import { Injectable, NotFoundException, BadRequestException } from '@nestjs/common';
import { PrismaService } from '../../common/prisma.service';
import * as QRCode from 'qrcode';

interface OfflineValidation {
  bookingRef: string;
  validatorId: string;
  gateId?: string;
  validatedAt: string;
}

@Injectable()
export class TicketsService {
  constructor(private prisma: PrismaService) {}

  async listTickets(filters: { search?: string; status?: string; skip: number; take: number }) {
    const where: any = {};
    if (filters.search) {
      where.OR = [
        { bookingRef: { contains: filters.search, mode: 'insensitive' } },
        { barcodePayload: { contains: filters.search, mode: 'insensitive' } },
        { booking: { bookingRef: { contains: filters.search, mode: 'insensitive' } } },
      ];
    }
    if (filters.status) {
      where.booking = { status: filters.status };
    }
    const tickets = await this.prisma.ticket.findMany({
      where,
      include: {
        booking: {
          include: {
            schedule: { include: { originStation: true, destinationStation: true, train: true } },
            seats: { include: { seat: { include: { coach: true } } } },
            passenger: { include: { user: true } },
          },
        },
      },
      skip: filters.skip,
      take: filters.take,
      orderBy: { issuedAt: 'desc' },
    });
    const total = await this.prisma.ticket.count({ where });
    return {
      items: tickets.map((t) => ({
        id: t.id,
        ticketNumber: t.barcodePayload,
        bookingRef: t.bookingRef,
        booking: {
          bookingRef: t.booking.bookingRef,
          status: t.booking.status,
          totalMinor: t.booking.totalMinor,
          currency: t.booking.currency,
          displayCurrency: t.booking.displayCurrency,
          displayTotalMinor: t.booking.displayTotalMinor,
          passenger: t.booking.passenger?.user || { fullName: 'Guest', email: t.booking.contactEmail },
          contactEmail: t.booking.contactEmail,
        },
        schedule: t.booking.schedule,
        seat: t.booking.seats[0]?.seat,
        status: t.status,
        validatedAt: t.validatedAt,
        createdAt: t.issuedAt,
      })),
      total,
      skip: filters.skip,
      take: filters.take,
    };
  }

  async generate(bookingId: string) {
    if (!bookingId) {
      throw new BadRequestException('Booking ID is required');
    }
    
    const booking = await this.prisma.booking.findUnique({
      where: { id: bookingId },
      include: { 
        schedule: { include: { originStation: true, destinationStation: true, train: true } }, 
        seats: { include: { seat: { include: { coach: true } } } } 
      },
    });
    if (!booking) throw new NotFoundException(`Booking ${bookingId} not found`);
    
    const qrPayload = await QRCode.toDataURL(`edr:tkt:${booking.id}:${booking.bookingRef}`);
    const barcodePayload = `EDR${booking.bookingRef}${booking.id.substring(0, 8).toUpperCase()}`;
    
    const ticket = await this.prisma.ticket.upsert({
      where: { bookingId },
      update: { qrPayload, barcodePayload },
      create: { bookingId, bookingRef: booking.bookingRef, qrPayload, barcodePayload },
    });

    // Update all booked seats from HELD to BOOKED and create permanent seat blocks
    const seatIds = booking.seats.map(bs => bs.seatId);
    for (const seatId of seatIds) {
      // Update seat status to BOOKED
      await this.prisma.seat.update({
        where: { id: seatId },
        data: { status: 'BOOKED' },
      });
      // Create permanent seat blocks for all booked seats
      await this.prisma.seatBlock.create({
        data: {
          seatId,
          reason: `Permanently booked in ticket ${ticket.id}`,
          blockedBy: 'SYSTEM',
          approvedBy: 'SYSTEM',
        }
      }).catch(() => null); // Ignore if already exists
    }
    
    return ticket;
  }

  async updateSeats(bookingId: string, newSeatIds: string[]) {
    const booking = await this.prisma.booking.findUnique({
      where: { id: bookingId },
      include: { seats: true, ticket: true },
    });
    if (!booking) throw new NotFoundException(`Booking ${bookingId} not found`);
    if (!booking.ticket) throw new BadRequestException('No ticket found for this booking');

