from rest_framework import status, views, serializers, pagination
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 business import models as business_models
from .stock_change_views.mixins import StockChangeViewMixin


class PurchaseOrderItemSerializer(serializers.ModelSerializer):
    class Meta:
        model = business_models.PurchaseOrderItem
        fields = [
            'id', 'product', 'price', 'color', 'quantity', 'unit',
            'empty_diff_percent', 'quantity_of_rolls', 'num_of_rolls',
            'batch_number', 'remarks', 'created_at', 'updated_at',
        ]
        read_only_fields = ['id', 'created_at', 'updated_at']


class PurchaseOrderSerializer(serializers.ModelSerializer):
    supplier_name = serializers.CharField(source='supplier.name', read_only=True)
    operator_name = serializers.CharField(source='operator.name', read_only=True)
    warehouse_name = serializers.CharField(source='warehouse.name', read_only=True)
    items = PurchaseOrderItemSerializer(many=True, read_only=True)

    class Meta:
        model = business_models.PurchaseOrder
        fields = [
            'id', 'supplier', 'supplier_name', 'purchase_date', 'kind',
            'operator', 'operator_name', 'warehouse', 'warehouse_name',
            'status', 'remarks', 'created_at', 'updated_at', 'items',
        ]
        read_only_fields = ['id', 'created_at', 'updated_at', 'items', 'supplier_name', 'operator_name', 'warehouse_name']


class PurchaseOrderPagination(pagination.LimitOffsetPagination):
    default_limit = 20
    max_limit = 100


class PurchaseOrderView(StockChangeViewMixin, views.APIView):
    """采购订单查询与创建"""

    permission_classes = [IsAuthenticated]
    pagination_class = PurchaseOrderPagination

    def get(self, request):
        if not self.check_employee_permission(request):
            return self.permission_error_response('无权限访问')
        
        merchant = request.user.employee.merchant
        queryset = business_models.PurchaseOrder.objects.filter(merchant=merchant).prefetch_related('items', 'supplier', 'operator', 'warehouse')
        paginator = self.pagination_class()
        page = paginator.paginate_queryset(queryset.order_by('-created_at'), request, view=self)
        serializer = PurchaseOrderSerializer(page, many=True)
        return paginator.get_paginated_response(serializer.data)

    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_id') or data.get('warehouse')
        order_date = data.get('order_date')
        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)
        if not order_date:
            return Response({'error': '缺少 order_date'}, status=status.HTTP_400_BAD_REQUEST)
        if not isinstance(items, list) or not items:
            return Response({'error': 'items 需要为非空数组'}, 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:
            warehouse = 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)

        operator = request.user.employee

        try:
            purchase_order = business_services.create_purchase_order(
                merchant=merchant,
                supplier=supplier,
                order_date=order_date,
                warehouse=warehouse,
                operator=operator,
                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,
        )