"""商品中心 async ViewSets（多租户基类来自 apps.core.viewset）。"""

from decimal import Decimal

from asgiref.sync import sync_to_async
from adrf.viewsets import ModelViewSet
from rest_framework.decorators import action
from rest_framework.response import Response

from apps.core.viewset import BaseTenantViewSet, StandardAsyncPagination
from .models import Category, Brand, Unit, Product, UnitConversion
from .serializers import (
    CategorySerializer,
    BrandSerializer,
    UnitSerializer,
    ProductSerializer,
)


class CategoryViewSet(BaseTenantViewSet):
    model = Category
    serializer_class = CategorySerializer
    search_fields = ["code", "name"]


class BrandViewSet(BaseTenantViewSet):
    model = Brand
    serializer_class = BrandSerializer
    search_fields = ["code", "name"]


class UnitViewSet(BaseTenantViewSet):
    model = Unit
    serializer_class = UnitSerializer
    search_fields = ["code", "name"]


class ProductViewSet(BaseTenantViewSet):
    model = Product
    serializer_class = ProductSerializer
    search_fields = ["code", "name", "barcode", "spec"]
    quota_kind = "products"   # 套餐配额：商品数上限（批次 C1）

    @action(detail=True, methods=["get"], url_path="units")
    async def units(self, request, pk=None):
        """商品的可用录入单位与换算价：GET /api/v1/catalog/products/<id>/units/

        返回基本单位 + 全部 UnitConversion（rate 与按 rate 折算的销售价），
        供开单页"选择录入单位"使用。
        """
        tenant = await self.get_tenant()
        if tenant is None:
            from rest_framework.exceptions import ValidationError
            raise ValidationError({"tenant": "无法识别租户"})

        def _load():
            product = (
                Product.objects.filter(tenant=tenant, pk=pk)
                .select_related("base_unit")
                .first()
            )
            if product is None:
                return None
            convs = list(
                UnitConversion.objects.filter(product=product)
                .select_related("unit")
                .order_by("unit__code")
            )
            base_unit = product.base_unit
            rows = []
            if base_unit is not None:
                rows.append({
                    "unit_id": base_unit.id,
                    "unit_code": base_unit.code,
                    "unit_name": base_unit.name,
                    "rate": "1",
                    "is_base": True,
                    "price": str(product.sale_price),
                    "cost_price": str(product.cost_price),
                })
            for c in convs:
                rows.append({
                    "unit_id": c.unit_id,
                    "unit_code": c.unit.code,
                    "unit_name": c.unit.name,
                    "rate": str(c.rate),
                    "is_base": False,
                    "price": str((product.sale_price * c.rate).quantize(Decimal("0.0001"))),
                    "cost_price": str((product.cost_price * c.rate).quantize(Decimal("0.0001"))),
                })
            return {
                "product_id": product.id,
                "product_code": product.code,
                "product_name": product.name,
                "base_unit_id": base_unit.id if base_unit else None,
                "base_unit_name": base_unit.name if base_unit else "",
                "sale_price": str(product.sale_price),
                "cost_price": str(product.cost_price),
                "min_sale_price": str(product.min_sale_price or 0),
                "tax_rate": str(product.tax_rate or 0),
                "is_batch_managed": product.is_batch_managed,
                "shelf_life_days": product.shelf_life_days,
                "units": rows,
            }

        data = await sync_to_async(_load)()
        if data is None:
            from rest_framework.exceptions import NotFound
            raise NotFound("product not found")
        return Response(data)