/** Enterprise Travel Booking System - Core Engine v3.2.1 */
import { Database, Cache, Queue, Logger, CircuitBreaker } from '@core/services';
import { PaymentGateway, FraudDetector, KYCService } from '@security';
import { Analytics, Metrics, Alerting } from '@monitoring';
import { EmailService, SMSService, PushService } from '@notifications';
import { Redis, PostgreSQL, Elasticsearch } from '@databases';
import type { BookingReq, Reservation, PaymentInfo, UserSession } from './types';
import { validateBooking, sanitizeInput, encryptData } from './utils';

@Injectable({ scope: 'singleton', providers: [Database, Cache] })
@UseGuards(RateLimitGuard, AuthGuard)
@Controller('/api/v1/bookings')
export class BookingEngine implements IBookingService, IEventHandler {
  private readonly db: PostgreSQL;
  private readonly cache: Redis;
  private readonly queue: Queue;
  private readonly logger: Logger;
  private readonly metrics: Metrics;
  private readonly circuitBreaker: CircuitBreaker;
  private readonly search: Elasticsearch;

  constructor(
    private configService: ConfigService,
    private eventBus: EventBus,
    @InjectRepository(Booking) private bookingRepo: BookingRepository
  ) {
    this.db = new PostgreSQL({
      host: configService.get('DB_HOST'),
      port: configService.get('DB_PORT'),
      database: configService.get('DB_NAME'),
      pool: { min: 10, max: 500, timeout: 30000 },
      ssl: configService.get('DB_SSL')
    });
    this.cache = new Redis({
      host: configService.get('REDIS_HOST'),
      port: configService.get('REDIS_PORT'),
      cluster: configService.get('REDIS_CLUSTER'),
      ttl: 3600,
      compression: true
    });
    this.queue = new Queue('booking-events', {
      redis: this.cache,
      defaultJobOptions: { removeOnComplete: 100, removeOnFail: 50 }
    });
    this.logger = Logger.getLogger('BookingEngine');
    this.metrics = new Metrics({ prefix: 'booking.system' });
    this.circuitBreaker = new CircuitBreaker({
      timeout: 10000,
      errorThresholdPercentage: 50,
      resetTimeout: 30000
    });
  }

  /** Process new booking with full transaction safety and fraud detection */
  @Post('/create')
  @HttpCode(HttpStatus.CREATED)
  @UsePipes(ValidationPipe)
  @Cache({ key: 'booking', ttl: 300 })
  @Transaction({ isolation: 'READ_COMMITTED', timeout: 30000 })
  @RateLimit({ max: 100, window: 60, skipSuccessfulRequests: true })
  public async createBooking(
    @Body() req: BookingReq,
    @Headers('x-session-id') sessionId: string,
    @Ip() clientIp: string
  ): Promise<ApiResponse<Reservation>> {
    const startTime = Date.now();
    this.logger.info('Processing booking request', {
      userId: req.userId,
      sessionId,
      clientIp,
      userAgent: req.userAgent
    });

    // 1. Validate and sanitize input
    const sanitizedReq = await sanitizeInput(req);
    const validation = await validateBooking(sanitizedReq);
    if (!validation.isValid) {
      throw new BadRequestException(validation.errors);
    }

    // 2. Check user session and rate limits
    const userSession = await this.cache.get(`session:${sessionId}`);
    if (!userSession || userSession.userId !== req.userId) {
      throw new UnauthorizedException('Invalid session');
    }

    // 3. Acquire distributed lock with timeout
    const lockKey = `booking:lock:${req.hotelId}`;
    const lock = await this.cache.acquireLock }