From 39645bfe2980825509527917097f9acf8378b8ce Mon Sep 17 00:00:00 2001
From: Filip Strajnar <filip.strajnar@gmail.com>
Date: Sat, 11 May 2024 15:17:41 +0200
Subject: [PATCH] Implemented comparison of IEnumerables in
 RecursiveFieldsEqual.

---
 AioNet.Reflection/DeepComparison.cs | 51 ++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/AioNet.Reflection/DeepComparison.cs b/AioNet.Reflection/DeepComparison.cs
index 5be99dd..2d41aef 100644
--- a/AioNet.Reflection/DeepComparison.cs
+++ b/AioNet.Reflection/DeepComparison.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
@@ -36,7 +37,7 @@ namespace AioNet.Reflection
             // If type is IEnumerable, compare individual elements.
             if (type.GetInterface("System.Collections.IEnumerable") != null)
             {
-                throw new NotImplementedException();
+                return RecursiveEnumerableEquals(first, second);
             }
 
             IEnumerable<FieldInfo> fields = type.GetRuntimeFields();
@@ -50,5 +51,53 @@ namespace AioNet.Reflection
                 );
             });
         }
+
+        private static bool RecursiveEnumerableEquals<T>(T first, T second)
+        {
+            // Throwing exceptions if casting to System.Collections.IEnumerable doesn't work.
+            IEnumerator firstEnumerator = ((IEnumerable)first).GetEnumerator();
+            IEnumerator secondEnumerator = ((IEnumerable)second).GetEnumerator();
+
+            while (firstEnumerator.MoveNext())
+            {
+                // If the second enumerator doesn't advance when first does,
+                // this means that first enumerator has more elements, so they
+                // can't be equal.
+                if (!secondEnumerator.MoveNext())
+                {
+                    return false;
+                }
+
+                Type firstType = firstEnumerator.Current.GetType();
+                Type secondType = secondEnumerator.Current.GetType();
+
+                // If types don't match, they can't be equal.
+                if (!(firstType == secondType))
+                {
+                    return false;
+                }
+
+                bool elementsEqual = RecursiveFieldsEqual(
+                    firstEnumerator.Current,
+                    secondEnumerator.Current,
+                    firstType
+                );
+                // If the two elements are not equal, then the entire enumerable is not equal.
+                if (!elementsEqual)
+                {
+                    return false;
+                }
+            }
+
+            // If second enumerator can move even though first can't, it's
+            // longer and therefore the two are not equal.
+            if (secondEnumerator.MoveNext())
+            {
+                return false;
+            }
+
+            // If there were no differences found, we return true.
+            return true;
+        }
     }
 }