use acadrust::entities::Spline;
use cadkernel::geom2d::Curve as KernelCurve;
use cadkernel::space::{NurbsCurve3, Parameterization};

use crate::command::EntityTransform;
use crate::entities::common::{
    dropdown_grip, edit_prop as edit, edit_scalar_prop as edit_scalar, parse_f64,
    ro_prop as ro, round_grip, square_grip,
};
use crate::entities::traits::RenderConvertible;
use crate::scene::convert::acad_to_render::{RenderEntity, RenderObject};
use crate::scene::model::object::{GripApply, GripDef, PropSection, PropValue, Property};
use crate::t;

pub(crate) fn uses_fit_method(spline: &Spline) -> bool {
    let degree = spline.degree.max(1) as usize;
    !spline.fit_points.is_empty() && spline.control_points.len() <= degree
}

pub(crate) fn shows_fit_points(spline: &Spline) -> bool {
    !spline.fit_points.is_empty() && (!spline.cv_frame_visible || spline.flags.periodic)
}

pub(crate) fn shows_control_vertices(spline: &Spline) -> bool {
    !shows_fit_points(spline)
        && !(uses_fit_method(spline) && spline.flags.periodic)
        && control_vertices(spline).len() >= 2
}

pub(crate) fn fit_nurbs3(spline: &Spline) -> Option<NurbsCurve3> {
    if !uses_fit_method(spline) {
        return None;
    }
    let mut points: Vec<_> = spline.fit_points.iter()
        .map(|point| [point.x, point.y, point.z]).collect();
    let parameterization = match spline.knot_parameterization {
        1 => Parameterization::Centripetal,
        2 => Parameterization::Uniform,
        _ => Parameterization::Chord,
    };
    if spline.flags.periodic {
        return NurbsCurve3::interpolate_periodic(&points, parameterization);
    }
    if spline.flags.closed && points.first() != points.last() {
        if let Some(first) = points.first().copied() { points.push(first); }
    }
    let tangent = |value: acadrust::types::Vector3| {
        let value = [value.x, value.y, value.z];
        (value.iter().map(|component| component * component).sum::<f64>() > 1e-18)
            .then_some(value)
    };
    NurbsCurve3::interpolate_fit(&points, tangent(spline.begin_tangent),
        tangent(spline.end_tangent), parameterization)
}

pub(crate) fn nurbs3(spline: &Spline) -> Option<NurbsCurve3> {
    let curve = if uses_fit_method(spline) {
        fit_nurbs3(spline)?
    } else {
        let degree = usize::try_from(spline.degree).ok()?;
        let weights = if spline.weights.is_empty() {
            vec![1.0; spline.control_points.len()]
        } else {
            spline.weights.clone()
        };
        NurbsCurve3::new_strict(
            degree,
            spline.control_points.iter().map(|point| [point.x, point.y, point.z]).collect(),
            spline.knots.clone(),
            weights,
        )?
    };
    Some(curve.with_periodicity(spline.flags.closed || spline.flags.periodic))
}

/// NURBS knot locations on a control-point spline, evaluated on its own
/// curve: distinct interior knot values (the clamped ends already snap as
/// endpoints). Fit-method splines invent their knots at the fit nodes, which
/// already snap as endpoints, so they contribute nothing — re-offering them
/// would double every marker.
pub(crate) fn spline_knot_points(spline: &Spline) -> Vec<glam::DVec3> {
    const MAX_KNOT_SNAPS: usize = 1024;
    if uses_fit_method(spline) {
        return Vec::new();
    }
    let Some(curve) = nurbs3(spline) else {
        return Vec::new();
    };
    let (from, to) = curve.domain();
    if !(from.is_finite() && to.is_finite()) || !(to > from) {
        return Vec::new();
    }
    let span = to - from;
    let mut knots: Vec<f64> = curve
        .knots()
        .iter()
        .copied()
        .filter(|k| k.is_finite() && *k > from + span * 1e-9 && *k < to - span * 1e-9)
        .collect();
    knots.sort_by(f64::total_cmp);
    knots.dedup();
    if knots.len() > MAX_KNOT_SNAPS {
        let step = knots.len().div_ceil(MAX_KNOT_SNAPS);
        knots = knots.into_iter().step_by(step).collect();
    }
    knots
        .into_iter()
        .map(|k| glam::DVec3::from_array(curve.point_at_knot(k)))
        .filter(|p| p.is_finite())
        .collect()
}

pub(crate) fn replace_with_nurbs(spline: &mut Spline, curve: &NurbsCurve3) {
    let mut fit_points = spline.fit_points.clone();
    spline.degree = curve.degree() as i32;
    spline.knots = curve.knots().to_vec();
    spline.control_points = curve.control_points().iter()
        .map(|point| acadrust::types::Vector3::new(point[0], point[1], point[2])).collect();
    spline.weights = curve.weights().to_vec();
    if !fit_points.is_empty() {
        if let (Some(first), Some(point)) = (fit_points.first_mut(), spline.control_points.first()) {
            *first = *point;
        }
        if let (Some(last), Some(point)) = (fit_points.last_mut(), spline.control_points.last()) {
            *last = *point;
        }
    }
    spline.fit_points = fit_points;
    spline.begin_tangent = acadrust::types::Vector3::ZERO;
    spline.end_tangent = acadrust::types::Vector3::ZERO;
    spline.flags.rational = spline.weights.windows(2)
        .any(|pair| (pair[0] - pair[1]).abs() > 1e-12);
    spline.flags.closed = false;
    spline.flags.periodic = false;
    spline.dwg_flags1 &= !1;
    spline.dxf_flags &= !(32 | 1024);
}

