import { promises as fs } from 'fs';
import { exec } from 'child_process';
import { promisify } from 'util';
import path from 'path';
import { createHash } from 'crypto';

const execAsync = promisify(exec);

/**
 * Utilitaires pour les opérations de backup
 */
export class BackupUtils {
  /**
   * Calcule un hash SHA-256 d'un fichier
   */
  static async calculateFileHash(filePath: string): Promise<string> {
    try {
      const fileBuffer = await fs.readFile(filePath);
      return createHash('sha256').update(fileBuffer).digest('hex');
    } catch (error) {
      throw new Error(`Failed to calculate hash for ${filePath}: ${error}`);
    }
  }

  /**
   * Résout le chemin de la base de données selon la configuration
   */
  static resolveDatabasePath(): string {
    if (process.env.BACKUP_DATABASE_PATH) {
      return path.resolve(process.cwd(), process.env.BACKUP_DATABASE_PATH);
    } else if (process.env.DATABASE_URL) {
      return path.resolve(process.env.DATABASE_URL.replace('file:', ''));
    } else {
      return path.resolve(process.cwd(), 'prisma', 'dev.db');
    }
  }

  /**
   * Résout le chemin de stockage des backups
   */
  static resolveBackupStoragePath(): string {
    if (process.env.BACKUP_STORAGE_PATH) {
      return path.resolve(process.cwd(), process.env.BACKUP_STORAGE_PATH);
    }
    
    return process.env.NODE_ENV === 'production' 
      ? path.join(process.cwd(), 'data', 'backups')
      : path.join(process.cwd(), 'backups');
  }

  /**
   * Crée une sauvegarde SQLite en utilisant la commande .backup
   */
  static async createSQLiteBackup(sourcePath: string, backupPath: string): Promise<void> {
    // Vérifier que le fichier source existe
    try {
      await fs.stat(sourcePath);
    } catch {
      throw new Error(`Source database not found: ${sourcePath}`);
    }
    
    // Méthode 1: Utiliser sqlite3 CLI (plus fiable)
    try {
      const command = `sqlite3 "${sourcePath}" ".backup '${backupPath}'"`;
      await execAsync(command);
      console.log(`✅ SQLite backup created using CLI: ${backupPath}`);
      return;
    } catch (cliError) {
      console.warn(`⚠️ SQLite CLI backup failed, trying copy method:`, cliError);
    }

    // Méthode 2: Copie simple du fichier (fallback)
    try {
      await fs.copyFile(sourcePath, backupPath);
      console.log(`✅ SQLite backup created using file copy: ${backupPath}`);
    } catch (copyError) {
      throw new Error(`Failed to create SQLite backup: ${copyError}`);
    }
  }

  /**
   * Compresse un fichier avec gzip
   */
  static async compressFile(filePath: string): Promise<string> {
    const compressedPath = `${filePath}.gz`;
    
    try {
      const command = `gzip -c "${filePath}" > "${compressedPath}"`;
      await execAsync(command);
      console.log(`✅ File compressed: ${compressedPath}`);
      return compressedPath;
    } catch (error) {
      console.warn(`⚠️ Compression failed, keeping uncompressed file:`, error);
      return filePath;
    }
  }

  /**
   * Décompresse un fichier gzip temporairement
   */
  static async decompressFileTemp(compressedPath: string, tempPath: string): Promise<void> {
    try {
      await execAsync(`gunzip -c "${compressedPath}" > "${tempPath}"`);
    } catch (error) {
      throw new Error(`Failed to decompress ${compressedPath}: ${error}`);
    }
  }

  /**
   * Formate la taille de fichier en unités lisibles
   */
  static formatFileSize(bytes: number): string {
    const units = ['B', 'KB', 'MB', 'GB'];
    let size = bytes;
    let unitIndex = 0;
    
    while (size >= 1024 && unitIndex < units.length - 1) {
      size /= 1024;
      unitIndex++;
    }
    
    return `${size.toFixed(1)} ${units[unitIndex]}`;
  }

  /**
   * S'assure qu'un dossier existe
   */
  static async ensureDirectory(dirPath: string): Promise<void> {
    try {
      await fs.access(dirPath);
    } catch {
      await fs.mkdir(dirPath, { recursive: true });
      console.log(`📁 Created directory: ${dirPath}`);
    }
  }

  /**
   * Parse le nom de fichier de backup pour extraire les métadonnées
   */
  static parseBackupFilename(filename: string): { type: 'manual' | 'automatic'; date: Date | null } {
    // Nouveau format: towercontrol_manual_2025-09-18T14-12-05-737Z.db
    // Ancien format: towercontrol_2025-09-18T14-12-05-737Z.db (considéré comme automatic)
    let type: 'manual' | 'automatic' = 'automatic';
    let dateMatch = filename.match(/towercontrol_(manual|automatic)_(\d{4}-\d{2}-\d{2}T\d{2}-\d{2}-\d{2}-\d{3}Z)/);
    
    if (!dateMatch) {
      // Format ancien sans type - considérer comme automatic
      dateMatch = filename.match(/towercontrol_(\d{4}-\d{2}-\d{2}T\d{2}-\d{2}-\d{2}-\d{3}Z)/);
      if (dateMatch) {
        dateMatch = [dateMatch[0], 'automatic', dateMatch[1]]; // Restructurer pour compatibilité
      }
    } else {
      type = dateMatch[1] as 'manual' | 'automatic';
    }
    
    let date: Date | null = null;
    if (dateMatch && dateMatch[2]) {
      // Convertir le format de fichier vers ISO string valide
      // Format: 2025-09-18T14-12-05-737Z -> 2025-09-18T14:12:05.737Z
      const isoString = dateMatch[2]
        .replace(/T(\d{2})-(\d{2})-(\d{2})-(\d{3})Z/, 'T$1:$2:$3.$4Z');
      date = new Date(isoString);
    }
    
    return { type, date };
  }

  /**
   * Génère un nom de fichier de backup
   */
  static generateBackupFilename(type: 'manual' | 'automatic'): string {
    const timestamp = new Date().toISOString().replace(/[:.]/g, '-');
    return `towercontrol_${type}_${timestamp}.db`;
  }

  /**
   * Écrit une entrée dans le fichier de log
   */
  static async writeLogEntry(
    logPath: string, 
    type: 'manual' | 'automatic', 
    action: 'created' | 'skipped' | 'failed', 
    details: string, 
    extra?: { hash?: string; size?: number; previousHash?: string }
  ): Promise<void> {
    try {
      const date = new Date().toLocaleString('fr-FR');
      
      let logEntry = `[${date}] ${type.toUpperCase()} BACKUP ${action.toUpperCase()}: ${details}`;
      
      if (extra) {
        if (extra.hash) {
          logEntry += ` | Hash: ${extra.hash.substring(0, 12)}...`;
        }
        if (extra.size) {
          logEntry += ` | Size: ${BackupUtils.formatFileSize(extra.size)}`;
        }
        if (extra.previousHash) {
          logEntry += ` | Previous: ${extra.previousHash.substring(0, 12)}...`;
        }
      }
      
      logEntry += '\n';
      
      await fs.appendFile(logPath, logEntry);
    } catch (error) {
      console.error('Error writing to backup log:', error);
      // Ne pas faire échouer l'opération si on ne peut pas logger
    }
  }
}