Refactor message grouping

DiscordChatExporter.Core/Internal/Extensions.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using System.Drawing;
+using System.Linq;
 using System.Net;
 
 namespace DiscordChatExporter.Core.Internal
@@ -17,5 +19,34 @@ namespace DiscordChatExporter.Core.Internal
         public static Color ResetAlpha(this Color color) => Color.FromArgb(1, color);
 
         public static string HtmlEncode(this string value) => WebUtility.HtmlEncode(value);
+
+        public static IEnumerable<IReadOnlyList<T>> GroupAdjacentWhile<T>(this IEnumerable<T> source,
+            Func<IReadOnlyList<T>, T, bool> groupPredicate)
+        {
+            // Create buffer
+            var buffer = new List<T>();
+
+            // Enumerate source
+            foreach (var element in source)
+            {
+                // If buffer is not empty and group predicate failed - yield and flush buffer
+                if (buffer.Any() && !groupPredicate(buffer, element))
+                {
+                    yield return buffer;
+                    buffer = new List<T>(); // new instance to reset reference
+                }
+
+                // Add element to buffer
+                buffer.Add(element);
+            }
+
+            // If buffer still has something after the source has been enumerated - yield
+            if (buffer.Any())
+                yield return buffer;
+        }
+
+        public static IEnumerable<IReadOnlyList<T>> GroupAdjacentWhile<T>(this IEnumerable<T> source,
+            Func<IReadOnlyList<T>, bool> groupPredicate)
+            => source.GroupAdjacentWhile((buffer, _) => groupPredicate(buffer));
     }
 }