//! Truck surfaces in the evaluator's form ([`EvalSurface`]), which the CPU and GPU evaluators
//! share. Surfaces the evaluators cannot express (a revolved intersection curve) or that are
//! too large for them give `None`; their faces are evaluated here instead.

use solidcraft_geom::Vec3;
use solidcraft_geom::bspline::MAX_SPLINE_DEGREE;
use solidcraft_geom::tess::{EvalCurve, EvalSurface, MAX_EVAL_KNOTS, MAX_EVAL_POINTS};
use truck_meshalgo::prelude::*;
use truck_modeling as mt;

use crate::body::from_p3;

/// `surface` in the evaluator's form, parameterised exactly as truck parameterises it.
pub(crate) fn eval_surface(surface: &mt::Surface) -> Option<EvalSurface> {
    let s = match surface {
        mt::Surface::Plane(p) => {
            EvalSurface::Plane { origin: from_p3(p.subs(0.0, 0.0)), du: from_v3(p.uder(0.0, 0.0)), dv: from_v3(p.vder(0.0, 0.0)) }
        }
        mt::Surface::BSplineSurface(b) => {
            let ctrl = b.control_points().iter().map(|row| row.iter().map(|p| [p.x, p.y, p.z, 1.0]).collect()).collect();
            nurbs(b.degrees(), b.knot_vecs(), ctrl)?
        }
        mt::Surface::NurbsSurface(n) => {
            let ctrl = n.control_points().iter().map(|row| row.iter().map(|h| [h.x, h.y, h.z, h.w]).collect()).collect();
            nurbs((n.udegree(), n.vdegree()), n.knot_vecs(), ctrl)?
        }
        mt::Surface::RevolutedCurve(proc) => {
            let rev = proc.entity();
            let profile = eval_curve(rev.entity_curve())?;
            let axis = from_v3(rev.axis()).normalized()?;
            let m = proc.transform();
            // cgmath is column-major: m[column][row].
            let transform = [0, 1, 2].map(|r| [m[0][r], m[1][r], m[2][r], m[3][r]]);
            if transform.iter().flatten().any(|x| !x.is_finite()) {
                return None;
            }
            EvalSurface::Revolved { profile, origin: from_p3(rev.origin()), axis, transform, swap: !proc.orientation() }
        }
    };
    Some(s)
}

fn from_v3(v: mt::Vector3) -> Vec3 {
    Vec3::new(v.x, v.y, v.z)
}

fn knots(k: &mt::KnotVec) -> Option<Vec<f64>> {
    let v: Vec<f64> = k.iter().copied().collect();
    (v.len() <= MAX_EVAL_KNOTS && v.iter().all(|x| x.is_finite())).then_some(v)
}

/// Truck's `control_points[i][j]` (i along u) as the evaluator's u-fastest array.
fn nurbs((pu, pv): (usize, usize), kv: &(mt::KnotVec, mt::KnotVec), rows: Vec<Vec<[f64; 4]>>) -> Option<EvalSurface> {
    let nu = rows.len();
    let nv = rows.first()?.len();
    if pu == 0 || pv == 0 || pu > MAX_SPLINE_DEGREE || pv > MAX_SPLINE_DEGREE || nu.checked_mul(nv)? > MAX_EVAL_POINTS {
        return None;
    }
    let mut ctrl = Vec::with_capacity(nu * nv);
    for j in 0..nv {
        for row in &rows {
            ctrl.push(<[[f64; 4]]>::get(row, j).copied()?);
        }
    }
    if ctrl.iter().flatten().any(|x| !x.is_finite()) {
        return None;
    }
    let knots = [knots(&kv.0)?, knots(&kv.1)?];
    (knots[0].len() == nu + pu + 1 && knots[1].len() == nv + pv + 1).then_some(EvalSurface::Nurbs { degree: [pu, pv], knots, count: [nu, nv], ctrl })
}

/// A profile curve in the evaluator's form (a line extends for ever, as truck's does).
pub(crate) fn eval_curve(c: &mt::Curve) -> Option<EvalCurve> {
    let (degree, kv, ctrl): (usize, Vec<f64>, Vec<[f64; 4]>) = match c {
        mt::Curve::Line(l) => (1, vec![0.0, 0.0, 1.0, 1.0], vec![[l.0.x, l.0.y, l.0.z, 1.0], [l.1.x, l.1.y, l.1.z, 1.0]]),
        mt::Curve::BSplineCurve(b) => (b.degree(), knots(b.knot_vec())?, b.control_points().iter().map(|p| [p.x, p.y, p.z, 1.0]).collect()),
        mt::Curve::NurbsCurve(n) => (n.degree(), knots(n.knot_vec())?, n.control_points().iter().map(|h| [h.x, h.y, h.z, h.w]).collect()),
        mt::Curve::IntersectionCurve(_) => return None,
    };
    let ok = (1..=MAX_SPLINE_DEGREE).contains(&degree)
        && ctrl.len() <= MAX_EVAL_POINTS
        && kv.len() == ctrl.len() + degree + 1
        && ctrl.iter().flatten().all(|x| x.is_finite());
    ok.then_some(EvalCurve { degree, knots: kv, ctrl })
}

