "EXTEND  Select boundary edges [{} picked, Enter = done]:",
                self.edge_set.len()
            )
            .into_owned(),
            TrimMode::Fence(pick) => crate::tf!(
                "EXTEND{edge}  Fence: pick points [{} placed, Enter = extend crossed]:",
                pick.len()
            )
            .into_owned(),
            TrimMode::CrossFirst => {
                crate::tf!("EXTEND{edge}  Crossing: first corner:").into_owned()
            }
            TrimMode::CrossSecond(_) => {
                crate::tf!("EXTEND{edge}  Crossing: opposite corner:").into_owned()
            }
            TrimMode::Erase => t!("EXTEND  [Enter = done]:").into_owned(),
        }
    }

    fn options(&self) -> Vec<crate::command::CmdOption> {
        use crate::command::CmdOption;
        match self.mode {
            TrimMode::Pick => vec![
                CmdOption::new("Boundary edges", "B"),
                CmdOption::new("Fence", "F"),
                CmdOption::new("Crossing", "C"),
                CmdOption::new(
                    if self.implied_edges {
                        "Edge: Extend"
                    } else {
                        "Edge: No extend"
                    },
                    "E",
                ),
                CmdOption::enter("Done"),
            ],
            _ => vec![CmdOption::enter("Done")],
        }
    }

    fn wants_text_input(&self) -> bool {
        true
    }

    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
        match text.trim().to_uppercase().as_str() {
            "B" | "BOUNDARY" | "T" | "CUTTING" => {
                self.edge_set.clear();
                self.mode = TrimMode::SelectEdges;
                Some(CmdResult::NeedPoint)
            }
            "F" | "FENCE" => {
                self.mode = TrimMode::Fence(FencePick::fence());
                Some(CmdResult::NeedPoint)
            }
            "C" | "CROSSING" => {
                self.mode = TrimMode::CrossFirst;
                Some(CmdResult::NeedPoint)
            }
            "E" | "EDGE" => {
                self.implied_edges = !self.implied_edges;
                self.rebuild_geos();
                Some(CmdResult::NeedPoint)
            }
            _ => None,
        }
    }

    fn set_shift(&mut self, shift: bool) {
        self.shift = shift;
    }

    fn needs_entity_pick(&self) -> bool {
        matches!(self.mode, TrimMode::Pick | TrimMode::SelectEdges)
    }

    fn on_entity_pick(&mut self, handle: Handle, pt: DVec3) -> CmdResult {
        if handle.is_null() {
            return CmdResult::NeedPoint;
        }
        match self.mode {
            TrimMode::SelectEdges => {
                if let Some(pos) = self.edge_set.iter().position(|h| *h == handle) {
                    self.edge_set.remove(pos);
                } else {
                    self.edge_set.push(handle);
                }
                CmdResult::NeedPoint
            }
            _ => {
                let (px, py) = (pt.x, pt.y);
                let new_entities = if self.shift {
                    // Shift+click swaps to Trim for this pick (#336).
                    pick_trim_at(&self.all_entities, &self.geos, handle, px, py)
                } else {
                    pick_extend_at(&self.all_entities, &self.geos, handle, px, py).map(|e| vec![e])
                };
                if let Some(new_entities) = new_entities {
                    // Same snapshot bookkeeping as TRIM: drop the old entry,
                    // append the pieces as NULL-handle placeholders, and let
                    // on_entity_replaced assign the real handles.
                    if let Some(pos) = self
                        .all_entities
                        .iter()
                        .position(|e| e.common().handle == handle)
                    {
                        self.all_entities.remove(pos);
                        self.all_entities.extend(new_entities.clone());
                        self.edge_set.retain(|h| *h != handle);
                        self.rebuild_geos();
                    }
                    CmdResult::ReplaceEntity(handle, new_entities)
                } else {
                    CmdResult::NeedPoint
                }
            }
        }
    }

    fn on_entity_replaced(&mut self, _old: Handle, new_handles: &[codec::Handle]) {
        // The last new_handles.len() entries are the pieces appended with NULL
        // handles in on_entity_pick — assign their real document handles.
        let start = self.all_entities.len().saturating_sub(new_handles.len());
        for (e, &h) in self.all_entities[start..]
            .iter_mut()
            .zip(new_handles.iter())
        {
            match e {
                EntityType::Line(l) => l.common.handle = h,
                EntityType::Arc(a) => a.common.handle = h,
                EntityType::Ray(r) => r.common.handle = h,
                EntityType::XLine(x) => x.common.handle = h,
                EntityType::Ellipse(e) => e.common.handle = h,
                EntityType::Spline(s) => s.common.handle = h,
                EntityType::LwPolyline(p) => p.common.handle = h,
                _ => {}
            }
        }
        self.rebuild_geos();
    }

    fn on_hover_entity(&mut self, handle: Handle, pt: DVec3) -> Vec<WireModel> {
        match self.mode {
            TrimMode::SelectEdges => {
                let mut out: Vec<WireModel> = self
                    .edge_set
                    .iter()
                    .filter_map(|h| self.entity_index.get(&self.all_entities, *h))
                    .map(|e| WireModel::solid("edge_sel".into(), entity_pts(e), OPT_YELLOW, false))
                    .collect();
                if !handle.is_null() && !self.edge_set.contains(&handle) {
                    if let Some(e) = self.entity_index.get(&self.all_entities, handle) {
                        let mut c = OPT_YELLOW;
                        c[3] = 0.45;
                        out.push(WireModel::solid(
                            "edge_cand".into(),
                            entity_pts(e),
                            c,
                            false,
                        ));
                    }
                }
                return out;
            }
            TrimMode::Pick => {}
            _ => return vec![],
        }
        if self.shift {
            // Shift held: preview the trim result instead.
            if let Some(pieces) = pick_trim_at(&self.all_entities, &self.geos, handle, pt.x, pt.y) {
                let mut out = Vec::new();
                for (i, e) in pieces.iter().enumerate() {
                    out.push(WireModel::solid(
                        format!("trim_keep_{i}"),
                        entity_pts(e),
                        WireModel::CYAN,
                        false,
                    ));
                }
                return out;
            }
            return vec![];
        }
        if handle.is_null() {
            return vec![];
        }

        let entity = self.entity_index.get(&self.all_entities, handle);
        match entity {
            Some(EntityType::Line(l)) => {
                let ax = l.start.x;
                let ay = l.start.y;
                let bx = l.end.x;
                let by = l.end.y;
                let dx = bx - ax;
                let dy = by - ay;
                let len2 = dx * dx + dy * dy;
                let t_click = if len2 > 1e-12 {
                    ((pt.x as f64 - ax) * dx + (pt.y as f64 - ay) * dy) / len2
                } else {
                    0.5
                };
                if let Some(ext) = extend_line(l, t_click, &self.geos) {
                    return extend_hover_wires(
                        &EntityType::Line(l.clone()),
                        &ext,
                        &self.all_entities,
                        handle,
                        self.implied_edges,
                    );
                }
            }
            Some(EntityType::Arc(a)) => {
                let ang = (pt.y as f64 - a.center.y).atan2(pt.x as f64 - a.center.x);
                let t_click = arc_t(ang, a.start_angle, a.end_angle);
                if let Some(ext) = extend_arc(a, t_click, &self.geos) {
                    return extend_hover_wires(
                        &EntityType::Arc(a.clone()),
                        &ext,
                        &self.all_entities,
                        handle,
                        self.implied_edges,
                    );
                }
            }
            Some(EntityType::Ellipse(e)) => {
                let a = (e.major_axis.x.powi(2) + e.major_axis.y.powi(2)).sqrt();
                if a >= 1e-9 {
                    let b = a * e.minor_axis_ratio;
                    if b >= 1e-9 {
                        let (nx, ny) = (e.major_axis.x / a, e.major_axis.y / a);
                        let t0 = e.start_parameter;
                        let mut t1 = e.end_parameter;
                        if t1 <= t0 {
                            t1 += TAU;
                        }
                        let rx = pt.x as f64 - e.center.x;
                        let ry = pt.y as f64 - e.center.y;
                        let xl = rx * nx + ry * ny;
                        let yl = -rx * ny + ry * nx;
                        let t_ell = ellipse_closest_parameter(a, b, xl, yl);
                        let t_click = arc_t(t_ell, t0, t1);
                        if let Some(ext) = extend_ellipse(e, t_click, &self.geos) {
                            return extend_hover_wires(
                                &EntityType::Ellipse(e.clone()),
                                &ext,
                                &self.all_entities,
                                handle,
                                self.implied_edges,
                            );
                        }
                    }
                }
            }
            Some(EntityType::LwPolyline(p)) => {
                if let Some(ext) = extend_lwpoly(p, pt.x as f64, pt.y as f64, &self.geos) {
                    return extend_hover_wires(
                        &EntityType::LwPolyline(p.clone()),
                        &ext,
                        &self.all_entities,
                        handle,
                        self.implied_edges,
                    );
                }
            }
            Some(EntityType::Spline(s)) => {
                let t_click = spline_nearest_t(s, pt.x as f64, pt.y as f64)
                    .and_then(|t_actual| {
                        let (t0, t1) = spline_range(s)?;
                        Some(t_to_rel(t_actual, t0, t1))
                    })
                    .unwrap_or(0.5);
                if let Some(ext) = extend_spline(s, t_click, &self.geos) {
                    return extend_hover_wires(
                        &EntityType::Spline(s.clone()),
                        &ext,
                        &self.all_entities,
                        handle,
                        self.implied_edges,
                    );
                }
            }
            _ => {}
        }
        vec![]
    }

    fn on_point(&mut self, pt: DVec3) -> CmdResult {
        match &mut self.mode {
            TrimMode::Fence(pick) => {
                pick.push([pt.x, pt.y]);
                CmdResult::NeedPoint
            }
            TrimMode::CrossFirst => {
                self.mode = TrimMode::CrossSecond([pt.x, pt.y]);
                CmdResult::NeedPoint
            }
            TrimMode::CrossSecond(p1) => {
                let p1 = *p1;
                let p2 = [pt.x, pt.y];
                self.mode = TrimMode::Pick;
                let rect = [p1, [p1[0], p2[1]], p2, [p2[0], p1[1]], p1];
                let window = CrossingWindow {
                    min: [p1[0].min(p2[0]), p1[1].min(p2[1])],
                    max: [p1[0].max(p2[0]), p1[1].max(p2[1])],
                };
                self.fence_run(&rect, Some(window))
            }
            _ => CmdResult::NeedPoint,
        }
    }

    fn on_preview_wires(&mut self, pt: DVec3) -> Vec<WireModel> {
        match &self.mode {
            TrimMode::Fence(pick) if !pick.is_empty() => {
                let mut out = vec![pick.preview([pt.x, pt.y], "extend_fence")];
                let mut fpts = pick.path();
                fpts.push([pt.x, pt.y]);
                out.extend(fence_result_preview(
                    &self.all_entities,
                    &self.geos,
                    &fpts,
                    None,
                    !self.shift,
                    self.implied_edges,
                ));
                out
            }
            TrimMode::CrossSecond(p1) => {
                let p1 = *p1;
                let p2 = [pt.x, pt.y];
                let mut out = vec![crossing_box_preview(p1, p2, "extend_cross")];
                let rect = [p1, [p1[0], p2[1]], p2, [p2[0], p1[1]], p1];
                let window = CrossingWindow {
                    min: [p1[0].min(p2[0]), p1[1].min(p2[1])],
                    max: [p1[0].max(p2[0]), p1[1].max(p2[1])],
                };
                out.extend(fence_result_preview(
                    &self.all_entities,
                    &self.geos,
                    &rect,
                    Some(window),
                    !self.shift,
                    self.implied_edges,
                ));
                out
            }
            _ => Vec::new(),
        }
    }

    fn on_enter(&mut self) -> CmdResult {
        match std::mem::replace(&mut self.mode, TrimMode::Pick) {
            TrimMode::SelectEdges => {
                self.rebuild_geos();
                CmdResult::NeedPoint
            }
            TrimMode::Fence(pick) if pick.is_usable() => self.fence_run(&pick.path(), None),
            TrimMode::Fence(_)
            | TrimMode::CrossFirst
            | TrimMode::CrossSecond(_)
            | TrimMode::Erase => CmdResult::NeedPoint,
            TrimMode::Pick => CmdResult::Cancel,
        }
    }
    fn on_escape(&mut self) -> CmdResult {
        if !matches!(self.mode, TrimMode::Pick) {
            self.mode = TrimMode::Pick;
            return CmdResult::NeedPoint;
        }
        CmdResult::Cancel
    }
}

