//! The corpus runner behind `cargo xtask corpus [--part NAME] [--no-write]`: build every part of
//! the meshing test corpus ([`crate::corpus`]), tessellate it, run each [`Stage`] on it and write
//! the results table to docs/meshing/corpus.md.
//!
//! The table is a fixed part columns block (bodies, faces, the boundary surface and the time to
//! build it) followed by one column group per stage. A mesher joins the corpus by implementing
//! [`Stage`] over a [`Loaded`] part (its tessellated boundary surfaces are ready in
//! `Loaded::surfaces`) and adding itself to [`stages`]. A stage that fails on a part shows the
//! error in its first column; the run goes on.

use std::fmt::Write as _;
use std::path::Path;
use std::time::Instant;

use crate::corpus::{self, CATEGORIES, Part};
use modelcraft_geometry::{Design, Measure, SurfaceMesh};
use modelcraft_mesh::cdt::{CdtOptions, tetrahedralize};
use modelcraft_mesh::surface::{BoundarySurface, SurfaceOptions};

pub const FILE: &str = "docs/meshing/corpus.md";
/// Chordal tolerance of the boundary surface, relative to the part's bounding-box diagonal.
const RELATIVE_TOLERANCE: f64 = 1e-3;

/// A built part with its boundary surfaces.
pub struct Loaded<'a> {
    pub part: &'a Part,
    pub design: Design,
    /// SolidCraft's measures, one per body in the design's order.
    pub measures: Vec<Measure>,
    /// One per body, in the design's order.
    pub surfaces: Vec<SurfaceMesh>,
    /// The chordal tolerance the surfaces were made with (mm).
    pub tolerance: f64,
}

/// A column group of the results table: a mesher, a check.
pub trait Stage {
    fn headers(&self) -> &'static [&'static str];
    /// One cell per header.
    fn run(&self, part: &Loaded) -> Result<Vec<String>, String>;
}

/// The stages, in column order. Meshers add theirs here.
fn stages() -> Vec<Box<dyn Stage>> {
    vec![Box::new(SurfaceVolume), Box::new(BoundaryCheck), Box::new(TetCdt)]
}

/// The boundary surface's enclosed volume against SolidCraft's measured volume and the closed
/// form: a surface that is open, inverted or misplaced shows here first.
struct SurfaceVolume;

impl Stage for SurfaceVolume {
    fn headers(&self) -> &'static [&'static str] {
        &["enclosed mm³", "SolidCraft mm³", "rel. diff", "exact mm³"]
    }

    fn run(&self, l: &Loaded) -> Result<Vec<String>, String> {
        let enclosed: f64 = l.surfaces.iter().map(SurfaceMesh::enclosed_volume).sum();
        let measured: f64 = l.measures.iter().map(|m| m.volume).sum();
        let rel = if measured.abs() > 0.0 { (enclosed - measured) / measured } else { f64::NAN };
        Ok(vec![format!("{enclosed:.1}"), format!("{measured:.1}"), format!("{rel:.1e}"), l.part.volume.map_or("–".into(), |v| format!("{v:.1}"))])
    }
}

/// Boundary surface preparation (`modelcraft_mesh::surface`): welded, closed, manifold, outward
/// and free of self-intersections, or the first defects found, which keep the part from being
/// volume meshed.
struct BoundaryCheck;

impl Stage for BoundaryCheck {
    fn headers(&self) -> &'static [&'static str] {
        &["boundary", "genus", "feature edges", "check ms"]
    }

    fn run(&self, l: &Loaded) -> Result<Vec<String>, String> {
        let start = Instant::now();
        let (mut vertices, mut genus, mut features) = (0, Vec::new(), 0);
        for (body, mesh) in l.design.bodies.iter().zip(&l.surfaces) {
            let options = SurfaceOptions { weld_distance: mesh.weld_distance, ..SurfaceOptions::default() };
            let s = BoundarySurface::new(&mesh.positions, &mesh.triangles, &mesh.tri_face, &options).map_err(|e| format!("{}: {e}", body.name))?;
            vertices += s.points().len();
            genus.extend(s.shells().iter().map(|sh| if sh.void { format!("{} (void)", sh.genus) } else { sh.genus.to_string() }));
            features += s.feature_edges().len();
        }
        let ms = start.elapsed().as_secs_f64() * 1e3;
        Ok(vec![format!("ok, {vertices} vertices"), genus.join(", "), features.to_string(), format!("{ms:.1}")])
    }
}

