import { Injectable, NotFoundException } from '@nestjs/common';
import { PrismaService } from '../../common/prisma.service';
import { SearchTripsDto, FareQuoteDto } from './search.dto';
import { CurrencyService } from '../currency/currency.service';
import { FareEngineService } from '../fare-engine/fare-engine.service';
import { SegmentsService } from '../segments/segments.service';
import { Currency } from '@prisma/client';

const POINTS_TO_MINOR = 10;

@Injectable()
export class SearchService {
  constructor(
    private prisma: PrismaService,
    private currencyService: CurrencyService,
    private fareEngine: FareEngineService,
    private segmentsService: SegmentsService,
  ) {}

  async searchTrips(dto: SearchTripsDto) {
    const outbound = await this.searchSchedules(
      dto.originStationId,
      dto.destinationStationId,
      dto.date,
      dto.adultCount,
      dto.childCount,
      dto.nationality,
    );

    if (dto.journeyType === 'ROUND_TRIP') {
      const allInbound = await this.searchSchedules(
        dto.destinationStationId,
        dto.originStationId,
        dto.returnDate ?? dto.date,
        dto.adultCount,
        dto.childCount,
        dto.nationality,
      );

      const latestOutboundArrival = outbound.length > 0
        ? Math.max(...outbound.map((s) => new Date(s.arrivalAt).getTime()))
        : Date.now();

      const inbound = allInbound.filter((schedule) =>
        new Date(schedule.departureAt).getTime() > latestOutboundArrival
      );

      return { journeyType: 'ROUND_TRIP', outbound, inbound };
    }

    return { journeyType: 'ONE_WAY', outbound };
  }

  private async searchSchedules(
    originStationId: string,
    destinationStationId: string,
    dateStr: string,
    adultCount: number,
    childCount?: number,
    nationality?: string,
  ) {
    const [y, m, d] = dateStr.split('-').map(Number);
    const date = new Date(y, m - 1, d, 0, 0, 0, 0);
    const nextDay = new Date(y, m - 1, d + 1, 0, 0, 0, 0);
    const totalPassengers = adultCount + (childCount ?? 0);

    const schedules = await this.prisma.trainSchedule.findMany({
      where: {
        status: { in: ['SCHEDULED', 'BOARDING'] },
        departureAt: { gte: date, lt: nextDay },
        stopTimes: { some: { stationId: originStationId } },
      },
      include: {
        train: true,
        originStation: true,
        destinationStation: true,
        stopTimes: { include: { station: true }, orderBy: { sequence: 'asc' } },
        coachAssignments: {
          include: { coach: { include: { seats: true, coachType: { include: { seatClasses: true } } } } },
        },
      },
    });

    const results = [];

    for (const schedule of schedules) {
      const originStop = schedule.stopTimes.find((s: any) => s.stationId === originStationId);
      const destStop = schedule.stopTimes.find((s: any) => s.stationId === destinationStationId);

      if (!originStop || !destStop || originStop.sequence >= destStop.sequence) continue;

      const availabilityByClass: Record<string, number> = {};

      for (const assignment of schedule.coachAssignments) {
        const seatClassNames = assignment.coach.coachType?.seatClasses?.map((sc: any) => sc.name) || ['Standard'];
        const isBedCoach = assignment.coach.seats.some((s: any) => s.bedPosition);

        if (isBedCoach) {
          const bedPositions = ['upper', 'middle', 'lower'];
          for (const bedPosition of bedPositions) {
            let count = 0;
            for (const seat of assignment.coach.seats) {
              if (seat.bedPosition !== bedPosition) continue;
              if (seat.status === 'BLOCKED') continue;
              if (!seat.seatNumber || !seat.seatNumber.trim()) continue;

              const free = await this.segmentsService.isSeatFreeForLeg(
                schedule.id, seat.id,
                originStop.sequence, destStop.sequence,
              );
              if (free) count++;
            }