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

    /// Every face of `solid` evaluates as truck evaluates it, over its own parameter box.
    fn assert_matches_truck(solid: &Solid) -> [usize; 4] {
        let mut kinds = [0; 4];
        for face in solid.face_iter() {
            let surface = face.surface();
            let kind = match surface {
                mt::Surface::Plane(_) => 0,
                mt::Surface::BSplineSurface(_) => 1,
                mt::Surface::NurbsSurface(_) => 2,
                mt::Surface::RevolutedCurve(_) => 3,
            };
            let Some(eval) = eval_surface(&surface) else { panic!("not evaluable: {surface:?}") };
            // Sample the face's parameter box from its boundary vertices.
            let pts: Vec<(f64, f64)> = face.vertex_iter().filter_map(|v| surface.search_parameter(v.point(), None, 100)).collect();
            if pts.is_empty() {
                continue;
            }
            let (u0, u1) = pts.iter().fold((f64::MAX, f64::MIN), |(a, b), p| (a.min(p.0), b.max(p.0)));
            let (v0, v1) = pts.iter().fold((f64::MAX, f64::MIN), |(a, b), p| (a.min(p.1), b.max(p.1)));
            for i in 0..=6 {
                for j in 0..=6 {
                    let (u, v) = (u0 + (u1 - u0) * i as f64 / 6.0, v0 + (v1 - v0) * j as f64 / 6.0);
                    let (p, n) = eval.eval(u, v);
                    let want = from_p3(surface.subs(u, v));
                    assert!(p.dist(want) < 1e-9 * (1.0 + want.len()), "point at ({u}, {v}): {p:?} vs {want:?}");
                    let wn = from_v3(surface.normal(u, v));
                    if wn.len() > 0.5 {
                        assert!(n.dist(wn) < 1e-6, "normal at ({u}, {v}): {n:?} vs {wn:?} ({surface:?})");
                    }
                    kinds[kind] += 1;
                }
            }
        }
        kinds
    }

    fn solid(b: crate::Body) -> Solid {
        (*b.solid).clone()
    }

    #[test]
    fn primitives_evaluate_like_truck() {
        let Ok(bx) = crate::box_solid(Vec3::new(-1.0, -2.0, 0.0), Vec3::new(3.0, 4.0, 5.0)) else { panic!("box") };
        let Ok(cyl) = crate::cylinder(Vec3::new(1.0, 2.0, 3.0), Vec3::new(0.0, 1.0, 1.0), 2.5, 7.0) else { panic!("cylinder") };
        let Ok(sph) = crate::sphere(Vec3::new(0.0, 0.0, 1.0), 4.0) else { panic!("sphere") };
        let Ok(tor) = crate::torus(Vec3::ZERO, 6.0, 1.5) else { panic!("torus") };
        let mut kinds = [0; 4];
        for b in [bx, cyl, sph, tor] {
            for (k, n) in kinds.iter_mut().zip(assert_matches_truck(&solid(b))) {
                *k += n;
            }
        }
        // Planes, rational patches (sphere) and revolved profiles (cylinder, torus) all covered.
        assert!(kinds[0] > 0 && kinds[3] > 0 && kinds[1] + kinds[2] > 0, "{kinds:?}");
    }

    #[test]
    fn transformed_and_mirrored_bodies_evaluate_like_truck() {
        let Ok(cyl) = crate::cylinder(Vec3::ZERO, Vec3::Z, 2.0, 5.0) else { panic!("cylinder") };
        // Column-major: x → 3 − x, z → z + 1.
        let mirror = [[-1.0, 0.0, 0.0, 0.0], [0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 1.0, 0.0], [3.0, 0.0, 1.0, 1.0]];
        let Ok(m) = crate::transform_matrix(&cyl, mirror) else { panic!("transform") };
        assert!(assert_matches_truck(&solid(m)).iter().sum::<usize>() > 0);
    }
}