/// Conservative world bounds of a fit-method spline. Fit points are interpolation
/// constraints, not control-hull vertices, so their box can exclude the curve.
/// The shared kernel reconstructs the same spatial interpolation used by the
/// curve consumers, then its control hull bounds every point of that curve.
pub(crate) fn fit_geometry_bounds(spline: &Spline) -> Option<cadkernel::brep::Aabb> {
    let curve = fit_nurbs3(spline)?;
    cadkernel::brep::Aabb::around(curve.control_points().iter().copied())
}
fn to_render(spl: &Spline) -> RenderEntity {
    let n = spl.control_points.len();
    if n < 2 {
        // A fit-point spline (DWG scenario 2 / R2013+) stores only the points
        // the curve passes through — no control points or knots. Interpolate a
        // smooth Catmull-Rom curve through them and hand it back as a dense
        // polyline so it still draws.
        if spl.fit_points.len() >= 2 {
            // Drawn from the same interpolation TRIM and snap use, so that
            // what is on screen is the curve those commands cut. The two had
            // parted: this drew a C² cubic solved here (or a Catmull-Rom for a
            // closed spline), while the kernel interpolated its own — near
            // enough to look right and far enough apart that a trim landed
            // beside the line it was aimed at.
            let planar = crate::entities::curve::spline_curve(spl);
            let pts = match &planar {
                Some(curve) => crate::entities::curve::curve_points(curve),
                // A fit spline through points in space is not a planar curve,
                // so the kernel has nothing to say about it and the solve
                // here remains the only description of its shape.
                None if spl.flags.periodic => periodic_fit_spline_polyline(spl),
                None if spl.flags.closed => {
                    catmull_rom_polyline(&spl.fit_points, true)
                }
                None => fit_spline_polyline(spl),
            };
            let snap = planar
                .as_ref()
                .map(crate::entities::curve::snap_from)
                .unwrap_or_default();
            // Fit points are on the curve, so they stay on offer as ends in
            // their own right — but never through `key_vertices`, whose
            // consecutive entries the snap engine joins and offers the middle
            // of. The chord between two fit points of a curvy spline does not
            // run along it.
            let mut snap_pts = snap.snap_pts;
            snap_pts.extend(spl.fit_points.iter().map(|p| {
                (
                    glam::DVec3::new(p.x, p.y, p.z),
                    crate::scene::model::wire_model::SnapHint::Endpoint,
                )
            }));
            snap_pts.extend(
                spline_knot_points(spl)
                    .into_iter()
                    .map(|p| (p, crate::scene::model::wire_model::SnapHint::Knot)),
            );
            let key_vertices = if planar.is_some() {
                Vec::new()
            } else {
                spl.fit_points.iter().map(|p| [p.x, p.y, p.z]).collect()
            };
            return RenderEntity {
                pick_tris: Vec::new(),
                object: RenderObject::Lines(pts),
                snap_pts,
                tangent_geoms: vec![],
                key_vertices,
                fill_tris: vec![],
            };
        }
        return RenderEntity {
            pick_tris: Vec::new(),
            object: RenderObject::Lines(Vec::new()),
            snap_pts: vec![],
            tangent_geoms: vec![],
            key_vertices: vec![],
            fill_tris: vec![],
        };
    }

    // Snap sources from the spline's own curve. A spline is not a chain of
    // straight segments, so nothing goes in `key_vertices`: consecutive
    // entries there are joined and their midpoints offered, and the chord
    // between two fit points of a curvy spline does not run along it.
    //
    // Fit points are on the curve and stay on offer, as ends in their own
    // right. Control points are not on the curve and are dropped — snapping
    // to one put the cursor in empty space beside the geometry.
    let curve_snap = crate::entities::curve::spline_curve(spl)
        .map(|curve| crate::entities::curve::snap_from(&curve));
    let (snap_pts, key_vertices) = match curve_snap {
        Some(snap) => {
            let mut points = snap.snap_pts;
            if uses_fit_method(spl) {
                points.extend(spl.fit_points.iter().map(|p| {
                    (
                        glam::DVec3::new(p.x, p.y, p.z),
                        crate::scene::model::wire_model::SnapHint::Endpoint,
                    )
                }));
            }
            points.extend(
                spline_knot_points(spl)
                    .into_iter()
                    .map(|p| (p, crate::scene::model::wire_model::SnapHint::Knot)),
            );
            (points, Vec::new())
        }
        // A spline through points in space is not a planar curve, so the
        // kernel has nothing to say about it. Its stored points remain the
        // only thing to offer.
        None => {
            let source = if uses_fit_method(spl) {
                &spl.fit_points
            } else {
                &spl.control_points
            };
            (
                Vec::new(),
                source.iter().map(|p| [p.x, p.y, p.z]).collect::<Vec<_>>(),
            )
        }
    };

    // Sampled through the spline's own curve — the same definition EXTRUDE
    // and REVOLVE read — and closed back onto its start when the flags say
    // it is periodic and the two ends do not already meet.
    let is_closed = spl.flags.closed || spl.flags.periodic;
    let mut points = crate::entities::curve::spline_curve(spl)
        .map(|planar| crate::entities::curve::curve_points(&planar))
        .unwrap_or_else(|| measurement_polyline(spl));
    if is_closed {
        if let (Some(first), Some(last)) = (points.first().copied(), points.last().copied()) {
            let gap = ((last[0] - first[0]).powi(2)
                + (last[1] - first[1]).powi(2)
                + (last[2] - first[2]).powi(2))
            .sqrt();
            if gap > 1e-6 {
                points.push(first);
            }
        }
    }
    let object = RenderObject::Lines(points);

    RenderEntity {
        pick_tris: Vec::new(),
        object,
        snap_pts,
        tangent_geoms: vec![],
        key_vertices,
        fill_tris: vec![],
    }
}

pub(crate) fn measurement_polyline(spl: &Spline) -> Vec<[f64; 3]> {
    if uses_fit_method(spl) {
        if spl.fit_points.len() < 2 {
            return spl.fit_points.iter().map(|p| [p.x, p.y, p.z]).collect();
        }
        return if spl.flags.periodic {
            periodic_fit_spline_polyline(spl)
        } else if spl.flags.closed {
            catmull_rom_polyline(&spl.fit_points, true)
        } else {
            fit_spline_polyline(spl)
        };
    }

    let count = spl.control_points.len();
    if count < 2 {
        return spl.control_points.iter().map(|p| [p.x, p.y, p.z]).collect();
    }

    let degree = spl.degree.max(0) as usize;
    if degree == 0 || degree >= count {
        return spl.control_points.iter().map(|p| [p.x, p.y, p.z]).collect();
    }
    // The kernel's space curve holds rational and polynomial curves alike.
    let controls: Vec<[f64; 3]> = spl
        .control_points
        .iter()
        .map(|point| [point.x, point.y, point.z])
        .collect();
    let weights = (spl.weights.len() == count).then(|| {
        spl.weights
            .iter()
            .map(|weight| if weight.abs() < 1e-12 { 1.0 } else { *weight })
            .collect()
    });
    match NurbsCurve3::new(degree, controls, spl.knots.clone(), weights) {
        Some(curve) => {
            curve.tessellate_angle(cadkernel::tessellation::DEFAULT_ANGLE)
        }
        None => spl.control_points.iter().map(|p| [p.x, p.y, p.z]).collect(),
    }
}

