From c5435f482ff3efd857f4dec8d3f02e98c0f5e779 Mon Sep 17 00:00:00 2001
From: Mike Marynowski <mikem@singulink.com>
Date: Thu, 7 Mar 2024 01:35:18 -0500
Subject: [PATCH] Impl SortedMoneySet.TransformValues with nullable outputs,
 add tests

---
 .../SortedMoneySet.cs                         | 31 ++++++++++++++-
 .../SortedMoneySetTests/TransformValues.cs    | 39 +++++++++++++++++--
 2 files changed, 65 insertions(+), 5 deletions(-)

diff --git a/Source/Singulink.Globalization.Currency/SortedMoneySet.cs b/Source/Singulink.Globalization.Currency/SortedMoneySet.cs
index fe70cd2..d29aa95 100644
--- a/Source/Singulink.Globalization.Currency/SortedMoneySet.cs
+++ b/Source/Singulink.Globalization.Currency/SortedMoneySet.cs
@@ -409,6 +409,8 @@ public void TransformValues(Func<Money, decimal> transform)
         if (Count == 0)
             return;
 
+        // TODO: Optimize if no values change.
+
         foreach (var kvp in _amountLookup.ToList())
         {
             decimal newAmount = transform(new Money(kvp.Value, kvp.Key));
@@ -420,6 +422,31 @@ public void TransformValues(Func<Money, decimal> transform)
         }
     }
 
+    /// <summary>
+    /// Applies the specified transformation to each value's amount in this set. Values transformed to a <see langword="null"/> amount are removed.
+    /// </summary>
+    public void TransformValues(Func<Money, decimal?> transform)
+    {
+        if (Count == 0)
+            return;
+
+        // TODO: Optimize if no values change.
+
+        foreach (var kvp in _amountLookup.ToList())
+        {
+            decimal? newAmountOrNull = transform(new Money(kvp.Value, kvp.Key));
+
+            if (newAmountOrNull is not decimal newAmount)
+            {
+                _amountLookup.Remove(kvp.Key);
+            }
+            else if (newAmount != kvp.Value)
+            {
+                _amountLookup[kvp.Key] = newAmount;
+            }
+        }
+    }
+
     /// <summary>
     /// Applies the specified transformation to each value's amount in this set.
     /// </summary>
@@ -428,6 +455,8 @@ public void TransformAmounts(Func<decimal, decimal> transform)
         if (Count == 0)
             return;
 
+        // TODO: Optimize if no values change.
+
         foreach (var kvp in _amountLookup.ToList())
         {
             decimal oldAmount = kvp.Value;
@@ -472,7 +501,7 @@ public int TrimZeroAmounts()
     {
         List<Currency> currenciesToRemove = null;
 
-        foreach (var kvp in _amountLookup.ToList())
+        foreach (var kvp in _amountLookup)
         {
             if (kvp.Value == 0)
             {
diff --git a/Tests/Singulink.Globalization.Currency.Tests/SortedMoneySetTests/TransformValues.cs b/Tests/Singulink.Globalization.Currency.Tests/SortedMoneySetTests/TransformValues.cs
index 09395f5..10dceec 100644
--- a/Tests/Singulink.Globalization.Currency.Tests/SortedMoneySetTests/TransformValues.cs
+++ b/Tests/Singulink.Globalization.Currency.Tests/SortedMoneySetTests/TransformValues.cs
@@ -11,7 +11,7 @@ public class TransformValues
     private readonly SortedMoneySet _set = ImmutableSet.ToSet();
 
     [TestMethod]
-    public void AllAmountsTransformed_UpdatesValues()
+    public void NonNullOutput_AllAmountsTransformed_UpdatesValue()
     {
         _set.TransformValues(x => x.Amount * 2);
         _set.Count.ShouldBe(3);
@@ -19,17 +19,48 @@ public void AllAmountsTransformed_UpdatesValues()
     }
 
     [TestMethod]
-    public void IdentityTransform_NoChange()
+    public void NonNullOutput_IdentityTransform_NoChange()
     {
         _set.TransformValues(x => x.Amount);
         _set.ShouldBe(ImmutableSet);
     }
 
     [TestMethod]
-    public void EmptySet_NoChange()
+    public void NonNullOutput_EmptySet_NoChange()
     {
         SortedMoneySet emptySet = [];
         emptySet.TransformValues(x => x.Amount * 2);
         emptySet.Count.ShouldBe(0);
     }
-}
\ No newline at end of file
+
+    [TestMethod]
+    public void NullableOutput_AllAmountsTransformed_UpdatesValue()
+    {
+        _set.TransformValues(x => (decimal?)x.Amount * 2);
+        _set.Count.ShouldBe(3);
+        _set.ShouldBe([new(200m, "USD"), new(100m, "CAD"), new(50m, "EUR")]);
+    }
+
+    [TestMethod]
+    public void NullableOutput_IdentityTransform_NoChange()
+    {
+        _set.TransformValues(x => (decimal?)x.Amount);
+        _set.ShouldBe(ImmutableSet);
+    }
+
+    [TestMethod]
+    public void NullableOutput_EmptySet_NoChange()
+    {
+        SortedMoneySet emptySet = [];
+        emptySet.TransformValues(x => (decimal?)x.Amount * 2);
+        emptySet.Count.ShouldBe(0);
+    }
+
+    [TestMethod]
+    public void NullableOutput_NullTransform_RemovesNullValues()
+    {
+        _set.TransformValues(x => x.Amount == 100m ? null : x.Amount);
+        _set.Count.ShouldBe(2);
+        _set.ShouldBe([new(50m, "CAD"), new(25m, "EUR")]);
+    }
+}