"""inventory async ViewSets。

库存账面与流水是只读对外接口（写入走 services）；
仓库可增删改。
"""

from adrf.viewsets import ModelViewSet, ReadOnlyModelViewSet
from datetime import timedelta

from django.utils import timezone

from apps.core.viewset import BaseTenantViewSet
from apps.core.viewset import StandardAsyncPagination
from .models import Warehouse, Stock, StockBatch, StockMovement
from .serializers import WarehouseSerializer, StockSerializer, StockMovementSerializer, StockBatchSerializer


class WarehouseViewSet(BaseTenantViewSet):
    model = Warehouse
    serializer_class = WarehouseSerializer
    search_fields = ["code", "name"]


class StockViewSet(BaseTenantViewSet):
    model = Stock
    serializer_class = StockSerializer
    search_fields = ["product__code", "product__name", "warehouse__code"]
    http_method_names = ["get", "head", "options"]  # 只读
    select_related_fields = ("product", "warehouse", "product__base_unit")


class StockMovementViewSet(BaseTenantViewSet):
    model = StockMovement
    serializer_class = StockMovementSerializer
    search_fields = ["product__code", "product__name", "source_ref"]
    http_method_names = ["get", "head", "options"]  # 只读
    select_related_fields = ("product", "warehouse")


class StockBatchViewSet(BaseTenantViewSet):
    """批次库存（只读；写入走 inbound/outbound 服务）。"""

    model = StockBatch
    serializer_class = StockBatchSerializer
    search_fields = ["batch_no", "product__code", "product__name", "warehouse__code"]
    http_method_names = ["get", "head", "options"]  # 只读
    select_related_fields = ("product", "warehouse", "product__base_unit")

    async def get_queryset(self):
        qs = await super().get_queryset()
        # 支持按 product / warehouse 过滤，且默认只看有量批次
        product_id = self.request.query_params.get("product")
        warehouse_id = self.request.query_params.get("warehouse")
        in_stock = self.request.query_params.get("in_stock", "")
        near_expiry = self.request.query_params.get("near_expiry", "")
        expiry_days = self.request.query_params.get("expiry_days", "30")
        if product_id:
            qs = qs.filter(product_id=product_id)
        if warehouse_id:
            qs = qs.filter(warehouse_id=warehouse_id)
        if in_stock in ("1", "true", "True"):
            qs = qs.filter(on_hand__gt=0)
        if near_expiry in ("1", "true", "True"):
            try:
                days = max(0, min(int(expiry_days), 3650))
            except (TypeError, ValueError):
                days = 30
            cutoff = timezone.localdate() + timedelta(days=days)
            qs = qs.filter(expiry_date__isnull=False, expiry_date__lte=cutoff)
        return qs