/// Sample a Catmull-Rom spline through `pts` into a dense polyline. The curve
/// passes through every input point; open ends use reflected phantom points so
/// they don't kink, closed curves wrap around.
fn catmull_rom_polyline(pts: &[acadrust::types::Vector3], closed: bool) -> Vec<[f64; 3]> {
    let n = pts.len();
    if n < 2 {
        return pts.iter().map(|p| [p.x, p.y, p.z]).collect();
    }
    let get = |i: isize| -> [f64; 3] {
        let j = if closed {
            let m = n as isize;
            (((i % m) + m) % m) as usize
        } else {
            i.clamp(0, n as isize - 1) as usize
        };
        [pts[j].x, pts[j].y, pts[j].z]
    };
    let seg_count = if closed { n } else { n - 1 };
    let mut out = Vec::new();
    for seg in 0..seg_count {
        let p1 = get(seg as isize);
        let p2 = get(seg as isize + 1);
        // Reflect at open ends so the tangent isn't pulled toward a clamped dup.
        let p0 = if !closed && seg == 0 {
            [
                2.0 * p1[0] - p2[0],
                2.0 * p1[1] - p2[1],
                2.0 * p1[2] - p2[2],
            ]
        } else {
            get(seg as isize - 1)
        };
        let p3 = if !closed && seg == seg_count - 1 {
            [
                2.0 * p2[0] - p1[0],
                2.0 * p2[1] - p1[1],
                2.0 * p2[2] - p1[2],
            ]
        } else {
            get(seg as isize + 2)
        };
        let point_at = |t: f64| {
            let (t2, t3) = (t * t, t * t * t);
            let mut q = [0.0f64; 3];
            for k in 0..3 {
                q[k] = 0.5
                    * (2.0 * p1[k]
                        + (-p0[k] + p2[k]) * t
                        + (2.0 * p0[k] - 5.0 * p1[k] + 4.0 * p2[k] - p3[k]) * t2
                        + (-p0[k] + 3.0 * p1[k] - 3.0 * p2[k] + p3[k]) * t3);
            }
            q
        };
        let tangent_at = |t: f64| {
            let mut q = [0.0; 3];
            for k in 0..3 {
                let a = -p0[k] + p2[k];
                let b = 2.0 * p0[k] - 5.0 * p1[k] + 4.0 * p2[k] - p3[k];
                let c = -p0[k] + 3.0 * p1[k] - 3.0 * p2[k] + p3[k];
                q[k] = 0.5 * (a + 2.0 * b * t + 3.0 * c * t * t);
            }
            q
        };
        let sampled = cadkernel::tessellation::sample_curve3_angle(
            point_at,
            tangent_at,
            cadkernel::tessellation::DEFAULT_ANGLE,
        );
        out.extend(sampled.into_iter().skip(usize::from(seg > 0)));
    }
    out
}

/// Interpolate an open fit-point spline into a dense polyline: the C² cubic that
/// passes through every fit point, clamped to the stored start/end tangents when
/// present (natural end otherwise), so its ends follow the specified tangents
/// instead of the local slopes Catmull-Rom would use.
fn fit_spline_polyline(spl: &Spline) -> Vec<[f64; 3]> {
    let p: Vec<[f64; 3]> = spl.fit_points.iter().map(|q| [q.x, q.y, q.z]).collect();
    let n = p.len();
    if n < 2 {
        return p;
    }

    let Some((h, slopes)) = fit_spline_slopes(spl, &p) else {
        return p;
    };

    // Evaluate each segment as a cubic Hermite (dP/du = slope · h_i).
    let mut out = Vec::new();
    for i in 0..n - 1 {
        let point_at = |u: f64| {
            let (u2, u3) = (u * u, u * u * u);
            let h00 = 2.0 * u3 - 3.0 * u2 + 1.0;
            let h10 = u3 - 2.0 * u2 + u;
            let h01 = -2.0 * u3 + 3.0 * u2;
            let h11 = u3 - u2;
            let mut q = [0.0f64; 3];
            for k in 0..3 {
                let m0 = slopes[k][i] * h[i];
                let m1 = slopes[k][i + 1] * h[i];
                q[k] = h00 * p[i][k] + h10 * m0 + h01 * p[i + 1][k] + h11 * m1;
            }
            q
        };
        let tangent_at = |u: f64| {
            let u2 = u * u;
            let (h00, h10, h01, h11) = (
                6.0 * u2 - 6.0 * u,
                3.0 * u2 - 4.0 * u + 1.0,
                -6.0 * u2 + 6.0 * u,
                3.0 * u2 - 2.0 * u,
            );
            let mut q = [0.0; 3];
            for k in 0..3 {
                let m0 = slopes[k][i] * h[i];
                let m1 = slopes[k][i + 1] * h[i];
                q[k] = h00 * p[i][k] + h10 * m0 + h01 * p[i + 1][k] + h11 * m1;
            }
            q
        };
        let sampled = cadkernel::tessellation::sample_curve3_angle(
            point_at,
            tangent_at,
            cadkernel::tessellation::DEFAULT_ANGLE,
        );
        out.extend(sampled.into_iter().skip(usize::from(i > 0)));
    }
    out
}

fn periodic_fit_spline_polyline(spl: &Spline) -> Vec<[f64; 3]> {
    let points: Vec<[f64; 3]> = spl
        .fit_points
        .iter()
        .map(|point| [point.x, point.y, point.z])
        .collect();
    let parameterization = match spl.knot_parameterization {
        2 => Parameterization::Uniform,
        1 => Parameterization::Centripetal,
        _ => Parameterization::Chord,
    };
    NurbsCurve3::interpolate_periodic(&points, parameterization)
        .map(|curve| curve.tessellate_angle(cadkernel::tessellation::DEFAULT_ANGLE))
        .unwrap_or_else(|| catmull_rom_polyline(&spl.fit_points, true))
}

