baseline: 批次A-D 成果 + membership 半成品（测试红）

backend/apps/purchase/services.py

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+"""采购业务服务：确认订单 / 进货单过账（写库存 + 生成应付）。"""
+
+from __future__ import annotations
+
+from datetime import date
+from decimal import Decimal
+
+from django.db import transaction
+
+from apps.inventory import services as inv_services
+from apps.finance import services as fin_services
+from apps.core.services import (
+    compute_tax,
+    parse_price,
+    resolve_line_quantity,
+    resolve_tax_rate,
+)
+
+from .models import PurchaseOrder, PurchaseOrderLine, PurchaseBill, PurchaseBillLine
+
+
+def _resolve_line(product, ln):
+    """解析采购行：换算基本单位数量 + 录入单位/数量；价格按录入单位。
+
+    返回 (qty, price, src_unit, src_qty, amount, tax_rate, tax_amount)（D4 加税）。
+    """
+    parsed = resolve_line_quantity(product, ln)
+    qty = parsed["quantity"]
+    src_unit = parsed["source_unit"]
+    src_qty = parsed["source_quantity"]
+    # 单价校验（与销售侧同口径）：必须 > 0，否则拒绝
+    # （此前直接 Decimal(str(...)) 未校验，0 价只能靠下游"金额>0"兜住，
+    #   错误码不精确；0 成本入库还会污染加权平均成本）
+    price = parse_price(product, ln.get("unit_price"))
+    if src_unit is not None:
+        from apps.catalog.models import UnitConversion
+        conv = UnitConversion.objects.filter(product=product, unit=src_unit).first()
+        rate = conv.rate if conv else None
+        amount = src_qty * price
+    else:
+        rate = None
+        amount = qty * price
+
+    tax_rate = resolve_tax_rate(product, ln)
+    tax = compute_tax(amount, tax_rate)
+    return qty, price, src_unit, src_qty, amount, tax_rate, tax["tax"]
+
+
+def _generate_bill_no(tenant, prefix: str) -> str:
+    """取候选单号（唯一性由 create_with_unique_bill_no 的重试保证）。"""
+    Model = PurchaseOrder if prefix == "PO" else PurchaseBill
+    from apps.core.services import next_bill_no
+
+    return next_bill_no(tenant, prefix, Model)
+
+
+@transaction.atomic
+def create_purchase_bill(
+    *, tenant, supplier, warehouse, bill_date=None, remark="", lines=None,
+    order=None,
+) -> PurchaseBill:
+    """新建一张进货单（草稿态）。lines: list of dict(product, quantity, unit_price)。"""
+    bill_date = bill_date or date.today()
+    from apps.core.services import create_with_unique_bill_no
+
+    bill = create_with_unique_bill_no(
+        PurchaseBill,
+        tenant=tenant,
+        prefix="PB",
+        defaults=dict(
+            supplier=supplier,
+            warehouse=warehouse,
+            order=order,
+            bill_date=bill_date,
+            total_amount=Decimal("0"),
+            state="draft",
+            remark=remark,
+        ),
+    )
+    total = Decimal("0")
+    for ln in lines or []:
+        product = ln["product"]
+        qty, price, src_unit, src_qty, amount, tax_rate, tax_amount = _resolve_line(product, ln)
+        PurchaseBillLine.objects.create(
+            tenant=tenant,
+            bill=bill,
+            product=product,
+            quantity=qty,
+            unit_price=price,
+            amount=amount,
+            batch_no=str(ln.get("batch_no") or ""),
+            production_date=ln.get("production_date"),
+            expiry_date=ln.get("expiry_date"),
+            source_unit=src_unit,
+            source_quantity=src_qty,
+            tax_rate=tax_rate,
+            tax_amount=tax_amount,
+        )
+        total += amount
+    if total <= 0:
+        raise ValueError(f"进货单金额必须大于 0（行合计 {total}）；请检查数量与单价")
+
+    bill.total_amount = total
+    bill.save(update_fields=["total_amount", "updated_at"])
+    return bill
+
+
+@transaction.atomic
+def confirm_purchase_bill(bill: PurchaseBill, *, user=None) -> PurchaseBill:
+    """进货单过账：写库存 + 生成应付单。
+
+    必须状态是 draft；过账后变 confirmed。
+    """
+    if bill.state != "draft":
+        raise ValueError(f"purchase bill {bill.bill_no} not in draft state")
+    # 1. 写库存
+    for line in bill.lines.select_related("product").all():
+        inv_services.inbound(
+            tenant=bill.tenant,
+            warehouse=bill.warehouse,
+            product=line.product,
+            quantity=line.quantity,
+            unit_cost=line.unit_price,
+            source_type="purchase",
+            source_ref=bill.bill_no,
+            batch_no=line.batch_no,
+            production_date=line.production_date,
+            expiry_date=line.expiry_date,
+        )
+    # 2. 生成应付（D4：把行税额合计传给凭证做进项税拆分）
+    from django.db.models import Sum as _Sum
+
+    tax_total = bill.lines.aggregate(t=_Sum("tax_amount"))["t"] or Decimal("0")
+    fin_services.create_payable_from_purchase(
+        tenant=bill.tenant,
+        supplier=bill.supplier,
+        total_amount=bill.total_amount,
+        source_ref=bill.bill_no,
+        bill_date=bill.bill_date,
+        tax_amount=tax_total,
+    )
+    # 3. 改状态
+    bill.state = "confirmed"
+    bill.save(update_fields=["state", "updated_at"])
+
+    from apps.core import audit as audit_log
+
+    audit_log.log_bill_posted(
+        tenant=bill.tenant, bill=bill, user=user,
+        extra={"lines": bill.lines.count()},
+    )
+    return bill