import { v4 as uuidv4 } from 'uuid';
import { 
  Task, 
  TaskType, 
  TaskStatus, 
  TaskPriority, 
  TaskResult,
  TaskProgressUpdate,
  CreateTaskRequest,
  TASK_WS_EVENTS,
} from '@media-manager/shared';
import { wsManager } from '../websocket/index.js';
import { logger } from '../utils/logger.js';
import { config } from '../config/index.js';

// 任务执行器类型
export type TaskExecutor = (
  task: Task, 
  updateProgress: (update: Partial<TaskProgressUpdate>) => void
) => Promise<TaskResult>;

// 检查是否启用 Redis
const USE_REDIS = process.env.USE_REDIS_QUEUE === 'true';

/**
 * 全局异步任务队列服务
 * 管理所有后台任务的创建、执行、进度追踪
 */
class TaskQueueService {
  // 用户任务列表 Map<userId, Task[]>
  private userTasks: Map<number, Task[]> = new Map();
  
  // 任务执行器 Map<TaskType, TaskExecutor>
  private executors: Map<TaskType, TaskExecutor> = new Map();
  
  // 正在执行的任务数量限制（每用户）
  private maxConcurrentTasks = 3;

  /**
   * 注册任务执行器
   */
  registerExecutor(type: TaskType, executor: TaskExecutor): void {
    this.executors.set(type, executor);
    logger.info(`Task executor registered: ${type}`);
  }

  /**
   * 创建新任务
   */
  createTask(userId: number, request: CreateTaskRequest): Task & { userId: number } {
    const task: Task & { userId: number; [key: string]: unknown } = {
      id: uuidv4(),
      type: request.type,
      title: request.title || this.getDefaultTitle(request.type),
      description: request.description,
      status: 'pending',
      progress: 0,
      priority: request.priority || 'normal',
      createdAt: new Date().toISOString(),
      accountId: request.accountId,
      userId, // 存储 userId 用于任务执行
      // 合并额外数据
      ...(request.data || {}),
    };

    // 添加到用户任务列表
    if (!this.userTasks.has(userId)) {
      this.userTasks.set(userId, []);
    }
    this.userTasks.get(userId)!.push(task);

    // 通知前端任务已创建
    this.notifyUser(userId, TASK_WS_EVENTS.TASK_CREATED, { task });

    logger.info(`Task created: ${task.id} (${task.type}) for user ${userId}`);

    // 尝试执行任务
    this.tryExecuteNext(userId);

    return task;
  }

  /**
   * 获取用户的所有任务
   */
  getUserTasks(userId: number): Task[] {
    return this.userTasks.get(userId) || [];
  }

  /**
   * 获取用户的活跃任务（pending + running）
   */
  getActiveTasks(userId: number): Task[] {
    const tasks = this.userTasks.get(userId) || [];
    return tasks.filter(t => t.status === 'pending' || t.status === 'running');
  }

  /**
   * 取消任务
   */
  cancelTask(userId: number, taskId: string): boolean {
    const tasks = this.userTasks.get(userId);
    if (!tasks) return false;

    const task = tasks.find(t => t.id === taskId);
    if (!task) return false;

    if (task.status === 'pending') {
      task.status = 'cancelled';
      task.completedAt = new Date().toISOString();
      this.notifyUser(userId, TASK_WS_EVENTS.TASK_CANCELLED, { task });
      logger.info(`Task cancelled: ${taskId}`);
      return true;
    }

    // 正在运行的任务暂不支持取消
    return false;
  }

  /**
   * 清理已完成的任务（保留最近N个）
   */
  cleanupCompletedTasks(userId: number, keepCount = 10): void {
    const tasks = this.userTasks.get(userId);
    if (!tasks) return;

    const completedTasks = tasks.filter(t => 
      t.status === 'completed' || t.status === 'failed' || t.status === 'cancelled'
    );

    if (completedTasks.length > keepCount) {
      // 按完成时间排序，保留最新的
      completedTasks.sort((a, b) => 
        new Date(b.completedAt || 0).getTime() - new Date(a.completedAt || 0).getTime()
      );
      
      const toRemove = completedTasks.slice(keepCount);
      const toRemoveIds = new Set(toRemove.map(t => t.id));
      
      this.userTasks.set(userId, tasks.filter(t => !toRemoveIds.has(t.id)));
    }
  }

  /**
   * 尝试执行下一个任务（支持并行执行多个任务）
   */
  private tryExecuteNext(userId: number): void {
    const tasks = this.userTasks.get(userId);
    if (!tasks) return;

    // 检查当前运行中的任务数量
    const runningCount = tasks.filter(t => t.status === 'running').length;
    const availableSlots = this.maxConcurrentTasks - runningCount;
    
    if (availableSlots <= 0) {
      return;
    }

    // 找到待执行的任务（按优先级排序）
    const pendingTasks = tasks.filter(t => t.status === 'pending');
    if (pendingTasks.length === 0) return;