/// Slopes used by spatial fit interpolation.
fn fit_spline_slopes(spl: &Spline, p: &[[f64; 3]]) -> Option<(Vec<f64>, [Vec<f64>; 3])> {
    let n = p.len();
    if n < 2 {
        return None;
    }

    // Parameterise the fit points (unnormalised, so a unit end tangent — how the
    // tangents are stored — is a consistent dP/dt). Match the spline's knot
    // parameterisation: 2 = uniform, 1 = centripetal (√chord), else chord.
    let dist = |a: [f64; 3], b: [f64; 3]| {
        let (dx, dy, dz) = (b[0] - a[0], b[1] - a[1], b[2] - a[2]);
        (dx * dx + dy * dy + dz * dz).sqrt()
    };
    let mut t = vec![0.0f64; n];
    for i in 1..n {
        let d = dist(p[i - 1], p[i]).max(1e-9);
        let step = match spl.knot_parameterization {
            2 => 1.0,
            1 => d.sqrt(),
            _ => d,
        };
        t[i] = t[i - 1] + step;
    }
    let h: Vec<f64> = (0..n - 1).map(|i| (t[i + 1] - t[i]).max(1e-9)).collect();

    let nonzero = |v: &acadrust::types::Vector3| v.x * v.x + v.y * v.y + v.z * v.z > 1e-18;
    let begin = nonzero(&spl.begin_tangent).then(|| {
        [
            spl.begin_tangent.x,
            spl.begin_tangent.y,
            spl.begin_tangent.z,
        ]
    });
    let end = nonzero(&spl.end_tangent)
        .then(|| [spl.end_tangent.x, spl.end_tangent.y, spl.end_tangent.z]);

    // Solve for the knot slopes m_i = dP/dt per coordinate. The tridiagonal is
    // the C² continuity system; the end rows are the clamped tangent (m fixed)
    // or the natural condition (S'' = 0) when no tangent is stored.
    let mut slopes = [vec![0.0f64; n], vec![0.0f64; n], vec![0.0f64; n]];
    for k in 0..3 {
        let seg_slope = |i: usize| (p[i + 1][k] - p[i][k]) / h[i];
        let (mut a, mut b, mut c, mut d) = (vec![0.0; n], vec![0.0; n], vec![0.0; n], vec![0.0; n]);
        match begin {
            Some(bt) => {
                b[0] = 1.0;
                d[0] = bt[k];
            }
            None => {
                b[0] = 2.0;
                c[0] = 1.0;
                d[0] = 3.0 * seg_slope(0);
            }
        }
        for i in 1..n - 1 {
            a[i] = h[i];
            b[i] = 2.0 * (h[i - 1] + h[i]);
            c[i] = h[i - 1];
            d[i] = 3.0 * (h[i] * seg_slope(i - 1) + h[i - 1] * seg_slope(i));
        }
        match end {
            Some(et) => {
                b[n - 1] = 1.0;
                d[n - 1] = et[k];
            }
            None => {
                a[n - 1] = 1.0;
                b[n - 1] = 2.0;
                d[n - 1] = 3.0 * seg_slope(n - 2);
            }
        }
        thomas_solve(&a, &b, &c, &mut d);
        slopes[k] = d;
    }
    Some((h, slopes))
}

/// In-place Thomas solve for a tridiagonal system (`a` sub-, `b` main-, `c`
/// super-diagonal; `d` right-hand side, overwritten with the solution).
fn thomas_solve(a: &[f64], b: &[f64], c: &[f64], d: &mut [f64]) {
    let n = d.len();
    let mut cp = vec![0.0f64; n];
    cp[0] = c[0] / b[0];
    d[0] /= b[0];
    for i in 1..n {
        let m = b[i] - a[i] * cp[i - 1];
        cp[i] = c[i] / m;
        d[i] = (d[i] - a[i] * d[i - 1]) / m;
    }
    for i in (0..n - 1).rev() {
        d[i] -= cp[i] * d[i + 1];
    }
}

pub(crate) const SPLINE_MODE_GRIP_ID: usize = usize::MAX - 1;

fn control_vertices(spline: &Spline) -> Vec<acadrust::types::Vector3> {
    if !uses_fit_method(spline) {
        return spline.control_points.clone();
    }
    let Some(planar) = crate::entities::curve::spline_curve(spline) else {
        return Vec::new();
    };
    let KernelCurve::Nurbs(curve) = &planar.curve else {
        return Vec::new();
    };
    curve
        .control_points()
        .iter()
        .map(|point| {
            let point = planar.plane.point_at(*point);
            acadrust::types::Vector3::new(point[0], point[1], point[2])
        })
        .collect()
}

pub(crate) fn control_vertex_count(spline: &Spline) -> usize {
    control_vertices(spline).len()
}

fn choice_prop(
    label: &str,
    field: &'static str,
    selected: &str,
    options: &[&str],
) -> Property {
    Property {
        label: label.into(),
        field,
        value: PropValue::Choice {
            selected: selected.to_string(),
            options: options.iter().map(|option| option.to_string()).collect(),
        },
    }
}

fn index_prop(label: &str, field: &'static str, index: usize, count: usize) -> Property {
    Property {
        label: label.into(),
        field,
        value: PropValue::EditText(if count == 0 {
            "0".to_string()
        } else {
            (index + 1).to_string()
        }),
    }
}

