Split output file into multiple partitions (#116)

DiscordChatExporter.Core/Models/Extensions.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
 
 namespace DiscordChatExporter.Core.Models
 {
@@ -31,5 +33,45 @@ namespace DiscordChatExporter.Core.Models
 
             throw new ArgumentOutOfRangeException(nameof(format));
         }
+
+        public static IReadOnlyList<ChatLog> SplitIntoPartitions(this ChatLog chatLog, int partitionLimit)
+        {
+            // If chat log has fewer messages than the limit - just return chat log in a list
+            if (chatLog.Messages.Count <= partitionLimit)
+                return new[] {chatLog};
+
+            var result = new List<ChatLog>();
+
+            // Loop through messages
+            var buffer = new List<Message>();
+            foreach (var message in chatLog.Messages)
+            {
+                // Add message to buffer
+                buffer.Add(message);
+
+                // If reached the limit - split and reset buffer
+                if (buffer.Count >= partitionLimit)
+                {
+                    // Add to result
+                    var chatLogPartition = new ChatLog(chatLog.Guild, chatLog.Channel, chatLog.From, chatLog.To, buffer,
+                        chatLog.Mentionables);
+                    result.Add(chatLogPartition);
+
+                    // Reset the buffer instead of clearing to avoid mutations on existing references
+                    buffer = new List<Message>();
+                }
+            }
+
+            // Add what's remaining in buffer
+            if (buffer.Any())
+            {
+                // Add to result
+                var chatLogPartition = new ChatLog(chatLog.Guild, chatLog.Channel, chatLog.From, chatLog.To, buffer,
+                    chatLog.Mentionables);
+                result.Add(chatLogPartition);
+            }
+
+            return result;
+        }
     }
 }