            if (count > 0) {
              const matchingClass = seatClassNames.find((className: string) => {
                const classNameLower = className.toLowerCase();
                return (
                  (bedPosition === 'upper' && classNameLower.includes('upper')) ||
                  (bedPosition === 'middle' && classNameLower.includes('middle')) ||
                  (bedPosition === 'lower' && classNameLower.includes('lower'))
                );
              });
              if (matchingClass) {
                if (!availabilityByClass[matchingClass]) availabilityByClass[matchingClass] = 0;
                availabilityByClass[matchingClass] += count;
              }
            }
          }
        } else {
          let availableSeatsInCoach = 0;
          for (const seat of assignment.coach.seats) {
            if (seat.status === 'BLOCKED') continue;
            if (!seat.seatNumber || !seat.seatNumber.trim()) continue;

            const free = await this.segmentsService.isSeatFreeForLeg(
              schedule.id, seat.id,
              originStop.sequence, destStop.sequence,
            );
            if (free) availableSeatsInCoach++;
          }

          for (const seatClassName of seatClassNames) {
            if (!availabilityByClass[seatClassName]) availabilityByClass[seatClassName] = 0;
            availabilityByClass[seatClassName] += availableSeatsInCoach;
          }
        }
      }

      const legDepartureAt = originStop.plannedDepartureAt ?? schedule.departureAt;
      const legArrivalAt = destStop.plannedArrivalAt ?? schedule.arrivalAt;

      const faresByClass = await this.calculateFaresForSegment(
        schedule,
        originStationId,
        destinationStationId,
        nationality,
      );

      const coachTypes = await this.buildCoachTypeDetails(schedule, faresByClass);

      results.push({
        scheduleId: schedule.id,
        trainNumber: schedule.train.number,
        trainName: schedule.train.name,
        origin: {
          id: originStop.stationId,
          code: originStop.station.code,
          name: originStop.station.name,
          city: originStop.station.city,
          sequence: originStop.sequence,
        },
        destination: {
          id: destStop.stationId,
          code: destStop.station.code,
          name: destStop.station.name,
          city: destStop.station.city,
          sequence: destStop.sequence,
        },
        departureAt: legDepartureAt,
        arrivalAt: legArrivalAt,
        durationMinutes: Math.round(
          (new Date(legArrivalAt).getTime() - new Date(legDepartureAt).getTime()) / 60_000,
        ),
        status: schedule.status,
        stops: schedule.stopTimes
          .filter((st: any) => st.sequence >= originStop.sequence && st.sequence <= destStop.sequence)
          .map((st: any) => ({
            stationId: st.stationId,
            stationName: st.station.name,
            sequence: st.sequence,
            plannedArrivalAt: st.plannedArrivalAt,
            plannedDepartureAt: st.plannedDepartureAt,
          })),
        availabilityByClass,
        hasAvailability: Object.values(availabilityByClass).some(n => n >= totalPassengers),
        faresByClass,
        coachTypes,
      });
    }

    return results;
  }

  async getFareQuote(dto: FareQuoteDto) {
    const schedule = await this.prisma.trainSchedule.findUnique({
      where: { id: dto.scheduleId },
      include: {
        originStation: true,
        destinationStation: true,
        stopTimes: { include: { station: true }, orderBy: { sequence: 'asc' } },
      },
    });
    if (!schedule) throw new NotFoundException('Schedule not found');

    const originStop = schedule.stopTimes.find((s: any) => s.stationId === dto.originStationId);
    const destStop = schedule.stopTimes.find((s: any) => s.stationId === dto.destinationStationId);
    if (!originStop || !destStop || originStop.sequence >= destStop.sequence) {
      throw new NotFoundException('Origin or destination not found on this schedule');
    }

    const seatClass = await this.prisma.seatClass.findFirst({ where: { name: dto.seatClassName } });

    const segmentRoute = `${originStop.station.code}-${destStop.station.code}`;
    const fullRoute = `${schedule.originStation.code}-${schedule.destinationStation.code}`;
    const now = new Date();
    const nationality = dto.nationality;

    const candidates = await this.prisma.fareRule.findMany({
      where: {
        seatClassId: seatClass?.id,
        validFrom: { lte: now },
        OR: [
          { validUntil: null },
          { validUntil: { gte: now } },
        ],
      },
    });

    const bestMatch = this.selectBestFareRule(
      candidates,
      dto.scheduleId,
      segmentRoute,
      fullRoute,
      nationality,
    );

    const baseFareMinor = bestMatch?.baseFareMinor ?? this.defaultFare(dto.seatClassName);