    // Remove old seat blocks
    const oldSeatIds = booking.seats.map(bs => bs.seatId);
    for (const seatId of oldSeatIds) {
      await this.prisma.seatBlock.deleteMany({
        where: { 
          seatId,
          reason: { contains: booking.ticket.id }
        }
      });
    }

    // Remove old booking seats
    await this.prisma.bookingSeat.deleteMany({ where: { bookingId } });

    // Create new seat blocks
    for (const seatId of newSeatIds) {
      await this.prisma.seatBlock.create({
        data: {
          seatId,
          reason: `Permanently booked in ticket ${booking.ticket.id}`,
          blockedBy: 'SYSTEM',
          approvedBy: 'SYSTEM',
        }
      }).catch(() => null);
    }

    // Create new booking seats (placeholder with minimal data)
    for (let i = 0; i < newSeatIds.length; i++) {
      await this.prisma.bookingSeat.create({
        data: {
          bookingId,
          seatId: newSeatIds[i],
          passengerName: `Passenger ${i + 1}`,
        }
      });
    }

    return { success: true, updatedSeats: newSeatIds.length };
  }

  async getByMerchantOrderId(merchantOrderId: string) {
    const intent = await this.prisma.paymentIntent.findUnique({
      where: { merchantOrderId },
      select: { bookingId: true },
    });
    if (!intent) throw new NotFoundException(`No payment intent found for order ${merchantOrderId}`);
    const booking = await this.prisma.booking.findUnique({
      where: { id: intent.bookingId },
      include: { schedule: { include: { originStation: true, destinationStation: true, train: true } }, seats: { include: { seat: { include: { coach: true } } } }, ticket: true },
    });
    if (!booking?.ticket) throw new NotFoundException('Ticket not found');
    const seat = booking.seats[0];
    return {
      id: booking.ticket.id, bookingId: booking.id, bookingRef: booking.bookingRef, status: booking.status,
      fromStationName: booking.schedule.originStation.name, toStationName: booking.schedule.destinationStation.name,
      departureAt: booking.schedule.departureAt, trainName: booking.schedule.train.name,
      coachLabel: seat?.seat.coach.number, seatLabel: seat?.seat.seatNumber, passengerName: seat?.passengerName,
      priceMinor: booking.totalMinor, currency: booking.currency, qrPayload: booking.ticket.qrPayload,
      barcodePayload: booking.ticket.barcodePayload,
    };
  }

  async getByRef(bookingRef: string) {
    const booking = await this.prisma.booking.findUnique({
      where: { bookingRef },
      include: { 
        schedule: { include: { originStation: true, destinationStation: true, train: true } }, 
        seats: { include: { seat: { include: { coach: true } } } }, 
        ticket: true 
      },
    });
    if (!booking?.ticket) throw new NotFoundException('Ticket not found');
    const seat = booking.seats[0];
    return {
      id: booking.ticket.id, 
      bookingId: booking.id, 
      bookingRef: booking.bookingRef, 
      status: booking.status,
      fromStationName: booking.schedule.originStation.name, 
      toStationName: booking.schedule.destinationStation.name,
      departureAt: booking.schedule.departureAt, 
      trainName: booking.schedule.train.name,
      coachLabel: seat?.seat.coach.number, 
      seatLabel: seat?.seat.seatNumber, 
      passengerName: seat?.passengerName,
      priceMinor: booking.totalMinor, 
      currency: booking.currency, 
      qrPayload: booking.ticket.qrPayload,
      barcodePayload: booking.ticket.barcodePayload
    };
  }