fn convert_to_control_method(spline: &mut Spline) -> bool {
    if !uses_fit_method(spline) {
        let valid = spline.control_points.len() >= 2;
        if valid {
            spline.fit_points.clear();
            spline.begin_tangent = acadrust::types::Vector3::ZERO;
            spline.end_tangent = acadrust::types::Vector3::ZERO;
            spline.dwg_flags1 &= !1;
            spline.dxf_flags &= !(32 | 1024);
        }
        return valid;
    }
    let Some(planar) = crate::entities::curve::spline_curve(spline) else {
        return false;
    };
    let KernelCurve::Nurbs(curve) = &planar.curve else {
        return false;
    };
    spline.degree = curve.degree() as i32;
    spline.knots = curve.knots().to_vec();
    spline.control_points = curve
        .control_points()
        .iter()
        .map(|point| {
            let point = planar.plane.point_at(*point);
            acadrust::types::Vector3::new(point[0], point[1], point[2])
        })
        .collect();
    spline.weights = if curve.is_rational() {
        curve.weights().to_vec()
    } else {
        Vec::new()
    };
    spline.flags.rational = curve.is_rational();
    spline.flags.planar = true;
    spline.fit_points.clear();
    spline.begin_tangent = acadrust::types::Vector3::ZERO;
    spline.end_tangent = acadrust::types::Vector3::ZERO;
    true
}

fn convert_to_fit_method(spline: &mut Spline) -> bool {
    if uses_fit_method(spline) {
        return true;
    }
    if spline.fit_points.len() < 2 {
        return false;
    }
    spline.control_points.clear();
    spline.knots.clear();
    spline.weights.clear();
    spline.flags.rational = false;
    spline.dwg_flags1 |= 1;
    spline.dxf_flags |= 32 | 1024;
    true
}

fn derived_fit_points(spline: &Spline) -> Vec<acadrust::types::Vector3> {
    if spline.flags.closed || spline.flags.periodic {
        return Vec::new();
    }
    let Some(curve) = nurbs3(spline) else {
        return Vec::new();
    };
    let (start, end) = curve.domain();
    if !(start.is_finite() && end.is_finite() && end > start) {
        return Vec::new();
    }
    let tolerance = (end - start).abs().max(1.0) * 1.0e-12;
    let mut parameters = vec![start];
    for knot in curve.knots().iter().copied() {
        if knot > start + tolerance
            && knot < end - tolerance
            && parameters
                .last()
                .is_none_or(|previous| (knot - *previous).abs() > tolerance)
        {
            parameters.push(knot);
        }
    }
    parameters.push(end);
    parameters
        .into_iter()
        .map(|parameter| {
            let point = curve.point_at_knot(parameter);
            acadrust::types::Vector3::new(point[0], point[1], point[2])
        })
        .collect()
}

fn can_show_fit_points(spline: &Spline) -> bool {
    spline.fit_points.len() >= 2 || derived_fit_points(spline).len() >= 2
}

fn prepare_fit_point_view(spline: &mut Spline) -> bool {
    if spline.fit_points.len() < 2 {
        spline.fit_points = derived_fit_points(spline);
    }
    spline.fit_points.len() >= 2
}

fn grips(spline: &Spline) -> Vec<GripDef> {
    let derived_control = control_vertices(spline);
    let show_fit = shows_fit_points(spline);
    let show_control_vertices = !show_fit
        && !(uses_fit_method(spline) && spline.flags.periodic)
        && derived_control.len() >= 2;
    let source = if show_control_vertices {
        derived_control
    } else if show_fit {
        spline.fit_points.clone()
    } else {
        spline.control_points.clone()
    };
    let mut grips: Vec<_> = source
        .iter()
        .enumerate()
        .map(|(i, p)| {
            let world = glam::DVec3::new(p.x, p.y, p.z);
            if show_control_vertices {
                round_grip(i, world)
            } else {
                square_grip(i, world)
            }
        })
        .collect();
    if let Some(first) = source.first() {
        grips.push(dropdown_grip(
            SPLINE_MODE_GRIP_ID,
            glam::DVec3::new(first.x, first.y, first.z),
        ));
    }
    grips
}

fn properties(spline: &Spline) -> Vec<PropSection> {
    let fit_method = uses_fit_method(spline);
    let show_fit = shows_fit_points(spline);
    let method = if show_fit { "Fit" } else { "Control Vertices" };
    let closed = spline.flags.closed || spline.flags.periodic;
    let can_show_control = control_vertices(spline).len() >= 2
        && !(fit_method && spline.flags.periodic);
    let yes_no = |b: bool| if b { "Yes" } else { "No" };
    let knot_param = match spline.knot_parameterization {
        0 => "Chord",
        1 => "Square Root",
        2 => "Uniform",
        15 => "Custom",
        _ => "Custom",
    };
    let current = crate::scene::view::dispatch::prop_current_vertex();
    let mut data_points = if show_fit {
        let count = spline.fit_points.len();
        let index = current.min(count.saturating_sub(1));
        let point = spline.fit_points.get(index);
        vec![
            ro(
                t!("Number of fit points").as_ref(),
                "fit_pt_count",
                count.to_string(),
            ),
            index_prop(
                t!("Current fit point").as_ref(),
                "current_fit_point",
                index,
                count,
            ),
            edit(
                t!("Fit point X").as_ref(),
                "fit_pt_x",
                point.map(|value| value.x).unwrap_or(0.0),
            ),
            edit(
                t!("Fit point Y").as_ref(),
                "fit_pt_y",
                point.map(|value| value.y).unwrap_or(0.0),
            ),
            edit(
                t!("Fit point Z").as_ref(),
                "fit_pt_z",
                point.map(|value| value.z).unwrap_or(0.0),
            ),
            if matches!(spline.knot_parameterization, 0..=2) {
                choice_prop(
                    t!("Knot parameterization").as_ref(),
                    "knot_param",
                    knot_param,
                    &["Chord", "Square Root", "Uniform"],
                )
            } else {
                ro(
                    t!("Knot parameterization").as_ref(),
                    "knot_param",
                    crate::i18n::translate(knot_param).into_owned(),
                )
            },
        ]
    } else {
        let controls = control_vertices(spline);
        let count = controls.len();
        let index = current.min(count.saturating_sub(1));
        let point = controls.get(index);
        let weight = spline.weights.get(index).copied().unwrap_or(1.0);
        vec![
            ro(
                t!("Number of control points").as_ref(),
                "ctrl_pt_count",
                count.to_string(),
            ),
            index_prop(
                t!("Current Control point").as_ref(),
                "current_control_point",
                index,
                count,
            ),
            edit(
                t!("Control point X").as_ref(),
                "ctrl_pt_x",
                point.map(|value| value.x).unwrap_or(0.0),
            ),
            edit(
                t!("Control point Y").as_ref(),
                "ctrl_pt_y",
                point.map(|value| value.y).unwrap_or(0.0),
            ),
            edit(
                t!("Control point Z").as_ref(),
                "ctrl_pt_z",
                point.map(|value| value.z).unwrap_or(0.0),
            ),
            edit_scalar(t!("Weight").as_ref(), "weight", weight),
        ]
    };
    data_points.push(if can_show_control {
        choice_prop(
            t!("CV frame").as_ref(),
            "cv_frame",
            if spline.cv_frame_visible { "Show" } else { "Hide" },
            &["Hide", "Show"],
        )
    } else {
        ro(t!("CV frame").as_ref(), "cv_frame", t!("Hide").into_owned())
    });

