//! Certificación del **reparto con LOD**: una bandada de 16 humanoides alejándose
//! del ojo, repartida por [`reparto_sdf`] dentro del presupuesto del uniform
//! (16 seres / 240 primitivas).
//!
//! Sin LOD, 16 caras enteras son ~500 primitivas: el empacador cortaba la lista y los
//! del fondo desaparecían (o peor, salían mutilados). Acá se ve que entran los 16 y
//! —lo que importa— que la degradación NO se nota: el que perdió la cara está lo
//! bastante lejos como para que no hubiera cara que ver.
//!
//! `cargo run -p llimphi-voxel --example manada_lod_demo --release`

use std::fs::File;
use std::io::BufWriter;

use llimphi_3d::glam::Vec3;
use llimphi_3d::{Camera3d, VoxelGrid, VoxelRenderer, VOXEL_MAX_SER_PRIMS};
use llimphi_hal::{wgpu, Hal};
use llimphi_raster::peniko::Color;
use llimphi_raster::{vello, Renderer};
use llimphi_voxel::{reparto_sdf, Age, CharSpec, Clip, DetalleSer, EnCuadro};

const W: u32 = 1280;
const H: u32 = 720;
const FMT: wgpu::TextureFormat = wgpu::TextureFormat::Rgba8Unorm;
const BG: [u8; 3] = [22, 26, 36];

const DIM: u32 = 128;
const FLOOR_H: u32 = 2;
/// Cuántos y con qué separación (en unidades de mundo; un adulto mide ~1.8).
const N: usize = 16;
const PASO: f32 = 3.4;

fn main() {
    let hal = pollster::block_on(Hal::new(None)).expect("hal");
    let mut renderer = Renderer::new(&hal).expect("renderer");
    let dir = std::env::var("CLAUDE_JOB_DIR").map(|d| format!("{d}/tmp")).unwrap_or("/tmp".into());

    // Bandada en diagonal (para que no se tapen entre sí), alejándose en Z.
    let specs: Vec<CharSpec> = (0..N)
        .map(|i| {
            let mut c = CharSpec::new(format!("ser{i}"), Age::Adult);
            // Colores variados para distinguirlos (hash simple por índice).
            let t = i as f32 / N as f32;
            c.shirt = [0.20 + 0.5 * t, 0.62 - 0.3 * t, 0.55 + 0.3 * (1.0 - t)];
            c
        })
        .collect();

    let x0 = DIM as f32 * 0.5;
    let z0 = DIM as f32 * 0.18;
    let cuadro: Vec<EnCuadro> = specs
        .iter()
        .enumerate()
        .map(|(i, spec)| EnCuadro {
            spec,
            pos: Vec3::new(
                x0 + (i as f32 * 0.9).sin() * 4.0 + (i as f32 % 2.0 - 0.5) * 3.0,
                FLOOR_H as f32,
                z0 + i as f32 * PASO,
            ),
            yaw: 0.0, // todos de frente a la cámara
            clip: if i % 3 == 0 { Clip::Wave } else { Clip::Walk },
            fase: i as f32 * 0.7,
        })
        .collect();

    // Cámara delante de la fila, a la altura de la cara del primero.
    let half = DIM as f32 * 0.5;
    let ojo_grid = Vec3::new(x0, FLOOR_H as f32 + 2.6, z0 - 4.2);
    let camera = Camera3d::orbit(
        Vec3::new(x0 - half, FLOOR_H as f32 + 1.4 - half, z0 + 10.0 - half),
        0.0,
        6_f32.to_radians(),
        16.0,
    );

    let sers = reparto_sdf(&cuadro, ojo_grid, true);

    println!("manada_lod_demo — {N} humanoides, presupuesto {VOXEL_MAX_SER_PRIMS} primitivas");
    let mut total = 0;
    for (i, s) in sers.iter().enumerate() {
        let dist = ojo_grid.distance(Vec3::from(s.pos) + Vec3::new(0.0, 0.9, 0.0));
        let d = DetalleSer::por_distancia(dist, 1.8);
        total += s.prims.len();
        println!(
            "  #{i:2} dist={dist:5.1}  {:?}\t{} prims\t(acumulado {total})",
            d,
            s.prims.len()
        );
    }
    println!("  → {} seres, {total} primitivas de {VOXEL_MAX_SER_PRIMS}", sers.len());
    assert_eq!(sers.len(), N, "entran los {N}");
    assert!(total <= VOXEL_MAX_SER_PRIMS, "presupuesto excedido: {total}");
    // Nadie mutilado: el cuerpo entero son 10 primitivas.
    for (i, s) in sers.iter().enumerate() {
        assert!(s.prims.len() >= 10, "#{i} salió incompleto ({} prims)", s.prims.len());
    }