/// The constrained Delaunay tetrahedralization (`modelcraft_mesh::cdt`) of each body's boundary:
/// tetrahedra, Steiner points on boundary edges, cavities refilled by gift-wrapping, and the
/// validity gate on the rounded mesh (every tetrahedron positive, volume equal to the boundary's).
struct TetCdt;

impl Stage for TetCdt {
    fn headers(&self) -> &'static [&'static str] {
        &["CDT tets", "Steiner", "cavities", "tet gate", "CDT ms"]
    }

    fn run(&self, l: &Loaded) -> Result<Vec<String>, String> {
        let start = Instant::now();
        let (mut tets, mut steiner, mut cavities) = (0, 0, 0);
        for (body, mesh) in l.design.bodies.iter().zip(&l.surfaces) {
            let options = SurfaceOptions { weld_distance: mesh.weld_distance, ..SurfaceOptions::default() };
            let s = BoundarySurface::new(&mesh.positions, &mesh.triangles, &mesh.tri_face, &options).map_err(|e| format!("{}: {e}", body.name))?;
            let m = tetrahedralize(&s, &CdtOptions::default()).map_err(|e| format!("{}: {e}", body.name))?;
            m.gate(s.volume()).and_then(|r| r.into_result()).map_err(|e| format!("{}: rounded mesh: {e}", body.name))?;
            tets += m.tets.len();
            steiner += m.steiner.len();
            cavities += m.stats.cavities;
        }
        let ms = start.elapsed().as_secs_f64() * 1e3;
        Ok(vec![tets.to_string(), steiner.to_string(), cavities.to_string(), "pass".into(), format!("{ms:.0}")])
    }
}

fn load(part: &Part) -> Result<(Loaded<'_>, f64), String> {
    let start = Instant::now();
    let design = corpus::load(part).map_err(|e| e.to_string())?;
    if let Some(e) = design.errors.first() {
        return Err(format!("feature {} failed: {}", e.feature, e.message));
    }
    let measures = design.bodies.iter().map(|b| b.measure().map_err(|e| format!("measure {}: {e}", b.name))).collect::<Result<Vec<_>, _>>()?;
    let (mut lo, mut hi) = ([f64::INFINITY; 3], [f64::NEG_INFINITY; 3]);
    for m in &measures {
        for i in 0..3 {
            lo[i] = lo[i].min(m.bbox_min[i]);
            hi[i] = hi[i].max(m.bbox_max[i]);
        }
    }
    let diagonal = (0..3).map(|i| (hi[i] - lo[i]).powi(2)).sum::<f64>().sqrt();
    let tolerance = RELATIVE_TOLERANCE * if diagonal.is_finite() && diagonal > 0.0 { diagonal } else { 1.0 };
    let surfaces =
        design.bodies.iter().map(|b| b.tessellate(tolerance).map_err(|e| format!("tessellate {}: {e}", b.name))).collect::<Result<Vec<_>, _>>()?;
    let ms = start.elapsed().as_secs_f64() * 1e3;
    Ok((Loaded { part, design, measures, surfaces, tolerance }, ms))
}

/// A failed part or stage: the error, then blanks to fill `width` cells.
fn error_cells(e: &str, width: usize) -> impl Iterator<Item = String> {
    std::iter::once(format!("error: {e}")).chain(std::iter::repeat_n(String::new(), width.saturating_sub(1)))
}

