import { Injectable, NotFoundException, BadRequestException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { Deposit } from '../entities/deposit.entity';
import { Student } from '../entities/student.entity';
import { DepositInstallment } from '../entities/deposit-installment.entity';

import { CreateDepositDto, RefundDepositDto } from './dto/deposit.dto';

const money = (value: number | string | null | undefined) => Number(Number(value || 0).toFixed(2));

@Injectable()
export class DepositsService {

  constructor(
    @InjectRepository(Deposit) private repo: Repository<Deposit>,
    @InjectRepository(DepositInstallment)
    private installmentRepo: Repository<DepositInstallment>,
    @InjectRepository(Student)
    private studentRepo: Repository<Student>,
  ) {}

  async getStudentLookups() {
    return this.studentRepo.find({
      select: ['id', 'name', 'studentNo'],
      where: { status: 'active' },
      order: { name: 'ASC' },
    });
  }

  async findAll(query?: { studentId?: number; status?: string }) {
    const qb = this.repo
      .createQueryBuilder('d')
      .leftJoinAndSelect('d.student', 'student')
      .leftJoinAndSelect('d.installments', 'installments')
      .orderBy('d.createdAt', 'DESC');
    if (query?.studentId) qb.andWhere('d.studentId = :studentId', { studentId: query.studentId });
    if (query?.status) qb.andWhere('d.status = :status', { status: query.status });
    return qb.getMany();
  }

  async findOne(id: number) {
    const deposit = await this.repo.findOne({ where: { id }, relations: ['student', 'installments'] });
    if (!deposit) throw new NotFoundException('押金记录不存在');
    return deposit;
  }

  async create(dto: CreateDepositDto, userId?: number) {
    const student = await this.studentRepo.findOne({ where: { id: dto.studentId } });
    if (!student) throw new NotFoundException('学生不存在');
    const amount = money(dto.amount);
    if (!Number.isFinite(dto.amount) || Math.abs(dto.amount * 100 - Math.round(dto.amount * 100)) > 1e-8) {
      throw new BadRequestException('收取金额最多保留两位小数');
    }
    if (amount <= 0) throw new BadRequestException('收取金额必须大于0');

    const existing = await this.repo.findOne({ where: { studentId: dto.studentId } });
    if (existing) {
      existing.amount = money(Number(existing.amount || 0) + amount);
      existing.paidDate = dto.paidDate;
      existing.status = 'paid';
      existing.recordedBy = userId ?? null;
      existing.refundDate = null as unknown as string;
      existing.refundAmount = null as unknown as number;
      existing.refundedBy = null;
      existing.refundedAt = null;
      if (dto.notes) existing.notes = dto.notes;
      return this.repo.save(existing);
    }

    return this.repo.save(
      this.repo.create({
        studentId: dto.studentId,
        amount,
        paidDate: dto.paidDate,
        notes: dto.notes,
        status: 'paid',
        recordedBy: userId,
      }),
    );
  }

  async addInstallment(depositId: number, amount: number, dueDate: string) {
    const normalizedAmount = money(amount);
    if (!Number.isFinite(amount) || Math.abs(amount * 100 - Math.round(amount * 100)) > 1e-8) {
      throw new BadRequestException('分期金额最多保留两位小数');
    }
    if (normalizedAmount <= 0) throw new BadRequestException('分期金额必须大于0');
    const deposit = await this.repo.findOne({ where: { id: depositId } });
    if (!deposit) throw new NotFoundException('押金记录不存在');

    const installment = this.installmentRepo.create({
      depositId,
      amount: normalizedAmount,
      dueDate,
      status: 'pending',
    });
    return this.installmentRepo.save(installment);
  }

  async updateInstallment(id: number, data: { paidDate?: string; status?: string }) {
    const installment = await this.installmentRepo.findOne({ where: { id } });
    if (!installment) throw new NotFoundException('分期记录不存在');

    if (data.paidDate !== undefined) installment.paidDate = data.paidDate;
    if (data.status !== undefined) installment.status = data.status;
    return this.installmentRepo.save(installment);
  }

  async deleteInstallment(id: number) {
    const installment = await this.installmentRepo.findOne({ where: { id } });
    if (!installment) throw new NotFoundException('分期记录不存在');
    await this.installmentRepo.delete(id);
    return { message: '删除成功' };
  }

  async refund(id: number, dto: RefundDepositDto, userId?: number) {
    const deposit = await this.repo.findOne({ where: { id } });
    if (!deposit) throw new NotFoundException('押金记录不存在');
    if (deposit.status !== 'paid' || Number(deposit.amount) <= 0) {
      throw new BadRequestException('该学生当前没有可退押金');
    }

    const refundAmount = money(deposit.amount);

    deposit.refundDate = dto.refundDate;
    deposit.refundAmount = refundAmount;
    deposit.amount = 0;
    deposit.status = 'refunded';
    if (dto.notes) deposit.notes = dto.notes;
    deposit.refundedBy = userId ?? null;
    deposit.refundedAt = new Date();

    return this.repo.save(deposit);
  }

  async remove(id: number) {
    const deposit = await this.repo.findOne({ where: { id } });
    if (!deposit) throw new NotFoundException('押金记录不存在');
    await this.repo.delete(id);
    return { message: '删除成功' };
  }

  async getStats() {
    const qb = this.repo
      .createQueryBuilder('d')
      .select('d.status', 'status')
      .addSelect('COUNT(*)', 'count')
      .addSelect('SUM(d.amount)', 'totalAmount');
    qb.groupBy('d.status');
    return qb.getRawMany();
  }
}