// ── Autocomplete registry ─────────────────────────────────
inventory::submit!(crate::command::CommandRegistration { names: &["EXTEND"] }); // ExtendCommand
inventory::submit!(crate::command::CommandRegistration { names: &["TRIM"] }); // TrimCommand

#[cfg(test)]
mod tests {
    use super::*;
    use std::f64::consts::PI;

    fn xline_at(x1: f64, y1: f64, x2: f64, y2: f64, h: u64) -> EntityType {
        let mut l = LineEnt::new();
        l.start = Vector3::new(x1, y1, 0.0);
        l.end = Vector3::new(x2, y2, 0.0);
        l.common.handle = Handle::new(h);
        EntityType::Line(l)
    }

    /// Edge: Extend — the target must lengthen to the BOUNDARY'S extrapolation
    /// when the boundary doesn't physically cross the target's path (#336).
    #[test]
    fn edge_extend_reaches_implied_boundary() {
        let target = xline_at(0.0, 0.0, 2.0, 0.0, 1);
        let boundary = xline_at(5.0, 2.0, 5.0, 8.0, 2);
        let all = vec![target.clone(), boundary];
        // Edge off: the boundary's drawn extent never meets y=0 — no extend.
        let geos = build_geos(&all);
        assert!(pick_extend_at(&all, &geos, Handle::new(1), 1.9, 0.0).is_none());
        // Edge on: the implied boundary crosses y=0 at x=5 — extend to (5,0).
        let mut implied = build_geos(&all);
        imply_edge_geos(&mut implied);
        match pick_extend_at(&all, &implied, Handle::new(1), 1.9, 0.0) {
            Some(EntityType::Line(l)) => {
                assert!(
                    (l.end.x - 5.0).abs() < 1e-6 && l.end.y.abs() < 1e-6,
                    "extends to the implied boundary, got ({}, {})",
                    l.end.x,
                    l.end.y
                );
            }
            other => panic!("expected an extended Line, got {other:?}"),
        }
    }

    /// #336 repro: two lines forming an X; a fence across one overhanging arm
    /// must trim that arm back to the intersection.
    #[test]
    fn fence_trims_x_arm() {
        let all = vec![
            xline_at(0.0, 0.0, 10.0, 10.0, 1),
            xline_at(0.0, 10.0, 10.0, 0.0, 2),
        ];
        let geos = build_geos(&all);
        let fence = [[8.0, 10.0], [10.0, 8.0]];
        let repl = fence_pass(&all, &geos, &fence, None, false);
        assert_eq!(
            repl.len(),
            1,
            "exactly the crossed line is trimmed: {repl:?}"
        );
        assert_eq!(repl[0].0, Handle::new(1));
        assert_eq!(repl[0].1.len(), 1);
        match &repl[0].1[0] {
            EntityType::Line(l) => {
                assert!(
                    (l.end.x - 5.0).abs() < 1e-6 && (l.end.y - 5.0).abs() < 1e-6,
                    "arm cut back to the intersection, got end ({}, {})",
                    l.end.x,
                    l.end.y
                );
            }
            other => panic!("expected a Line, got {other:?}"),
        }
    }

    fn circle(r: f64) -> CircleEnt {
        let mut c = CircleEnt::new();
        c.center = Vector3::new(0.0, 0.0, 0.0);
        c.radius = r;
        c
    }

    /// A circle crossed by a horizontal cutter (cuts at angle 0 and π, i.e.
    /// t = 0.0 and 0.5) becomes a single Arc; clicking the top half removes it
    /// and leaves the bottom half (π → 0 CCW), clicking the bottom does the
    /// reverse.
    #[test]
    fn trims_circle_into_arc_on_clicked_half() {
        let c = circle(10.0);
        let ts = [0.0, 0.5];

        // Click top (t = 0.25) → removes top, keeps bottom half (start π, end 0).
        let top = trim_circle(&c, &ts, 0.25);
        assert_eq!(top.len(), 1, "circle should trim to exactly one arc");
        match &top[0] {
            EntityType::Arc(a) => {
                assert!((norm(a.start_angle) - PI).abs() < 1e-9);
                assert!(norm(a.end_angle).abs() < 1e-9);
                assert_eq!(a.radius, 10.0);
                assert!(a.common.handle.is_null());
            }
            _ => panic!("expected an Arc"),
        }

        // Click bottom (t = 0.75) → keeps top half (start 0, end π).
        let bottom = trim_circle(&c, &ts, 0.75);
        match &bottom[0] {
            EntityType::Arc(a) => {
                assert!(norm(a.start_angle).abs() < 1e-9);
                assert!((norm(a.end_angle) - PI).abs() < 1e-9);
            }
            _ => panic!("expected an Arc"),
        }
    }

    /// Fewer than two crossings can't cut a closed circle, so it is left as-is.
    #[test]
    fn circle_with_one_or_zero_cuts_is_left_unchanged() {
        let c = circle(5.0);
        assert!(trim_circle(&c, &[], 0.3).is_empty());
        assert!(trim_circle(&c, &[0.4], 0.3).is_empty());
    }

    #[test]
    fn trim_polyline_arc_segment_preserves_bulge() {
        use std::f64::consts::FRAC_PI_8;
        // Arc from (0, 0) to (2, 0) with bulge 1.0 (semicircle sweeping CCW under the chord)
        let mut poly = LwPolyline::new();
        poly.common.handle = Handle::new(10);
        let mut v0 = LwVertex::from_coords(0.0, 0.0);
        v0.bulge = 1.0;
        let v1 = LwVertex::from_coords(2.0, 0.0);
        poly.vertices = vec![v0, v1];

        // Vertical cutter line at x = 1.0 crossing the arc at (1.0, -1.0)
        let mut cutter = LineEnt::new();
        cutter.start = Vector3::new(1.0, -2.0, 0.0);
        cutter.end = Vector3::new(1.0, 2.0, 0.0);
        cutter.common.handle = Handle::new(20);

        let all = vec![EntityType::LwPolyline(poly), EntityType::Line(cutter)];
        let geos = build_geos(&all);

        // Click first half near (0.5, -0.8) -> first half removed, second half kept from (1.0, -1.0) to (2.0, 0.0)
        let res = pick_trim_at(&all, &geos, Handle::new(10), 0.5, -0.8)
            .expect("should trim polyline arc");
        assert_eq!(res.len(), 1);
        match &res[0] {
            EntityType::LwPolyline(p) => {
                assert_eq!(p.vertices.len(), 2);
                let p0 = &p.vertices[0];
                let p1 = &p.vertices[1];
                assert!(
                    (p0.location.x - 1.0).abs() < 1e-5,
                    "expected x=1.0, got {}",
                    p0.location.x
                );
                assert!(
                    (p0.location.y + 1.0).abs() < 1e-5,
                    "expected y=-1.0, got {}",
                    p0.location.y
                );
                assert!(
                    (p1.location.x - 2.0).abs() < 1e-5,
                    "expected x=2.0, got {}",
                    p1.location.x
                );
                assert!(
                    p1.location.y.abs() < 1e-5,
                    "expected y=0.0, got {}",
                    p1.location.y
                );
                // The surviving quarter circle should have bulge = tan(pi / 8)
                let expected_bulge = FRAC_PI_8.tan();
                assert!(
                    (p0.bulge - expected_bulge).abs() < 1e-4,
                    "surviving arc should retain quarter-circle bulge {}, got {}",
                    expected_bulge,
                    p0.bulge
                );
                assert_eq!(p1.bulge, 0.0);
            }
            other => panic!("expected LwPolyline, got {other:?}"),
        }

        // Click second half near (1.5, -0.8) -> second half removed, first half kept from (0.0, 0.0) to (1.0, -1.0)
        let res2 = pick_trim_at(&all, &geos, Handle::new(10), 1.5, -0.8)
            .expect("should trim polyline arc");
        assert_eq!(res2.len(), 1);
        match &res2[0] {
            EntityType::LwPolyline(p) => {
                assert_eq!(p.vertices.len(), 2);
                let p0 = &p.vertices[0];
                let p1 = &p.vertices[1];
                assert!(
                    p0.location.x.abs() < 1e-5,
                    "expected x=0.0, got {}",
                    p0.location.x
                );
                assert!(
                    p0.location.y.abs() < 1e-5,
                    "expected y=0.0, got {}",
                    p0.location.y
                );
                assert!(
                    (p1.location.x - 1.0).abs() < 1e-5,
                    "expected x=1.0, got {}",
                    p1.location.x
                );
                assert!(
                    (p1.location.y + 1.0).abs() < 1e-5,
                    "expected y=-1.0, got {}",
                    p1.location.y
                );
                let expected_bulge = FRAC_PI_8.tan();
                assert!(
                    (p0.bulge - expected_bulge).abs() < 1e-4,
                    "surviving arc should retain quarter-circle bulge {}, got {}",
                    expected_bulge,
                    p0.bulge
                );
                assert_eq!(p1.bulge, 0.0);
            }
            other => panic!("expected LwPolyline, got {other:?}"),
        }
    }

    #[test]
    fn trim_multi_segment_polyline_with_arc() {
        use std::f64::consts::FRAC_PI_8;
        // Segment 0: straight line from (-2, 0) to (0, 0)
        // Segment 1: arc from (0, 0) to (2, 0) with bulge 1.0
        let mut poly = LwPolyline::new();
        poly.common.handle = Handle::new(30);
        let v0 = LwVertex::from_coords(-2.0, 0.0);
        let mut v1 = LwVertex::from_coords(0.0, 0.0);
        v1.bulge = 1.0;
        let v2 = LwVertex::from_coords(2.0, 0.0);
        poly.vertices = vec![v0, v1, v2];

        // Vertical cutter at x = 1.0
        let mut cutter = LineEnt::new();
        cutter.start = Vector3::new(1.0, -2.0, 0.0);
        cutter.end = Vector3::new(1.0, 2.0, 0.0);
        cutter.common.handle = Handle::new(40);

        let all = vec![EntityType::LwPolyline(poly), EntityType::Line(cutter)];
        let geos = build_geos(&all);

        // Click the far end of the arc near (1.5, -0.8) -> removes end, keeps straight seg + first half of arc
        let res = pick_trim_at(&all, &geos, Handle::new(30), 1.5, -0.8).expect("should trim");
        assert_eq!(res.len(), 1);
        match &res[0] {
            EntityType::LwPolyline(p) => {
                assert_eq!(p.vertices.len(), 3);
                // Vertex 0: (-2, 0), straight
                assert!((p.vertices[0].location.x + 2.0).abs() < 1e-5);
                assert!(p.vertices[0].bulge.abs() < 1e-5);
                // Vertex 1: (0, 0), arc with quarter-turn bulge
                assert!(p.vertices[1].location.x.abs() < 1e-5);
                let expected_bulge = FRAC_PI_8.tan();
                assert!((p.vertices[1].bulge - expected_bulge).abs() < 1e-4);
                // Vertex 2: (1, -1), end
                assert!((p.vertices[2].location.x - 1.0).abs() < 1e-5);
                assert!((p.vertices[2].location.y + 1.0).abs() < 1e-5);
            }
            other => panic!("expected LwPolyline, got {other:?}"),
        }
    }

    #[test]
    fn trim_negative_bulge_polyline_arc() {
        use std::f64::consts::FRAC_PI_8;
        // Negative bulge means CW arc: from (0, 0) to (2, 0) arches above the chord (y > 0)
        let mut poly = LwPolyline::new();
        poly.common.handle = Handle::new(50);
        let mut v0 = LwVertex::from_coords(0.0, 0.0);
        v0.bulge = -1.0;
        let v1 = LwVertex::from_coords(2.0, 0.0);
        poly.vertices = vec![v0, v1];

