// 化身 GLB -> 36 帧旋转 PNG（绕 Y 轴 10° 步进），服务端预渲染。
// 用法: node render.js --glb <path> --out <dir> [--frames 36] [--size 256x512]
import { argv } from 'node:process';
import fs from 'node:fs';
import path from 'node:path';
import createGL from 'gl';
import { PNG } from 'pngjs';
import * as THREE from 'three';
import { GLTFLoader } from 'three/addons/loaders/GLTFLoader.js';

function parseArgs() {
  const a = {};
  for (let i = 2; i < argv.length; i++) {
    if (argv[i].startsWith('--')) {
      const key = argv[i].slice(2);
      const val = argv[i + 1] !== undefined && !argv[i + 1].startsWith('--') ? argv[++i] : true;
      a[key] = val;
    }
  }
  if (!a.glb || !a.out) {
    console.error('用法: node render.js --glb <path> --out <dir> [--frames 36] [--size 256x512]');
    process.exit(1);
  }
  a.frames = a.frames === true ? 36 : parseInt(a.frames, 10) || 36;
  const [w, h] = (a.size === true ? '256x512' : String(a.size)).split('x').map(Number);
  a.width = w || 256;
  a.height = h || 512;
  return a;
}

const args = parseArgs();
const { width, height, frames } = args;

const gl = createGL(width, height, { preserveDrawingBuffer: true });
if (!gl) {
  console.error('headless-gl 初始化失败（容器内需 mesa/libglvnd）');
  process.exit(2);
}

const canvas = {
  width,
  height,
  style: {},
  addEventListener: () => {},
  removeEventListener: () => {},
  clientWidth: width,
  clientHeight: height,
  getContext: () => gl,
};

const renderer = new THREE.WebGLRenderer({ canvas, context: gl, antialias: false });
renderer.setClearColor(0xffffff, 1);
renderer.setSize(width, height, false);

const scene = new THREE.Scene();
scene.add(new THREE.AmbientLight(0xffffff, 1.1));
const dirLight = new THREE.DirectionalLight(0xffffff, 1.4);
dirLight.position.set(3, 6, 4);
scene.add(dirLight);
scene.add(new THREE.DirectionalLight(0xffffff, 0.5).translateY(-4).translateX(-3));

const camera = new THREE.PerspectiveCamera(35, width / height, 0.1, 100);

const loader = new GLTFLoader();

const loadGlb = () =>
  new Promise((resolve, reject) => {
    // Buffer 需转成 ArrayBuffer 才能触发 GLB 头解析
    const bin = fs.readFileSync(args.glb);
    const ab = bin.buffer.slice(bin.byteOffset, bin.byteOffset + bin.byteLength);
    loader.parse(ab, '', (gltf) => resolve(gltf.scene), (err) => reject(err));
  });

loadGlb()
  .then((object) => {
    scene.add(object);
    render(object);
  })
  .catch((err) => {
    console.error('GLB 解析失败:', err && err.message ? err.message : err);
    process.exit(3);
  });

function render(object) {
  // 包围盒 -> 相机半径与观测高度
  const box = new THREE.Box3().setFromObject(object);
  const center = box.getCenter(new THREE.Vector3());
  const size = box.getSize(new THREE.Vector3());
  const radius = Math.max(size.x, size.z) * 1.6 + 0.6;
  const lookY = center.y + size.y * 0.35;
  const cameraY = center.y + size.y * 0.35;

  fs.mkdirSync(args.out, { recursive: true });
  const pixels = new Uint8Array(width * height * 4);
  const rowSize = width * 4;
  const png = new PNG({ width, height });

  for (let i = 0; i < frames; i++) {
    const angle = (i / frames) * Math.PI * 2;
    camera.position.set(Math.sin(angle) * radius, cameraY, Math.cos(angle) * radius);
    camera.lookAt(0, lookY, 0);
    renderer.render(scene, camera);

    gl.readPixels(0, 0, width, height, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
    const buf = Buffer.from(pixels.buffer);
    for (let y = 0; y < height; y++) {
      buf.copy(png.data, y * rowSize, (height - 1 - y) * rowSize, (height - y) * rowSize);
    }
    const out = path.join(args.out, `frame_${String(i).padStart(3, '0')}.png`);
    fs.writeFileSync(out, PNG.sync.write(png));
  }

  console.log(`rendered ${frames} frames -> ${args.out}`);
  process.exit(0);
}