import { Worker } from 'worker_threads';

// 创建固定大小的线程池（6个线程）
class QueryThreadPool {
  constructor(size = 6) {
    this.size = size;           // 线程池大小，默认为6
    this.workers = [];          // 存储worker对象的数组
    this.taskQueue = [];        // 任务队列，存储等待处理的任务
    this.initWorkers();         // 初始化worker线程
  }

  initWorkers() {
    for (let i = 0; i < this.size; i++) {
      const worker = new Worker(new URL('./pollingTask.js', import.meta.url)); // 创建指向generatTask.js的worker
      this.workers.push({
        worker, // worker对象
        busy: false // 是否正在处理任务的标志
      });
    }
  }

  async executeTask(taskBatch) {
    return new Promise((resolve, reject) => {
      // 寻找空闲的worker
      const availableWorker = this.workers.find(w => !w.busy);
      
      if (availableWorker) {
        // 有空闲worker，直接执行任务
        this.runTaskOnWorker(availableWorker, taskBatch, resolve, reject);
      } else {
        // 没有空闲worker，将任务加入队列
        this.taskQueue.push({ taskBatch, resolve, reject });
      }
    });
  }

  runTaskOnWorker(workerObj, taskBatch, resolve, reject) {
    workerObj.busy = true;
    
    workerObj.worker.once('message', (result) => {
      workerObj.busy = false;
      resolve(result);
      
      // 检查是否有排队的任务
      this.processQueuedTasks();
    });
    
    workerObj.worker.once('error', (error) => {
      workerObj.busy = false;
      reject(error);
      
      // 检查是否有排队的任务
      this.processQueuedTasks();
    });
    
    workerObj.worker.postMessage(taskBatch);
  }

  processQueuedTasks() {
    if (this.taskQueue.length > 0) {
      const availableWorker = this.workers.find(w => !w.busy);
      if (availableWorker) {
        const queuedTask = this.taskQueue.shift();
        this.runTaskOnWorker(
          availableWorker, 
          queuedTask.taskBatch, 
          queuedTask.resolve, 
          queuedTask.reject
        );
      }
    }
  }

  async executeAllTasks(taskBatches) {
    const promises = taskBatches.map(batch => this.executeTask(batch));
    return Promise.all(promises);
  }

  // 清理资源
  terminate() {
    this.workers.forEach(({ worker }) => {
      worker.terminate();
    });
  }
}

export default new QueryThreadPool();