    let method_prop = if fit_method && can_show_control {
        choice_prop(
            t!("Method").as_ref(),
            "spline_method",
            method,
            &["Fit", "Control Vertices"],
        )
    } else {
        ro(
            t!("Method").as_ref(),
            "spline_method",
            crate::i18n::translate(method).into_owned(),
        )
    };
    let mut misc = vec![
        method_prop,
        ro(t!("Degree").as_ref(), "degree", spline.degree.to_string()),
        ro(
            t!("Closed").as_ref(),
            "closed",
            crate::i18n::translate(yes_no(closed)).into_owned(),
        ),
        ro(
            t!("Periodic").as_ref(),
            "periodic",
            crate::i18n::translate(yes_no(spline.flags.periodic)).into_owned(),
        ),
        ro(
            t!("Planar").as_ref(),
            "planar",
            crate::i18n::translate(yes_no(crate::entities::curve::spline_is_planar(spline)))
                .into_owned(),
        ),
    ];
    if show_fit && !spline.flags.periodic {
        misc.extend([
            edit_scalar(
                t!("Start tangent vector X").as_ref(),
                "start_tan_x",
                spline.begin_tangent.x,
            ),
            edit_scalar(
                t!("Start tangent vector Y").as_ref(),
                "start_tan_y",
                spline.begin_tangent.y,
            ),
            edit_scalar(
                t!("Start tangent vector Z").as_ref(),
                "start_tan_z",
                spline.begin_tangent.z,
            ),
            edit_scalar(
                t!("End tangent vector X").as_ref(),
                "end_tan_x",
                spline.end_tangent.x,
            ),
            edit_scalar(
                t!("End tangent vector Y").as_ref(),
                "end_tan_y",
                spline.end_tangent.y,
            ),
            edit_scalar(
                t!("End tangent vector Z").as_ref(),
                "end_tan_z",
                spline.end_tangent.z,
            ),
        ]);
    }
    if show_fit {
        misc.push(edit(
            t!("Fit tolerance").as_ref(),
            "fit_tolerance",
            spline.fit_tolerance,
        ));
    }

    vec![
        PropSection {
            title: t!("Data Points").into_owned(),
            props: data_points,
        },
        PropSection {
            title: t!("Misc").into_owned(),
            props: misc,
        },
    ]
}

fn apply_geom_prop(spline: &mut Spline, field: &str, value: &str) {
    match field {
        "spline_method" => {
            if value == "Fit" {
                if prepare_fit_point_view(spline) {
                    spline.cv_frame_visible = false;
                }
            } else if value == "Control Vertices" {
                if !spline.flags.periodic && control_vertices(spline).len() >= 2 {
                    spline.cv_frame_visible = true;
                }
            }
            return;
        }
        "knot_param" => {
            if shows_fit_points(spline)
                && !uses_fit_method(spline)
                && !convert_to_fit_method(spline)
            {
                return;
            }
            spline.knot_parameterization = match value {
                "Chord" => 0,
                "Square Root" => 1,
                "Uniform" => 2,
                _ => return,
            };
            return;
        }
        "cv_frame" => {
            spline.cv_frame_visible = value == "Show"
                && !(uses_fit_method(spline) && spline.flags.periodic)
                && control_vertices(spline).len() >= 2;
            return;
        }
        _ => {}
    }
    if uses_fit_method(spline)
        && spline.flags.periodic
        && matches!(
            field,
            "ctrl_pt_x"
                | "ctrl_pt_y"
                | "ctrl_pt_z"
                | "weight"
                | "start_tan_x"
                | "start_tan_y"
                | "start_tan_z"
                | "end_tan_x"
                | "end_tan_y"
                | "end_tan_z"
        )
    {
        return;
    }
    if matches!(field, "ctrl_pt_x" | "ctrl_pt_y" | "ctrl_pt_z" | "weight") {
        if !shows_fit_points(spline) && !spline.fit_points.is_empty() {
            if !convert_to_control_method(spline) {
                return;
            }
        } else if uses_fit_method(spline) && !convert_to_control_method(spline) {
            return;
        }
    }
    if shows_fit_points(spline)
        && !uses_fit_method(spline)
        && matches!(
            field,
            "fit_pt_x"
                | "fit_pt_y"
                | "fit_pt_z"
                | "start_tan_x"
                | "start_tan_y"
                | "start_tan_z"
                | "end_tan_x"
                | "end_tan_y"
                | "end_tan_z"
        )
        && !convert_to_fit_method(spline)
    {
        return;
    }
    let Some(v) = parse_f64(value) else { return };
    let control_index = crate::scene::view::dispatch::prop_current_vertex()
        .min(spline.control_points.len().saturating_sub(1));
    let fit_index = crate::scene::view::dispatch::prop_current_vertex()
        .min(spline.fit_points.len().saturating_sub(1));
    match field {
        "ctrl_pt_x" => {
            if let Some(cp) = spline.control_points.get_mut(control_index) {
                cp.x = v;
            }
        }
        "ctrl_pt_y" => {
            if let Some(cp) = spline.control_points.get_mut(control_index) {
                cp.y = v;
            }
        }
        "ctrl_pt_z" => {
            if let Some(cp) = spline.control_points.get_mut(control_index) {
                cp.z = v;
            }
        }
        "weight" => {
            if v > 0.0 && !spline.control_points.is_empty() {
                if spline.weights.len() != spline.control_points.len() {
                    spline.weights = vec![1.0; spline.control_points.len()];
                }
                spline.weights[control_index] = v;
                spline.flags.rational = spline
                    .weights
                    .iter()
                    .any(|weight| (*weight - spline.weights[0]).abs() > 1e-12);
            }
        }
        "fit_pt_x" => {
            if let Some(fp) = spline.fit_points.get_mut(fit_index) {
                fp.x = v;
            }
        }
        "fit_pt_y" => {
            if let Some(fp) = spline.fit_points.get_mut(fit_index) {
                fp.y = v;
            }
        }
        "fit_pt_z" => {
            if let Some(fp) = spline.fit_points.get_mut(fit_index) {
                fp.z = v;
            }
        }
        "fit_tolerance" => {
            if v.is_finite() && v >= 0.0 {
                spline.fit_tolerance = v;
            }
        }
        "start_tan_x" | "start_tan_y" | "start_tan_z" => {
            match field {
                "start_tan_x" => spline.begin_tangent.x = v,
                "start_tan_y" => spline.begin_tangent.y = v,
                "start_tan_z" => spline.begin_tangent.z = v,
                _ => {}
            }
        }
        "end_tan_x" | "end_tan_y" | "end_tan_z" => {
            match field {
                "end_tan_x" => spline.end_tangent.x = v,
                "end_tan_y" => spline.end_tangent.y = v,
                "end_tan_z" => spline.end_tangent.z = v,
                _ => {}
            }
        }
        _ => {}
    }
    spline.flags.planar = crate::entities::curve::spline_is_planar(spline);
}

