/** Small independent edit jobs cannot queue behind whole-view lighting. */
export class EditMeshController {
  constructor({capture,onError=()=>{},workerFactory}={}) {
    this.capture=capture;this.onError=onError;this.epoch=0;this.job=0;
    this.pending=new Map();this.tickets=new Map();this.ready=new Map();this.busy=null;
    try {
      this.worker=workerFactory ? workerFactory() : new Worker(new URL('./edit-mesh-worker.js',import.meta.url),{type:'module'});
      this.worker.onmessage=({data})=>this.receive(data);
      this.worker.onerror=event=>{event.preventDefault();this.fail(event.message);};
    } catch(error) {this.fail(error.message);}
  }
  fail(error) {this.error=error;this.dispose();this.onError(error);}
  request(ids) {
    if(this.error||this.disposed)return;
    for(const id of ids) {
      const job=++this.job;
      this.pending.set(id,job);this.tickets.set(id,job);this.ready.delete(id);
    }
  }
  cancel(id) {this.pending.delete(id);this.tickets.delete(id);this.ready.delete(id);}
  reset() {this.epoch++;this.pending.clear();this.tickets.clear();this.ready.clear();this.busy=null;}
  isCurrent(result) {return result.epoch===this.epoch&&this.tickets.get(result.id)===result.editJob;}
  pump() {
    if(this.error||this.disposed||this.busy||this.ready.size>=2||!this.pending.size)return;
    const [id,editJob]=this.pending.entries().next().value;
    this.pending.delete(id);
    try {
      const start=performance.now(),packet={...this.capture(id),epoch:this.epoch,editJob};
      const transfers=packet.sections.map(s=>s.cells.buffer);
      if(packet.light)transfers.push(packet.light.data.buffer,packet.light.blockLevels.buffer,packet.light.skyLevels.buffer);
      this.busy={id,editJob,epoch:this.epoch};this.worker.postMessage(packet,transfers);
      this.prepareMilliseconds=performance.now()-start;
    } catch(error) {this.fail(error.message);}
  }
  receive(result) {
    if(this.disposed||result.epoch!==this.epoch||result.editJob!==this.busy?.editJob)return;
    this.busy=null;
    if(!this.isCurrent(result))return;
    if(result.error){this.fail(result.error);return;}
    this.meshMilliseconds=result.milliseconds;this.ready.set(result.id,result);
  }
  dispose() {this.disposed=true;this.reset();this.worker?.terminate();}
}