02.Flight Booking System

class FlightBookingSystem {
  constructor(agencyName) {
    this.agencyName = agencyName;
    this.flights = [];
    this.bookings = [];
    this.bookingsCount = 0;
  }

  addFlight(flightNumber, destination, departureTime, price) {
    const element = this.flights.find((x) => x.flightNumber === flightNumber);
    price = Number(price);

    if (element) {
      return `Flight ${flightNumber} to ${destination} is already available.`;
    }

    this.flights.push({
      flightNumber,
      destination,
      departureTime,
      price,
    });

    return `Flight ${flightNumber} to ${destination} has been added to the system.`;
  }

  bookFlight(passengerName, flightNumber) {
    const element = this.flights.find((x) => x.flightNumber === flightNumber);

    if (!element) {
      return `Flight ${flightNumber} is not available for booking.`;
    }

    this.bookings.push({
      passengerName,
      flightNumber,
    });

    this.bookingsCount++;

    return `Booking for passenger ${passengerName} on flight ${flightNumber} is confirmed.`;
  }

  cancelBooking(passengerName, flightNumber) {
    const element = this.bookings.find(
      (x) =>
        x.flightNumber === flightNumber && x.passengerName === passengerName
    );

    if (!element) {
      throw new Error(
        `Booking for passenger ${passengerName} on flight ${flightNumber} not found.`
      );
    }

    this.bookingsCount--;
    const indexElement = this.bookings.findIndex(
      (x) =>
        x.flightNumber === flightNumber && x.passengerName === passengerName
    );
    this.bookings.splice(indexElement, 1)[0];

    return `Booking for passenger ${passengerName} on flight ${flightNumber} is cancelled.`;
  }

  showBookings(criteria) {
    if (this.bookings.length === 0) {
      throw new Error(`No bookings have been made yet.`);
    }

    if (criteria === "all") {

      let line = `All bookings(${this.bookingsCount}):\n`;

      this.bookings.forEach(
        (x) =>
          (line += `${x.passengerName} booked for flight ${x.flightNumber}.\n`)
      );
      return line;

    }
    else if (criteria === "cheap") {

      let cheapBookings = this.bookings.filter((booking) => {
        const flight = this.flights.find(
          (x) => x.flightNumber === booking.flightNumber
        );
        return flight && flight.price <= 100;
      });

      if (cheapBookings.length === 0) {
        return `No cheap bookings found.`;
      }

      let line = `Cheap bookings:`;
      cheapBookings.forEach(
        (x) =>
          (line += `\n${x.passengerName} booked for flight ${x.flightNumber}.`)
      );
      return line;

    }
    else if (criteria === "expensive") {

      let expensiveBookings = this.bookings.filter((booking) => {
        const flight = this.flights.find(
          (x) => x.flightNumber === booking.flightNumber
        );
        return flight && flight.price > 100;
      });

      if (expensiveBookings.length === 0) {
        return "No expensive bookings found.";
      }

      let line = "Expensive bookings:";
      expensiveBookings.forEach(
        (x) =>
          (line += `\n${x.passengerName} booked for flight ${x.flightNumber}.`)
      );
      return line;
    }
  }
}

const system = new FlightBookingSystem("TravelWorld");
console.log(system.addFlight("AA101", "Los Angeles", "09:00 AM", 250));
console.log(system.addFlight("BB202", "New York", "10:30 AM", 180));
console.log(system.bookFlight("Alice", "AA101"));
console.log(system.bookFlight("Bob", "BB202"));
console.log(system.showBookings("expensive"));
console.log(system.showBookings("cheap"));