        // Vertical cutter at x = 1.0 crossing at (1.0, 1.0)
        let mut cutter = LineEnt::new();
        cutter.start = Vector3::new(1.0, -2.0, 0.0);
        cutter.end = Vector3::new(1.0, 2.0, 0.0);
        cutter.common.handle = Handle::new(60);

        let all = vec![EntityType::LwPolyline(poly), EntityType::Line(cutter)];
        let geos = build_geos(&all);

        // Click first half near (0.5, 0.8) -> removes first half, keeps second half from (1.0, 1.0) to (2.0, 0.0)
        let res = pick_trim_at(&all, &geos, Handle::new(50), 0.5, 0.8).expect("should trim CW arc");
        assert_eq!(res.len(), 1);
        match &res[0] {
            EntityType::LwPolyline(p) => {
                assert_eq!(p.vertices.len(), 2);
                let p0 = &p.vertices[0];
                let p1 = &p.vertices[1];
                assert!((p0.location.x - 1.0).abs() < 1e-5);
                assert!((p0.location.y - 1.0).abs() < 1e-5);
                assert!((p1.location.x - 2.0).abs() < 1e-5);
                assert!(p1.location.y.abs() < 1e-5);
                let expected_bulge = -FRAC_PI_8.tan();
                assert!(
                    (p0.bulge - expected_bulge).abs() < 1e-4,
                    "expected negative bulge {}, got {}",
                    expected_bulge,
                    p0.bulge
                );
            }
            other => panic!("expected LwPolyline, got {other:?}"),
        }
    }

    #[test]
    fn trim_closed_polyline_with_arc() {
        use std::f64::consts::FRAC_PI_8;
        // Closed polyline:
        // Vertex 0: (0, 0), bulge 1.0 (arc to (2, 0) below chord, peak at y=-1)
        // Vertex 1: (2, 0), bulge 0.0 (straight to (2, 2))
        // Vertex 2: (2, 2), bulge 0.0 (straight to (0, 2))
        // Vertex 3: (0, 2), bulge 0.0 (straight back to (0, 0))
        let mut poly = LwPolyline::new();
        poly.common.handle = Handle::new(70);
        poly.is_closed = true;
        let mut v0 = LwVertex::from_coords(0.0, 0.0);
        v0.bulge = 1.0;
        let v1 = LwVertex::from_coords(2.0, 0.0);
        let v2 = LwVertex::from_coords(2.0, 2.0);
        let v3 = LwVertex::from_coords(0.0, 2.0);
        poly.vertices = vec![v0, v1, v2, v3];

        // Cutter 1: x = 1.0 cuts the arc at (1.0, -1.0)
        let mut c1 = LineEnt::new();
        c1.start = Vector3::new(1.0, -3.0, 0.0);
        c1.end = Vector3::new(1.0, -0.5, 0.0);
        c1.common.handle = Handle::new(80);

        // Cutter 2: y = 1.0 cuts vertical edges at x=0 and x=2
        let mut c2 = LineEnt::new();
        c2.start = Vector3::new(-1.0, 1.0, 0.0);
        c2.end = Vector3::new(3.0, 1.0, 0.0);
        c2.common.handle = Handle::new(81);

        let all = vec![
            EntityType::LwPolyline(poly),
            EntityType::Line(c1),
            EntityType::Line(c2),
        ];
        let geos = build_geos(&all);

        // Click first half of arc near (0.5, -0.8):
        // Nearest cuts are at (1.0, -1.0) on seg 0 and at (0.0, 1.0) on seg 3.
        // Trim removes that corner/arc portion and leaves an open polyline
        let res = pick_trim_at(&all, &geos, Handle::new(70), 0.5, -0.8)
            .expect("should trim closed polyline");
        assert_eq!(res.len(), 1);
        match &res[0] {
            EntityType::LwPolyline(p) => {
                assert!(!p.is_closed);
                // Starts at (1.0, -1.0) with remaining quarter-circle arc
                let start_v = &p.vertices[0];
                assert!((start_v.location.x - 1.0).abs() < 1e-5);
                assert!((start_v.location.y + 1.0).abs() < 1e-5);
                let expected_bulge = FRAC_PI_8.tan();
                assert!((start_v.bulge - expected_bulge).abs() < 1e-4);
            }
            other => panic!("expected LwPolyline, got {other:?}"),
        }
    }

    /// #1318 repro: a 3D polyline whose first segment is not horizontal has no
    /// plan-view shape, so it samples to nothing. The seam test then compared
    /// two empty ends as equal and sliced the empty sample from index 1.
    #[test]
    fn sampling_skips_segments_with_no_plan_shape() {
        use codec::entities::{Polyline3D, Vertex3DPolyline};

        let mut pl = Polyline3D::new();
        pl.vertices = vec![
            // Vertical: an upright curve plane, dropped by `entity_curve_xy`.
            Vertex3DPolyline::from_xyz(0.0, 0.0, 0.0),
            Vertex3DPolyline::from_xyz(0.0, 0.0, 10.0),
            // Horizontal, so this one does sample.
            Vertex3DPolyline::from_xyz(10.0, 0.0, 10.0),
        ];

        let pts = sample_entity_xy(&EntityType::Polyline3D(pl));
        assert!(
            !pts.is_empty(),
            "the horizontal segment still has to be sampled"
        );
        assert!(
            pts.iter().all(|p| p.iter().all(|c| c.is_finite())),
            "sampled points stay finite: {pts:?}"
        );
    }

    /// The same skip must not swallow a leading segment that does sample, and
    /// must keep dropping the duplicated seam vertex between two of them.
    #[test]
    fn sampling_still_joins_segments_at_their_seam() {
        use codec::entities::{Polyline3D, Vertex3DPolyline};

        let mut pl = Polyline3D::new();
        pl.vertices = vec![
            Vertex3DPolyline::from_xyz(0.0, 0.0, 0.0),
            Vertex3DPolyline::from_xyz(10.0, 0.0, 0.0),
            Vertex3DPolyline::from_xyz(10.0, 10.0, 0.0),
        ];

        let pts = sample_entity_xy(&EntityType::Polyline3D(pl));
        let seam = [10.0, 0.0];
        assert_eq!(
            pts.iter().filter(|p| **p == seam).count(),
            1,
            "the shared vertex appears once, not twice: {pts:?}"
        );
    }

    #[test]
    fn preview_sampling_skips_edge_on_polyline2d_arc_segments() {
        use codec::entities::{Polyline2D, Vertex2D};

        let mut pl = Polyline2D::new();
        let mut start = Vertex2D::new(Vector3::new(0.0, 0.0, 0.0));
        start.bulge = 1.0;
        pl.vertices = vec![start, Vertex2D::new(Vector3::new(2.0, 0.0, 0.0))];
        pl.normal = Vector3::new(1.0, 0.0, 0.0);

        let pts = preview_sample_xy(&EntityType::Polyline2D(pl));
        assert!(
            pts.is_empty(),
            "edge-on arc segments are skipped instead of panicking: {pts:?}"
        );
    }

    #[test]
    fn trim_circle_with_tangent_arcs_touching_at_endpoints() {
        use codec::entities::{Arc as ArcEnt, Circle as CircleEnt};
        let mut c = CircleEnt::new();
        c.common.handle = Handle::new(1);
        c.center = Vector3::new(0.0, 0.0, 0.0);
        c.radius = 10.0;

        // Arc 1: center (20, 0), r = 10, from PI/2 to PI (endpoint at (10, 0))
        let mut a1 = ArcEnt::new();
        a1.common.handle = Handle::new(2);
        a1.center = Vector3::new(20.0, 0.0, 0.0);
        a1.radius = 10.0;
        a1.start_angle = std::f64::consts::FRAC_PI_2;
        a1.end_angle = std::f64::consts::PI;

        // Arc 2: center (-20, 0), r = 10, from 0 to PI/2 (endpoint at (-10, 0))
        let mut a2 = ArcEnt::new();
        a2.common.handle = Handle::new(3);
        a2.center = Vector3::new(-20.0, 0.0, 0.0);
        a2.radius = 10.0;
        a2.start_angle = 0.0;
        a2.end_angle = std::f64::consts::FRAC_PI_2;

        let all = vec![
            EntityType::Circle(c),
            EntityType::Arc(a1),
            EntityType::Arc(a2),
        ];
        let geos = build_geos(&all);

        // Click on top of the circle at (0, 10)
        let survivors = pick_trim_at(&all, &geos, Handle::new(1), 0.0, 10.0);
        assert!(
            survivors.is_some(),
            "trimming circle between two tangent arc endpoints must succeed"
        );
        let pieces = survivors.unwrap();
        assert_eq!(pieces.len(), 1, "expected 1 surviving arc piece");
        if let EntityType::Arc(arc) = &pieces[0] {
            assert!((arc.radius - 10.0).abs() < 1e-6);
            let span = {
                let s = (arc.end_angle - arc.start_angle).rem_euclid(TAU);
                if s == 0.0 {
                    TAU
                } else {
                    s
                }
            };
            let mid_ang = arc.start_angle + span * 0.5;
            let mid_y = mid_ang.sin();
            assert!(
                mid_y < 0.0,
                "bottom half should survive when clicking top half"
            );
        } else {
            panic!("expected Arc survivor");
        }
    }

    #[test]
    fn test_trim_circle_between_two_tangent_lines() {
        use codec::entities::{Circle as CircleEnt, Line as LineEnt};
        let mut c = CircleEnt::new();
        c.common.handle = Handle::new(1);
        c.center = Vector3::new(0.0, 0.0, 0.0);
        c.radius = 10.0;

        // Line 1: tangent at top (0, 10), from (-20, 10) to (20, 10)
        let mut l1 = LineEnt::new();
        l1.common.handle = Handle::new(2);
        l1.start = Vector3::new(-20.0, 10.0, 0.0);
        l1.end = Vector3::new(20.0, 10.0, 0.0);

        // Line 2: tangent at bottom (0, -10), from (-20, -10) to (20, -10)
        let mut l2 = LineEnt::new();
        l2.common.handle = Handle::new(3);
        l2.start = Vector3::new(-20.0, -10.0, 0.0);
        l2.end = Vector3::new(20.0, -10.0, 0.0);

        let all = vec![
            EntityType::Circle(c),
            EntityType::Line(l1),
            EntityType::Line(l2),
        ];
        let geos = build_geos(&all);

        // Trim circle by clicking right side at (10, 0)
        let survivors = pick_trim_at(&all, &geos, Handle::new(1), 10.0, 0.0);
        assert!(
            survivors.is_some(),
            "trimming circle between two tangent lines must succeed"
        );
        let pieces = survivors.unwrap();
        assert_eq!(pieces.len(), 1, "expected 1 surviving arc piece");
        let EntityType::Arc(arc) = &pieces[0] else {
            panic!("expected Arc")
        };

        let arc_start = glam::DVec3::new(
            arc.radius * arc.start_angle.cos(),
            arc.radius * arc.start_angle.sin(),
            0.0,
        );
        let arc_end = glam::DVec3::new(
            arc.radius * arc.end_angle.cos(),
            arc.radius * arc.end_angle.sin(),
            0.0,
        );

        println!("arc start: {:?}, end: {:?}", arc_start, arc_end);

        // Now trim line 1 by clicking at (10, 10)
        let l1_survivors = pick_trim_at(&all, &geos, Handle::new(2), 10.0, 10.0);
        assert!(l1_survivors.is_some(), "trimming line 1 must succeed");
        let l1_pieces = l1_survivors.unwrap();
        assert_eq!(l1_pieces.len(), 1);
        let EntityType::Line(trimmed_l1) = &l1_pieces[0] else {
            panic!("expected Line")
        };
        println!(
            "trimmed line 1 start: {:?}, end: {:?}",
            trimmed_l1.start, trimmed_l1.end
        );

        // Check distance between trimmed line 1 end and arc start
        let line_end = glam::DVec3::new(trimmed_l1.end.x, trimmed_l1.end.y, trimmed_l1.end.z);
        let diff = (line_end - arc_start).length();
        println!(
            "Distance between line endpoint and arc endpoint: {:e}",
            diff
        );