/// Run the corpus; with `write` (and every part) write [`FILE`] under the workspace `root`.
pub fn run(root: &Path, only: Option<&str>, write: bool) -> Result<(), String> {
    let mut parts = corpus::parts().map_err(|e| e.to_string())?;
    if let Some(name) = only {
        parts.retain(|p| p.name == name);
        if parts.is_empty() {
            return Err(format!("no corpus part named `{name}`"));
        }
    }
    let stages = stages();
    const PART_COLUMNS: &[&str] = &["part", "categories", "bodies", "faces", "triangles", "tol. mm", "build ms"];
    let mut header = PART_COLUMNS.to_vec();
    for s in &stages {
        header.extend_from_slice(s.headers());
    }
    let mut rows: Vec<Vec<String>> = Vec::new();
    let mut failures = 0;
    for part in &parts {
        eprintln!("corpus: {}", part.name);
        let mut row = vec![part.name.clone(), part.categories.join(", ")];
        match load(part) {
            Err(e) => {
                failures += 1;
                row.extend(error_cells(&e, header.len() - row.len()));
            }
            Ok((l, ms)) => {
                let faces: usize = l.measures.iter().map(|m| m.faces).sum();
                let triangles: usize = l.surfaces.iter().map(|s| s.triangles.len()).sum();
                row.extend([
                    l.design.bodies.len().to_string(),
                    faces.to_string(),
                    triangles.to_string(),
                    format!("{:.3}", l.tolerance),
                    format!("{ms:.0}"),
                ]);
                for s in &stages {
                    let width = s.headers().len();
                    match s.run(&l) {
                        Ok(cells) if cells.len() == width => row.extend(cells),
                        Ok(cells) => {
                            failures += 1;
                            row.extend(error_cells(&format!("stage gave {} cells for {width} columns", cells.len()), width));
                        }
                        Err(e) => {
                            failures += 1;
                            row.extend(error_cells(&e, width));
                        }
                    }
                }
            }
        }
        rows.push(row);
    }
    let table = markdown_table(&header, &rows);
    println!("{table}");
    if write && only.is_none() {
        let path = root.join(FILE);
        std::fs::write(&path, document(&table, &parts)).map_err(|e| format!("{}: {e}", path.display()))?;
        println!("corpus: wrote {FILE}");
    }
    if failures > 0 { Err(format!("corpus: {failures} part(s) or stage(s) failed")) } else { Ok(()) }
}

fn markdown_table(header: &[&str], rows: &[Vec<String>]) -> String {
    let mut s = format!("| {} |\n|{}\n", header.join(" | "), "---|".repeat(header.len()));
    for r in rows {
        let _ = writeln!(s, "| {} |", r.iter().map(|c| c.replace('|', "\\|")).collect::<Vec<_>>().join(" | "));
    }
    s
}

fn document(table: &str, parts: &[Part]) -> String {
    let mut s = String::from(
        "# Meshing test corpus\n\n\
         Generated by `cargo xtask corpus`; do not edit. The parts are our own: SolidCraft recipes in\n\
         `tests/corpus/<name>/recipe.json` and analytic shapes generated in code\n\
         (`crates/testkit/src/corpus.rs`). Each run rebuilds every part, tessellates it at a chordal\n\
         tolerance of 1e-3 of its bounding-box diagonal and runs every stage on it. Times are wall\n\
         clock on the machine that ran it; every other column is deterministic.\n\n\
         ## Results\n\n",
    );
    s.push_str(table);
    s.push_str("\n## Categories\n\n| category | stresses | parts |\n|---|---|---|\n");
    for (c, what) in CATEGORIES {
        let n = parts.iter().filter(|p| p.categories.iter().any(|x| x == c)).count();
        let _ = writeln!(s, "| {c} | {what} | {n} |");
    }
    s.push_str("\n## Parts\n\n");
    for p in parts {
        let _ = writeln!(s, "- `{}`: {}", p.name, p.description);
    }
    s
}

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

    /// The analytic shapes come out of boundary preparation valid, with their genus.
    #[test]
    fn analytic_parts_are_valid_boundaries() {
        let expected =
            [("analytic-sphere", "0"), ("analytic-torus", "1"), ("analytic-cylinder", "0"), ("analytic-pipe", "1"), ("analytic-plate-hole", "1")];
        let parts = corpus::analytic_parts();
        for (name, genus) in expected {
            let part = parts.iter().find(|p| p.name == name).unwrap();
            let (loaded, _) = load(part).unwrap();
            let cells = BoundaryCheck.run(&loaded).unwrap();
            assert_eq!(cells[1], genus, "{name}: {cells:?}");
        }
    }

    /// The constrained Delaunay tetrahedralization passes the gate on parts that exercise each
    /// of its stages: an assembly whose rounding needs a few-ulp repair, cavities refilled by
    /// gift-wrapping, and a holed plate.
    #[test]
    fn cdt_meshes_corpus_parts() {
        let mut parts = corpus::parts().unwrap();
        parts.retain(|p| ["bolted-assembly", "thin-wall-enclosure", "analytic-plate-hole"].contains(&p.name.as_str()));
        assert_eq!(parts.len(), 3);
        for part in &parts {
            let (loaded, _) = load(part).unwrap();
            let cells = TetCdt.run(&loaded).unwrap_or_else(|e| panic!("{}: {e}", part.name));
            assert_eq!(cells[3], "pass", "{}: {cells:?}", part.name);
            assert!(cells[0].parse::<usize>().unwrap() > 0);
        }
    }
}