// PyodideWorkerPool.js
export default class PyodideWorkerPool {
    constructor(poolSize = 2) {
      this.poolSize = poolSize;
      this.workers = [];
      this.onMessageCallbacks = [];
      this.initPool();
    }
  
    initPool() {
      for (let i = 0; i < this.poolSize; i++) {
        this.workers.push(this.createWorker());
      }
    }
  
    createWorker() {
      const workerInfo = {
        worker: new Worker('js/pyodideWorker.js'),
        busy: false,
        loaded: false
      };
  
      // 监听 Worker 消息
      workerInfo.worker.onmessage = (event) => {
        const { type } = event.data;
        if (type === "finish") {
          workerInfo.loaded = true;
        }
        if (type === "executionComplete" || type === "error") {
          workerInfo.busy = false;
        }
        // 让外部知道“是哪个 worker 发来的消息”
        for (let cb of this.onMessageCallbacks) {
          cb(event, workerInfo);
        }
        this.updateIsPythonLoadOK();
      };
  
      return workerInfo;
    }
  
    addOnMessageListener(callback) {
      this.onMessageCallbacks.push(callback);
    }
  
    updateIsPythonLoadOK() {
      // 只要至少一个 Worker loaded 就算可以执行
      const anyLoaded = this.workers.some(w => w.loaded === true);
      window.isPythonLoadOK = anyLoaded;
    }
  
    // 找到不忙、且已loaded的 Worker
    getFreeWorker() {
      return this.workers.find(w => w.busy === false && w.loaded === true) || null;
    }
  
    // 让指定 Worker 执行
    runPython(workerInfo, code) {
      if (workerInfo.busy) {
        throw new Error("该 Worker 正在执行脚本，无法重复使用");
      }
      if (!workerInfo.loaded) {
        throw new Error("该 Worker 尚未加载 Pyodide，无法执行 Python");
      }
      workerInfo.busy = true;
      workerInfo.worker.postMessage({ type: "runPython", code });
    }
  
    // 停止并替换
    terminateAndReplace(workerInfo) {
      workerInfo.worker.terminate();
      const idx = this.workers.indexOf(workerInfo);
      if (idx !== -1) {
        const newW = this.createWorker();
        this.workers[idx] = newW;
      }
      this.updateIsPythonLoadOK();
    }
  
    destroyPool() {
      for (let wInfo of this.workers) {
        wInfo.worker.terminate();
      }
      this.workers = [];
      this.updateIsPythonLoadOK();
    }
  }