        // Now test an angled / non-axis-aligned case from external point
        let c_center = glam::DVec3::new(123.45, 67.89, 0.0);
        let c_radius = 25.0;
        let p_ext1 = glam::DVec3::new(200.0, 150.0, 0.0);
        let p_ext2 = glam::DVec3::new(50.0, -20.0, 0.0);

        let get_tangents = |p: glam::DVec3| {
            let k_curve = kernel::geom2d::Curve::Circle(kernel::geom2d::Circle {
                centre: [c_center.x, c_center.y],
                radius: c_radius,
            });
            let pts = kernel::geom2d::tangent_from(&k_curve, [p.x, p.y]);
            (
                glam::DVec3::new(pts[0].point[0], pts[0].point[1], 0.0),
                glam::DVec3::new(pts[1].point[0], pts[1].point[1], 0.0),
            )
        };
        let t1 = get_tangents(p_ext1).0;
        let t2 = get_tangents(p_ext2).1;

        let mut c_rot = CircleEnt::new();
        c_rot.common.handle = Handle::new(10);
        c_rot.center = Vector3::new(c_center.x, c_center.y, c_center.z);
        c_rot.radius = c_radius;

        // Line 1 from p_ext1 extending PAST t1 to make it a boundary line crossing tangent
        let dir1 = (t1 - p_ext1).normalize();
        let mut l_rot1 = LineEnt::new();
        l_rot1.common.handle = Handle::new(11);
        l_rot1.start = Vector3::new(p_ext1.x, p_ext1.y, 0.0);
        l_rot1.end = Vector3::new((t1 + dir1 * 20.0).x, (t1 + dir1 * 20.0).y, 0.0);

        let dir2 = (t2 - p_ext2).normalize();
        let mut l_rot2 = LineEnt::new();
        l_rot2.common.handle = Handle::new(12);
        l_rot2.start = Vector3::new(p_ext2.x, p_ext2.y, 0.0);
        l_rot2.end = Vector3::new((t2 + dir2 * 20.0).x, (t2 + dir2 * 20.0).y, 0.0);

        let all_rot = vec![
            EntityType::Circle(c_rot.clone()),
            EntityType::Line(l_rot1.clone()),
            EntityType::Line(l_rot2.clone()),
        ];
        let geos_rot = build_geos(&all_rot);

        // Click circle between them
        let mid_click = c_center + (t1 + t2 - 2.0 * c_center).normalize() * c_radius;
        let rot_survivors = pick_trim_at(
            &all_rot,
            &geos_rot,
            Handle::new(10),
            mid_click.x,
            mid_click.y,
        );
        assert!(
            rot_survivors.is_some(),
            "trimming circle between angled tangent lines must succeed"
        );
        let pieces = rot_survivors.unwrap();
        assert_eq!(pieces.len(), 1, "expected 1 surviving arc piece");
        let EntityType::Arc(a) = &pieces[0] else {
            panic!("expected Arc")
        };
        let a_start = c_center
            + glam::DVec3::new(
                a.radius * a.start_angle.cos(),
                a.radius * a.start_angle.sin(),
                0.0,
            );
        let a_end = c_center
            + glam::DVec3::new(
                a.radius * a.end_angle.cos(),
                a.radius * a.end_angle.sin(),
                0.0,
            );
        let err_t1 = (a_start - t1).length().min((a_end - t1).length());
        let err_t2 = (a_start - t2).length().min((a_end - t2).length());
        assert!(
            err_t1 < 1e-9,
            "cut point must land within grip tolerance of t1: got {err_t1:e}"
        );
        assert!(
            err_t2 < 1e-9,
            "cut point must land within grip tolerance of t2: got {err_t2:e}"
        );
    }

    #[test]
    fn trim_ellipse_with_tangent_arcs_touching_at_endpoints() {
        use codec::entities::{Arc as ArcEnt, Ellipse as EllipseEnt};
        let mut e = EllipseEnt::new();
        e.common.handle = Handle::new(10);
        e.center = Vector3::new(0.0, 0.0, 0.0);
        e.major_axis = Vector3::new(20.0, 0.0, 0.0);
        e.minor_axis_ratio = 0.5; // b = 10
        e.start_parameter = 0.0;
        e.end_parameter = std::f64::consts::TAU;

        // Arc 1 touches right vertex at (20, 0): center (30, 0), r = 10, from PI/2 to PI
        let mut a1 = ArcEnt::new();
        a1.common.handle = Handle::new(11);
        a1.center = Vector3::new(30.0, 0.0, 0.0);
        a1.radius = 10.0;
        a1.start_angle = std::f64::consts::FRAC_PI_2;
        a1.end_angle = std::f64::consts::PI;

        // Arc 2 touches left vertex at (-20, 0): center (-30, 0), r = 10, from 0 to PI/2
        let mut a2 = ArcEnt::new();
        a2.common.handle = Handle::new(12);
        a2.center = Vector3::new(-30.0, 0.0, 0.0);
        a2.radius = 10.0;
        a2.start_angle = 0.0;
        a2.end_angle = std::f64::consts::FRAC_PI_2;

        let all = vec![
            EntityType::Ellipse(e),
            EntityType::Arc(a1),
            EntityType::Arc(a2),
        ];
        let geos = build_geos(&all);

        // Click top of ellipse at (0, 10)
        let survivors = pick_trim_at(&all, &geos, Handle::new(10), 0.0, 10.0);
        assert!(
            survivors.is_some(),
            "trimming ellipse between two tangent arc endpoints must succeed"
        );
        let pieces = survivors.unwrap();
        assert_eq!(pieces.len(), 1, "expected 1 surviving ellipse piece");
        if let EntityType::Ellipse(ell) = &pieces[0] {
            assert!((ell.major_axis.x - 20.0).abs() < 1e-6);
        } else {
            panic!("expected Ellipse survivor");
        }
    }

    #[test]
    fn trim_ellipse_selection_tracking_near_breakpoint() {
        use codec::entities::{Ellipse as EllipseEnt, Line as LineEnt};
        use std::f64::consts::TAU;

        let mut e = EllipseEnt::new();
        e.common.handle = Handle::new(10);
        e.center = Vector3::new(0.0, 0.0, 0.0);
        e.major_axis = Vector3::new(20.0, 0.0, 0.0);
        e.minor_axis_ratio = 0.5; // a = 20, b = 10
        e.start_parameter = 0.0;
        e.end_parameter = TAU;

        // Cutting line 1 crossing at t = PI/4 (45 degrees parametric):
        // At t = PI/4: x = 20 * cos(PI/4) = 14.142, y = 10 * sin(PI/4) = 7.071
        // (Polar angle is atan2(7.071, 14.142) = 26.56 degrees!)
        let mut l1 = LineEnt::new();
        l1.common.handle = Handle::new(11);
        l1.start = Vector3::new(0.0, 0.0, 0.0);
        l1.end = Vector3::new(30.0, 15.0, 0.0); // passes through (14.142, 7.071)

        // Cutting line 2 crossing at t = 3*PI/4:
        let mut l2 = LineEnt::new();
        l2.common.handle = Handle::new(12);
        l2.start = Vector3::new(0.0, 0.0, 0.0);
        l2.end = Vector3::new(-30.0, 15.0, 0.0);

        let all = vec![
            EntityType::Ellipse(e),
            EntityType::Line(l1),
            EntityType::Line(l2),
        ];
        let geos = build_geos(&all);

        // Click 1: Click at t = 40 deg parametric (x = 20*cos(40°), y = 10*sin(40°))
        // Polar angle is atan(0.5 * tan(40°)) ≈ 22.7°.
        // This is before PI/4. Surviving piece should run between the cuts.
        let t_before = 40.0_f64.to_radians();
        let px_before = 20.0 * t_before.cos();
        let py_before = 10.0 * t_before.sin();
        let res_before = pick_trim_at(&all, &geos, Handle::new(10), px_before, py_before);
        assert!(res_before.is_some(), "trimming at 40 deg must succeed");
        let pieces_before = res_before.unwrap();
        assert_eq!(pieces_before.len(), 1);

        // Click 2: Click at t = 50 deg parametric (x = 20*cos(50°), y = 10*sin(50°))
        // Polar angle is atan(0.5 * tan(50°)) ≈ 30.77°.
        // Visually and parametrically, 50° is in the top segment (between PI/4 and 3*PI/4).
        // Without the fix, 30.77° polar angle would be < 45° parametric, selecting the WRONG segment!
        let t_after = 50.0_f64.to_radians();
        let px_after = 20.0 * t_after.cos();
        let py_after = 10.0 * t_after.sin();
        let res_after = pick_trim_at(&all, &geos, Handle::new(10), px_after, py_after);
        assert!(res_after.is_some(), "trimming at 50 deg must succeed");
        let pieces_after = res_after.unwrap();
        assert_eq!(pieces_after.len(), 1);

        // Click 3 & 4: Click slightly INSIDE and OUTSIDE the ellipse near 50 deg.
        // Even when displaced by 3 units (pick-box offset when zoomed out),
        // orthogonal projection must still correctly identify the top segment!
        let nx = 10.0 * t_after.cos();
        let ny = 20.0 * t_after.sin();
        let nlen = nx.hypot(ny);
        let (unx, uny) = (nx / nlen, ny / nlen);

        // Displaced outside:
        let res_out = pick_trim_at(
            &all,
            &geos,
            Handle::new(10),
            px_after + 3.0 * unx,
            py_after + 3.0 * uny,
        );
        assert!(
            res_out.is_some(),
            "trimming at displaced outside point must succeed"
        );

        // Displaced inside:
        let res_in = pick_trim_at(
            &all,
            &geos,
            Handle::new(10),
            px_after - 3.0 * unx,
            py_after - 3.0 * uny,
        );
        assert!(
            res_in.is_some(),
            "trimming at displaced inside point must succeed"
        );

        if let (
            EntityType::Ellipse(surv_after),
            EntityType::Ellipse(surv_out),
            EntityType::Ellipse(surv_in),
        ) = (&pieces_after[0], &res_out.unwrap()[0], &res_in.unwrap()[0])
        {
            assert!(
                (surv_out.start_parameter - surv_after.start_parameter).abs() < 1e-4,
                "displaced outside point should select the same segment as point on curve"
            );
            assert!(
                (surv_in.start_parameter - surv_after.start_parameter).abs() < 1e-4,
                "displaced inside point should select the same segment as point on curve"
            );
        }
    }

    #[test]
    fn trim_arc_selection_tracking_near_start_endpoint() {
        use codec::entities::{Arc as ArcEnt, Line as LineEnt};
        // Arc from 0.5 to 2.0 rad (~28.6° to 114.6°), radius 10.0
        let mut a = ArcEnt::new();
        a.common.handle = Handle::new(20);
        a.center = Vector3::new(0.0, 0.0, 0.0);
        a.radius = 10.0;
        a.start_angle = 0.5;
        a.end_angle = 2.0;

        // Boundary line crossing arc at midpoint ~ 1.25 rad
        let mid = 1.25_f64;
        let mut l = LineEnt::new();
        l.common.handle = Handle::new(21);
        l.start = Vector3::new(0.0, 0.0, 0.0);
        l.end = Vector3::new(20.0 * mid.cos(), 20.0 * mid.sin(), 0.0);

        let all = vec![EntityType::Arc(a), EntityType::Line(l)];
        let geos = build_geos(&all);

        // Hover slightly CW of start endpoint (e.g. angle = 0.49 rad, outside the arc by ~0.5 degree)
        let click_ang = 0.49_f64;
        let px = 10.0 * click_ang.cos();
        let py = 10.0 * click_ang.sin();
        let res = pick_trim_at(&all, &geos, Handle::new(20), px, py);
        assert!(res.is_some(), "trim near start endpoint must succeed");
        let pieces = res.unwrap();
        assert_eq!(pieces.len(), 1, "expected 1 surviving arc piece");
        if let EntityType::Arc(surv) = &pieces[0] {
            // It must remove the start-half [0.5, 1.25] and keep the end-half [1.25, 2.0].
            // If the bug were present, it would snap to 1.0 (end-half removed, start-half kept).
            assert!(
                (surv.end_angle - 2.0).abs() < 0.05,
                "survivor should be the end-half [1.25, 2.0], got start={} end={}",
                surv.start_angle,
                surv.end_angle
            );
        } else {
            panic!("expected Arc survivor");
        }
    }

