hld

Class & Component Design

Controller-Service-Repository Pattern

The code follows a strict 3-layer architecture to ensure separation of concerns.

• Controllers (src/controllers/):
  • Parse requests.
  • Call Services.
  • Return standard SuccessResponse or ErrorResponse.
  • Example: FlightController.createFlight extracts body params and calls FlightService.
• Services (src/services/):
  • Contain business rules.
  • Example: FlightService.createFlight calls validateDateTime helper to ensure arrival > departure.
  • Example: FlightService.getAllFlights builds complex filters (price range, date, trip route).
• Repositories (src/repositories/):
  • Handle DB queries.
  • Example: FlightRepository.getAllFlights uses Sequelize include to join Airplane, Airport, and City tables.
  • Example: FlightRepository.updateRemainingSeats manages DB transactions and locking.

2.3 Key Algorithms & Logic

A. Flight Search (Dynamic Filtering)

Scenario: A user searches for flights from Mumbai (BOM) to Delhi (DEL) within a price range. The service builds a dynamic query.

The getAllFlights method supports dynamic filtering:

• Trips: MUM-DEL -> splits into departureAirportId and arrivalAirportId.
• Price: 1000-5000 -> converts to Op.between.