fn apply_grip(spline: &mut Spline, grip_id: usize, apply: GripApply) {
    if grip_id == SPLINE_MODE_GRIP_ID {
        return;
    }
    // First CV edit makes the displayed kernel controls authoritative.
    let editing_fit = shows_fit_points(spline);
    if editing_fit && !uses_fit_method(spline) {
        if !convert_to_fit_method(spline) {
            return;
        }
    } else if !editing_fit
        && (uses_fit_method(spline) || !spline.fit_points.is_empty())
        && !spline.flags.periodic
    {
        if !convert_to_control_method(spline) {
            return;
        }
    }
    let target = if editing_fit {
        spline.fit_points.get_mut(grip_id)
    } else {
        spline.control_points.get_mut(grip_id)
    };
    if let Some(cp) = target {
        match apply {
            GripApply::Absolute(p) => {
                cp.x = p.x as f64;
                cp.y = p.y as f64;
                cp.z = p.z as f64;
            }
            GripApply::Translate(d) => {
                cp.x += d.x as f64;
                cp.y += d.y as f64;
                cp.z += d.z as f64;
            }
        }
    }
}

fn apply_transform(spline: &mut Spline, t: &EntityTransform) {
    if let EntityTransform::Mirror {
        p1,
        p2,
        working_normal,
    } = t
    {
        let transform = crate::scene::view::transform::reflection_about_working_line(
            *p1,
            *p2,
            *working_normal,
        );
        acadrust::Entity::apply_transform(spline, &transform);
        spline.flags.planar = crate::entities::curve::spline_is_planar(spline);
        return;
    }
    crate::scene::view::transform::apply_standard_entity_transform(spline, t, |entity, p1, p2| {
        for cp in &mut entity.control_points {
            crate::scene::view::transform::reflect_xy_point(&mut cp.x, &mut cp.y, p1, p2);
        }
        for fp in &mut entity.fit_points {
            crate::scene::view::transform::reflect_xy_point(&mut fp.x, &mut fp.y, p1, p2);
        }
    });
    spline.flags.planar = crate::entities::curve::spline_is_planar(spline);
}

impl RenderConvertible for Spline {
    fn to_render(&self, _document: &acadrust::CadDocument) -> Option<RenderEntity> {
        Some(to_render(self))
    }
}

impl crate::entities::traits::Grippable for Spline {
    fn grips(&self) -> Vec<GripDef> {
        grips(self)
    }
    fn apply_grip(&mut self, grip_id: usize, apply: GripApply) {
        apply_grip(self, grip_id, apply);
    }
    fn grip_menu(&self, grip_id: usize) -> Vec<crate::scene::model::object::GripMenuItem> {
        use crate::scene::model::object::{GripMenuAction, GripMenuItem};
        if grip_id == SPLINE_MODE_GRIP_ID {
            let fit_method = uses_fit_method(self);
            let can_show_control = control_vertices(self).len() >= 2
                && !(fit_method && self.flags.periodic);
            let can_show_fit = can_show_fit_points(self);
            return if !shows_fit_points(self) {
                vec![
                    can_show_fit.then_some(GripMenuItem {
                        label: "Fit",
                        action: GripMenuAction::ShowFit,
                    }),
                    can_show_control.then_some(GripMenuItem {
                        label: "✓ Control Vertices",
                        action: GripMenuAction::ShowControlVertices,
                    }),
                ]
                .into_iter()
                .flatten()
                .collect()
            } else {
                vec![
                    Some(GripMenuItem {
                        label: "✓ Fit",
                        action: GripMenuAction::ShowFit,
                    }),
                    can_show_control.then_some(GripMenuItem {
                        label: "Control Vertices",
                        action: GripMenuAction::ShowControlVertices,
                    }),
                ]
                .into_iter()
                .flatten()
                .collect()
            };
        }
        vec![GripMenuItem {
            label: "Stretch",
            action: GripMenuAction::Stretch,
        }]
    }
    fn apply_grip_menu(
        &mut self,
        _grip_id: usize,
        action: crate::scene::model::object::GripMenuAction,
    ) {
        use crate::scene::model::object::GripMenuAction as A;
        match action {
            A::ShowFit => {
                if prepare_fit_point_view(self) {
                    self.cv_frame_visible = false;
                    return;
                }
            }
            A::ShowControlVertices
                if !(uses_fit_method(self) && self.flags.periodic)
                    && control_vertices(self).len() >= 2 =>
            {
                self.cv_frame_visible = true;
                return;
            }
            _ => {}
        }
    }
}