    const adultCount = dto.adultCount;
    const childCount = dto.childCount ?? 0;
    const adultFareMinor = baseFareMinor * adultCount;
    const paidChildrenCount = Math.max(0, childCount - 1);
    const childFareMinor = baseFareMinor * paidChildrenCount;
    const totalBaseFareMinor = adultFareMinor + childFareMinor;

    let discountMinor = 0;
    if (dto.promoCode) {
      const promo = await this.prisma.promotion.findUnique({ where: { code: dto.promoCode } });
      if (promo?.active && promo.validUntil > now) {
        discountMinor = promo.percentOff
          ? Math.round(totalBaseFareMinor * promo.percentOff / 100)
          : (promo.amountOffMinor ?? 0);
      }
    }

    const loyaltyMinor = (dto.loyaltyRedemptionPoints ?? 0) * POINTS_TO_MINOR;
    const taxesMinor = Math.round(totalBaseFareMinor * 0.05);
    const totalMinor = Math.max(0, totalBaseFareMinor - discountMinor - loyaltyMinor + taxesMinor);

    const displayCurrency = dto.displayCurrency ?? Currency.ETB;
    const displayTotalMinor = displayCurrency !== Currency.ETB
      ? await this.currencyService.convertAmount(totalMinor, Currency.ETB, displayCurrency)
      : totalMinor;

    return {
      scheduleId: dto.scheduleId,
      originStationId: dto.originStationId,
      destinationStationId: dto.destinationStationId,
      segmentRoute,
      seatClassName: dto.seatClassName,
      nationality: dto.nationality,
      adultCount, childCount,
      baseFareMinor, adultFareMinor, childFareMinor,
      freeChildrenCount: Math.min(childCount, 1),
      paidChildrenCount, totalBaseFareMinor,
      discountMinor, loyaltyRedemptionMinor: loyaltyMinor,
      taxesFeesMinor: taxesMinor, totalMinor,
      currency: 'ETB', displayCurrency, displayTotalMinor,
    };
  }

  private async calculateFaresForSegment(
    schedule: any,
    originStationId: string,
    destinationStationId: string,
    nationality?: string,
  ): Promise<Array<{ seatClassName: string; baseFareMinor: number }>> {
    const seatClassIds: string[] = Array.from(
      new Set(
        schedule.coachAssignments
          .flatMap((a: any) => a.coach.coachType?.seatClasses || [])
          .map((sc: any) => sc.id)
          .filter((id: any) => id)
      )
    );

    if (seatClassIds.length === 0) {
      console.log(`No seat classes assigned to schedule ${schedule.id}`);
      return [];
    }

    const seatClasses = await this.prisma.seatClass.findMany({
      where: {
        isActive: true,
        id: { in: seatClassIds }
      },
      orderBy: { baseFareMinor: 'asc' },
    });

    if (seatClasses.length === 0) {
      console.log(`No active seat classes for schedule ${schedule.id}`);
      return [];
    }

    if (schedule.routeId) {
      const results = await Promise.all(
        seatClasses.map(async (sc) => {
          try {
            const fare = await this.fareEngine.calculate({
              routeId: schedule.routeId,
              originStationId,
              destinationStationId,
              seatClassId: sc.id,
              nationality,
            });
            return {
              seatClassName: fare.seatClassName,
              baseFareMinor: fare.baseFarePerPassengerMinor,
            };
          } catch (error) {
            console.error(`Failed to calculate fare for ${sc.name}:`, (error as Error).message);
            return null;
          }
        }),
      );

      const validResults = results.filter((r): r is { seatClassName: string; baseFareMinor: number } => r !== null);
      if (validResults.length > 0) {
        return validResults;
      }
    }

    const originStation = await this.prisma.station.findUnique({ where: { id: originStationId } });
    const destStation = await this.prisma.station.findUnique({ where: { id: destinationStationId } });

    if (originStation && destStation) {
      const segmentRoute = `${originStation.code}-${destStation.code}`;
      const now = new Date();

      const fareRules = await this.prisma.fareRule.findMany({
        where: {
          route: segmentRoute,
          seatClassId: { in: seatClassIds },
          validFrom: { lte: now },
          OR: [
            { validUntil: null },
            { validUntil: { gte: now } },
          ],
        },
      });

