import { LoadingManager, type Material, type Mesh, type Texture } from 'three';
import { OBJExporter } from 'three/addons/exporters/OBJExporter.js';
import { ColladaLoader } from 'three/addons/loaders/ColladaLoader.js';

const TRANSPARENT_PIXEL = 'data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=';

/**
 * 将 Collada 几何转换为 MuJoCo WASM 可读取的 OBJ。
 * ColladaLoader 会先统一为 Y-up；额外旋转到 MuJoCo 使用的 Z-up，并烘焙节点变换与单位缩放。
 */
export function convertDaeToObj(data: Uint8Array, path: string): Uint8Array {
  const manager = new LoadingManager();
  // 转换只需要几何。拦截贴图 URL，避免为浏览器内存文件发起无效网络请求。
  manager.setURLModifier(() => TRANSPARENT_PIXEL);
  const loader = new ColladaLoader(manager);
  const text = new TextDecoder('utf-8').decode(data);
  const xml = new DOMParser().parseFromString(text, 'application/xml');
  if (xml.querySelector('parsererror')) throw new Error('Collada XML 格式无效');
  const upAxis =
    xml.getElementsByTagName('up_axis')[0]?.textContent?.trim().toUpperCase() ?? 'Y_UP';
  // 禁用 ColladaLoader 自带的 Z-up → Y-up 旋转，改为直接统一到 MuJoCo 的 Z-up。
  if (upAxis === 'Z_UP') xml.getElementsByTagName('up_axis')[0]!.textContent = 'Y_UP';
  const normalized = new XMLSerializer().serializeToString(xml);
  const result = loader.parse(normalized, path.slice(0, path.lastIndexOf('/') + 1));
  if (!result?.scene) throw new Error('Collada 文件无法解析');
  const scene = result.scene;
  if (upAxis === 'Y_UP') scene.rotation.x += Math.PI / 2;
  else if (upAxis === 'X_UP') scene.rotation.y -= Math.PI / 2;
  scene.updateMatrixWorld(true);
  let meshCount = 0;
  scene.traverse((object) => {
    const mesh = object as Mesh;
    if (!mesh.isMesh) return;
    meshCount += 1;
    const materials = Array.isArray(mesh.material) ? mesh.material : [mesh.material];
    for (const material of materials) if (material) material.name = '';
  });
  if (!meshCount) throw new Error('Collada 文件不包含可转换的三角网格');
  try {
    const output = new OBJExporter().parse(scene);
    if (!/^v\s/m.test(output) || !/^f\s/m.test(output))
      throw new Error('Collada 文件未生成有效三角面');
    return new TextEncoder().encode(output);
  } finally {
    scene.traverse((object) => {
      const mesh = object as Mesh;
      if (!mesh.isMesh) return;
      mesh.geometry?.dispose();
      const materials: Material[] = Array.isArray(mesh.material) ? mesh.material : [mesh.material];
      for (const material of materials) {
        for (const value of Object.values(material))
          if (value && typeof value === 'object' && (value as Texture).isTexture)
            (value as Texture).dispose();
        material.dispose();
      }
    });
  }
}