    #[test]
    fn test_tangent_circles_or_arcs_trim() {
        use codec::entities::{Arc as ArcEnt, Circle as CircleEnt};
        let mut c1 = CircleEnt::new();
        c1.common.handle = Handle::new(1);
        c1.center = Vector3::new(0.0, 0.0, 0.0);
        c1.radius = 10.0;

        let mut c2 = CircleEnt::new();
        c2.common.handle = Handle::new(2);
        c2.center = Vector3::new(20.0, 0.0, 0.0);
        c2.radius = 10.0;

        let all = vec![
            EntityType::Circle(c1.clone()),
            EntityType::Circle(c2.clone()),
        ];
        let geos = build_geos(&all);
        let curve1 = entity_curve_xy(&EntityType::Circle(c1.clone())).unwrap();
        let ts = cut_params(&curve1, Handle::new(1), &geos);
        assert_eq!(
            ts,
            vec![0.0],
            "circle1 tangent to circle2 must have cut at t=0"
        );

        // Arc1 touching circle2 tangently
        let mut a1 = ArcEnt::new();
        a1.common.handle = Handle::new(3);
        a1.center = Vector3::new(0.0, 0.0, 0.0);
        a1.radius = 10.0;
        a1.start_angle = -1.0;
        a1.end_angle = 1.0;

        let all_arc = vec![EntityType::Arc(a1.clone()), EntityType::Circle(c2.clone())];
        let geos_arc = build_geos(&all_arc);
        let curve_arc = entity_curve_xy(&EntityType::Arc(a1.clone())).unwrap();
        let ts_arc = cut_params(&curve_arc, Handle::new(3), &geos_arc);
        assert_eq!(
            ts_arc,
            vec![0.5],
            "arc1 tangent to circle2 at midpoint must have cut at t=0.5"
        );

        let trim_res = pick_trim_at(&all_arc, &geos_arc, Handle::new(3), 10.0, 5.0);
        assert!(
            trim_res.is_some(),
            "trimming arc1 at tangent circle2 must succeed"
        );
        let pieces = trim_res.unwrap();
        assert_eq!(
            pieces.len(),
            1,
            "trimming half of arc should leave 1 survivor piece"
        );

        // 1. External tangency: Test across multiple angles and slight epsilons
        for angle in [0.0f64, 0.5, 1.0, 1.57, 2.5, std::f64::consts::PI, 4.0, 5.0] {
            for eps in [-1e-8, 0.0, 1e-8] {
                let dist = 20.0 + eps;
                let dx = dist * angle.cos();
                let dy = dist * angle.sin();
                let mut c_off = CircleEnt::new();
                c_off.common.handle = Handle::new(4);
                c_off.center = Vector3::new(dx, dy, 0.0);
                c_off.radius = 10.0;
                let all_off = vec![EntityType::Circle(c1.clone()), EntityType::Circle(c_off)];
                let geos_off = build_geos(&all_off);
                let ts_off = cut_params(&curve1, Handle::new(1), &geos_off);
                assert_eq!(
                    ts_off.len(),
                    1,
                    "must find exactly 1 tangency cut at angle {angle}, eps {eps}"
                );
                let expected_t = (angle / TAU).rem_euclid(1.0);
                let actual_t = ts_off[0];
                let diff = (actual_t - expected_t).abs();
                let cyclic_diff = diff.min(1.0 - diff);
                assert!(
                    cyclic_diff < 1e-5,
                    "tangency t must match angle: got {actual_t}, expected {expected_t}"
                );
            }
        }

        // 2. Internal tangency: c1 (r=10) and c_inner (r=4) at (6, 0)
        let mut c_inner = CircleEnt::new();
        c_inner.common.handle = Handle::new(5);
        c_inner.center = Vector3::new(6.0, 0.0, 0.0);
        c_inner.radius = 4.0;
        let all_int = vec![
            EntityType::Circle(c1.clone()),
            EntityType::Circle(c_inner.clone()),
        ];
        let geos_int = build_geos(&all_int);
        let ts_int = cut_params(&curve1, Handle::new(1), &geos_int);
        assert_eq!(
            ts_int,
            vec![0.0],
            "internal tangency on c1 must have cut at t=0"
        );

        // And from c_inner's perspective (r=4 inside r=10):
        let curve_inner = entity_curve_xy(&EntityType::Circle(c_inner.clone())).unwrap();
        let ts_inner = cut_params(&curve_inner, Handle::new(5), &geos_int);
        assert_eq!(
            ts_inner,
            vec![0.0],
            "internal tangency on c_inner must have cut at t=0"
        );

        // 3. Two arcs touching tangently at (10, 0)
        // a_left: center (0, 0), radius 10, start=0, end=PI (passes through (10,0) at start t=0)
        let mut a_left = ArcEnt::new();
        a_left.common.handle = Handle::new(6);
        a_left.center = Vector3::new(0.0, 0.0, 0.0);
        a_left.radius = 10.0;
        a_left.start_angle = 0.0;
        a_left.end_angle = std::f64::consts::PI;

        // a_right: center (20, 0), radius 10, start=PI/2, end=3*PI/2 (passes through (10,0) at angle PI, midpoint t=0.5)
        let mut a_right = ArcEnt::new();
        a_right.common.handle = Handle::new(7);
        a_right.center = Vector3::new(20.0, 0.0, 0.0);
        a_right.radius = 10.0;
        a_right.start_angle = std::f64::consts::FRAC_PI_2;
        a_right.end_angle = 3.0 * std::f64::consts::FRAC_PI_2;

        let all_arcs = vec![
            EntityType::Arc(a_left.clone()),
            EntityType::Arc(a_right.clone()),
        ];
        let geos_arcs = build_geos(&all_arcs);
        let curve_right = entity_curve_xy(&EntityType::Arc(a_right.clone())).unwrap();
        let ts_right = cut_params(&curve_right, Handle::new(7), &geos_arcs);
        assert_eq!(
            ts_right,
            vec![0.5],
            "a_right must be cut at midpoint t=0.5 by tangent a_left"
        );

        let trim_right = pick_trim_at(&all_arcs, &geos_arcs, Handle::new(7), 15.0, 8.0);
        assert!(
            trim_right.is_some(),
            "trimming a_right at tangent a_left must succeed"
        );

        // 4. Circle trimmed by 2 tangent circles
        // c1 at (0, 0) r=10. c_right at (20, 0) r=10. c_left at (-20, 0) r=10.
        let mut c_left = CircleEnt::new();
        c_left.common.handle = Handle::new(8);
        c_left.center = Vector3::new(-20.0, 0.0, 0.0);
        c_left.radius = 10.0;
        let all_3c = vec![
            EntityType::Circle(c1.clone()),
            EntityType::Circle(c2.clone()),
            EntityType::Circle(c_left.clone()),
        ];
        let geos_3c = build_geos(&all_3c);
        let ts_3c = cut_params(&curve1, Handle::new(1), &geos_3c);
        assert_eq!(
            ts_3c.len(),
            2,
            "c1 touched by 2 tangent circles must have 2 cut points"
        );
        assert_eq!(ts_3c, vec![0.0, 0.5]);

        let trim_3c = pick_trim_at(&all_3c, &geos_3c, Handle::new(1), 0.0, 10.0);
        assert!(
            trim_3c.is_some(),
            "c1 with 2 tangent circles must be trimmable"
        );
        if let Some(surv) = trim_3c {
            assert_eq!(surv.len(), 1, "trimming c1 should leave 1 arc survivor");
        }

        // 5. Extending an arc to meet a tangent circle
        // a_short: center (0, 0), radius 10, start=0.5, end=1.5 (span ~ 1.0 rad)
        // Tangent circle c2 is at (20, 0), tangent point is at (10, 0) which is angle 0.
        // Clicking near start extends start CW towards 0.0.
        let mut a_short = ArcEnt::new();
        a_short.common.handle = Handle::new(9);
        a_short.center = Vector3::new(0.0, 0.0, 0.0);
        a_short.radius = 10.0;
        a_short.start_angle = 0.5;
        a_short.end_angle = 1.5;
        let all_ext = vec![
            EntityType::Arc(a_short.clone()),
            EntityType::Circle(c2.clone()),
        ];
        let geos_ext = build_geos(&all_ext);
        let ext_res = pick_extend_at(
            &all_ext,
            &geos_ext,
            Handle::new(9),
            10.0 * 0.6_f64.cos(),
            10.0 * 0.6_f64.sin(),
        );
        assert!(
            ext_res.is_some(),
            "extending arc towards tangent circle must succeed"
        );
        if let Some(EntityType::Arc(ext_arc)) = ext_res {
            let start_norm = norm(ext_arc.start_angle);
            assert!(
                start_norm < 1e-5 || (TAU - start_norm) < 1e-5,
                "extended arc start must reach 0.0 (tangent point)"
            );
        }
    }

    #[test]
    fn test_skinny_ellipse_crossing_arc() {
        use codec::entities::{Arc as ArcEnt, Ellipse as EllipseEnt};
        let mut e = EllipseEnt::new();
        e.common.handle = Handle::new(100);
        e.center = Vector3::new(0.0, 0.0, 0.0);
        e.major_axis = Vector3::new(100.0, 0.0, 0.0);
        e.minor_axis_ratio = 0.05; // b = 5, very skinny!
        e.start_parameter = 0.0;
        e.end_parameter = std::f64::consts::TAU;

        // Test arcs that physically cross the ellipse near its ends (x = 80, 90, 95, 98, 99)
        for &r in &[80.0, 90.0, 95.0, 98.0, 99.0] {
            let mut a = ArcEnt::new();
            a.common.handle = Handle::new(101);
            a.center = Vector3::new(0.0, 0.0, 0.0);
            a.radius = r;
            a.start_angle = -0.3;
            a.end_angle = 0.3;

            let all = vec![EntityType::Ellipse(e.clone()), EntityType::Arc(a)];
            let geos = build_geos(&all);

            // Trim the ellipse tip beyond the arc (near x = 99.5, y = 0)
            let ell_res = pick_trim_at(&all, &geos, Handle::new(100), 99.9, 0.0);
            // Trim the arc near y = 0 (x = r, y = 0)
            let arc_res = pick_trim_at(&all, &geos, Handle::new(101), r, 0.0);
            assert!(
                ell_res.is_some(),
                "ellipse trim should succeed for crossing arc at r={r}"
            );
            assert!(
                arc_res.is_some(),
                "arc trim should succeed for crossing arc at r={r}"
            );
        }

        // Test off-axis arc crossing near the tip (center at (96, 20), radius 20, passing near (96, 0))
        {
            let mut a = ArcEnt::new();
            a.common.handle = Handle::new(102);
            a.center = Vector3::new(96.0, 20.0, 0.0);
            a.radius = 20.0;
            // Angle around -PI/2 (bottom point is (96, 0))
            a.start_angle = -std::f64::consts::FRAC_PI_2 - 0.4;
            a.end_angle = -std::f64::consts::FRAC_PI_2 + 0.4;

            let all = vec![EntityType::Ellipse(e.clone()), EntityType::Arc(a)];
            let geos = build_geos(&all);

            let ell_res = pick_trim_at(&all, &geos, Handle::new(100), 99.0, 0.0);
            let arc_res = pick_trim_at(&all, &geos, Handle::new(102), 96.0, 0.0);
            assert!(
                ell_res.is_some(),
                "ellipse trim should succeed with off-axis crossing arc"
            );
            assert!(
                arc_res.is_some(),
                "arc trim should succeed with off-axis crossing arc"
            );
        }
    }

    #[test]
    fn test_trim_line_tangent_to_arc() {
        use codec::entities::{Arc as ArcEnt, Line as LineEnt};
        let mut l1 = LineEnt::new();
        l1.common.handle = Handle::new(1);
        l1.start = Vector3::new(-10.0, 0.0, 0.0);
        l1.end = Vector3::new(10.0, 0.0, 0.0);

        let mut a = ArcEnt::new();
        a.common.handle = Handle::new(2);
        a.center = Vector3::new(0.0, 5.0, 0.0);
        a.radius = 5.0;
        a.start_angle = -std::f64::consts::FRAC_PI_2;
        a.end_angle = std::f64::consts::PI;

        let all = vec![EntityType::Line(l1.clone()), EntityType::Arc(a.clone())];
        let geos = build_geos(&all);
        let curve_line = entity_curve_xy(&EntityType::Line(l1.clone())).unwrap();
        let ts_line = cut_params(&curve_line, Handle::new(1), &geos);
        assert!(!ts_line.is_empty(), "line must have cut point where tangent arc touches it: ts={:?}", ts_line);

        let curve_arc = entity_curve_xy(&EntityType::Arc(a.clone())).unwrap();
        let ts_arc = cut_params(&curve_arc, Handle::new(2), &geos);
        println!("ts_arc: {:?}", ts_arc);
    }

