import { BadRequestException, ConflictException, ForbiddenException, Injectable, NotFoundException } from '@nestjs/common';
import { DesignListStatus, OrderStatus, Prisma } from '@prisma/client';
import { PrismaService } from '../prisma/prisma.service';
import { CreateOrderDto } from './dto/create-order.dto';
import { OrderQueryDto } from './dto/order-query.dto';

const PAYMENT_TIMEOUT_MS = 30 * 60 * 1000;

function generateOrderNo(): string {
  const now = new Date();
  const ymd =
    now.getUTCFullYear().toString() +
    String(now.getUTCMonth() + 1).padStart(2, '0') +
    String(now.getUTCDate()).padStart(2, '0');
  const rand = Math.random().toString(36).slice(2, 8).toUpperCase();
  return `${ymd}${rand}`;
}

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

  private serialize(order: any) {
    return {
      ...order,
      totalAmount: Number(order.totalAmount),
      paidAt: order.paidAt?.toISOString?.() ?? null,
      paymentExpiresAt: order.paymentExpiresAt?.toISOString?.() ?? null,
      createdAt: order.createdAt.toISOString(),
      updatedAt: order.updatedAt.toISOString(),
      items: order.items?.map((item: any) => ({
        ...item,
        price: Number(item.price),
      })),
    };
  }

  async listByUser(userId: string, query: OrderQueryDto) {
    await this.expirePendingOrders({ userId });
    const where = { userId, ...(query.status ? { status: query.status } : {}) };
    const [rows, total] = await this.prisma.$transaction([
      this.prisma.order.findMany({
        where,
        include: { items: true, payment: true },
        orderBy: { createdAt: 'desc' },
        skip: (query.page - 1) * query.pageSize,
        take: query.pageSize,
      }),
      this.prisma.order.count({ where }),
    ]);
    return { list: rows.map((row) => this.serialize(row)), total, page: query.page, pageSize: query.pageSize };
  }

  async findOne(userId: string, id: string) {
    await this.expirePendingOrders({ id, userId });
    const order = await this.prisma.order.findUnique({ where: { id }, include: { items: true, payment: true } });
    if (!order) throw new NotFoundException('订单不存在');
    if (order.userId !== userId) throw new ForbiddenException('无权访问该订单');
    return this.serialize(order);
  }

  async create(userId: string, dto: CreateOrderDto) {
    if (dto.requestId) {
      const existing = await this.prisma.order.findFirst({
        where: { userId, requestId: dto.requestId },
        include: { items: true, payment: true },
      });
      if (existing) return this.serialize(existing);
    }

    const address = await this.prisma.address.findUnique({ where: { id: dto.addressId } });
    if (!address) throw new NotFoundException('地址不存在');
    if (address.userId !== userId) throw new ForbiddenException('无权使用该地址');

    const design = dto.designListId
      ? await this.prisma.designList.findUnique({ where: { id: dto.designListId } })
      : null;
    if (dto.designListId && !design) throw new NotFoundException('设计清单不存在');
    if (design && design.userId !== userId) throw new ForbiddenException('无权使用该设计清单');

    const products = await this.prisma.product.findMany({
      where: { id: { in: dto.items.map((item) => item.productId) }, status: 'ON_SALE' },
    });
    if (products.length !== new Set(dto.items.map((item) => item.productId)).size) {
      throw new BadRequestException('存在无效或已下架商品');
    }

    const byId = new Map(products.map((product) => [product.id, product]));
    const total = dto.items.reduce(
      (sum, item) => sum.plus(new Prisma.Decimal(byId.get(item.productId)!.price).mul(item.quantity)),
      new Prisma.Decimal(0),
    );
    const addressSnapshot = {
      id: address.id,
      name: address.name,
      phone: address.phone,
      province: address.province,
      city: address.city,
      district: address.district,
      detail: address.detail,
    };
    const paymentExpiresAt = new Date(Date.now() + PAYMENT_TIMEOUT_MS);

    try {
      const created = await this.prisma.$transaction(async (tx) => {
        let orderNo = generateOrderNo();
        for (let attempt = 0; attempt < 3; attempt += 1) {
          const collision = await tx.order.findUnique({ where: { orderNo }, select: { id: true } });
          if (!collision) break;
          orderNo = generateOrderNo();
        }

        const order = await tx.order.create({
          data: {
            orderNo,
            user: { connect: { id: userId } },
            requestId: dto.requestId,
            totalAmount: total,
            paymentExpiresAt,
            addressSnapshot: addressSnapshot as Prisma.InputJsonValue,
            designList: dto.designListId ? { connect: { id: dto.designListId } } : undefined,
            items: {
              create: dto.items.map((item) => ({
                productId: item.productId,
                name: byId.get(item.productId)!.name,
                price: byId.get(item.productId)!.price,
                quantity: item.quantity,
              })),
            },
            payment: { create: { status: 'PENDING' } },
          },
          include: { items: true, payment: true },
        });

        if (dto.designListId) {
          await tx.designList.updateMany({
            where: {
              id: dto.designListId,
              status: { in: [DesignListStatus.DRAFT, DesignListStatus.SUBMITTED] },
            },
            data: { status: DesignListStatus.PROCESSING },
          });
        }
        return order;
      });
      return this.serialize(created);
    } catch (error) {
      if (error instanceof Prisma.PrismaClientKnownRequestError && error.code === 'P2002') {
        const existing = dto.requestId
          ? await this.prisma.order.findFirst({
              where: { userId, requestId: dto.requestId },
              include: { items: true, payment: true },
            })
          : null;
        if (existing) return this.serialize(existing);
        throw new ConflictException('订单号冲突，请重试');
      }
      throw error;
    }
  }

  async cancel(userId: string, id: string) {
    const order = await this.getOwned(userId, id);
    if (order.status !== OrderStatus.PENDING) throw new ConflictException('仅待付款订单可取消');
    const updated = await this.prisma.order.update({
      where: { id },
      data: { status: OrderStatus.CANCELLED },
      include: { items: true, payment: true },
    });
    return this.serialize(updated);
  }

  async confirm(userId: string, id: string) {
    const order = await this.getOwned(userId, id);
    if (order.status !== OrderStatus.SHIPPED) throw new ConflictException('仅待收货订单可确认收货');
    const updated = await this.prisma.$transaction(async (tx) => {
      const completed = await tx.order.update({
        where: { id },
        data: { status: OrderStatus.COMPLETED },
        include: { items: true, payment: true },
      });
      if (order.designListId) {
        await tx.designList.updateMany({
          where: { id: order.designListId, status: DesignListStatus.PROCESSING },
          data: { status: DesignListStatus.DONE },
        });
      }
      return completed;
    });
    return this.serialize(updated);
  }

  private async getOwned(userId: string, id: string) {
    await this.expirePendingOrders({ id, userId });
    const order = await this.prisma.order.findUnique({ where: { id }, include: { items: true, payment: true } });
    if (!order) throw new NotFoundException('订单不存在');
    if (order.userId !== userId) throw new ForbiddenException('无权操作该订单');
    return order;
  }

  private async expirePendingOrders(where: Prisma.OrderWhereInput) {
    await this.prisma.order.updateMany({
      where: {
        ...where,
        status: OrderStatus.PENDING,
        paymentExpiresAt: { lte: new Date() },
      },
      data: { status: OrderStatus.PAYMENT_EXPIRED },
    });
  }
}