import AsyncStorage from '@react-native-async-storage/async-storage';
import * as BackgroundFetch from 'expo-background-fetch';
import * as TaskManager from 'expo-task-manager';

// 任务类型定义
export interface BackgroundTask {
  id: string;
  name: string;
  handler: (data?: any) => Promise<void>;
  options?: {
    minimumInterval?: number; // 最小间隔时间（分钟）
    stopOnTerminate?: boolean; // 应用终止时是否停止
    startOnBoot?: boolean; // 设备重启时是否启动
  };
}

// 任务状态
export interface TaskStatus {
  id: string;
  isRegistered: boolean;
  lastExecution?: Date;
  nextExecution?: Date;
  executionCount: number;
  lastError?: string;
}

// 后台任务管理器类
class BackgroundTaskManager {
  private static instance: BackgroundTaskManager;
  private tasks: Map<string, BackgroundTask> = new Map();
  private taskStatuses: Map<string, TaskStatus> = new Map();
  private isInitialized = false;

  // 单例模式
  public static getInstance(): BackgroundTaskManager {
    if (!BackgroundTaskManager.instance) {
      BackgroundTaskManager.instance = new BackgroundTaskManager();
    }
    return BackgroundTaskManager.instance;
  }

  // 初始化后台任务管理器
  public async initialize(): Promise<void> {
    if (this.isInitialized) {
      return;
    }

    try {
      this.isInitialized = true;

      // 注册后台任务
      await this.registerBackgroundTask();
      
      // 加载已保存的任务状态
      await this.loadTaskStatuses();
      
      console.log('后台任务管理器初始化成功');
    } catch (error) {
      console.error('后台任务管理器初始化失败:', error);
      throw error;
    }
  }

  // 注册后台任务
  private async registerBackgroundTask(): Promise<void> {
    const BACKGROUND_FETCH_TASK = 'background-fetch-task';

    console.log('注册后台获取任务');
    
    // 定义后台获取任务
    TaskManager.defineTask(BACKGROUND_FETCH_TASK, async () => {
      console.log('后台获取任务被系统调用');
      const now = new Date();
      
      try {
        console.log(`开始执行后台任务 - ${now.toISOString()}`);
        
        // 执行所有注册的任务
        const results = await this.executeAllTasks();
        
        console.log('后台任务执行完成:', results);
        
        // 返回成功状态
        return BackgroundFetch.BackgroundFetchResult.NewData;
      } catch (error) {
        console.error('后台任务执行失败:', error);
        return BackgroundFetch.BackgroundFetchResult.Failed;
      }
    });

    // 注册后台获取任务
    try {
      const status = await BackgroundFetch.getStatusAsync();
      if (status === BackgroundFetch.BackgroundFetchStatus.Available) {
        await BackgroundFetch.registerTaskAsync(BACKGROUND_FETCH_TASK, {
          minimumInterval: 15 * 60, // 15分钟（以秒为单位）
          stopOnTerminate: false,
          startOnBoot: true,
        });
        console.log('后台获取任务注册成功');
      } else {
        console.warn('后台获取不可用，状态:', status);
      }
    } catch (error) {
      console.error('注册后台获取任务失败:', error);
    }
  }

  // 注册自定义任务
  public async registerTask(task: BackgroundTask): Promise<void> {
    try {
      // 检查任务是否已存在
      if (this.tasks.has(task.id)) {
        console.warn(`任务 ${task.id} 已存在，将被覆盖`);
      }

      // 保存任务
      this.tasks.set(task.id, task);

      // 初始化任务状态
      if (!this.taskStatuses.has(task.id)) {
        this.taskStatuses.set(task.id, {
          id: task.id,
          isRegistered: true,
          executionCount: 0,
        });
      }

      // 保存任务状态
      await this.saveTaskStatuses();

      console.log(`任务 ${task.id} 注册成功`);
    } catch (error) {
      console.error(`注册任务 ${task.id} 失败:`, error);
      throw error;
    }
  }

  // 取消注册任务
  public async unregisterTask(taskId: string): Promise<void> {
    try {
      // 移除任务
      this.tasks.delete(taskId);

      // 更新任务状态
      const status = this.taskStatuses.get(taskId);
      if (status) {
        status.isRegistered = false;
        await this.saveTaskStatuses();
      }

      console.log(`任务 ${taskId} 取消注册成功`);
    } catch (error) {
      console.error(`取消注册任务 ${taskId} 失败:`, error);
      throw error;
    }
  }

