import { NextResponse } from 'next/server';
import { prisma } from '@/lib/db';
import { getSessionUser } from '@/lib/auth';

export async function POST(request: Request) {
  try {
    const body = await request.json();
    const {
      scheduleId,
      passengerName,
      passengerEmail,
      passengerPhone,
      seats, // Array of strings, e.g. ["1", "2"] or ["1A", "1B"]
    } = body;

    if (!scheduleId || !passengerName || !passengerEmail || !passengerPhone || !seats || !Array.isArray(seats) || seats.length === 0) {
      return NextResponse.json(
        { error: 'Missing required booking details or seat selections' },
        { status: 400 }
      );
    }

    // Fetch schedule to get the price
    const schedule = await prisma.schedule.findUnique({
      where: { id: Number(scheduleId) },
    });

    if (!schedule) {
      return NextResponse.json({ error: 'Schedule not found' }, { status: 404 });
    }

    // Check optional user session link
    const userSession = await getSessionUser();
    const userId = userSession ? userSession.userId : null;

    // Calculate total price
    const unitPrice = Number(schedule.price);
    const totalPrice = unitPrice * seats.length;

    // Generate unique booking code
    const bookingCode = 'TRV-' + Math.random().toString(36).substring(2, 8).toUpperCase();

    // Perform database transaction to ensure atomic operations (no double seat bookings)
    const booking = await prisma.$transaction(async (tx) => {
      // 1. Check if any selected seat is already occupied for this schedule
      const occupied = await tx.bookingSeat.findMany({
        where: {
          scheduleId: Number(scheduleId),
          seatNumber: { in: seats },
          booking: {
            status: { in: ['PENDING', 'PAID'] },
          },
        },
      });

      if (occupied.length > 0) {
        throw new Error('One or more selected seats have already been booked. Please choose other seats.');
      }

      // 2. Create the booking record
      const newBooking = await tx.booking.create({
        data: {
          bookingCode,
          scheduleId: Number(scheduleId),
          userId,
          passengerName,
          passengerEmail,
          passengerPhone,
          totalPrice,
          status: 'PENDING',
        },
      });

      // 3. Create the booking seat records
      const seatRecords = seats.map((seat: string) => ({
        bookingId: newBooking.id,
        scheduleId: Number(scheduleId),
        seatNumber: seat,
      }));

      await tx.bookingSeat.createMany({
        data: seatRecords,
      });

      return newBooking;
    });

    return NextResponse.json({ success: true, bookingCode: booking.bookingCode, bookingId: booking.id });
  } catch (error: any) {
    console.error('Create booking transaction error:', error);
    return NextResponse.json(
      { error: error.message || 'Failed to process booking. Please try again.' },
      { status: 400 }
    );
  }
}