From 963f7a04e587c17da7734338ff5a0d1961dc9695 Mon Sep 17 00:00:00 2001
From: hjhan <hongjun.han@yieldchain.com>
Date: Tue, 11 Aug 2026 11:04:08 +0800
Subject: [PATCH] =?UTF-8?q?refactor(return-leg):=20=E6=96=B0=E5=A2=9E=20Di?=
 =?UTF-8?q?videndCalc=20=E5=88=86=E7=BA=A2=E5=A2=9E=E5=80=BC=E7=A8=8E?=
 =?UTF-8?q?=E5=90=8E=E8=AE=A1=E7=AE=97=20+=20=E4=BF=AE=E5=A4=8D=20MtmCalc?=
 =?UTF-8?q?=20=E5=8F=82=E6=95=B0=E7=B1=BB=E5=9E=8B?=
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DividendCalc: 增值税后票息 = payment/(1+tax)*(1-tax),
原 SwapEodPositionService 4处重复此公式(1804/1894/1906/2095)。
本次先建纯函数+测试, 4处inline替换下次做。

附带修复: MtmCalc shortRatio 参数从 decimal 改为 int
(原代码6处声明中5处是int, 仅1696是decimal, 统一为int)。
1696行 shortRatio 声明同步改为 int。

验证: 编译0错误, DividendCalc 4个测试全过,
全量507测试7失败(基线一致)。
---
 .../SwapModule/ReturnLegs/DividendCalcTest.cs | 37 +++++++++++++++++++
 .../SwapModule/ReturnLegs/DividendCalc.cs     | 18 +++++++++
 .../Modules/SwapModule/ReturnLegs/MtmCalc.cs  |  4 +-
 .../SwapModule/SwapEodPositionService.cs      |  2 +-
 4 files changed, 59 insertions(+), 2 deletions(-)
 create mode 100644 UnitTestProject/Modules/SwapModule/ReturnLegs/DividendCalcTest.cs
 create mode 100644 YLErpDAL/Modules/SwapModule/ReturnLegs/DividendCalc.cs

diff --git a/UnitTestProject/Modules/SwapModule/ReturnLegs/DividendCalcTest.cs b/UnitTestProject/Modules/SwapModule/ReturnLegs/DividendCalcTest.cs
new file mode 100644
index 00000000..20a842ad
--- /dev/null
+++ b/UnitTestProject/Modules/SwapModule/ReturnLegs/DividendCalcTest.cs
@@ -0,0 +1,37 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using YLErp.Modules.SwapModule.ReturnLegs;
+
+namespace UnitTestProject.Modules.SwapModule.ReturnLegs
+{
+    [TestClass]
+    public class DividendCalcTest
+    {
+        [TestMethod]
+        public void AfterTax_零税率_等于原值()
+        {
+            Assert.AreEqual(1000m, DividendCalc.AfterTax(1000m, 0m));
+        }
+
+        [TestMethod]
+        public void AfterTax_6pct增值税()
+        {
+            // 1000 / 1.06 * 0.94 = 886.79...
+            Assert.AreEqual(886.79m, DividendCalc.AfterTax(1000m, 0.06m));
+        }
+
+        [TestMethod]
+        public void AfterTax_负票息()
+        {
+            // -500 / 1.06 * 0.94 = -443.40
+            Assert.AreEqual(-443.40m, DividendCalc.AfterTax(-500m, 0.06m));
+        }
+
+        [TestMethod]
+        public void AfterTaxRaw_不四舍五入()
+        {
+            var raw = DividendCalc.AfterTaxRaw(1000m, 0.06m);
+            Assert.AreNotEqual(886.79m, raw, "Raw 版本不四舍五入");
+            Assert.IsTrue(raw > 886.79m && raw < 886.80m);
+        }
+    }
+}
diff --git a/YLErpDAL/Modules/SwapModule/ReturnLegs/DividendCalc.cs b/YLErpDAL/Modules/SwapModule/ReturnLegs/DividendCalc.cs
new file mode 100644
index 00000000..1b9f898f
--- /dev/null
+++ b/YLErpDAL/Modules/SwapModule/ReturnLegs/DividendCalc.cs
@@ -0,0 +1,18 @@
+namespace YLErp.Modules.SwapModule.ReturnLegs;
+
+/// <summary>
+/// 标的端分红（票息）计算。
+///
+/// 增值税后票息 = 税前票息 / (1+税率) × (1-税率)
+/// 原代码在 SwapEodPositionService 4处重复此公式(1804/1894/1906/2095)。
+/// </summary>
+public static class DividendCalc
+{
+    /// <summary>增值税后票息，四舍五入到 2 位。</summary>
+    public static decimal AfterTax(decimal payment, decimal tax)
+        => Math.Round(payment / (1 + tax) * (1 - tax), 2);
+
+    /// <summary>增值税后票息（不四舍五入，供中间计算用）。</summary>
+    public static decimal AfterTaxRaw(decimal payment, decimal tax)
+        => payment / (1 + tax) * (1 - tax);
+}
diff --git a/YLErpDAL/Modules/SwapModule/ReturnLegs/MtmCalc.cs b/YLErpDAL/Modules/SwapModule/ReturnLegs/MtmCalc.cs
index 482fbe90..82701e11 100644
--- a/YLErpDAL/Modules/SwapModule/ReturnLegs/MtmCalc.cs
+++ b/YLErpDAL/Modules/SwapModule/ReturnLegs/MtmCalc.cs
@@ -10,11 +10,13 @@ namespace YLErp.Modules.SwapModule.ReturnLegs;
 /// </summary>
 public static class MtmCalc
 {
-    /// <summary>标的市值。多头为正、空头为负。</summary>
+    /// <summary>标的市值。多头为正、空头为负。shortRatio: 多头=1, 空头=-1。</summary>
     public static decimal MarketValue(decimal price, decimal qty, decimal contractSize, int shortRatio)
         => price * qty * contractSize * shortRatio;
 
     /// <summary>盯市未实现盈亏 = (标的价 - 成本全价) × 数量 × 合约乘数 × 多空 × 收付。</summary>
+    /// <param name="shortRatio">多头=1, 空头=-1。</param>
+    /// <param name="ratio">收取=1, 支付=-1。</param>
     public static decimal UnrealizedPnl(decimal price, decimal costGrossPrice, decimal qty, decimal contractSize, int shortRatio, decimal ratio)
         => (price - costGrossPrice) * qty * contractSize * shortRatio * ratio;
 }
diff --git a/YLErpDAL/Modules/SwapModule/SwapEodPositionService.cs b/YLErpDAL/Modules/SwapModule/SwapEodPositionService.cs
index af4a85bc..5a4b46e8 100644
--- a/YLErpDAL/Modules/SwapModule/SwapEodPositionService.cs
+++ b/YLErpDAL/Modules/SwapModule/SwapEodPositionService.cs
@@ -1693,7 +1693,7 @@ namespace YLErp.Modules.SwapModule
         {
             payQty = Math.Abs(payQty);
             decimal ratio = eventFlow.PayDirection == (int)SwapDirectionEnum.收取 ? 1 : -1;//收取为正，支付为负
-            decimal shortRatio = newEodPayPosition.PositionType == (int)PositionTypeFlag.Long ? 1 : -1;//多空方向
+            int shortRatio = newEodPayPosition.PositionType == (int)PositionTypeFlag.Long ? 1 : -1;//多空方向
             newEodPayPosition.ValueDate = eventFlow.PayDate.Value;
             newEodPayPosition.PositionId = eventFlow.PositionId;
             newEodPayPosition.ClientId = td.ClientId;