  // 手动执行任务
  public async executeTask(taskId: string, data?: any): Promise<void> {
    try {
      const task = this.tasks.get(taskId);
      if (!task) {
        throw new Error(`任务 ${taskId} 不存在`);
      }

      console.log(`开始执行任务: ${taskId}`);
      
      // 执行任务
      await task.handler(data);
      
      // 更新任务状态
      const status = this.taskStatuses.get(taskId);
      if (status) {
        status.lastExecution = new Date();
        status.executionCount += 1;
        status.lastError = undefined;
        await this.saveTaskStatuses();
      }

      console.log(`任务 ${taskId} 执行成功`);
    } catch (error) {
      console.error(`执行任务 ${taskId} 失败:`, error);
      
      // 更新错误状态
      const status = this.taskStatuses.get(taskId);
      if (status) {
        status.lastError = error instanceof Error ? error.message : String(error);
        await this.saveTaskStatuses();
      }
      
      throw error;
    }
  }

  // 执行所有任务
  public async executeAllTasks(): Promise<{ [taskId: string]: 'success' | 'failed' }> {
    const results: { [taskId: string]: 'success' | 'failed' } = {};
    
    for (const [taskId, task] of this.tasks) {
      try {
        await this.executeTask(taskId);
        results[taskId] = 'success';
      } catch (error) {
        console.error(`执行任务 ${taskId} 失败:`, error);
        results[taskId] = 'failed';
      }
    }
    
    return results;
  }

  // 获取任务状态
  public getTaskStatus(taskId: string): TaskStatus | undefined {
    return this.taskStatuses.get(taskId);
  }

  // 获取所有任务状态
  public getAllTaskStatuses(): TaskStatus[] {
    return Array.from(this.taskStatuses.values());
  }

  // 获取已注册的任务列表
  public getRegisteredTasks(): BackgroundTask[] {
    return Array.from(this.tasks.values());
  }

  // 检查后台任务状态
  public async getBackgroundTaskStatus(): Promise<BackgroundFetch.BackgroundFetchStatus | null> {
    return await BackgroundFetch.getStatusAsync();
  }

  // 保存任务状态到本地存储
  private async saveTaskStatuses(): Promise<void> {
    try {
      const statuses = Array.from(this.taskStatuses.values());
      await AsyncStorage.setItem('@background_task_statuses', JSON.stringify(statuses));
    } catch (error) {
      console.error('保存任务状态失败:', error);
    }
  }

  // 从本地存储加载任务状态
  private async loadTaskStatuses(): Promise<void> {
    try {
      const statusesJson = await AsyncStorage.getItem('@background_task_statuses');
      if (statusesJson) {
        const statuses: TaskStatus[] = JSON.parse(statusesJson);
        statuses.forEach(status => {
          this.taskStatuses.set(status.id, status);
        });
      }
    } catch (error) {
      console.error('加载任务状态失败:', error);
    }
  }

  // 清理过期的任务状态
  public async cleanupTaskStatuses(): Promise<void> {
    const now = new Date();
    const thirtyDaysAgo = new Date(now.getTime() - 30 * 24 * 60 * 60 * 1000);
    
    for (const [taskId, status] of this.taskStatuses) {
      if (status.lastExecution && status.lastExecution < thirtyDaysAgo && !status.isRegistered) {
        this.taskStatuses.delete(taskId);
      }
    }
    
    await this.saveTaskStatuses();
  }

  // 调试函数：强制触发后台任务执行
  public async debugExecuteBackgroundTask(): Promise<void> {
    console.log('=== 调试：手动触发后台任务执行 ===');
    
    try {
      // 获取后台任务状态
      const status = await this.getBackgroundTaskStatus();
      console.log('后台获取状态:', status);
      
      // 执行所有注册的任务
      console.log('当前注册的任务数量:', this.tasks.size);
      this.tasks.forEach((task, id) => {
        console.log(`- 任务ID: ${id}, 名称: ${task.name}`);
      });
      
      const results = await this.executeAllTasks();
      console.log('任务执行结果:', results);
      
      // 显示任务状态
      const taskStatuses = this.getAllTaskStatuses();
      taskStatuses.forEach(status => {
        console.log(`任务 ${status.id} 状态:`, {
          isRegistered: status.isRegistered,
          executionCount: status.executionCount,
          lastExecution: status.lastExecution?.toISOString(),
          lastError: status.lastError
        });
      });
      
    } catch (error) {
      console.error('调试执行失败:', error);
    }
    
    console.log('=== 调试执行完成 ===');
  }
}

// 导出单例实例
export const backgroundTaskManager = BackgroundTaskManager.getInstance();

// 导出类型
export type { BackgroundTask as BackgroundTaskType, TaskStatus as TaskStatusType };