      if (fareRules.length > 0) {
        console.log(`Found ${fareRules.length} fare rules for segment ${segmentRoute}`);
        const seatClassMap = Object.fromEntries(seatClasses.map(sc => [sc.id, sc.name]));
        return fareRules.map(rule => ({
          seatClassName: seatClassMap[rule.seatClassId] || 'Unknown',
          baseFareMinor: rule.baseFareMinor,
        }));
      }
    }

    console.log(`No fares found, using defaults for ${originStationId} to ${destinationStationId}`);
    return seatClasses.map(sc => ({
      seatClassName: sc.name,
      baseFareMinor: this.getDefaultFareForClass(sc.name),
    }));
  }

  private async buildCoachTypeDetails(
    schedule: any,
    faresByClass: Array<{ seatClassName: string; baseFareMinor: number }>,
  ): Promise<Array<{
    coachTypeId: string;
    coachTypeName: string;
    coachTypeCode: string;
    classes: Array<{ name: string; baseFareMinor: number }>;
  }>> {
    const coachTypeMap = new Map<
      string,
      { coachType: any; classNames: Set<string> }
    >();

    for (const assignment of schedule.coachAssignments) {
      const coachType = assignment.coach.coachType;
      if (!coachType) continue;

      if (!coachTypeMap.has(coachType.id)) {
        coachTypeMap.set(coachType.id, {
          coachType,
          classNames: new Set(),
        });
      }

      const entry = coachTypeMap.get(coachType.id)!;
      coachType.seatClasses?.forEach((sc: any) => entry.classNames.add(sc.name));
    }

    const result = [];
    for (const [, { coachType, classNames }] of coachTypeMap) {
      const classes = Array.from(classNames)
        .map((className) => {
          const fareInfo = faresByClass.find((f) => f.seatClassName === className);
          return {
            name: className,
            baseFareMinor: fareInfo?.baseFareMinor ?? this.getDefaultFareForClass(className),
          };
        })
        .sort((a, b) => a.baseFareMinor - b.baseFareMinor);

      result.push({
        coachTypeId: coachType.id,
        coachTypeName: coachType.name,
        coachTypeCode: coachType.code,
        classes,
      });
    }

    return result.sort((a, b) => {
      const minPriceA = Math.min(...a.classes.map((c) => c.baseFareMinor));
      const minPriceB = Math.min(...b.classes.map((c) => c.baseFareMinor));
      return minPriceA - minPriceB;
    });
  }

  private getDefaultFareForClass(className: string): number {
    const defaults: Record<string, number> = {
      'Economy Regular': 35000,
      'Economy Bed': 49000,
      'VIP Bed': 63000,
    };
    return defaults[className] ?? 35000;
  }

  private defaultFare(seatClassName: string): number {
    const fares: Record<string, number> = {
      'Economy Regular': 45000,
      'Economy Bed': 65000,
      'VIP Bed': 95000,
    };
    return fares[seatClassName] ?? 45000;
  }

  private selectBestFareRule(
    candidates: any[],
    scheduleId: string,
    segmentRoute: string,
    fullRoute: string,
    nationality?: string,
  ): any | null {
    const priorities = [
      { tripId: scheduleId, route: segmentRoute, nationality },
      { tripId: scheduleId, route: segmentRoute, nationality: null },
      { tripId: scheduleId, route: fullRoute, nationality },
      { tripId: scheduleId, route: fullRoute, nationality: null },
      { tripId: scheduleId, route: null, nationality },
      { tripId: scheduleId, route: null, nationality: null },
      { tripId: null, route: segmentRoute, nationality },
      { tripId: null, route: segmentRoute, nationality: null },
      { tripId: null, route: fullRoute, nationality },
      { tripId: null, route: fullRoute, nationality: null },
      { tripId: null, route: null, nationality },
      { tripId: null, route: null, nationality: null },
    ];

    for (const priority of priorities) {
      const match = candidates.find(
        (c) =>
          c.tripId === priority.tripId &&
          c.route === priority.route &&
          c.nationality === priority.nationality,
      );
      if (match) return match;
    }

    return null;
  }
}