From 154a5566a81103173ae01cbbf3c15f72086e8f79 Mon Sep 17 00:00:00 2001
From: Oliver Booth <me@olivr.me>
Date: Sat, 23 Apr 2022 12:38:19 +0100
Subject: [PATCH] Add Rune.Repeat

---
 CHANGELOG.md                     |  1 +
 X10D.Tests/src/Text/RuneTests.cs | 39 ++++++++++++++++++++++++++
 X10D/src/Text/RuneExtensions.cs  | 47 ++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+)
 create mode 100644 X10D.Tests/src/Text/RuneTests.cs
 create mode 100644 X10D/src/Text/RuneExtensions.cs

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 175c5aa..21383d9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -33,6 +33,7 @@
 - Added `Random.NextUnitVector2()`
 - Added `Random.NextUnitVector3()`
 - Added `Random.NextRotation()`
+- Added `Rune.Repeat(int)`
 - Added `bool.GetBytes()`
 - Added `byte.GetBytes()`
 - Added `byte.IsEven()`
diff --git a/X10D.Tests/src/Text/RuneTests.cs b/X10D.Tests/src/Text/RuneTests.cs
new file mode 100644
index 0000000..e85a8a5
--- /dev/null
+++ b/X10D.Tests/src/Text/RuneTests.cs
@@ -0,0 +1,39 @@
+using System.Text;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using X10D.Text;
+
+namespace X10D.Tests.Text;
+
+[TestClass]
+public class RuneTests
+{
+    [TestMethod]
+    public void RepeatShouldBeCorrect()
+    {
+        const string expected = "aaaaaaaaaa";
+        var rune = new Rune('a');
+        string actual = rune.Repeat(10);
+
+        Assert.AreEqual(expected, actual);
+    }
+    
+    [TestMethod]
+    public void RepeatOneCountShouldBeLength1String()
+    {
+        string repeated = new Rune('a').Repeat(1);
+        Assert.AreEqual(1, repeated.Length);
+        Assert.AreEqual("a", repeated);
+    }
+    
+    [TestMethod]
+    public void RepeatZeroCountShouldBeEmpty()
+    {
+        Assert.AreEqual(string.Empty, new Rune('a').Repeat(0));
+    }
+    
+    [TestMethod]
+    public void RepeatNegativeCountShouldThrow()
+    {
+        Assert.ThrowsException<ArgumentOutOfRangeException>(() => new Rune('a').Repeat(-1));
+    }
+}
diff --git a/X10D/src/Text/RuneExtensions.cs b/X10D/src/Text/RuneExtensions.cs
new file mode 100644
index 0000000..9441773
--- /dev/null
+++ b/X10D/src/Text/RuneExtensions.cs
@@ -0,0 +1,47 @@
+using System.Text;
+
+namespace X10D.Text;
+
+/// <summary>
+///     Extension methods for <see cref="Rune" />.
+/// </summary>
+public static class RuneExtensions
+{
+    /// <summary>
+    ///     Returns a string composed of the current rune repeated a specified number of times.
+    /// </summary>
+    /// <param name="value">The rune to repeat.</param>
+    /// <param name="count">The number of times to repeat.</param>
+    /// <returns>
+    ///     A <see cref="string" /> composed of <paramref name="value" /> repeated <paramref name="count" /> times.
+    /// </returns>
+    public static string Repeat(this Rune value, int count)
+    {
+        if (count < 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(count), ExceptionMessages.CountMustBeGreaterThanOrEqualTo0);
+        }
+
+        if (count == 0)
+        {
+            return string.Empty;
+        }
+
+        if (count == 1)
+        {
+            return value.ToString();
+        }
+
+        int utf8SequenceLength = value.Utf8SequenceLength;
+        Span<byte> utf8 = stackalloc byte[utf8SequenceLength];
+        value.EncodeToUtf8(utf8);
+
+        Span<byte> buffer = stackalloc byte[utf8.Length * count];
+        for (var index = 0; index < count; index++)
+        {
+            utf8.CopyTo(buffer.Slice(index * utf8.Length, utf8.Length));
+        }
+
+        return Encoding.UTF8.GetString(buffer);
+    }
+}