//! Does a resource have a CLEANER home in its container than the one we picked?
//!
//! After the pad-scoring fix, only two resources on the disc still decode to an
//! index run with degenerate triangles — `e201_bdy_03_m` (2 containers) and
//! `_rou_f402_dead` (9). Degeneracy says the run does not fit the pool, so either
//! the vertex block is wrong or the candidate list never offered the right one.
//! This walks every candidate vertex-run start for the resource's declaration and
//! scores each `(start, pad)` the way the anchor now does — degenerate triangles
//! first, then winding, plus coverage — so the answer is one of:
//!   * a strictly cleaner candidate exists (the selection is at fault),
//!   * several are equally clean (genuinely ambiguous), or
//!   * nothing is clean (the block is not in the candidate list at all).
//!
//! Usage: better_home <container.xpr> <resource-name>
use sylpheed_formats::mesh::{debug_resource_params, debug_vertex_run_starts, Xbg7Model};

fn be16(b: &[u8], at: usize) -> u32 {
    ((b[at] as u32) << 8) | b[at + 1] as u32
}

fn main() {
    let a: Vec<String> = std::env::args().collect();
    let bytes = std::fs::read(&a[1]).expect("container");
    let name = &a[2];

    let Some((markers, stride)) = debug_resource_params(&bytes, name) else {
        eprintln!("no such XBG7 resource: {name}");
        std::process::exit(1);
    };
    let (vc, ic) = markers[0];
    println!("{name}: {} marker(s), first = {vc} verts / {ic} indices, stride {stride}", markers.len());

    // Where did the decoder put it?
    let ours = Xbg7Model::stage_models(&bytes)
        .into_iter()
        .find(|m| m.name == *name)
        .and_then(|m| m.meshes.first().and_then(|s| s.vbuf_offset));
    println!("our anchor: {ours:?}");

    let starts = debug_vertex_run_starts(&bytes, stride);
    println!("{} candidate vertex-run starts for stride {stride}", starts.len());

    // Score every (start, pad): degenerate triangles, winding against the stored
    // normals, and whether the run covers the pool exactly.
    let mut rows: Vec<(usize, f32, usize, usize, usize, bool)> = Vec::new(); // degen, wind, start, pad, max_idx, covered
    for &vb in &starts {
        for pad in 0..=3usize {
            if vb < ic * 2 + pad {
                continue;
            }
            let ib = vb - ic * 2 - pad;
            if ib + ic * 2 > bytes.len() || vb + vc * stride > bytes.len() {
                continue;
            }
            let idx: Vec<u32> = (0..ic).map(|k| be16(&bytes, ib + k * 2)).collect();
            let max_idx = *idx.iter().max().unwrap_or(&0) as usize;
            if max_idx >= vc {
                continue; // out of range — not a candidate at all
            }
            let pos: Vec<[f32; 3]> = (0..vc)
                .map(|v| {
                    let at = vb + v * stride;
                    [
                        f32::from_be_bytes(bytes[at..at + 4].try_into().unwrap()),
                        f32::from_be_bytes(bytes[at + 4..at + 8].try_into().unwrap()),
                        f32::from_be_bytes(bytes[at + 8..at + 12].try_into().unwrap()),
                    ]
                })
                .collect();
            if pos.iter().any(|p| p.iter().any(|c| !c.is_finite() || c.abs() > 1e6)) {
                continue;
            }
            let mut degen = 0usize;
            let (mut agree, mut counted) = (0usize, 0usize);
            for t in idx.chunks_exact(3) {
                let (x, y, z) = (t[0] as usize, t[1] as usize, t[2] as usize);
                if x == y || y == z || x == z {
                    degen += 1;
                    continue;
                }
                // Winding needs normals; use the geometric centroid normal as a
                // stand-in so this stays declaration-agnostic: a consistent mesh
                // has all faces pointing away from the centroid on a convex-ish
                // hull. Weak, so degeneracy leads the sort.
                let e1 = [pos[y][0] - pos[x][0], pos[y][1] - pos[x][1], pos[y][2] - pos[x][2]];
                let e2 = [pos[z][0] - pos[x][0], pos[z][1] - pos[x][1], pos[z][2] - pos[x][2]];
                let f = [
                    e1[1] * e2[2] - e1[2] * e2[1],
                    e1[2] * e2[0] - e1[0] * e2[2],
                    e1[0] * e2[1] - e1[1] * e2[0],
                ];
                let cx: [f32; 3] = {
                    let mut c = [0.0f32; 3];
                    for p in &pos {
                        for k in 0..3 {
                            c[k] += p[k] / pos.len() as f32;
                        }
                    }
                    c
                };
                let out = [pos[x][0] - cx[0], pos[x][1] - cx[1], pos[x][2] - cx[2]];
                counted += 1;
                if f[0] * out[0] + f[1] * out[1] + f[2] * out[2] > 0.0 {
                    agree += 1;
                }
            }
            let w = if counted == 0 { 0.0 } else { agree as f32 / counted as f32 };
            rows.push((degen, w.max(1.0 - w), vb, pad, max_idx, max_idx + 1 == vc));
        }
    }
    rows.sort_by(|a, b| a.0.cmp(&b.0).then(b.1.total_cmp(&a.1)));
    println!("\n{} in-range candidates; best 12 by (degenerate, winding):", rows.len());
    for (d, w, vb, pad, mx, cov) in rows.iter().take(12) {
        let mark = if Some(*vb) == ours { "  <-- ours" } else { "" };
        println!(
            "  vb 0x{vb:07X} pad {pad}  degen {d:>4}  wind {w:.3}  max_idx {mx}/{}  {}{mark}",
            vc - 1,
            if *cov { "covers" } else { "SHORT" }
        );
    }
    let clean = rows.iter().filter(|r| r.0 == 0 && r.5).count();
    println!("\n{clean} candidates are degenerate-free AND cover the pool exactly");
}