    // 按优先级排序
    pendingTasks.sort((a, b) => {
      const priorityOrder = { high: 0, normal: 1, low: 2 };
      return priorityOrder[a.priority] - priorityOrder[b.priority];
    });

    // 并行启动多个任务（不使用 await，让它们并行执行）
    const tasksToStart = pendingTasks.slice(0, availableSlots);
    for (const task of tasksToStart) {
      // 使用 void 来明确表示我们不等待这个 Promise
      void this.executeTask(userId, task);
    }
  }

  /**
   * 执行任务
   */
  private async executeTask(userId: number, task: Task): Promise<void> {
    const executor = this.executors.get(task.type);
    if (!executor) {
      logger.error(`No executor registered for task type: ${task.type}`);
      task.status = 'failed';
      task.error = `不支持的任务类型: ${task.type}`;
      task.completedAt = new Date().toISOString();
      this.notifyUser(userId, TASK_WS_EVENTS.TASK_FAILED, { task });
      return;
    }

    // 更新任务状态为运行中
    task.status = 'running';
    task.startedAt = new Date().toISOString();
    task.progress = 0;
    this.notifyUser(userId, TASK_WS_EVENTS.TASK_STARTED, { task });

    logger.info(`Task started: ${task.id} (${task.type})`);

    // 进度更新回调
    const updateProgress = (update: Partial<TaskProgressUpdate>) => {
      if (update.progress !== undefined) task.progress = update.progress;
      if (update.currentStep !== undefined) task.currentStep = update.currentStep;
      if (update.currentStepIndex !== undefined) task.currentStepIndex = update.currentStepIndex;
      
      this.notifyUser(userId, TASK_WS_EVENTS.TASK_PROGRESS, {
        taskId: task.id,
        progress: task.progress,
        currentStep: task.currentStep,
        currentStepIndex: task.currentStepIndex,
        message: update.message,
      });
    };

    try {
      const result = await executor(task, updateProgress);
      
      task.status = 'completed';
      task.progress = 100;
      task.result = result;
      task.completedAt = new Date().toISOString();
      
      this.notifyUser(userId, TASK_WS_EVENTS.TASK_COMPLETED, { task });
      logger.info(`Task completed: ${task.id}, result: ${result.message}`);
    } catch (error) {
      task.status = 'failed';
      task.error = error instanceof Error ? error.message : '任务执行失败';
      task.completedAt = new Date().toISOString();
      
      this.notifyUser(userId, TASK_WS_EVENTS.TASK_FAILED, { task });
      logger.error(`Task failed: ${task.id}`, error);
    }

    // 清理旧任务并尝试执行下一个
    this.cleanupCompletedTasks(userId);
    this.tryExecuteNext(userId);
  }

  /**
   * 通知用户
   */
  private notifyUser(userId: number, event: string, data: Record<string, unknown>): void {
    wsManager.sendToUser(userId, event, {
      event: event.split(':')[1], // 提取事件名
      ...data,
    });
  }

  /**
   * 获取默认任务标题
   */
  private getDefaultTitle(type: TaskType): string {
    const titles: Record<TaskType, string> = {
      sync_comments: '同步评论',
      sync_works: '同步作品',
      sync_account: '同步账号信息',
      publish_video: '发布视频',
      batch_reply: '批量回复评论',
    };
    return titles[type] || '未知任务';
  }

  /**
   * 发送任务列表给用户
   */
  sendTaskList(userId: number): void {
    const tasks = this.getUserTasks(userId);
    wsManager.sendToUser(userId, TASK_WS_EVENTS.TASK_LIST, {
      event: 'list',
      tasks,
    });
  }

  /**
   * 启动 Worker（内存队列模式下为空操作）
   */
  startWorker(): void {
    logger.info('Memory Task Queue started (no worker needed)');
  }

  /**
   * 停止 Worker
   */
  async stopWorker(): Promise<void> {
    logger.info('Memory Task Queue stopped');
  }

  /**
   * 关闭服务
   */
  async close(): Promise<void> {
    logger.info('Memory Task Queue Service closed');
  }
}

// 内存队列单例
const memoryTaskQueueService = new TaskQueueService();

// 根据配置选择队列实现
let taskQueueService: TaskQueueService;

if (USE_REDIS) {
  // 动态导入 Redis 队列
  import('./RedisTaskQueue.js').then(({ redisTaskQueueService }) => {
    (taskQueueService as unknown) = redisTaskQueueService;
    logger.info('Using Redis Task Queue');
  }).catch((err) => {
    logger.warn('Failed to load Redis Task Queue, falling back to memory queue:', err.message);
    taskQueueService = memoryTaskQueueService;
  });
  // 初始设置为内存队列（在 Redis 加载完成前使用）
  taskQueueService = memoryTaskQueueService;
} else {
  taskQueueService = memoryTaskQueueService;
  logger.info('Using Memory Task Queue');
}

export { taskQueueService };