  async validate(bookingRef: string, validatorId: string, gateId?: string) {
    const booking = await this.prisma.booking.findUnique({ where: { bookingRef } });
    if (!booking) throw new NotFoundException('Booking not found');
    const ticket = await this.prisma.ticket.findUnique({ where: { bookingId: booking.id } });
    if (!ticket) throw new NotFoundException('Ticket not found');
    if (ticket.validatedAt) {
      await this.prisma.gateValidationLog.create({
        data: { ticketId: ticket.id, validatorId, gateId, status: 'REJECTED', reason: 'ALREADY_VALIDATED' }
      });
      throw new BadRequestException('Ticket already validated');
    }
    await this.prisma.ticket.update({ where: { id: ticket.id }, data: { validatedAt: new Date(), validatorId } });
    await this.prisma.gateValidationLog.create({
      data: { ticketId: ticket.id, validatorId, gateId, status: 'APPROVED' }
    });
    return { validated: true, ticketId: ticket.id, validatedAt: new Date() };
  }

  async getValidationLogs(ticketId: string) {
    return this.prisma.gateValidationLog.findMany({
      where: { ticketId },
      orderBy: { validatedAt: 'desc' }
    });
  }

  async exportOfflineData(tripId: string) {
    const bookings = await this.prisma.booking.findMany({
      where: { scheduleId: tripId, status: 'CONFIRMED' },
      include: {
        ticket: true,
        seats: { include: { seat: { include: { coach: true } } } },
        passenger: { include: { user: true } },
      },
    });

    return bookings.map((b) => ({
      bookingRef: b.bookingRef,
      ticketId: b.ticket?.id,
      passengerName: b.seats[0]?.passengerName,
      seatLabel: b.seats[0]?.seat.seatNumber,
      coachLabel: b.seats[0]?.seat.coach.number,
      qrPayload: b.ticket?.qrPayload,
      status: b.status,
      validatedAt: b.ticket?.validatedAt,
    }));
  }

  async validateOfflineBatch(validations: OfflineValidation[]) {
    const results = { success: 0, failed: 0, duplicate: 0, errors: [] as string[] };
    const processedRefs = new Set<string>();

    for (const v of validations) {
      if (processedRefs.has(v.bookingRef)) {
        results.duplicate++;
        continue;
      }
      processedRefs.add(v.bookingRef);

      try {
        const booking = await this.prisma.booking.findUnique({ where: { bookingRef: v.bookingRef } });
        if (!booking) {
          results.failed++;
          results.errors.push(`Booking ${v.bookingRef} not found`);
          continue;
        }

        const ticket = await this.prisma.ticket.findUnique({ where: { bookingId: booking.id } });
        if (!ticket) {
          results.failed++;
          results.errors.push(`Ticket for ${v.bookingRef} not found`);
          continue;
        }

        if (ticket.validatedAt) {
          results.duplicate++;
          continue;
        }

        await this.prisma.ticket.update({
          where: { id: ticket.id },
          data: { validatedAt: new Date(v.validatedAt), validatorId: v.validatorId },
        });

        await this.prisma.gateValidationLog.create({
          data: {
            ticketId: ticket.id,
            validatorId: v.validatorId,
            gateId: v.gateId,
            status: 'APPROVED',
            validatedAt: new Date(v.validatedAt),
          },
        });

        results.success++;
      } catch (err) {
        results.failed++;
        results.errors.push(`Error processing ${v.bookingRef}: ${err instanceof Error ? err.message : String(err)}`);
      }
    }

    return results;
  }

  async delete(id: string) {
    const ticket = await this.prisma.ticket.findUnique({ where: { id } });
    if (!ticket) throw new NotFoundException('Ticket not found');
    
    await this.prisma.gateValidationLog.deleteMany({ where: { ticketId: id } });
    
    // Remove seat blocks associated with this ticket
    await this.prisma.seatBlock.deleteMany({
      where: { 
        reason: { contains: id }
      }
    });
    
    await this.prisma.ticket.delete({ where: { id } });
    
    return { deleted: true, ticketId: id };
  }
}