    #[test]
    fn test_trim_arc_tangent_to_two_lines() {
        use codec::entities::{Arc as CadArc, Line as LineEnt};
        use crate::command::{TangentObject, WorkingPlane};
        use crate::modules::draw::draw::arc::{solve_arc_3_inputs, ArcPick};

        let mut l1 = LineEnt::new();
        l1.common.handle = Handle::new(1);
        l1.start = Vector3::new(-10.0, 0.0, 0.0);
        l1.end = Vector3::new(10.0, 0.0, 0.0);

        let mut l2 = LineEnt::new();
        l2.common.handle = Handle::new(2);
        l2.start = Vector3::new(0.0, -10.0, 0.0);
        l2.end = Vector3::new(0.0, 10.0, 0.0);

        let t1 = TangentObject::Line {
            p1: DVec3::new(-10.0, 0.0, 0.0),
            p2: DVec3::new(10.0, 0.0, 0.0),
        };
        let t2 = TangentObject::Line {
            p1: DVec3::new(0.0, -10.0, 0.0),
            p2: DVec3::new(0.0, 10.0, 0.0),
        };

        // Middle point: (1 - sqrt(0.5), 1 - sqrt(0.5)) -> radius ~ 1
        let mid = DVec3::new(1.0 - (0.5_f64).sqrt(), 1.0 - (0.5_f64).sqrt(), 0.0);
        let sol = solve_arc_3_inputs(
            ArcPick::Tangent { target: t1, hit: DVec3::new(2.0, 0.0, 0.0) },
            ArcPick::Point(mid),
            ArcPick::Tangent { target: t2, hit: DVec3::new(0.0, 2.0, 0.0) },
            WorkingPlane::default(),
        );

        let (center, radius, sa, ea) = sol.expect("must solve arc tangent to two lines");
        let mut arc = CadArc::new();
        arc.common.handle = Handle::new(3);
        arc.center = Vector3::new(center.x, center.y, center.z);
        arc.radius = radius;
        arc.start_angle = sa;
        arc.end_angle = ea;

        let all = vec![
            EntityType::Line(l1.clone()),
            EntityType::Line(l2.clone()),
            EntityType::Arc(arc.clone()),
        ];
        let geos = build_geos(&all);

        let curve_l1 = entity_curve_xy(&EntityType::Line(l1.clone())).unwrap();
        let ts_l1 = cut_params(&curve_l1, Handle::new(1), &geos);
        println!("ts_l1: {:?}", ts_l1);

        let curve_l2 = entity_curve_xy(&EntityType::Line(l2.clone())).unwrap();
        let ts_l2 = cut_params(&curve_l2, Handle::new(2), &geos);
        println!("ts_l2: {:?}", ts_l2);

        let curve_arc = entity_curve_xy(&EntityType::Arc(arc.clone())).unwrap();
        let ts_arc = cut_params(&curve_arc, Handle::new(3), &geos);
        println!("ts_arc: {:?}", ts_arc);

        assert!(!ts_l1.is_empty(), "Line 1 must be cut: ts_l1={:?}", ts_l1);
        assert!(!ts_l2.is_empty(), "Line 2 must be cut: ts_l2={:?}", ts_l2);

        // Test trimming line 1 arm between (1, 0) and (10, 0)
        let trim_l1 = pick_trim_at(&all, &geos, Handle::new(1), 5.0, 0.0);
        println!("trim_l1: {:?}", trim_l1);
        assert!(trim_l1.is_some(), "trimming line 1 arm must succeed");

        // Test trimming line 2 arm between (0, 1) and (0, 10)
        let trim_l2 = pick_trim_at(&all, &geos, Handle::new(2), 0.0, 5.0);
        println!("trim_l2: {:?}", trim_l2);
        assert!(trim_l2.is_some(), "trimming line 2 arm must succeed");

        // Test trimming the arc
        let trim_arc = pick_trim_at(&all, &geos, Handle::new(3), mid.x, mid.y);
        println!("trim_arc: {:?}", trim_arc);
    }

    #[test]
    fn test_trim_arc_tangent_angled_lines() {
        use codec::entities::{Arc as CadArc, Line as LineEnt};
        use crate::command::{TangentObject, WorkingPlane};
        use crate::modules::draw::draw::arc::{solve_arc_3_inputs, ArcPick};

        // Two lines meeting at (0, 0): one along (cos(20 deg), sin(20 deg)), other along (cos(80 deg), sin(80 deg))
        let a1 = 20.0_f64.to_radians();
        let a2 = 80.0_f64.to_radians();
        let dir1 = DVec3::new(a1.cos(), a1.sin(), 0.0);
        let dir2 = DVec3::new(a2.cos(), a2.sin(), 0.0);

        let mut l1 = LineEnt::new();
        l1.common.handle = Handle::new(1);
        l1.start = Vector3::new(-10.0 * dir1.x, -10.0 * dir1.y, 0.0);
        l1.end = Vector3::new(50.0 * dir1.x, 50.0 * dir1.y, 0.0);

        let mut l2 = LineEnt::new();
        l2.common.handle = Handle::new(2);
        l2.start = Vector3::new(-10.0 * dir2.x, -10.0 * dir2.y, 0.0);
        l2.end = Vector3::new(50.0 * dir2.x, 50.0 * dir2.y, 0.0);

        let t1 = TangentObject::Line {
            p1: DVec3::new(l1.start.x, l1.start.y, 0.0),
            p2: DVec3::new(l1.end.x, l1.end.y, 0.0),
        };
        let t2 = TangentObject::Line {
            p1: DVec3::new(l2.start.x, l2.start.y, 0.0),
            p2: DVec3::new(l2.end.x, l2.end.y, 0.0),
        };

        // Midpoint between points at distance 20 on the bisector
        let bisector_angle = (a1 + a2) * 0.5;
        let mid = DVec3::new(15.0 * bisector_angle.cos(), 15.0 * bisector_angle.sin(), 0.0);

        let sol = solve_arc_3_inputs(
            ArcPick::Tangent { target: t1, hit: DVec3::new(20.0 * dir1.x, 20.0 * dir1.y, 0.0) },
            ArcPick::Point(mid),
            ArcPick::Tangent { target: t2, hit: DVec3::new(20.0 * dir2.x, 20.0 * dir2.y, 0.0) },
            WorkingPlane::default(),
        );

        let (center, radius, sa, ea) = sol.expect("must solve arc tangent to two angled lines");
        let mut arc = CadArc::new();
        arc.common.handle = Handle::new(3);
        arc.center = Vector3::new(center.x, center.y, center.z);
        arc.radius = radius;
        arc.start_angle = sa;
        arc.end_angle = ea;

        let all = vec![
            EntityType::Line(l1.clone()),
            EntityType::Line(l2.clone()),
            EntityType::Arc(arc.clone()),
        ];
        let geos = build_geos(&all);

        let curve_l1 = entity_curve_xy(&EntityType::Line(l1.clone())).unwrap();
        let ts_l1 = cut_params(&curve_l1, Handle::new(1), &geos);
        println!("angled ts_l1: {:?}", ts_l1);

        let curve_l2 = entity_curve_xy(&EntityType::Line(l2.clone())).unwrap();
        let ts_l2 = cut_params(&curve_l2, Handle::new(2), &geos);
        println!("angled ts_l2: {:?}", ts_l2);

        // We expect l1 to have at least 2 cuts: the intersection with l2 at (0,0) and the tangent point with arc!
        assert!(ts_l1.len() >= 2, "Line 1 must have intersection and tangent cut: got {:?}", ts_l1);
        assert!(ts_l2.len() >= 2, "Line 2 must have intersection and tangent cut: got {:?}", ts_l2);

        // Trimming l1 arm past the tangent point
        let click_l1 = 40.0 * dir1;
        let trim_l1 = pick_trim_at(&all, &geos, Handle::new(1), click_l1.x, click_l1.y);
        println!("angled trim_l1: {:?}", trim_l1);
        assert!(trim_l1.is_some(), "trimming line 1 must succeed");
    }

    #[test]
    fn test_kernel_intersect_tangency() {
        use std::f64::consts::FRAC_PI_2;
        let line = Curve::Line(KernelLine { start: [-10.0, 0.0], end: [10.0, 0.0] });

        // Case 1: Exact tangency at interior of arc
        let arc_exact = Curve::Arc(KernelArc {
            centre: [0.0, 5.0],
            radius: 5.0,
            start_angle: -FRAC_PI_2 - 0.2,
            end_angle: -FRAC_PI_2 + 0.2,
        });
        let hits_exact = kernel_intersect(&line, &arc_exact, KernelTolerance::new(CUT_TOLERANCE));
        println!("hits_exact: {:?}", hits_exact);

        // Case 2: Distance slightly greater than R by 1e-12 (within tolerance 1e-7)
        let arc_eps = Curve::Arc(KernelArc {
            centre: [0.0, 5.0 + 1e-12],
            radius: 5.0,
            start_angle: -FRAC_PI_2 - 0.2,
            end_angle: -FRAC_PI_2 + 0.2,
        });
        let hits_eps = kernel_intersect(&line, &arc_eps, KernelTolerance::new(CUT_TOLERANCE));
        println!("hits_eps: {:?}", hits_eps);

        // Case 3: Distance slightly greater than R by 1e-9
        let arc_eps9 = Curve::Arc(KernelArc {
            centre: [0.0, 5.0 + 1e-9],
            radius: 5.0,
            start_angle: -FRAC_PI_2 - 0.2,
            end_angle: -FRAC_PI_2 + 0.2,
        });
        let hits_eps9 = kernel_intersect(&line, &arc_eps9, KernelTolerance::new(CUT_TOLERANCE));
        println!("hits_eps9: {:?}", hits_eps9);

        // Case 4: Tangency at arc start endpoint
        let arc_start = Curve::Arc(KernelArc {
            centre: [0.0, 5.0],
            radius: 5.0,
            start_angle: -FRAC_PI_2,
            end_angle: 0.0,
        });
        let hits_start = kernel_intersect(&line, &arc_start, KernelTolerance::new(CUT_TOLERANCE));
        println!("hits_start (-PI/2): {:?}", hits_start);

        // Case 5: Tangency at arc start endpoint with normalized angle 3*PI/2
        let arc_norm = Curve::Arc(KernelArc {
            centre: [0.0, 5.0],
            radius: 5.0,
            start_angle: 3.0 * FRAC_PI_2,
            end_angle: 0.0, // wait! In CCW, from 3*PI/2 to 0 is span PI/2, or 2*PI?
        });
        let hits_norm = kernel_intersect(&line, &arc_norm, KernelTolerance::new(CUT_TOLERANCE));
        println!("hits_norm (3*PI/2): {:?}", hits_norm);

        // Case 6: Tangency at arc end endpoint
        let arc_end = Curve::Arc(KernelArc {
            centre: [0.0, 5.0],
            radius: 5.0,
            start_angle: std::f64::consts::PI,
            end_angle: -FRAC_PI_2,
        });
        let hits_end = kernel_intersect(&line, &arc_end, KernelTolerance::new(CUT_TOLERANCE));
        println!("hits_end (-PI/2): {:?}", hits_end);

        // Case 7: Large coordinates (e.g. 5000, 5005)
        let line_large = Curve::Line(KernelLine { start: [4990.0, 5000.0], end: [5010.0, 5000.0] });
        let arc_large = Curve::Arc(KernelArc {
            centre: [5000.0, 5005.0],
            radius: 5.0,
            start_angle: -FRAC_PI_2,
            end_angle: 0.0,
        });
        let hits_large = kernel_intersect(&line_large, &arc_large, KernelTolerance::new(CUT_TOLERANCE));
        println!("hits_large: {:?}", hits_large);

