From 8bc29c49288da392551613371f96d0f5b57ac821 Mon Sep 17 00:00:00 2001
From: Oleksii Holub <Oleksii.Holub@3shape.com>
Date: Wed, 14 Nov 2018 17:51:03 +0200
Subject: [PATCH] Refactor SplitIntoPartitions

---
 DiscordChatExporter.Core/Models/Extensions.cs | 42 -------------------
 .../Services/ExportService.cs                 | 30 ++++++++++++-
 2 files changed, 29 insertions(+), 43 deletions(-)

diff --git a/DiscordChatExporter.Core/Models/Extensions.cs b/DiscordChatExporter.Core/Models/Extensions.cs
index 70efb2f..90817b9 100644
--- a/DiscordChatExporter.Core/Models/Extensions.cs
+++ b/DiscordChatExporter.Core/Models/Extensions.cs
@@ -1,6 +1,4 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
 
 namespace DiscordChatExporter.Core.Models
 {
@@ -33,45 +31,5 @@ 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;
-        }
     }
 }
\ No newline at end of file
diff --git a/DiscordChatExporter.Core/Services/ExportService.cs b/DiscordChatExporter.Core/Services/ExportService.cs
index c3604e7..4b68fae 100644
--- a/DiscordChatExporter.Core/Services/ExportService.cs
+++ b/DiscordChatExporter.Core/Services/ExportService.cs
@@ -83,6 +83,34 @@ namespace DiscordChatExporter.Core.Services
             }
         }
 
+        private IReadOnlyList<ChatLog> SplitIntoPartitions(ChatLog chatLog, int partitionLimit)
+        {
+            var result = new List<ChatLog>();
+
+            // Loop through all messages with an increment of partition limit
+            for (var i = 0; i < chatLog.Messages.Count; i += partitionLimit)
+            {
+                // Calculate how many messages left in total
+                var remainingMessageCount = chatLog.Messages.Count - i;
+
+                // Decide how many messages are going into this partition
+                // Each partition will have the same number of messages except the last one that might have fewer (all remaining messages)
+                var partitionMessageCount = partitionLimit.ClampMax(remainingMessageCount);
+
+                // Get messages that belong to this partition
+                var partitionMessages = new List<Message>();
+                for (var j = i; j < i + partitionMessageCount; j++)
+                    partitionMessages.Add(chatLog.Messages[j]);
+
+                // Create a partition and add to list
+                var partition = new ChatLog(chatLog.Guild, chatLog.Channel, chatLog.From, chatLog.To, partitionMessages,
+                    chatLog.Mentionables);
+                result.Add(partition);
+            }
+
+            return result;
+        }
+
         public void ExportChatLog(ChatLog chatLog, string filePath, ExportFormat format,
             int? partitionLimit = null)
         {
@@ -94,7 +122,7 @@ namespace DiscordChatExporter.Core.Services
             // Otherwise split into partitions and export separately
             else
             {
-                var partitions = chatLog.SplitIntoPartitions(partitionLimit.Value);
+                var partitions = SplitIntoPartitions(chatLog, partitionLimit.Value);
                 ExportChatLogPartitions(partitions, filePath, format);
             }
         }