    // Piso damero.
    let mut grid = VoxelGrid::new([DIM, DIM, DIM]);
    for x in 0..DIM {
        for z in 0..DIM {
            for y in 0..FLOOR_H {
                let c = if (x / 6 + z / 6) % 2 == 0 { [150, 146, 136] } else { [120, 116, 110] };
                grid.set(x, y, z, c);
            }
        }
    }

    let px = render(&hal, &mut renderer, &grid, sers, &camera);
    let cov = coverage(&px);
    let out = format!("{dir}/manada_lod.png");
    write_png(&px, &out);
    println!("✓ {cov} px cubiertos → {out}");
    assert!(cov > 20_000, "la bandada se renderizó ({cov} px)");
}

fn render(
    hal: &Hal,
    renderer: &mut Renderer,
    grid: &VoxelGrid,
    sers: Vec<llimphi_3d::SdfSer>,
    camera: &Camera3d,
) -> Vec<u8> {
    let mut vr = VoxelRenderer::new(&hal.device, &hal.queue, FMT, grid);
    vr.sun_dir = normalize([0.4, 0.7, 0.55]);
    vr.sers = sers;

    let inter = hal.device.create_texture(&wgpu::TextureDescriptor {
        label: Some("inter"),
        size: wgpu::Extent3d { width: W, height: H, depth_or_array_layers: 1 },
        mip_level_count: 1,
        sample_count: 1,
        dimension: wgpu::TextureDimension::D2,
        format: FMT,
        usage: wgpu::TextureUsages::STORAGE_BINDING
            | wgpu::TextureUsages::TEXTURE_BINDING
            | wgpu::TextureUsages::RENDER_ATTACHMENT
            | wgpu::TextureUsages::COPY_SRC,
        view_formats: &[],
    });
    let view = inter.create_view(&wgpu::TextureViewDescriptor::default());
    let base = vello::Scene::new();
    renderer
        .render_to_view(hal, &base, &view, W, H, Color::from_rgba8(BG[0], BG[1], BG[2], 255))
        .expect("base");
    let mut enc = hal.device.create_command_encoder(&wgpu::CommandEncoderDescriptor { label: None });
    vr.render(&hal.device, &hal.queue, &mut enc, &view, (W, H), camera);
    hal.queue.submit(std::iter::once(enc.finish()));
    let _ = hal.device.poll(wgpu::PollType::wait_indefinitely());
    readback(hal, &inter)
}

fn normalize(v: [f32; 3]) -> [f32; 3] {
    let l = (v[0] * v[0] + v[1] * v[1] + v[2] * v[2]).sqrt().max(1e-6);
    [v[0] / l, v[1] / l, v[2] / l]
}

fn coverage(px: &[u8]) -> usize {
    (0..(W * H) as usize)
        .filter(|&i| {
            let o = i * 4;
            (px[o] as i32 - BG[0] as i32).abs()
                + (px[o + 1] as i32 - BG[1] as i32).abs()
                + (px[o + 2] as i32 - BG[2] as i32).abs()
                > 12
        })
        .count()
}

fn readback(hal: &Hal, target: &wgpu::Texture) -> Vec<u8> {
    let unpadded = (W * 4) as usize;
    let align = wgpu::COPY_BYTES_PER_ROW_ALIGNMENT as usize;
    let padded = unpadded.div_ceil(align) * align;
    let buf = hal.device.create_buffer(&wgpu::BufferDescriptor {
        label: Some("readback"),
        size: (padded * H as usize) as u64,
        usage: wgpu::BufferUsages::MAP_READ | wgpu::BufferUsages::COPY_DST,
        mapped_at_creation: false,
    });
    let mut enc = hal.device.create_command_encoder(&wgpu::CommandEncoderDescriptor { label: None });
    enc.copy_texture_to_buffer(
        wgpu::TexelCopyTextureInfo { texture: target, mip_level: 0, origin: wgpu::Origin3d::ZERO, aspect: wgpu::TextureAspect::All },
        wgpu::TexelCopyBufferInfo { buffer: &buf, layout: wgpu::TexelCopyBufferLayout { offset: 0, bytes_per_row: Some(padded as u32), rows_per_image: Some(H) } },
        wgpu::Extent3d { width: W, height: H, depth_or_array_layers: 1 },
    );
    hal.queue.submit(std::iter::once(enc.finish()));
    let slice = buf.slice(..);
    let (tx, rx) = std::sync::mpsc::channel();
    slice.map_async(wgpu::MapMode::Read, move |r| {
        let _ = tx.send(r);
    });
    let _ = hal.device.poll(wgpu::PollType::wait_indefinitely());
    rx.recv().unwrap().unwrap();
    let data = slice.get_mapped_range();
    let mut pixels = Vec::with_capacity((W * H * 4) as usize);
    for row in 0..H as usize {
        let s = row * padded;
        pixels.extend_from_slice(&data[s..s + unpadded]);
    }
    drop(data);
    buf.unmap();
    pixels
}

fn write_png(pixels: &[u8], path: &str) {
    let file = File::create(path).expect("png");
    let mut enc = png::Encoder::new(BufWriter::new(file), W, H);
    enc.set_color(png::ColorType::Rgba);
    enc.set_depth(png::BitDepth::Eight);
    let mut w = enc.write_header().unwrap();
    w.write_image_data(pixels).unwrap();
}