#![allow(clippy::needless_range_loop)]
//! Bakes the hair of Tim's original "Animated Female Base Mesh" into the
//! bundled rigid equipment preset `female-hair` (design.md, t1019u): the hair
//! primitive (material ponytail01, last primitive) is skinned once at the rest
//! pose, expressed in the rest-pose space of the `head` joint, written as
//! OBJ + MTL + PNG, imported with the normal OBJ importer and bound to `head`
//! of the edited default female with zero offset.
//! Usage: bake_female_hair ORIGINAL_FEMALE.gltf HAIR_TEXTURE.png EDITED_FEMALE.gltf OUT.ppe
use paperdoll_renderer::{equipment, preview};
use std::io::Write;

fn inverse(m: [f32; 16]) -> [f32; 16] {
    let mut a = [[0f64; 8]; 4];
    for r in 0..4 {
        for c in 0..4 {
            a[r][c] = m[c * 4 + r] as f64;
        }
        a[r][4 + r] = 1.;
    }
    for c in 0..4 {
        let p = (c..4)
            .max_by(|&x, &y| a[x][c].abs().total_cmp(&a[y][c].abs()))
            .unwrap();
        a.swap(c, p);
        let d = a[c][c];
        for k in 0..8 {
            a[c][k] /= d;
        }
        for r in 0..4 {
            if r != c {
                let f = a[r][c];
                for k in 0..8 {
                    a[r][k] -= f * a[c][k];
                }
            }
        }
    }
    let mut out = [0f32; 16];
    for r in 0..4 {
        for c in 0..4 {
            out[c * 4 + r] = a[r][4 + c] as f32;
        }
    }
    out
}
fn apply(m: &[f32; 16], p: [f32; 3], w: f32) -> [f32; 3] {
    [0, 1, 2].map(|i| m[i] * p[0] + m[4 + i] * p[1] + m[8 + i] * p[2] + m[12 + i] * w)
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let a: Vec<String> = std::env::args().skip(1).collect();
    let body = preview::load_body_file(std::path::Path::new(&a[0]))?;
    let hair = body.surfaces.last().ok_or("no surfaces")?;
    let bones: Vec<[f32; 16]> = (0..body.joint_nodes.len())
        .map(|j| {
            preview::mul(
                preview::rest_joint_world(&body, j).unwrap(),
                body.inverse_binds[j],
            )
        })
        .collect();
    let head = body
        .joint_names
        .iter()
        .position(|n| n.to_ascii_lowercase().starts_with("head"))
        .ok_or("no head joint")?;
    let head_world = preview::animated_joint_world(&body, "", 0.0, head).ok_or("head")?;
    let to_head = inverse(head_world);
    let idx = &body.indices[hair.first..hair.first + hair.count];
    let mut used: Vec<u32> = idx.to_vec();
    used.sort_unstable();
    used.dedup();
    let map: std::collections::HashMap<u32, usize> =
        used.iter().enumerate().map(|(i, v)| (*v, i + 1)).collect();
    let dir = tempdir();
    let mut obj = std::fs::File::create(dir.join("female-hair.obj"))?;
    writeln!(obj, "# Hair of \"Animated Female Base Mesh\" by assetfactory (Sketchfab Standard), baked rigid to {}", body.joint_names[head])?;
    writeln!(obj, "mtllib female-hair.mtl\nusemtl hair")?;
    for v in &used {
        let i = *v as usize;
        let mut m = [0f32; 16];
        for (j, w) in body.joints[i].iter().zip(body.weights[i]) {
            for k in 0..16 {
                m[k] += bones[*j as usize][k] * w;
            }
        }
        let p = apply(&to_head, apply(&m, body.positions[i], 1.), 1.);
        let n = apply(&to_head, apply(&m, body.normals[i], 0.), 0.);
        let l = (n[0] * n[0] + n[1] * n[1] + n[2] * n[2]).sqrt().max(1e-9);
        let uv = body.uvs[i];
        writeln!(obj, "v {} {} {}", p[0], p[1], p[2])?;
        writeln!(obj, "vt {} {}", uv[0], 1. - uv[1])?;
        writeln!(obj, "vn {} {} {}", n[0] / l, n[1] / l, n[2] / l)?;
    }
    for t in idx.chunks_exact(3) {
        let f = [map[&t[0]], map[&t[1]], map[&t[2]]];
        writeln!(
            obj,
            "f {0}/{0}/{0} {1}/{1}/{1} {2}/{2}/{2}",
            f[0], f[1], f[2]
        )?;
    }
    drop(obj);
    std::fs::write(
        dir.join("female-hair.mtl"),
        "newmtl hair\nKd 1 1 1\nmap_Kd female-hair.png\n",
    )?;
    std::fs::copy(&a[1], dir.join("female-hair.png"))?;
    let edited = preview::load_body_file(std::path::Path::new(&a[2]))?;
    let mut preset = equipment::Preset::new("female-hair".into());
    preset.applies = [false, true];
    preset.provenance = "Hair of \"Animated Female Base Mesh\" by assetfactory, https://sketchfab.com/3d-models/animated-female-base-mesh-52fc9c15cf3e49d2a5a9cee6444964ec, Sketchfab Standard licence. Baked rigid to the head joint at the rest pose (was skinned to several bones).".into();
    let part = equipment::import_obj(&mut preset, &dir.join("female-hair.obj"))?;
    let head_edited = edited
        .joint_names
        .iter()
        .position(|n| n == &body.joint_names[head])
        .ok_or("head missing in edited body")?;
    preset.bind(1, &edited, part, head_edited)?;
    std::fs::write(&a[3], preset.encode()?)?;
    println!(
        "hair: {} vertices, {} triangles, bound to {}",
        used.len(),
        idx.len() / 3,
        body.joint_names[head]
    );
    Ok(())
}
fn tempdir() -> std::path::PathBuf {
    let d = std::env::temp_dir().join(format!("bake-hair-{}", std::process::id()));
    std::fs::create_dir_all(&d).unwrap();
    d
}