// Migration Management System
import { CBDAdapter } from './cbd-adapter.js';
import { MigrationOptions, MigrationResult, CNDError } from './types.js';

export class MigrationManager {
  constructor(private adapter: CBDAdapter) { }

  async from(source: string, options: MigrationOptions = {}): Promise<MigrationResult> {
    const startTime = Date.now();
    const result: MigrationResult = {
      source,
      tablesProcessed: [],
      recordsProcessed: 0,
      errors: [],
      duration: 0
    };

    try {
      console.log(`Migration Manager: Starting migration from ${source}`);

      const sourceConnection = await this.connectToSource(source);
      const migrationPlan = await this.createMigrationPlan(sourceConnection, options);

      if (options.dryRun) {
        console.log('Migration Manager: Dry run mode - no actual data migration');
        return this.createDryRunResult(migrationPlan, startTime);
      }

      // Execute migration
      for (const table of migrationPlan.tables) {
        try {
          const recordCount = await this.migrateTable(sourceConnection, table, options);
          result.tablesProcessed.push(table.name);
          result.recordsProcessed += recordCount;
        } catch (error) {
          const errorMsg = `Failed to migrate table ${table.name}: ${error}`;
          result.errors.push(errorMsg);
          console.error('Migration Manager:', errorMsg);
        }
      }

      result.duration = Date.now() - startTime;
      console.log(`Migration Manager: Completed in ${result.duration}ms`);

      return result;
    } catch (error) {
      result.errors.push(`Migration failed: ${error}`);
      result.duration = Date.now() - startTime;
      throw new CNDError(
        `Migration from ${source} failed: ${error}`,
        'MIGRATION_ERROR',
        { source, options, result }
      );
    }
  }

  async export(target: string, options: {
    tables?: string[];
    format?: 'sql' | 'json' | 'csv';
    compress?: boolean;
  } = {}): Promise<{
    file: string;
    size: number;
    tables: string[];
    records: number;
  }> {
    try {
      console.log(`Migration Manager: Exporting to ${target}`, options);

      // In real implementation, this would export data from CBD Engine
      return {
        file: target,
        size: 0,
        tables: options.tables || [],
        records: 0
      };
    } catch (error) {
      throw new CNDError(
        `Export to ${target} failed: ${error}`,
        'MIGRATION_EXPORT_ERROR',
        { target, options }
      );
    }
  }

  async backup(location: string, options: {
    compress?: boolean;
    includeSchema?: boolean;
    tables?: string[];
  } = {}): Promise<{
    location: string;
    size: number;
    timestamp: Date;
  }> {
    try {
      console.log(`Migration Manager: Creating backup at ${location}`, options);

      // In real implementation, this would create a backup using CBD Engine
      return {
        location,
        size: 0,
        timestamp: new Date()
      };
    } catch (error) {
      throw new CNDError(
        `Backup to ${location} failed: ${error}`,
        'MIGRATION_BACKUP_ERROR',
        { location, options }
      );
    }
  }

  async restore(location: string, options: {
    overwrite?: boolean;
    tables?: string[];
    skipData?: boolean;
  } = {}): Promise<{
    tables: string[];
    records: number;
    duration: number;
  }> {
    const startTime = Date.now();

    try {
      console.log(`Migration Manager: Restoring from ${location}`, options);

      // In real implementation, this would restore from backup using CBD Engine
      return {
        tables: options.tables || [],
        records: 0,
        duration: Date.now() - startTime
      };
    } catch (error) {
      throw new CNDError(
        `Restore from ${location} failed: ${error}`,
        'MIGRATION_RESTORE_ERROR',
        { location, options }
      );
    }
  }

  // Database-specific migration methods
  async fromPostgreSQL(connectionString: string, options: MigrationOptions = {}): Promise<MigrationResult> {
    return this.from(`postgresql://${connectionString}`, {
      ...options,
      tables: options.tables || await this.getPostgreSQLTables(connectionString)
    });
  }

  async fromMySQL(connectionString: string, options: MigrationOptions = {}): Promise<MigrationResult> {
    return this.from(`mysql://${connectionString}`, {
      ...options,
      tables: options.tables || await this.getMySQLTables(connectionString)
    });
  }

  async fromMongoDB(connectionString: string, options: MigrationOptions = {}): Promise<MigrationResult> {
    return this.from(`mongodb://${connectionString}`, {
      ...options,
      collections: options.collections || await this.getMongoCollections(connectionString)
    });
  }

  async fromSQLite(filePath: string, options: MigrationOptions = {}): Promise<MigrationResult> {
    return this.from(`sqlite://${filePath}`, {
      ...options,
      tables: options.tables || await this.getSQLiteTables(filePath)
    });
  }

  async fromCSV(filePath: string, tableName: string, options: {
    delimiter?: string;
    headers?: boolean;
    encoding?: string;
  } = {}): Promise<MigrationResult> {
    const startTime = Date.now();

    try {
      console.log(`Migration Manager: Importing CSV from ${filePath} to table ${tableName}`, options);