        // Test with cut_params:
        let geos_large = vec![Geo::Arc {
            handle: Handle::new(2),
            cx: 5000.0,
            cy: 5005.0,
            r: 5.0,
            a0: -FRAC_PI_2,
            a1: 0.0,
        }];
        let cuts_large = cut_params(&line_large, Handle::new(1), &geos_large);
        let _ = cuts_large;
    }

    #[test]
    fn test_arc_tangent_line_precision_sweep() {
        use codec::entities::{Arc as CadArc, Line as LineEnt};
        use crate::command::{TangentObject, WorkingPlane};
        use crate::modules::draw::draw::arc::{solve_arc_3_inputs, ArcPick};

        let mut max_dist = 0.0_f64;
        let mut failed_cuts = 0;

        for i in 1..36 {
            let angle_deg = i as f64 * 5.0; // 5 to 175 degrees
            let a2 = angle_deg.to_radians();

            let dir1 = DVec3::new(1.0, 0.0, 0.0);
            let dir2 = DVec3::new(a2.cos(), a2.sin(), 0.0);

            let mut l1 = LineEnt::new();
            l1.common.handle = Handle::new(1);
            l1.start = Vector3::new(-50.0, 0.0, 0.0);
            l1.end = Vector3::new(150.0, 0.0, 0.0);

            let mut l2 = LineEnt::new();
            l2.common.handle = Handle::new(2);
            l2.start = Vector3::new(-50.0 * dir2.x, -50.0 * dir2.y, 0.0);
            l2.end = Vector3::new(150.0 * dir2.x, 150.0 * dir2.y, 0.0);

            let t1 = TangentObject::Line {
                p1: DVec3::new(l1.start.x, l1.start.y, 0.0),
                p2: DVec3::new(l1.end.x, l1.end.y, 0.0),
            };
            let t2 = TangentObject::Line {
                p1: DVec3::new(l2.start.x, l2.start.y, 0.0),
                p2: DVec3::new(l2.end.x, l2.end.y, 0.0),
            };

            let bisector = (dir1 + dir2).normalize();
            let mid = bisector * 30.0;

            let sol = solve_arc_3_inputs(
                ArcPick::Tangent { target: t1, hit: DVec3::new(50.0, 0.0, 0.0) },
                ArcPick::Point(mid),
                ArcPick::Tangent { target: t2, hit: dir2 * 50.0 },
                WorkingPlane::default(),
            );

            if let Some((center, radius, sa, ea)) = sol {
                let mut arc = CadArc::new();
                arc.common.handle = Handle::new(3);
                arc.center = Vector3::new(center.x, center.y, center.z);
                arc.radius = radius;
                arc.start_angle = sa;
                arc.end_angle = ea;

                let all = vec![
                    EntityType::Line(l1.clone()),
                    EntityType::Line(l2.clone()),
                    EntityType::Arc(arc.clone()),
                ];
                let geos = build_geos(&all);

                let curve_l1 = entity_curve_xy(&EntityType::Line(l1.clone())).unwrap();
                let ts_l1 = cut_params(&curve_l1, Handle::new(1), &geos);

                let curve_l2 = entity_curve_xy(&EntityType::Line(l2.clone())).unwrap();
                let ts_l2 = cut_params(&curve_l2, Handle::new(2), &geos);

                if ts_l1.len() < 2 || ts_l2.len() < 2 {
                    failed_cuts += 1;
                    println!("FAILED at angle {angle_deg} deg: ts_l1={:?}, ts_l2={:?}", ts_l1, ts_l2);
                }

                // Check distance of arc endpoints to line
                let ep1 = [center.x + radius * sa.cos(), center.y + radius * sa.sin()];
                let d1 = (ep1[1] - 0.0).abs(); // distance to l1 (y=0)
                if d1 > max_dist { max_dist = d1; }
            }
        }
        println!("Sweep results: failed_cuts={failed_cuts}, max_dist={max_dist:e}");
        assert_eq!(failed_cuts, 0, "No cuts should fail across angle sweep");
    }
}

// ══════════════════════════════════════════════════════════════════════════
// ExtrimCommand — EXTRIM (Express-Tools cookie-cutter trim). #253
//
// Pick one boundary, then a side: every object crossing the boundary is trimmed
// on the picked side, and objects lying wholly on that side are erased. The side
// test is a parity count — a segment from a candidate point to the pick point
// that crosses the boundary an even number of times lands on the pick side.
// ══════════════════════════════════════════════════════════════════════════

/// Extend `Geo::Line` boundary edges so a line boundary cuts across the whole
/// drawing (EXTRIM treats a line boundary as infinite).
fn extend_line_geos(geos: &mut [Geo]) {
    for g in geos.iter_mut() {
        if let Geo::Line { handle, p1, p2 } = g {
            let (dx, dy) = (p2[0] - p1[0], p2[1] - p1[1]);
            if dx.hypot(dy) > 1e-9 {
                // Same as `imply_edge_geos`: the boundary reaches as far as its
                // line does, so say so rather than picking a length.
                *g = Geo::InfLine {
                    handle: *handle,
                    bx: p1[0],
                    by: p1[1],
                    dx,
                    dy,
                };
            }
        }
    }
}

/// Kept parametric intervals — those whose midpoint is NOT on the pick side.
fn extrim_keep(
    ts: &[f64],
    point_at: &dyn Fn(f64) -> [f64; 2],
    on_pick_side: &dyn Fn([f64; 2]) -> bool,
) -> Vec<(f64, f64)> {
    let mut bounds = vec![0.0f64];
    bounds.extend_from_slice(ts);
    bounds.push(1.0);
    bounds.dedup_by(|a, b| (*a - *b).abs() < 1e-6);
    bounds
        .windows(2)
        .filter_map(|w| {
            if w[1] - w[0] <= 1e-6 {
                return None;
            }
            let mid = point_at((w[0] + w[1]) * 0.5);
            if on_pick_side(mid) {
                None
            } else {
                Some((w[0], w[1]))
            }
        })
        .collect()
}

fn extrim_line(orig: &LineEnt, ts: &[f64], side: &dyn Fn([f64; 2]) -> bool) -> Vec<EntityType> {
    let p1 = [orig.start.x, orig.start.y];
    let p2 = [orig.end.x, orig.end.y];
    let z = orig.start.z;
    let pa = |t: f64| lerp2(p1, p2, t);
    extrim_keep(ts, &pa, side)
        .into_iter()
        .filter_map(|(ta, tb)| {
            let a = lerp2(p1, p2, ta);
            let b = lerp2(p1, p2, tb);
            if (b[0] - a[0]).hypot(b[1] - a[1]) < 1e-6 {
                return None;
            }
            let mut l = orig.clone();
            l.common.handle = Handle::NULL;
            l.start = Vector3::new(a[0], a[1], z);
            l.end = Vector3::new(b[0], b[1], z);
            Some(EntityType::Line(l))
        })
        .collect()
}

fn extrim_arc(orig: &ArcEnt, ts: &[f64], side: &dyn Fn([f64; 2]) -> bool) -> Vec<EntityType> {
    let a0 = orig.start_angle;
    let a1 = orig.end_angle;
    let span = {
        let s = norm(a1) - norm(a0);
        if s <= 0.0 {
            s + TAU
        } else {
            s
        }
    };
    let angle_at = |t: f64| norm(a0) + span * t;
    let (cx, cy, r) = (orig.center.x, orig.center.y, orig.radius);
    let pt = |t: f64| {
        let a = angle_at(t);
        [cx + r * a.cos(), cy + r * a.sin()]
    };
    extrim_keep(ts, &pt, side)
        .into_iter()
        .filter_map(|(ta, tb)| {
            if (tb - ta).abs() < 1e-6 {
                return None;
            }
            let mut a = orig.clone();
            a.common.handle = Handle::NULL;
            a.start_angle = angle_at(ta);
            a.end_angle = angle_at(tb);
            Some(EntityType::Arc(a))
        })
        .collect()
}

fn extrim_circle(orig: &CircleEnt, ts: &[f64], side: &dyn Fn([f64; 2]) -> bool) -> Vec<EntityType> {
    if ts.len() < 2 {
        return vec![];
    }
    let (cx, cy, r) = (orig.center.x, orig.center.y, orig.radius);
    let mut s = ts.to_vec();
    s.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
    let n = s.len();
    let mut out = Vec::new();
    for i in 0..n {
        let ta = s[i];
        let tb = if i + 1 < n { s[i + 1] } else { s[0] + 1.0 };
        let mt = ((ta + tb) * 0.5).rem_euclid(1.0) * TAU;
        let mid = [cx + r * mt.cos(), cy + r * mt.sin()];
        if side(mid) {
            continue; // removed side
        }
        let mut arc = ArcEnt::new();
        arc.common = orig.common.clone();
        arc.common.handle = Handle::NULL;
        arc.center = orig.center;
        arc.radius = orig.radius;
        arc.thickness = orig.thickness;
        arc.normal = orig.normal;
        arc.start_angle = ta.rem_euclid(1.0) * TAU;
        arc.end_angle = tb.rem_euclid(1.0) * TAU;
        out.push(EntityType::Arc(arc));
    }
    out
}

/// Sample any entity to a dense XY polyline for the sampled trim path.
/// Plan-view sampling of any entity, at the density the editing previews
/// have always used.
///
/// One tessellation rather than a case per type. The per-type version this
/// replaced had drifted from the drawing's own: it sampled an arc at 16
/// segments per radian against the renderer's 20, sampled a spline at a
/// fixed 96 points however long it was, and read an arc's centre as world
/// coordinates when the entity stores it in its OCS.
///
/// Unbounded curves come back empty — a ray has no finite point list, and
/// how far to run it is the caller's decision. [`fence_sample_xy`] makes it.
fn sample_entity_xy(e: &EntityType) -> Vec<[f64; 2]> {
    // A polyline is sampled through its exploded segments so that a caller
    // walking the result sees the same seams the rest of TRIM does.
    if matches!(
        e,
        EntityType::LwPolyline(_)
            | EntityType::Polyline(_)
            | EntityType::Polyline2D(_)
            | EntityType::Polyline3D(_)
    ) {
        let mut pts: Vec<[f64; 2]> = Vec::new();
        for seg in crate::modules::draw::modify::explode::explode_polyline_segments(e) {
            let sp = sample_entity_xy(&seg);
            // A segment with no plan-view shape samples to nothing — an
            // edge-on plane has no XY curve, so `entity_curve_xy` declines it.
            // Skipping it here also keeps the seam test below from comparing
            // two `None`s and then slicing an empty sample (#1318).
            if sp.is_empty() {
                continue;
            }
            if pts.last() == sp.first() {
                pts.extend_from_slice(&sp[1..]);
            } else {
                pts.extend(sp);
            }
        }
        return pts;
    }
    let Some(curve) = entity_curve_xy(e) else {
        return vec![];
    };
    if curve.extent() != KernelExtent::Bounded {
        return vec![];
    }
    curve.tessellate(SAMPLE_SEGMENTS_PER_RADIAN)
}

/// Dense XY sampling of any entity for the removal preview (lines are
/// subdivided and circles closed so the preview cut follows the boundary).
fn preview_sample_xy(e: &EntityType) -> Vec<[f64; 2]> {
    match e {
        EntityType::Line(l) => {
            let p1 = [l.start.x, l.start.y];
            let p2 = [l.end.x, l.end.y];
            (0..=24).map(|i| lerp2(p1, p2, i as f64 / 24.0)).collect()
        }
        EntityType::Circle(c) => {
            let steps = 64usize;
            (0..=steps)
                .map(|i| {
                    let a = TAU * (i as f64 / steps as f64);
                    [
                        c.center.x + c.radius * a.cos(),
                        c.center.y + c.radius * a.sin(),
                    ]
                })
                .collect()
        }
        // Polylines sample only their vertices — subdivide the straight
        // segments so the preview cut follows the boundary instead of
        // jumping at the nearest vertex (#340).
        EntityType::LwPolyline(_)
        | EntityType::Polyline(_)
        | EntityType::Polyline2D(_)
        | EntityType::Polyline3D(_) => {
            let mut pts: Vec<[f64; 2]> = Vec::new();
            for seg in crate::modules::draw::modify::explode::explode_polyline_segments(e) {
                let sp: Vec<[f64; 2]> = match &seg {
                    EntityType::Line(l) => {
                        let p1 = [l.start.x, l.start.y];
                        let p2 = [l.end.x, l.end.y];
                        (0..=24).map(|i| lerp2(p1, p2, i as f64 / 24.0)).collect()
                    }
                    _ => sample_entity_xy(&seg),
                };
                if sp.is_empty() {
                    continue;
                }
                if pts.last() == sp.first() {
                    pts.extend_from_slice(&sp[1..]);
                } else {
                    pts.extend(sp);
                }
            }
            pts
        }
        _ => sample_entity_xy(e),
    }
}

