"""purchase async ViewSets。

开单页动作接口：
- `create_bill`（POST /purchase/bills/create-bill/）：建草稿（支持批次号/生产日/到期日/录入单位）
- `confirm_bill`（POST /purchase/bills/<id>/confirm/）：过账（写库存 + 生成应付）
"""

from asgiref.sync import sync_to_async
from rest_framework import status
from rest_framework.decorators import action
from rest_framework.exceptions import ValidationError
from rest_framework.response import Response

from apps.core.services import InvalidLinePrice, InvalidLineQuantity
from apps.core.viewset import BaseTenantViewSet

from .models import PurchaseOrder, PurchaseBill
from .serializers import PurchaseOrderSerializer, PurchaseBillSerializer
from . import services as purchase_services


class PurchaseOrderViewSet(BaseTenantViewSet):
    model = PurchaseOrder
    serializer_class = PurchaseOrderSerializer
    search_fields = ["bill_no", "supplier__code", "supplier__name"]
    select_related_fields = ("supplier", "warehouse")
    prefetch_related_fields = (
        "lines", "lines__product", "lines__source_unit", "lines__product__base_unit",
    )


class PurchaseBillViewSet(BaseTenantViewSet):
    model = PurchaseBill
    serializer_class = PurchaseBillSerializer
    search_fields = ["bill_no", "supplier__code", "supplier__name"]
    select_related_fields = ("supplier", "warehouse")
    prefetch_related_fields = (
        "lines", "lines__product", "lines__source_unit", "lines__product__base_unit",
    )

    @action(detail=False, methods=["post"], url_path="create-bill")
    async def create_bill(self, request):
        """POST /api/v1/purchase/bills/create-bill/

        body: {supplier, warehouse, bill_date?, remark?, lines: [
            {product, quantity, unit_price, source_unit?, batch_no?,
             production_date?, expiry_date?}]}
        """
        tenant = await self.get_tenant()
        if tenant is None:
            raise ValidationError({"tenant": "无法识别租户"})
        payload = request.data or {}

        # 套餐配额：月度单据量（批次 C1）
        from apps.billing import quota as billing_quota

        def _quota_check():
            return billing_quota.check_and_count(tenant, "bills_monthly", delta=1)

        try:
            await sync_to_async(_quota_check)()
        except billing_quota.QuotaExceeded as exc:
            return Response(exc.as_dict(), status=status.HTTP_403_FORBIDDEN)

        supplier_id, warehouse_id = payload.get("supplier"), payload.get("warehouse")
        lines = payload.get("lines") or []
        if not supplier_id or not warehouse_id:
            raise ValidationError({"detail": "supplier 与 warehouse 必填"})
        if not lines:
            raise ValidationError({"detail": "lines 不能为空"})
        if not isinstance(lines, list):
            raise ValidationError({"detail": "lines 必须是数组"})
        # 逐行结构校验：非 dict 或缺 product 直接 400（否则下游 .get() 会 500）
        for idx, ln in enumerate(lines, start=1):
            if not isinstance(ln, dict):
                raise ValidationError({"detail": f"第 {idx} 行明细格式错误（应为对象）"})
            if not ln.get("product"):
                raise ValidationError({"detail": f"第 {idx} 行缺少 product"})

        from apps.partner.models import Supplier
        from apps.inventory.models import Warehouse
        from apps.catalog.models import Product

        def _load_refs():
            supplier = Supplier.objects.filter(tenant=tenant, pk=supplier_id).first()
            warehouse = Warehouse.objects.filter(tenant=tenant, pk=warehouse_id).first()
            products = {
                p.id: p for p in Product.objects.filter(
                    tenant=tenant, pk__in=[ln.get("product") for ln in lines]
                )
            }
            return supplier, warehouse, products

        supplier, warehouse, products = await sync_to_async(_load_refs)()
        if supplier is None:
            raise ValidationError({"supplier": "供应商不存在"})
        if warehouse is None:
            raise ValidationError({"warehouse": "仓库不存在"})

        resolved_lines = []
        for ln in lines:
            product = products.get(ln.get("product"))
            if product is None:
                raise ValidationError({"lines": f"商品 {ln.get('product')} 不存在"})
            if ln.get("unit_price") in (None, ""):
                raise ValidationError({"lines": f"商品 {product.code} 缺少进货单价"})
            resolved_lines.append({
                "product": product,
                "quantity": ln.get("quantity"),
                "unit_price": ln.get("unit_price"),
                "source_unit": ln.get("source_unit"),
                "batch_no": ln.get("batch_no") or "",
                "production_date": ln.get("production_date") or None,
                "expiry_date": ln.get("expiry_date") or None,
            })

        from datetime import date as _date

        kwargs = {
            "tenant": tenant,
            "supplier": supplier,
            "warehouse": warehouse,
            "lines": resolved_lines,
            "remark": payload.get("remark") or "",
        }
        bill_date = payload.get("bill_date")
        if bill_date:
            kwargs["bill_date"] = _date.fromisoformat(bill_date)

        # InvalidLine* 等由全局异常处理器统一映射
        try:
            bill = await sync_to_async(purchase_services.create_purchase_bill)(**kwargs)
        except ValueError as exc:
            return Response(
                {"code": "invalid_line", "detail": str(exc)},
                status=status.HTTP_400_BAD_REQUEST,
            )

        data = await sync_to_async(lambda: PurchaseBillSerializer(bill).data)()
        return Response(data, status=status.HTTP_201_CREATED)

    @action(detail=True, methods=["post"], url_path="confirm")
    async def confirm_bill(self, request, pk=None):
        """POST /api/v1/purchase/bills/<id>/confirm/"""
        bill = await self.aget_object()

        def _confirm():
            return purchase_services.confirm_purchase_bill(
                bill, user=request.user if request.user.is_authenticated else None,
            )

        try:
            await sync_to_async(_confirm)()
        except ValueError as exc:
            return Response(
                {"code": "invalid_state", "detail": str(exc)},
                status=status.HTTP_400_BAD_REQUEST,
            )

        def _reload():
            bill.refresh_from_db()
            return PurchaseBillSerializer(bill).data

        data = await sync_to_async(_reload)()
        return Response(data)