from decimal import Decimal, InvalidOperation

from rest_framework import status, views
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response

from basic_info import models as basic_models
from business import services as business_services
from .stock_change_views.mixins import StockChangeViewMixin


class PurchaseOrderView(StockChangeViewMixin, views.APIView):
    """创建采购订单并触发入库任务"""

    permission_classes = [IsAuthenticated]

    def post(self, request):
        if not self.check_employee_permission(request):
            return self.permission_error_response('无权限访问')

        merchant = request.user.employee.merchant
        data = request.data or {}

        supplier_id = data.get('supplier')
        warehouse_id = data.get('warehouse')
        order_date = data.get('order_date')
        total_amount = data.get('total_amount')
        items = data.get('items', [])
        remarks = data.get('remarks', '')

        if not supplier_id:
            return Response({'error': '缺少供应商 ID'}, status=status.HTTP_400_BAD_REQUEST)
        if not warehouse_id:
            return Response({'error': '缺少仓库 ID'}, status=status.HTTP_400_BAD_REQUEST)

        try:
            supplier = basic_models.Supplier.objects.get(id=supplier_id, merchant=merchant)
        except basic_models.Supplier.DoesNotExist:
            return Response({'error': f'供应商 {supplier_id} 不存在'}, status=status.HTTP_400_BAD_REQUEST)

        try:
            basic_models.WareHouse.objects.get(id=warehouse_id, merchant=merchant)
        except basic_models.WareHouse.DoesNotExist:
            return Response({'error': f'仓库 {warehouse_id} 不存在'}, status=status.HTTP_400_BAD_REQUEST)

        try:
            total_amount_decimal = Decimal(str(total_amount))
        except (InvalidOperation, TypeError):
            return Response({'error': 'total_amount 必须为合法数值'}, status=status.HTTP_400_BAD_REQUEST)

        try:
            purchase_order = business_services.create_purchase_order(
                merchant=merchant,
                supplier=supplier,
                order_date=order_date,
                total_amount=total_amount_decimal,
                warehouse_id=warehouse_id,
                items=items,
                remarks=remarks,
                created_by=request.user,
            )
        except ValueError as exc:
            return Response({'error': str(exc)}, status=status.HTTP_400_BAD_REQUEST)

        return Response(
            {
                'id': purchase_order.id,
                'message': '采购单创建成功，入库任务已排队',
            },
            status=status.HTTP_201_CREATED,
        )