import {
  BadRequestException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { BookingEntity, BookingStatus } from '../../entities/booking.entity';
import { BusinessServiceEntity } from '../../entities/business-service.entity';
import { BusinessEntity } from '../../entities/business.entity';
import { UserEntity } from '../../entities/user.entity';
import { CreateBookingDto } from './dto/create-booking.dto';
import { UpdateBookingDto } from './dto/update-booking.dto';

type FindAllFilters = {
  customerId?: string;
  businessId?: string;
  status?: BookingStatus;
};

@Injectable()
export class BookingsService {
  private readonly minLeadMinutes: number;

  constructor(
    private readonly config: ConfigService,
    @InjectRepository(BookingEntity)
    private readonly repo: Repository<BookingEntity>,
    @InjectRepository(UserEntity)
    private readonly userRepo: Repository<UserEntity>,
    @InjectRepository(BusinessEntity)
    private readonly businessRepo: Repository<BusinessEntity>,
    @InjectRepository(BusinessServiceEntity)
    private readonly businessServiceRepo: Repository<BusinessServiceEntity>,
  ) {
    const raw = this.config.get<string | undefined>('BOOKING_MIN_LEAD_MINUTES');
    const parsed = raw !== undefined ? Number.parseInt(String(raw), 10) : NaN;
    this.minLeadMinutes = Number.isFinite(parsed) && parsed >= 0 ? parsed : 60;
  }

  async findAll(filters: FindAllFilters): Promise<BookingEntity[]> {
    const qb = this.repo
      .createQueryBuilder('b')
      .leftJoinAndSelect('b.customer', 'customer')
      .leftJoinAndSelect('b.business', 'business')
      .leftJoinAndSelect('b.businessService', 'businessService')
      .leftJoinAndSelect('businessService.serviceTemplate', 'template')
      .orderBy('b.scheduledAt', 'ASC');

    if (filters.customerId) {
      qb.andWhere('b.customerId = :customerId', {
        customerId: filters.customerId,
      });
    }
    if (filters.businessId) {
      qb.andWhere('b.businessId = :businessId', {
        businessId: filters.businessId,
      });
    }
    if (filters.status) {
      qb.andWhere('b.status = :status', { status: filters.status });
    }

    return qb.getMany();
  }

  async findOne(id: string): Promise<BookingEntity> {
    const row = await this.repo.findOne({
      where: { id },
      relations: {
        customer: true,
        business: true,
        businessService: { serviceTemplate: true },
      },
    });
    if (!row) {
      throw new NotFoundException('Booking not found');
    }
    return row;
  }

  async create(dto: CreateBookingDto): Promise<BookingEntity> {
    const customer = await this.userRepo.findOne({
      where: { id: dto.customerId },
    });
    if (!customer) {
      throw new NotFoundException('User not found');
    }

    const business = await this.businessRepo.findOne({
      where: { id: dto.businessId },
    });
    if (!business) {
      throw new NotFoundException('Business not found');
    }

    const businessService = await this.businessServiceRepo.findOne({
      where: { id: dto.businessServiceId },
      relations: { business: true },
    });
    if (!businessService) {
      throw new NotFoundException('Business service not found');
    }

    if (businessService.businessId !== dto.businessId) {
      throw new BadRequestException(
        'businessService does not belong to the given business',
      );
    }

    const scheduledAt = this.parseScheduledAt(dto.scheduledAt);
    this.assertLeadTime(scheduledAt);

    const entity = this.repo.create({
      customerId: dto.customerId,
      businessId: dto.businessId,
      businessServiceId: dto.businessServiceId,
      scheduledAt,
      note: dto.note ?? null,
      status: BookingStatus.PENDING,
    });

    return this.repo.save(entity);
  }

  async update(id: string, dto: UpdateBookingDto): Promise<BookingEntity> {
    const row = await this.findOne(id);

    if (dto.scheduledAt !== undefined) {
      const scheduledAt = this.parseScheduledAt(dto.scheduledAt);
      this.assertLeadTime(scheduledAt);
      row.scheduledAt = scheduledAt;
    }

    if (dto.status !== undefined) {
      row.status = dto.status;
    }

    if (dto.note !== undefined) {
      row.note = dto.note;
    }

    return this.repo.save(row);
  }

  async remove(id: string): Promise<void> {
    const result = await this.repo.delete(id);
    if (!result.affected) {
      throw new NotFoundException('Booking not found');
    }
  }

  private parseScheduledAt(raw: string): Date {
    const d = new Date(raw);
    if (Number.isNaN(d.getTime())) {
      throw new BadRequestException('scheduledAt must be a valid ISO datetime');
    }
    return d;
  }

  private assertLeadTime(scheduledAt: Date): void {
    const minMs = this.minLeadMinutes * 60 * 1000;
    const earliest = Date.now() + minMs;
    if (scheduledAt.getTime() < earliest) {
      throw new BadRequestException(
        `scheduledAt must be at least ${this.minLeadMinutes} minute(s) after the current time`,
      );
    }
  }
}