feat: big

cost/models.py

@@ -2,9 +2,10 @@ from __future__ import annotations
 
 from dataclasses import dataclass
 from datetime import date
-from decimal import Decimal
+from decimal import Decimal, ROUND_HALF_UP
 from typing import Protocol, runtime_checkable
 
+from django.core.exceptions import ValidationError
 from django.db import models
 
 from flower.common import ModelBase
@@ -44,6 +45,8 @@ class CostCategory(ModelBase):
 class CostEntry(ModelBase):
     """支出明细"""
 
+    AMOUNT_QUANT = Decimal('0.01')
+
     merchant = models.ForeignKey(
         'basic_info.Merchant',
         on_delete=models.PROTECT,
@@ -56,7 +59,27 @@ class CostEntry(ModelBase):
         related_name='entries',
         verbose_name='支出类目',
     )
-    amount = models.DecimalField(max_digits=15, decimal_places=2, verbose_name='金额')
+    amount = models.DecimalField(max_digits=15, decimal_places=2, blank=True, verbose_name='金额')
+    unit_amount = models.DecimalField(
+        max_digits=15,
+        decimal_places=4,
+        null=True,
+        blank=True,
+        verbose_name='单价/基数金额',
+    )
+    quantity = models.DecimalField(
+        max_digits=12,
+        decimal_places=4,
+        null=True,
+        blank=True,
+        verbose_name='数量/倍数',
+    )
+    unit_name = models.CharField(
+        max_length=20,
+        null=True,
+        blank=True,
+        verbose_name='单位名称',
+    )
     occurred_at = models.DateField(verbose_name='发生日期')
     operator = models.ForeignKey(
         'basic_info.Employee',
@@ -84,6 +107,41 @@ class CostEntry(ModelBase):
     def __str__(self):
         return f'{self.category.name} {self.amount} ({self.occurred_at})'
 
+    @property
+    def has_amount_formula(self) -> bool:
+        """是否使用 unit_amount * quantity 推导最终金额。"""
+        return self.unit_amount is not None or self.quantity is not None
+
+    def calculate_amount(self) -> Decimal | None:
+        """根据单价和数量计算最终金额。"""
+        if self.unit_amount is None and self.quantity is None:
+            return None
+        if self.unit_amount is None or self.quantity is None:
+            raise ValidationError({
+                'unit_amount': 'unit_amount 和 quantity 必须同时填写或同时为空',
+                'quantity': 'unit_amount 和 quantity 必须同时填写或同时为空',
+            })
+        return (self.unit_amount * self.quantity).quantize(self.AMOUNT_QUANT, rounding=ROUND_HALF_UP)
+
+    def apply_amount_formula(self) -> None:
+        """如果存在公式字段，则用公式结果覆盖 amount。"""
+        calculated_amount = self.calculate_amount()
+        if calculated_amount is not None:
+            self.amount = calculated_amount
+
+    def clean(self):
+        super().clean()
+        self.apply_amount_formula()
+        if self.amount is None:
+            raise ValidationError({'amount': '普通支出必须填写 amount'})
+
+    def save(self, *args, **kwargs):
+        self.clean()
+        update_fields = kwargs.get('update_fields')
+        if update_fields is not None and self.has_amount_formula:
+            kwargs['update_fields'] = set(update_fields) | {'amount'}
+        return super().save(*args, **kwargs)
+
 
 # ==================== 六边形端口协议 ====================
 
@@ -94,10 +152,13 @@ class CostEntryInput:
 
     category_key: str
     category_name: str
-    amount: Decimal
+    amount: Decimal | None
     occurred_at: date
     source_module: str
     source_id: str
+    unit_amount: Decimal | None = None
+    quantity: Decimal | None = None
+    unit_name: str = ''
     remarks: str = ''