import cron from 'node-cron';
import githubService from './githubService.js';
import huggingfaceStorageService from './huggingfaceStorageService.js';
import fs from 'fs/promises';
import path from 'path';

/**
 * 自动备份服务
 * 负责定时将修改的PPT数据同步到GitHub仓库
 */
class AutoBackupService {
  constructor() {
    this.isInitialized = false;
    this.cronJob = null;
    this.backupInterval = '0 */8 * * *'; // 每8小时执行一次
    this.lastBackupTime = null;
    this.backupStats = {
      totalBackups: 0,
      successfulBackups: 0,
      failedBackups: 0,
      lastBackupResult: null
    };
    
    // 跟踪修改的PPT数据
    this.modifiedPPTs = new Map(); // userId -> Set of pptIds
    this.lastModificationCheck = new Date();
    
    console.log('🔄 AutoBackupService initialized');
  }

  /**
   * 初始化自动备份服务
   */
  async initialize() {
    try {
      console.log('🚀 Initializing AutoBackupService...');
      
      // 加载上次备份时间
      await this.loadBackupState();
      
      // 启动定时任务
      this.startCronJob();
      
      this.isInitialized = true;
      console.log('✅ AutoBackupService initialized successfully');
      console.log(`⏰ Next backup scheduled: ${this.getNextBackupTime()}`);
      
    } catch (error) {
      console.error('❌ Failed to initialize AutoBackupService:', error);
      throw error;
    }
  }

  /**
   * 启动定时任务
   */
  startCronJob() {
    if (this.cronJob) {
      this.cronJob.stop();
    }
    
    console.log(`⏰ Starting auto backup cron job: ${this.backupInterval}`);
    
    this.cronJob = cron.schedule(this.backupInterval, async () => {
      console.log('🔄 Auto backup triggered by cron job');
      await this.performAutoBackup();
    }, {
      scheduled: true,
      timezone: 'UTC'
    });
    
    console.log('✅ Auto backup cron job started');
  }

  /**
   * 停止定时任务
   */
  stopCronJob() {
    if (this.cronJob) {
      this.cronJob.stop();
      this.cronJob = null;
      console.log('🛑 Auto backup cron job stopped');
    }
  }

  /**
   * 记录PPT修改
   */
  recordPPTModification(userId, pptId) {
    if (!this.modifiedPPTs.has(userId)) {
      this.modifiedPPTs.set(userId, new Set());
    }
    
    this.modifiedPPTs.get(userId).add(pptId);
    console.log(`📝 Recorded modification: User ${userId}, PPT ${pptId}`);
  }

  /**
   * 获取修改的PPT列表
   */
  getModifiedPPTs() {
    const result = {};
    for (const [userId, pptIds] of this.modifiedPPTs.entries()) {
      result[userId] = Array.from(pptIds);
    }
    return result;
  }

  /**
   * 清除修改记录
   */
  clearModificationRecords() {
    this.modifiedPPTs.clear();
    console.log('🧹 Cleared modification records');
  }

  /**
   * 执行自动备份
   */
  async performAutoBackup() {
    const startTime = new Date();
    console.log(`🔄 Starting auto backup at ${startTime.toISOString()}`);
    
    const backupResult = {
      timestamp: startTime,
      success: false,
      totalUsers: 0,
      totalPPTs: 0,
      successfulBackups: 0,
      failedBackups: 0,
      errors: [],
      duration: 0
    };
    
    try {
      this.backupStats.totalBackups++;
      
      // 获取修改的PPT列表
      const modifiedPPTs = this.getModifiedPPTs();
      const userIds = Object.keys(modifiedPPTs);
      
      backupResult.totalUsers = userIds.length;
      
      if (userIds.length === 0) {
        console.log('ℹ️ No modified PPTs found, skipping backup');
        backupResult.success = true;
        return backupResult;
      }
      
      console.log(`📊 Found ${userIds.length} users with modified PPTs`);
      
      // 为每个用户备份修改的PPT
      for (const userId of userIds) {
        const pptIds = modifiedPPTs[userId];
        backupResult.totalPPTs += pptIds.length;
        
        console.log(`👤 Backing up ${pptIds.length} PPTs for user ${userId}`);
        
        for (const pptId of pptIds) {
          try {
            // 获取PPT数据
            const pptData = await githubService.getPPT(userId, pptId);
            
            if (!pptData) {
              console.warn(`⚠️ PPT ${pptId} not found for user ${userId}`);
              backupResult.failedBackups++;
              continue;
            }
            
            // 执行备份到GitHub
            await githubService.savePPT(userId, pptId, pptData);
            
            console.log(`✅ Successfully backed up PPT ${pptId} for user ${userId}`);
            backupResult.successfulBackups++;
            