/// Append the sub-runs of `pts` for which `take` holds to `out` as one wire's
/// point list, separated from earlier content by a NaN pen-up.
fn collect_runs(pts: &[[f64; 2]], take: &dyn Fn([f64; 2]) -> bool, out: &mut Vec<[f32; 3]>) {
    let mut run: Vec<[f64; 2]> = Vec::new();
    let flush = |run: &mut Vec<[f64; 2]>, out: &mut Vec<[f32; 3]>| {
        if run.len() >= 2 {
            if !out.is_empty() {
                out.push([f32::NAN, f32::NAN, f32::NAN]);
            }
            out.extend(run.iter().map(|p| [p[0] as f32, p[1] as f32, 0.0]));
        }
        run.clear();
    };
    for &p in pts {
        if take(p) {
            run.push(p);
        } else {
            flush(&mut run, out);
        }
    }
    flush(&mut run, out);
}

/// Build a preview wire from a NaN-break point list.
fn preview_wire(points: Vec<[f32; 3]>, color: [f32; 4], name: &str) -> WireModel {
    WireModel {
        bg_adapt: None,
        point_marker: None,
        taper_widths: Vec::new(),
        pattern_stations: Vec::new(),
        world_width: 0.0,
        depth_override: None,
        display_visible: true,
        snap_only: false,
        plot_visible: true,
        fill_is_3d: false,
        fill_is_2d_solid: false,
        render_instance: None,
        pick_tris: Vec::new(),
        pick_tris_low: Vec::new(),
        dash_from_start: false,
        dash_align_end: None,
        text_verts: Vec::new(),
        name: name.into(),
        points,
        points_low: Vec::new(),
        color,
        selected: false,
        pattern_length: 0.0,
        pattern: [0.0; 8],
        line_weight_px: 1.0,
        snap_pts: vec![],
        tangent_geoms: vec![],
        aci: 0,
        key_vertices: vec![],
        aabb: WireModel::UNBOUNDED_AABB,
        plinegen: true,
        fill_tris: vec![],
        fill_tris_low: Vec::new(),

        ..Default::default()
    }
}

/// Insert the exact boundary crossings between consecutive samples so a
/// sampled cut lands ON the boundary instead of at the nearest sample. A
/// polyline samples only its vertices, so without this a straight segment
/// crossing the boundary was cut at the wrong place — or not at all when
/// both endpoints were on the kept side (#340).
fn insert_boundary_crossings(pts: &[[f64; 2]], geos: &[Geo]) -> Vec<[f64; 2]> {
    let Some(last) = pts.last() else {
        return Vec::new();
    };
    let mut out: Vec<[f64; 2]> = Vec::with_capacity(pts.len());
    for w in pts.windows(2) {
        let (a, b) = (w[0], w[1]);
        out.push(a);
        let mut ts = line_seg_ts(a[0], a[1], b[0], b[1], Handle::NULL, geos);
        ts.sort_by(|x, y| x.partial_cmp(y).unwrap_or(std::cmp::Ordering::Equal));
        for t in ts {
            if t > 1e-6 && t < 1.0 - 1e-6 {
                out.push(lerp2(a, b, t));
            }
        }
    }
    out.push(*last);
    out
}

/// Sampled trim: `None` leaves the entity unchanged, `Some(vec![])` erases it,
/// `Some(runs)` replaces it with the surviving pieces as LwPolylines.
/// Classification is per SEGMENT midpoint (samples + exact crossings), so a
/// vertex sitting exactly on the boundary can't flip the parity test.
fn extrim_sampled(
    pts: &[[f64; 2]],
    geos: &[Geo],
    side: &dyn Fn([f64; 2]) -> bool,
) -> Option<Vec<EntityType>> {
    if pts.len() < 2 {
        return None;
    }
    let dense = insert_boundary_crossings(pts, geos);
    let seg_kept: Vec<bool> = dense
        .windows(2)
        .map(|w| !side([(w[0][0] + w[1][0]) * 0.5, (w[0][1] + w[1][1]) * 0.5]))
        .collect();
    if seg_kept.iter().all(|&k| k) {
        return None; // wholly on the kept side — untouched
    }
    if seg_kept.iter().all(|&k| !k) {
        return Some(vec![]); // wholly on the pick side — erased
    }
    let mut runs: Vec<Vec<[f64; 2]>> = Vec::new();
    let mut cur: Vec<[f64; 2]> = Vec::new();
    for (i, &kept) in seg_kept.iter().enumerate() {
        if kept {
            if cur.is_empty() {
                cur.push(dense[i]);
            }
            cur.push(dense[i + 1]);
        } else if cur.len() >= 2 {
            runs.push(std::mem::take(&mut cur));
        } else {
            cur.clear();
        }
    }
    if cur.len() >= 2 {
        runs.push(cur);
    }
    Some(
        runs.into_iter()
            .map(|run| {
                let mut pl = LwPolyline::new();
                pl.common.handle = Handle::NULL;
                pl.is_closed = false;
                pl.vertices = run
                    .into_iter()
                    .map(|p| LwVertex::from_coords(p[0], p[1]))
                    .collect();
                EntityType::LwPolyline(pl)
            })
            .collect(),
    )
}

pub struct ExtrimCommand {
    all: Vec<(Handle, EntityType)>,
    boundary: Option<Handle>,
    geos: Vec<Geo>,
}

impl ExtrimCommand {
    pub fn new(all: Vec<(Handle, EntityType)>) -> Self {
        let all = all
            .into_iter()
            .map(|(handle, entity)| (handle, entity_with_lwpolyline_world_xy(&entity)))
            .collect();
        Self {
            all,
            boundary: None,
            geos: Vec::new(),
        }
    }
}

impl CadCommand for ExtrimCommand {
    fn name(&self) -> &'static str {
        "EXTRIM"
    }

    fn prompt(&self) -> String {
        if self.boundary.is_none() {
            crate::t!("EXTRIM  Select cutting boundary:").into_owned()
        } else {
            crate::t!("EXTRIM  Click the side to trim away:").into_owned()
        }
    }

    fn needs_entity_pick(&self) -> bool {
        self.boundary.is_none()
    }

    fn on_entity_pick(&mut self, handle: Handle, _pt: DVec3) -> CmdResult {
        if handle.is_null() {
            return CmdResult::NeedPoint;
        }
        let Some((_, e)) = self.all.iter().find(|(h, _)| *h == handle) else {
            return CmdResult::NeedPoint;
        };
        let mut geos = build_geos(std::slice::from_ref(e));
        // Only a picked LINE boundary is treated as infinite. A polyline
        // explodes into per-segment Line geos — extending those turns a
        // closed boundary into a grid of infinite lines and the parity
        // side-test breaks (#340).
        if matches!(e, EntityType::Line(_)) {
            extend_line_geos(&mut geos);
        }
        if geos.is_empty() {
            return CmdResult::NeedPoint; // not a usable boundary; keep asking
        }
        self.boundary = Some(handle);
        self.geos = geos;
        CmdResult::NeedPoint
    }

    fn on_point(&mut self, pt: DVec3) -> CmdResult {
        let Some(bh) = self.boundary else {
            return CmdResult::NeedPoint;
        };
        let q = [pt.x, pt.y];
        let geos = self.geos.clone();
        let side =
            |m: [f64; 2]| line_seg_ts(m[0], m[1], q[0], q[1], Handle::NULL, &geos).len() % 2 == 0;
        let mut repl: Vec<(Handle, Vec<EntityType>)> = Vec::new();
        for (h, e) in &self.all {
            if *h == bh {
                continue;
            }
            match e {
                EntityType::Line(l) => {
                    let ts = line_seg_ts(l.start.x, l.start.y, l.end.x, l.end.y, *h, &geos);
                    if ts.is_empty() {
                        let mid = [(l.start.x + l.end.x) * 0.5, (l.start.y + l.end.y) * 0.5];
                        if side(mid) {
                            repl.push((*h, vec![]));
                        }
                    } else {
                        repl.push((*h, extrim_line(l, &ts, &side)));
                    }
                }
                EntityType::Arc(a) => {
                    let ts = arc_seg_ts(
                        a.center.x,
                        a.center.y,
                        a.radius,
                        a.start_angle,
                        a.end_angle,
                        *h,
                        &geos,
                    );
                    if ts.is_empty() {
                        let am = norm(a.start_angle);
                        let mid = [
                            a.center.x + a.radius * am.cos(),
                            a.center.y + a.radius * am.sin(),
                        ];
                        if side(mid) {
                            repl.push((*h, vec![]));
                        }
                    } else {
                        repl.push((*h, extrim_arc(a, &ts, &side)));
                    }
                }
                EntityType::Circle(c) => {
                    let ts = arc_seg_ts(c.center.x, c.center.y, c.radius, 0.0, TAU, *h, &geos);
                    if ts.len() < 2 {
                        if side([c.center.x, c.center.y]) {
                            repl.push((*h, vec![]));
                        }
                    } else {
                        repl.push((*h, extrim_circle(c, &ts, &side)));
                    }
                }
                EntityType::LwPolyline(_)
                | EntityType::Polyline(_)
                | EntityType::Polyline2D(_)
                | EntityType::Polyline3D(_)
                | EntityType::Ellipse(_)
                | EntityType::Spline(_) => {
                    let pts = sample_entity_xy(e);
                    if let Some(res) = extrim_sampled(&pts, &geos, &side) {
                        repl.push((*h, res));
                    }
                }
                _ => {}
            }
        }
        if repl.is_empty() {
            return CmdResult::Cancel;
        }
        CmdResult::ReplaceMany(repl, Vec::new())
    }

    fn on_preview_wires(&mut self, pt: DVec3) -> Vec<WireModel> {
        let Some(bh) = self.boundary else {
            return Vec::new();
        };
        if self.geos.is_empty() {
            return Vec::new();
        }
        let q = [pt.x, pt.y];
        let geos = &self.geos;
        let side =
            |m: [f64; 2]| line_seg_ts(m[0], m[1], q[0], q[1], Handle::NULL, geos).len() % 2 == 0;
        // Removed (pick side) → red, surviving → blue; the boundary → yellow.
        let mut removed: Vec<[f32; 3]> = Vec::new();
        let mut kept: Vec<[f32; 3]> = Vec::new();
        for (h, e) in &self.all {
            if *h == bh {
                continue;
            }
            let pts = preview_sample_xy(e);
            if pts.len() < 2 {
                continue;
            }
            collect_runs(&pts, &side, &mut removed);
            collect_runs(&pts, &|p| !side(p), &mut kept);
        }
        let mut boundary_pts: Vec<[f32; 3]> = Vec::new();
        if let Some((_, be)) = self.all.iter().find(|(h, _)| *h == bh) {
            boundary_pts = preview_sample_xy(be)
                .into_iter()
                .map(|p| [p[0] as f32, p[1] as f32, 0.0])
                .collect();
        }

        const YELLOW: [f32; 4] = [1.0, 0.90, 0.15, 1.0];
        const REMOVE_RED: [f32; 4] = [0.95, 0.30, 0.30, 1.0];
        let mut out = Vec::new();
        if boundary_pts.len() >= 2 {
            out.push(preview_wire(boundary_pts, YELLOW, "extrim_boundary"));
        }
        if kept.len() >= 2 {
            out.push(preview_wire(kept, WireModel::SELECTED, "extrim_keep"));
        }
        if removed.len() >= 2 {
            out.push(preview_wire(removed, REMOVE_RED, "extrim_remove"));
        }
        out
    }

    fn on_enter(&mut self) -> CmdResult {
        CmdResult::Cancel
    }

    fn on_escape(&mut self) -> CmdResult {
        CmdResult::Cancel
    }
}

inventory::submit!(crate::command::CommandRegistration { names: &["EXTRIM"] }); // ExtrimCommand