From e29354199d5d64bf31279d18fc2e6045d81e0886 Mon Sep 17 00:00:00 2001
From: Alan Edwardes <alan@alanedwardes.com>
Date: Sat, 10 Feb 2024 15:27:16 +0000
Subject: [PATCH] Makes DnsLabels comparison case insensitive.

---
 src/Ae.Dns.Protocol/DnsLabels.cs              | 23 +++++++++++++++++++
 tests/Ae.Dns.Tests/Protocol/DnsLabelsTests.cs | 22 ++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/src/Ae.Dns.Protocol/DnsLabels.cs b/src/Ae.Dns.Protocol/DnsLabels.cs
index dd6e470..92c2d58 100644
--- a/src/Ae.Dns.Protocol/DnsLabels.cs
+++ b/src/Ae.Dns.Protocol/DnsLabels.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Ae.Dns.Protocol
 {
@@ -43,6 +44,12 @@ namespace Ae.Dns.Protocol
         /// <inheritdoc/>
         public override string ToString() => _labels == null ? "<none>" : string.Join(".", _labels);
 
+        /// <inheritdoc/>
+        public override bool Equals(object? obj) => obj is DnsLabels labels && this == labels;
+
+        /// <inheritdoc/>
+        public override int GetHashCode() => HashCode.Combine(LabelsNeverNull);
+
         /// <summary>
         /// Convert a string to <see cref="DnsLabels"/>.
         /// </summary>
@@ -54,5 +61,21 @@ namespace Ae.Dns.Protocol
         /// </summary>
         /// <param name="labels"></param>
         public static implicit operator string(DnsLabels labels) => string.Join(".", labels.LabelsNeverNull);
+
+        /// <summary>
+        /// Test whether this instance equals the other instance.
+        /// </summary>
+        /// <param name="a"></param>
+        /// <param name="b"></param>
+        /// <returns></returns>
+        public static bool operator ==(DnsLabels a, DnsLabels b) => a.SequenceEqual(b, StringComparer.OrdinalIgnoreCase);
+
+        /// <summary>
+        /// Test whether this instance does not equal the other instance.
+        /// </summary>
+        /// <param name="a"></param>
+        /// <param name="b"></param>
+        /// <returns></returns>
+        public static bool operator !=(DnsLabels a, DnsLabels b) => !(a == b);
     }
 }
diff --git a/tests/Ae.Dns.Tests/Protocol/DnsLabelsTests.cs b/tests/Ae.Dns.Tests/Protocol/DnsLabelsTests.cs
index 5b05ba7..84250b3 100644
--- a/tests/Ae.Dns.Tests/Protocol/DnsLabelsTests.cs
+++ b/tests/Ae.Dns.Tests/Protocol/DnsLabelsTests.cs
@@ -60,5 +60,27 @@ public void TestCastStringEmpty()
         {
             Assert.Empty((string)DnsLabels.Empty);
         }
+
+        [Fact]
+        public void TestEquality()
+        {
+            Assert.True(new DnsLabels("test.com") == new DnsLabels("test.com"));
+            Assert.True(new DnsLabels("test.com") == new DnsLabels("TEST.COM"));
+            Assert.False(new DnsLabels("test.com") != new DnsLabels("TEST.COM"));
+            Assert.False(new DnsLabels("test.com") != new DnsLabels("test.com"));
+            Assert.True(new DnsLabels("test.com").Equals(new DnsLabels("test.com")));
+            Assert.True(new DnsLabels("test.com").Equals(new DnsLabels("TEST.COM")));
+        }
+
+        [Fact]
+        public void TestGetHashCode()
+        {
+            Assert.Distinct(new[]
+            {
+                DnsLabels.Empty.GetHashCode(),
+                new DnsLabels("test.com").GetHashCode(),
+                new DnsLabels("test.org").GetHashCode()
+            });
+        }
     }
 }