          } catch (error) {
            console.error(`❌ Failed to backup PPT ${pptId} for user ${userId}:`, error);
            backupResult.failedBackups++;
            backupResult.errors.push({
              userId,
              pptId,
              error: error.message
            });
          }
        }
      }
      
      // 清除修改记录
      this.clearModificationRecords();
      
      backupResult.success = backupResult.failedBackups === 0;
      
      if (backupResult.success) {
        this.backupStats.successfulBackups++;
        console.log(`✅ Auto backup completed successfully: ${backupResult.successfulBackups} PPTs backed up`);
      } else {
        this.backupStats.failedBackups++;
        console.error(`❌ Auto backup completed with errors: ${backupResult.failedBackups} failures`);
      }
      
    } catch (error) {
      console.error('❌ Auto backup failed:', error);
      backupResult.success = false;
      backupResult.errors.push({
        type: 'system',
        error: error.message
      });
      this.backupStats.failedBackups++;
    } finally {
      const endTime = new Date();
      backupResult.duration = endTime.getTime() - startTime.getTime();
      
      this.lastBackupTime = startTime;
      this.backupStats.lastBackupResult = backupResult;
      
      // 保存备份状态
      await this.saveBackupState();
      
      console.log(`🏁 Auto backup finished in ${backupResult.duration}ms`);
    }
    
    return backupResult;
  }

  /**
   * 手动触发备份
   */
  async triggerManualBackup() {
    console.log('🔄 Manual backup triggered');
    return await this.performAutoBackup();
  }

  /**
   * 获取下次备份时间
   */
  getNextBackupTime() {
    if (!this.cronJob) {
      return 'Not scheduled';
    }
    
    // 计算下次执行时间（简化版本）
    const now = new Date();
    const nextHour = Math.ceil(now.getHours() / 8) * 8;
    const nextBackup = new Date(now);
    
    if (nextHour >= 24) {
      nextBackup.setDate(nextBackup.getDate() + 1);
      nextBackup.setHours(0, 0, 0, 0);
    } else {
      nextBackup.setHours(nextHour, 0, 0, 0);
    }
    
    return nextBackup.toISOString();
  }

  /**
   * 获取备份统计信息
   */
  getBackupStats() {
    return {
      ...this.backupStats,
      lastBackupTime: this.lastBackupTime,
      nextBackupTime: this.getNextBackupTime(),
      modifiedPPTsCount: Array.from(this.modifiedPPTs.values())
        .reduce((total, pptSet) => total + pptSet.size, 0),
      isRunning: !!this.cronJob,
      backupInterval: this.backupInterval
    };
  }

  /**
   * 加载备份状态
   */
  async loadBackupState() {
    try {
      const stateFile = path.join(process.cwd(), 'data', 'backup-state.json');
      
      try {
        const stateData = await fs.readFile(stateFile, 'utf8');
        const state = JSON.parse(stateData);
        
        this.lastBackupTime = state.lastBackupTime ? new Date(state.lastBackupTime) : null;
        this.backupStats = { ...this.backupStats, ...state.backupStats };
        
        console.log('📂 Loaded backup state from file');
      } catch (error) {
        if (error.code !== 'ENOENT') {
          console.warn('⚠️ Failed to load backup state:', error.message);
        }
      }
    } catch (error) {
      console.warn('⚠️ Failed to load backup state:', error.message);
    }
  }

  /**
   * 保存备份状态
   */
  async saveBackupState() {
    try {
      const stateFile = path.join(process.cwd(), 'data', 'backup-state.json');
      const stateDir = path.dirname(stateFile);
      
      // 确保目录存在
      await fs.mkdir(stateDir, { recursive: true });
      
      const state = {
        lastBackupTime: this.lastBackupTime,
        backupStats: this.backupStats,
        savedAt: new Date().toISOString()
      };
      
      await fs.writeFile(stateFile, JSON.stringify(state, null, 2));
      console.log('💾 Saved backup state to file');
      
    } catch (error) {
      console.warn('⚠️ Failed to save backup state:', error.message);
    }
  }

  /**
   * 更新备份间隔
   */
  updateBackupInterval(cronExpression) {
    this.backupInterval = cronExpression;
    console.log(`⏰ Updated backup interval to: ${cronExpression}`);
    
    // 重启定时任务
    this.startCronJob();
  }

  /**
   * 清理服务
   */
  async cleanup() {
    console.log('🧹 Cleaning up AutoBackupService...');
    
    this.stopCronJob();
    await this.saveBackupState();
    
    console.log('✅ AutoBackupService cleanup completed');
  }
}

// 创建单例实例
const autoBackupService = new AutoBackupService();

export default autoBackupService;