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

from api_v1.views.stock_change_views.mixins import StockChangeViewMixin
from business import models as business_models
from business import pre_order_services


class PrePurchaseOrderItemSerializer(serializers.ModelSerializer):
    class Meta:
        model = business_models.PrePurchaseOrderItem
        fields = [
            'id',
            'product_id',
            'product_name',
            'color',
            'quantity',
            'unit',
            'spec',
            'quantity_of_rolls',
            'num_of_rolls',
            'order_quantity',
            'remarks',
            'created_at',
            'updated_at',
        ]
        read_only_fields = ['id', 'created_at', 'updated_at']


class PrePurchaseOrderSerializer(serializers.ModelSerializer):
    human_id = serializers.CharField(read_only=True)
    merchant_name = serializers.CharField(source='merchant.name', read_only=True)
    supplier_name = serializers.CharField(source='supplier.name', read_only=True)
    warehouse_name = serializers.CharField(source='warehouse.name', read_only=True)
    created_by_username = serializers.CharField(source='created_by.username', read_only=True)
    operator_name = serializers.CharField(source='operator.name', read_only=True)
    items = PrePurchaseOrderItemSerializer(many=True, read_only=True)

    class Meta:
        model = business_models.PrePurchaseOrder
        fields = [
            'id',
            'human_id',
            'merchant',
            'merchant_name',
            'supplier',
            'supplier_name',
            'warehouse',
            'warehouse_name',
            'created_by',
            'created_by_username',
            'operator',
            'operator_name',
            'kind',
            'remarks',
            'created_at',
            'updated_at',
            'items',
        ]
        read_only_fields = [
            'id',
            'human_id',
            'created_at',
            'updated_at',
            'merchant_name',
            'supplier_name',
            'warehouse_name',
            'created_by_username',
            'operator_name',
            'items',
        ]


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


class PrePurchaseOrderView(StockChangeViewMixin, views.APIView):
    """预采购单查询与创建"""

    permission_classes = [IsAuthenticated]
    pagination_class = PrePurchaseOrderPagination

    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 = pre_order_services.list_pre_purchase_orders(merchant=merchant)

        paginator = self.pagination_class()
        page = paginator.paginate_queryset(queryset.order_by('-created_at'), request, view=self)
        serializer = PrePurchaseOrderSerializer(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
        employee = request.user.employee
        data = request.data or {}

        try:
            pre_purchase_order = pre_order_services.create_pre_purchase_order(
                merchant=merchant,
                supplier_id=data.get('supplier') or data.get('supplier_id'),
                warehouse_id=data.get('warehouse') or data.get('warehouse_id'),
                operator=employee,
                created_by=request.user,
                kind=data.get('kind'),
                items=data.get('items'),
                remarks=data.get('remarks', ''),
            )
        except ValueError as exc:
            return Response({'error': str(exc)}, status=status.HTTP_400_BAD_REQUEST)

        return Response(PrePurchaseOrderSerializer(pre_purchase_order).data, status=status.HTTP_201_CREATED)


class PrePurchaseOrderDetailView(StockChangeViewMixin, views.APIView):
    permission_classes = [IsAuthenticated]

    def _get_order(self, request, pk: int):
        if not self.check_employee_permission(request):
            return None, self.permission_error_response('无权限访问')

        merchant = request.user.employee.merchant
        try:
            order = pre_order_services.get_pre_purchase_order(
                merchant=merchant,
                pre_purchase_order_id=pk,
            )
            return order, None
        except ValueError:
            return None, self.not_found_response('预采购单不存在')

    def get(self, request, pk: int):
        order, error_response = self._get_order(request, pk)
        if error_response:
            return error_response
        return Response(PrePurchaseOrderSerializer(order).data, status=status.HTTP_200_OK)

    def put(self, request, pk: int):
        return self._update(request, pk)

    def patch(self, request, pk: int):
        return self._update(request, pk)

    def _update(self, request, pk: int):
        order, error_response = self._get_order(request, pk)
        if error_response:
            return error_response

        data = request.data or {}

        try:
            updated = pre_order_services.update_pre_purchase_order(
                pre_purchase_order=order,
                supplier_id=data.get('supplier') or data.get('supplier_id'),
                warehouse_id=data.get('warehouse') or data.get('warehouse_id'),
                kind=data.get('kind'),
                items=data.get('items'),
                remarks=data.get('remarks'),
            )
        except ValueError as exc:
            return Response({'error': str(exc)}, status=status.HTTP_400_BAD_REQUEST)

        return Response(PrePurchaseOrderSerializer(updated).data, status=status.HTTP_200_OK)

    def delete(self, request, pk: int):
        order, error_response = self._get_order(request, pk)
        if error_response:
            return error_response

        pre_order_services.delete_pre_purchase_order(pre_purchase_order=order)
        return Response(status=status.HTTP_204_NO_CONTENT)