From 02765b8b197a3108b25c580035e753545e7f8762 Mon Sep 17 00:00:00 2001
From: Oliver Booth <me@olivr.me>
Date: Thu, 14 Jul 2022 10:22:37 +0100
Subject: [PATCH] Add IList<T>.Swap (#62)

---
 CHANGELOG.md                            |  1 +
 X10D.Tests/src/Collections/ListTests.cs | 53 +++++++++++++++++++++++++
 X10D/src/Collections/ListExtensions.cs  | 52 ++++++++++++++++++++++++
 3 files changed, 106 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 63bb7db..fd3e06f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@
 - X10D: Added `DateTime.GetIso8601WeekOfYear()` and `DateTimeOffset.GetIso8601WeekOfYear()`
 - X10D: Added `DirectoryInfo.Clear([bool])`
 - X10D: Added `IList<T>.RemoveRange(Range)`
+- X10D: Added `IList<T>.Swap(IList<T>)` (#62)
 - X10D: Added `Point.IsOnLine(LineF)`, `Point.IsOnLine(PointF, PointF)`, and `Point.IsOnLine(Vector2, Vector2)`
 - X10D: Added `PointF.IsOnLine(LineF)`, `PointF.IsOnLine(PointF, PointF)`, and `PointF.IsOnLine(Vector2, Vector2)`
 - X10D: Added `Point.ToSize()`
diff --git a/X10D.Tests/src/Collections/ListTests.cs b/X10D.Tests/src/Collections/ListTests.cs
index 87b9d20..dc6574a 100644
--- a/X10D.Tests/src/Collections/ListTests.cs
+++ b/X10D.Tests/src/Collections/ListTests.cs
@@ -154,4 +154,57 @@ public class ListTests
     {
         Assert.ThrowsException<ArgumentNullException>(() => ((List<int>?)null)!.Shuffle());
     }
+
+    [TestMethod]
+    public void Swap_ShouldThrowArgumentNullException_GivenNullSource()
+    {
+        Assert.ThrowsException<ArgumentNullException>(() => ((IList<int>?)null)!.Swap(new List<int>()));
+    }
+
+    [TestMethod]
+    public void Swap_ShouldThrowArgumentNullException_GivenNullTarget()
+    {
+        Assert.ThrowsException<ArgumentNullException>(() => new List<int>().Swap(null!));
+    }
+
+    [TestMethod]
+    public void Swap_ShouldSwapElements_GivenMatchingElementCount()
+    {
+        var first = new List<int> {1, 2, 3};
+        var second = new List<int> {4, 5, 6};
+
+        first.Swap(second);
+
+        CollectionAssert.AreEqual(new[] {4, 5, 6}, first, string.Join(' ', first));
+        CollectionAssert.AreEqual(new[] {1, 2, 3}, second, string.Join(' ', second));
+
+        first.Swap(second);
+
+        CollectionAssert.AreEqual(new[] {1, 2, 3}, first, string.Join(' ', first));
+        CollectionAssert.AreEqual(new[] {4, 5, 6}, second, string.Join(' ', second));
+    }
+
+    [TestMethod]
+    public void Swap_ShouldSwapElements_GivenDifferentElementCount()
+    {
+        var first = new List<int>
+        {
+            1,
+            2,
+            3,
+            4,
+            5
+        };
+        var second = new List<int> {6, 7};
+
+        first.Swap(second);
+
+        CollectionAssert.AreEqual(new[] {6, 7}, first, string.Join(' ', first));
+        CollectionAssert.AreEqual(new[] {1, 2, 3, 4, 5}, second, string.Join(' ', second));
+
+        first.Swap(second);
+
+        CollectionAssert.AreEqual(new[] {1, 2, 3, 4, 5}, first, string.Join(' ', first));
+        CollectionAssert.AreEqual(new[] {6, 7}, second, string.Join(' ', second));
+    }
 }
diff --git a/X10D/src/Collections/ListExtensions.cs b/X10D/src/Collections/ListExtensions.cs
index bd35d4b..87327b3 100644
--- a/X10D/src/Collections/ListExtensions.cs
+++ b/X10D/src/Collections/ListExtensions.cs
@@ -191,4 +191,56 @@ public static class ListExtensions
             (source[count], source[index]) = (source[index], source[count]);
         }
     }
+
+    /// <summary>
+    ///     Swaps all elements in a list with the elements in another list.
+    /// </summary>
+    /// <param name="source">The first list.</param>
+    /// <param name="other">The second list.</param>
+    /// <typeparam name="T">The type of the elements in <paramref name="source" /> and <paramref name="other" />.</typeparam>
+    /// <exception cref="ArgumentNullException">
+    ///     <para><paramref name="source" /> is <see langword="null" />.</para>
+    ///     -or-
+    ///     <para><paramref name="other" /> is <see langword="null" />.</para>
+    /// </exception>
+    public static void Swap<T>(this IList<T> source, IList<T> other)
+    {
+#if NET6_0_OR_GREATER
+        ArgumentNullException.ThrowIfNull(source);
+        ArgumentNullException.ThrowIfNull(other);
+#else
+        if (source is null)
+        {
+            throw new ArgumentNullException(nameof(source));
+        }
+
+        if (other is null)
+        {
+            throw new ArgumentNullException(nameof(other));
+        }
+#endif
+
+        int min = System.Math.Min(source.Count, other.Count);
+        for (var index = 0; index < min; index++)
+        {
+            (source[index], other[index]) = (other[index], source[index]);
+        }
+
+        if (other.Count < source.Count)
+        {
+            for (int index = min; index < source.Count;)
+            {
+                other.Add(source[index]);
+                source.RemoveAt(index);
+            }
+        }
+        else if (source.Count < other.Count)
+        {
+            for (int index = min; index < other.Count;)
+            {
+                source.Add(other[index]);
+                other.RemoveAt(index);
+            }
+        }
+    }
 }