impl crate::entities::traits::PropertyEditable for Spline {
    fn geometry_properties(&self, _text_style_names: &[String]) -> Vec<PropSection> {
        properties(self)
    }
    fn apply_geom_prop(&mut self, field: &str, value: &str) {
        apply_geom_prop(self, field, value);
    }
}

impl crate::entities::traits::Transformable for Spline {
    fn apply_transform(&mut self, t: &EntityTransform) {
        apply_transform(self, t);
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn knot_points_evaluate_distinct_interior_knots() {
        let mut spline = Spline::default();
        spline.degree = 3;
        spline.control_points = vec![
            acadrust::types::Vector3::new(0.0, 0.0, 0.0),
            acadrust::types::Vector3::new(1.0, 2.0, 0.0),
            acadrust::types::Vector3::new(3.0, 3.0, 1.0),
            acadrust::types::Vector3::new(5.0, 2.0, 0.0),
            acadrust::types::Vector3::new(6.0, 0.0, 1.0),
        ];
        spline.knots = vec![0.0, 0.0, 0.0, 0.0, 0.5, 1.0, 1.0, 1.0, 1.0];
        let pts = spline_knot_points(&spline);
        assert_eq!(pts.len(), 1, "one interior knot value: {pts:?}");
        let curve = nurbs3(&spline).expect("control-point spline builds");
        let expected = curve.point_at_knot(0.5);
        let got = [pts[0].x, pts[0].y, pts[0].z];
        let err = ((got[0] - expected[0]).powi(2)
            + (got[1] - expected[1]).powi(2)
            + (got[2] - expected[2]).powi(2))
        .sqrt();
        assert!(err < 1e-9, "knot point off the curve: {err}");
    }

    #[test]
    fn fit_method_splines_emit_no_knot_snaps() {
        // Interpolated curves invent their own knots at the fit nodes, which
        // already snap as endpoints — re-offering them as knots would double
        // every marker.
        let mut spline = Spline::default();
        spline.degree = 3;
        spline.fit_points = vec![
            acadrust::types::Vector3::new(0.0, 0.0, 0.0),
            acadrust::types::Vector3::new(4.0, 0.0, 1.0),
            acadrust::types::Vector3::new(4.0, 3.0, 2.0),
        ];
        assert!(spline_knot_points(&spline).is_empty());
    }

    #[test]
    fn fit_bounds_accept_closed_curves_with_unset_tangents() {
        let mut spline = Spline::default();
        spline.degree = 3;
        spline.flags.closed = true;
        spline.control_points.push(acadrust::types::Vector3::ZERO);
        spline.fit_points = vec![
            acadrust::types::Vector3::new(0.0, 0.0, 0.0),
            acadrust::types::Vector3::new(4.0, 0.0, 1.0),
            acadrust::types::Vector3::new(4.0, 3.0, 2.0),
            acadrust::types::Vector3::new(0.0, 3.0, 1.0),
        ];

        let bounds = fit_geometry_bounds(&spline).unwrap();
        for point in &spline.fit_points {
            for (value, min, max) in [
                (point.x, bounds.min[0], bounds.max[0]),
                (point.y, bounds.min[1], bounds.max[1]),
                (point.z, bounds.min[2], bounds.max[2]),
            ] {
                assert!(value >= min - 1e-9 && value <= max + 1e-9);
            }
        }
    }

    #[test]
    fn fit_tolerance_is_editable_and_rejects_invalid_values() {
        let mut spline = Spline::default();
        spline.fit_points = vec![
            acadrust::types::Vector3::ZERO,
            acadrust::types::Vector3::new(1.0, 0.0, 0.0),
        ];
        spline.fit_tolerance = 0.25;

        let tolerance = properties(&spline)
            .into_iter()
            .flat_map(|section| section.props)
            .find(|property| property.field == "fit_tolerance")
            .unwrap();
        assert!(matches!(tolerance.value, PropValue::EditText(_)));

        apply_geom_prop(&mut spline, "fit_tolerance", "1.5");
        assert_eq!(spline.fit_tolerance, 1.5);
        for invalid in ["-1", "NaN", "inf"] {
            apply_geom_prop(&mut spline, "fit_tolerance", invalid);
            assert_eq!(spline.fit_tolerance, 1.5);
        }
    }

    #[test]
    fn tangent_properties_edit_only_the_stored_component() {
        let mut spline = Spline::default();
        spline.fit_points = vec![
            acadrust::types::Vector3::ZERO,
            acadrust::types::Vector3::new(1.0, 1.0, 0.0),
        ];

        let start_y = properties(&spline)
            .into_iter()
            .flat_map(|section| section.props)
            .find(|property| property.field == "start_tan_y")
            .unwrap();
        assert_eq!(start_y.value, PropValue::EditText("0".into()));

        apply_geom_prop(&mut spline, "start_tan_y", "2.5");
        assert_eq!(
            spline.begin_tangent,
            acadrust::types::Vector3::new(0.0, 2.5, 0.0)
        );
    }

    #[test]
    fn showing_derived_fit_points_does_not_change_the_curve() {
        let mut spline = Spline::default();
        spline.degree = 3;
        spline.control_points = vec![
            acadrust::types::Vector3::new(0.0, 0.0, 0.0),
            acadrust::types::Vector3::new(1.0, 3.0, 0.0),
            acadrust::types::Vector3::new(4.0, 3.0, 0.0),
            acadrust::types::Vector3::new(5.0, 0.0, 0.0),
        ];
        spline.knots = cadkernel::space::clamped_uniform_knots(3, 4);
        let before = nurbs3(&spline).unwrap().point_at(0.37);

        assert!(prepare_fit_point_view(&mut spline));
        spline.cv_frame_visible = false;

        assert!(shows_fit_points(&spline));
        assert!(!uses_fit_method(&spline));
        let after = nurbs3(&spline).unwrap().point_at(0.37);
        assert!(
            cadkernel::space::Vec3::from(before)
                .distance(cadkernel::space::Vec3::from(after))
                < 1.0e-12
        );
    }
}