/** Standard Three.js backend. UI and catalogue never depend on THREE internals. */
export async function createThreeRenderer({canvas,gltf,binary,bytes,config}) {
  let timer;
  const modules=Promise.all([import(config.threeModule),import(config.threeLoader)]);
  const [T,{GLTFLoader}]=await Promise.race([modules,new Promise((_,reject)=>{timer=setTimeout(()=>reject(Error('Three.js CDN timeout')),config.cdnTimeoutMs||6500);})]).finally(()=>clearTimeout(timer));
  const loader=new GLTFLoader();
  const documentModel=await loader.parseAsync(bytes.buffer.slice(bytes.byteOffset,bytes.byteOffset+bytes.byteLength),'');
  const scene=new T.Scene();scene.add(documentModel.scene);
  const renderer=new T.WebGLRenderer({canvas,antialias:true,alpha:false,preserveDrawingBuffer:true,powerPreference:'high-performance'});
  renderer.outputColorSpace=T.SRGBColorSpace;
  renderer.toneMapping=T.ACESFilmicToneMapping;renderer.toneMappingExposure=1.05;
  renderer.shadowMap.enabled=true;renderer.shadowMap.type=T.PCFSoftShadowMap;renderer.shadowMap.autoUpdate=false;
  const ambient=new T.AmbientLight(0xffffff,.7);
  const skyLight=new T.HemisphereLight(0xf5f8ff,0x67604e,1.7);
  const sun=new T.DirectionalLight(0xffffff,3.0);
  const fill=new T.HemisphereLight(0xfff5df,0x77716a,0);
  scene.add(ambient,skyLight,sun,sun.target,fill);
  sun.castShadow=true;sun.shadow.mapSize.set(2048,2048);sun.shadow.bias=-.00008;sun.shadow.normalBias=.025;
  const persp=new T.PerspectiveCamera(),ortho=new T.OrthographicCamera();
  const textures=await Promise.all((gltf.textures||[]).map((_,i)=>documentModel.parser.getDependency('texture',i)));
  const images=[];
  for (let i=0;i<textures.length;i++) {
    const imageSpec=gltf.images[gltf.textures[i].source];
    if(imageSpec.bufferView!==undefined){const b=gltf.bufferViews[imageSpec.bufferView];const src=URL.createObjectURL(new Blob([binary.subarray(b.byteOffset||0,(b.byteOffset||0)+b.byteLength)],{type:imageSpec.mimeType}));images[i]={src};}
    textures[i].anisotropy=Math.min(8,renderer.capabilities.getMaxAnisotropy());
  }
  const entries=[],matCopies=new Map(),associations=documentModel.parser.associations;
  documentModel.scene.updateMatrixWorld(true);
  documentModel.scene.traverse(obj=>{
    if(!obj.isMesh)return;
    const association=associations.get(obj)||{};
    let parent=obj,nodeIndex=association.nodes;
    while(nodeIndex===undefined&&parent){const a=associations.get(parent);if(a?.nodes!==undefined)nodeIndex=a.nodes;parent=parent.parent;}
    if(nodeIndex===undefined)return;
    const node=gltf.nodes[nodeIndex],meshSpec=gltf.meshes[node.mesh];
    const primitiveIndex=association.primitives||0;
    const primitive=meshSpec.primitives[primitiveIndex]||meshSpec.primitives[0];
    const materialIndex=primitive.material;
    if(materialIndex===undefined)return;
    const spec=gltf.materials[materialIndex],name=node.name||meshSpec.name||obj.name;
    // Separate copies prevent a material variant from changing unrelated objects.
    let material=matCopies.get(materialIndex);
    if(!material){material=obj.material.clone();material.side=T.DoubleSide;matCopies.set(materialIndex,material);}
    obj.material=material;
    const box=new T.Box3().setFromObject(obj);
    const pbr=spec.pbrMetallicRoughness||{};
    const desc={object:obj,std:node.extras||{},transparent:spec.alphaMode==='BLEND',material:materialIndex,name,nodeIndex,
      count:obj.geometry.index?.count||obj.geometry.attributes.position.count,context:/^(90_|91_|28_|23_)/.test(name),
      legacySite:!!node.extras?.legacySite,siteLayer:node.extras?.siteLayer||null,castShadow:node.extras?.castShadow!==false,
      bounds:{min:box.min.toArray(),max:box.max.toArray()},glass:(spec.name||'').startsWith('glass'),
      interiorLayer:node.extras?.interiorLayer||null,interiorMaterial:!!spec.extras?.interiorMaterial,
      interiorStyle:spec.extras?.interiorStyle||0,pbr};
    obj.castShadow=desc.castShadow&&!desc.glass&&!desc.transparent;obj.receiveShadow=!desc.transparent;
    if(desc.transparent){material.transparent=true;material.depthWrite=false;}
    entries.push(desc);
  });
  const stamps=new Map(),textureCopies=new Map();
  function localTexture(index,role,materialIndex,scale) {
    const key=materialIndex+':'+role+':'+index+':'+scale.join(',');
    if(!textureCopies.has(key)){
      const tx=textures[index]?.clone();if(!tx)return null;
      tx.colorSpace=role==='map'?T.SRGBColorSpace:T.NoColorSpace;
      tx.repeat.set(...scale);tx.needsUpdate=true;textureCopies.set(key,tx);
    }
    return textureCopies.get(key);
  }
  function syncMaterials(){
    for(const [index,mat] of matCopies){
      const spec=gltf.materials[index],p=spec.pbrMetallicRoughness||{};
      const stamp=JSON.stringify([p,spec.normalTexture,spec.emissiveFactor,spec.name]);if(stamps.get(index)===stamp)continue;stamps.set(index,stamp);
      const rgba=p.baseColorFactor||[.7,.7,.7,1];mat.color.setRGB(...rgba.slice(0,3));
      // Legacy exterior factors were sRGB; tagged PBR / interior factors are already linear.
