const mongoose = require('mongoose');
const fs = require('fs').promises;
const path = require('path');
const Submission = require('./models/Submission');
const SourceText = require('./models/SourceText');
const User = require('./models/User');
const MONGODB_URI = 'mongodb+srv://nothingyu:wSg3lbO1PkHiRMq9@sandbox.ecysggv.mongodb.net/?retryWrites=true&w=majority&appName=sandbox';

class BackupSystem {
  constructor() {
    this.backupDir = path.join(__dirname, 'backups');
    this.ensureBackupDir();
  }

  async ensureBackupDir() {
    try {
      await fs.mkdir(this.backupDir, { recursive: true });
    } catch (error) {
      console.error('Failed to create backup directory:', error);
    }
  }

  async createBackup() {
    try {
      console.log('🔄 Creating database backup...');
      await mongoose.connect(MONGODB_URI);

      const timestamp = new Date().toISOString().replace(/[:.]/g, '-');
      const backupData = {
        timestamp,
        collections: {}
      };

      // Backup Users
      console.log('📋 Backing up users...');
      const users = await User.find({});
      backupData.collections.users = users.map(user => user.toObject());

      // Backup SourceTexts
      console.log('📚 Backing up source texts...');
      const sourceTexts = await SourceText.find({});
      backupData.collections.sourceTexts = sourceTexts.map(text => text.toObject());

      // Backup Submissions
      console.log('📝 Backing up submissions...');
      const submissions = await Submission.find({});
      backupData.collections.submissions = submissions.map(sub => sub.toObject());

      // Save backup to file
      const backupFile = path.join(this.backupDir, `backup-${timestamp}.json`);
      await fs.writeFile(backupFile, JSON.stringify(backupData, null, 2));

      console.log(`✅ Backup created: ${backupFile}`);
      console.log(`📊 Backup summary:`);
      console.log(`  - Users: ${users.length}`);
      console.log(`  - Source Texts: ${sourceTexts.length}`);
      console.log(`  - Submissions: ${submissions.length}`);

      return backupFile;
    } catch (error) {
      console.error('❌ Backup failed:', error);
      throw error;
    } finally {
      await mongoose.connection.close();
    }
  }

  async restoreBackup(backupFile) {
    try {
      console.log(`🔄 Restoring from backup: ${backupFile}`);
      await mongoose.connect(MONGODB_URI);

      const backupData = JSON.parse(await fs.readFile(backupFile, 'utf8'));

      // Clear existing data
      console.log('🗑️ Clearing existing data...');
      await User.deleteMany({});
      await SourceText.deleteMany({});
      await Submission.deleteMany({});

      // Restore Users
      console.log('👥 Restoring users...');
      if (backupData.collections.users) {
        await User.insertMany(backupData.collections.users);
      }

      // Restore SourceTexts
      console.log('📚 Restoring source texts...');
      if (backupData.collections.sourceTexts) {
        await SourceText.insertMany(backupData.collections.sourceTexts);
      }

      // Restore Submissions
      console.log('📝 Restoring submissions...');
      if (backupData.collections.submissions) {
        await Submission.insertMany(backupData.collections.submissions);
      }

      console.log('✅ Backup restored successfully!');
    } catch (error) {
      console.error('❌ Restore failed:', error);
      throw error;
    } finally {
      await mongoose.connection.close();
    }
  }

  async listBackups() {
    try {
      const files = await fs.readdir(this.backupDir);
      const backups = files.filter(file => file.startsWith('backup-') && file.endsWith('.json'));
      
      console.log('📋 Available backups:');
      backups.forEach(backup => {
        console.log(`  - ${backup}`);
      });
      
      return backups;
    } catch (error) {
      console.error('❌ Failed to list backups:', error);
      return [];
    }
  }

  async scheduleBackup() {
    // Create backup every 24 hours
    setInterval(async () => {
      try {
        await this.createBackup();
        console.log('✅ Scheduled backup completed');
      } catch (error) {
        console.error('❌ Scheduled backup failed:', error);
      }
    }, 24 * 60 * 60 * 1000); // 24 hours
  }
}

// Export for use in other files
module.exports = BackupSystem;

// If run directly, create a backup
if (require.main === module) {
  const backupSystem = new BackupSystem();
  backupSystem.createBackup()
    .then(() => {
      console.log('🎉 Backup completed successfully!');
      process.exit(0);
    })
    .catch(error => {
      console.error('💥 Backup failed:', error);
      process.exit(1);
    });
}