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();
      }
    });
  }
}