      if(!spec.extras?.interiorMaterial&&!spec.extras?.linearColor&&!spec.extras?.hardieRole)mat.color.convertSRGBToLinear();
      mat.opacity=rgba[3]??1;mat.roughness=p.roughnessFactor??.8;mat.metalness=p.metallicFactor??0;
      const tex=p.baseColorTexture;
      mat.map=tex?localTexture(tex.index,'map',index,tex.extensions?.KHR_texture_transform?.scale||[1,1]):null;
      mat.normalMap=spec.normalTexture?localTexture(spec.normalTexture.index,'normalMap',index,[1,1]):null;
      if(mat.normalScale&&spec.normalTexture)mat.normalScale.setScalar(spec.normalTexture.scale??1);
      if(spec.extras?.interiorStyle===1){mat.emissive.copy(mat.color);mat.emissiveIntensity=.75;}
      mat.needsUpdate=true;
    }
  }
  const temp=new T.Vector3();let oldVisible='',oldInterior='';
  function shadowFit(frame){
    const low=[Infinity,Infinity,Infinity],high=[-Infinity,-Infinity,-Infinity];
    for(const m of entries){if(!m.object.visible||m.glass)continue;for(let a=0;a<3;a++){low[a]=Math.min(low[a],m.bounds.min[a]);high[a]=Math.max(high[a],m.bounds.max[a]);}}
    if(!Number.isFinite(low[0]))return;
    if(frame.interior.enabled){low.splice(0,3,-9,-1,-6);high.splice(0,3,11,6,6);}
    const center=low.map((v,i)=>(v+high[i])/2);
    sun.target.position.fromArray(center);sun.position.fromArray(center).addScaledVector(temp.fromArray(frame.solar.light),120);
    sun.target.updateMatrixWorld();sun.updateMatrixWorld();
    const c=sun.shadow.camera;c.near=.1;c.far=320;c.position.copy(sun.position);c.up.set(0,1,0);c.lookAt(sun.target.position);c.updateMatrixWorld();
    let minX=Infinity,minY=Infinity,maxX=-Infinity,maxY=-Infinity;
    for(let a=0;a<8;a++){temp.set(a&1?high[0]:low[0],a&2?high[1]:low[1],a&4?high[2]:low[2]).applyMatrix4(c.matrixWorldInverse);minX=Math.min(minX,temp.x);maxX=Math.max(maxX,temp.x);minY=Math.min(minY,temp.y);maxY=Math.max(maxY,temp.y);}
    c.left=minX-2;c.right=maxX+2;c.bottom=minY-2;c.top=maxY+2;c.updateProjectionMatrix();renderer.shadowMap.needsUpdate=true;
  }
  return {backend:'three',label:'Three.js r'+T.REVISION,meshes:entries,images,
    resize(w,h,dpr){renderer.setPixelRatio(dpr);renderer.setSize(w,h,false);},
    draw(frame){
      syncMaterials();
      let key='';for(const m of entries){m.object.visible=!!frame.visible(m);key+=m.object.visible?'1':'0';}
      if(frame.solar.shadowDirty||key!==oldVisible||oldInterior!==frame.interior.mode){shadowFit(frame);oldVisible=key;oldInterior=frame.interior.mode;}
      sun.intensity=Math.max(0,frame.solar.direct)*3.0;sun.color.fromArray(frame.solar.sunColor);sun.castShadow=frame.solar.shadows;
      const day=frame.solar.dayFactor;skyLight.intensity=.18+1.5*day;ambient.intensity=.12+.45*day;
      fill.intensity=frame.interior.enabled&&frame.interior.fill?1.3:0;
      scene.background=new T.Color().setRGB(...frame.solar.sky).convertSRGBToLinear();
      const camera=frame.orthographic?ortho:persp;
      camera.position.fromArray(frame.eye);camera.up.set(0,1,0);camera.lookAt(temp.fromArray(frame.lookTarget));camera.updateMatrixWorld();
      camera.projectionMatrix.fromArray(frame.vp).multiply(camera.matrixWorld);camera.projectionMatrixInverse.copy(camera.projectionMatrix).invert();
      renderer.render(scene,camera);
    },
    dispose(){renderer.dispose();images.forEach(i=>i?.src&&URL.revokeObjectURL(i.src));textureCopies.forEach(t=>t.dispose());}
  };
}