      // In real implementation, this would parse CSV and import to CBD Engine
      return {
        source: filePath,
        tablesProcessed: [tableName],
        recordsProcessed: 0,
        errors: [],
        duration: Date.now() - startTime
      };
    } catch (error) {
      throw new CNDError(
        `CSV import from ${filePath} failed: ${error}`,
        'MIGRATION_CSV_ERROR',
        { filePath, tableName, options }
      );
    }
  }

  async fromJSON(filePath: string, tableName: string, options: {
    arrayPath?: string;
    flatten?: boolean;
  } = {}): Promise<MigrationResult> {
    const startTime = Date.now();

    try {
      console.log(`Migration Manager: Importing JSON from ${filePath} to table ${tableName}`, options);

      // In real implementation, this would parse JSON and import to CBD Engine
      return {
        source: filePath,
        tablesProcessed: [tableName],
        recordsProcessed: 0,
        errors: [],
        duration: Date.now() - startTime
      };
    } catch (error) {
      throw new CNDError(
        `JSON import from ${filePath} failed: ${error}`,
        'MIGRATION_JSON_ERROR',
        { filePath, tableName, options }
      );
    }
  }

  // Schema migration
  async migrateSchema(source: string, options: {
    includeIndexes?: boolean;
    includeConstraints?: boolean;
    dropExisting?: boolean;
  } = {}): Promise<{
    tables: string[];
    indexes: string[];
    constraints: string[];
  }> {
    try {
      console.log(`Migration Manager: Migrating schema from ${source}`, options);

      // In real implementation, this would extract and apply schema from source
      return {
        tables: [],
        indexes: [],
        constraints: []
      };
    } catch (error) {
      throw new CNDError(
        `Schema migration from ${source} failed: ${error}`,
        'MIGRATION_SCHEMA_ERROR',
        { source, options }
      );
    }
  }

  // Data validation
  async validateMigration(source: string, options: {
    sampleSize?: number;
    checkConstraints?: boolean;
    compareCounts?: boolean;
  } = {}): Promise<{
    isValid: boolean;
    issues: string[];
    statistics: Record<string, any>;
  }> {
    try {
      console.log(`Migration Manager: Validating migration from ${source}`, options);

      // In real implementation, this would validate migrated data
      return {
        isValid: true,
        issues: [],
        statistics: {}
      };
    } catch (error) {
      throw new CNDError(
        `Migration validation failed: ${error}`,
        'MIGRATION_VALIDATION_ERROR',
        { source, options }
      );
    }
  }

  // Progress monitoring
  async getMigrationProgress(migrationId: string): Promise<{
    id: string;
    status: 'running' | 'completed' | 'failed' | 'paused';
    progress: number;
    currentTable: string;
    recordsProcessed: number;
    estimatedTimeRemaining: number;
  }> {
    try {
      // In real implementation, this would track migration progress
      return {
        id: migrationId,
        status: 'completed',
        progress: 100,
        currentTable: '',
        recordsProcessed: 0,
        estimatedTimeRemaining: 0
      };
    } catch (error) {
      throw new CNDError(
        `Failed to get migration progress: ${error}`,
        'MIGRATION_PROGRESS_ERROR',
        { migrationId }
      );
    }
  }

  // Private helper methods
  private async connectToSource(source: string): Promise<any> {
    console.log(`Migration Manager: Connecting to source ${source}`);

    // In real implementation, this would create appropriate database connections
    return {
      type: this.parseSourceType(source),
      connection: source
    };
  }

  private parseSourceType(source: string): string {
    if (source.startsWith('postgresql://')) return 'postgresql';
    if (source.startsWith('mysql://')) return 'mysql';
    if (source.startsWith('mongodb://')) return 'mongodb';
    if (source.startsWith('sqlite://')) return 'sqlite';
    return 'unknown';
  }

  private async createMigrationPlan(sourceConnection: any, options: MigrationOptions): Promise<{
    tables: Array<{ name: string; type: string; options: any }>;
  }> {
    const tables = (options.tables || []).map(tableName => ({
      name: tableName,
      type: 'table',
      options: {
        batchSize: options.batchSize || 1000,
        transform: options.transform?.[tableName]
      }
    }));

    return { tables };
  }

  private createDryRunResult(migrationPlan: any, startTime: number): MigrationResult {
    return {
      source: 'dry-run',
      tablesProcessed: migrationPlan.tables.map((t: any) => t.name),
      recordsProcessed: 0,
      errors: [],
      duration: Date.now() - startTime
    };
  }

  private async migrateTable(
    sourceConnection: any,
    table: { name: string; options: any },
    options: MigrationOptions
  ): Promise<number> {
    console.log(`Migration Manager: Migrating table ${table.name}`);

    // In real implementation, this would:
    // 1. Extract data from source
    // 2. Transform data if transform function provided
    // 3. Insert data into CBD Engine in batches

    return 0; // Return number of records migrated
  }

  // Database-specific helper methods
  private async getPostgreSQLTables(connectionString: string): Promise<string[]> {
    console.log(`Migration Manager: Getting PostgreSQL tables from ${connectionString}`);
    return [];
  }

  private async getMySQLTables(connectionString: string): Promise<string[]> {
    console.log(`Migration Manager: Getting MySQL tables from ${connectionString}`);
    return [];
  }

  private async getMongoCollections(connectionString: string): Promise<string[]> {
    console.log(`Migration Manager: Getting MongoDB collections from ${connectionString}`);
    return [];
  }

  private async getSQLiteTables(filePath: string): Promise<string[]> {
    console.log(`Migration Manager: Getting SQLite tables from ${filePath}`);
    return [];
  }
}