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));
     }
 }

DiscordChatExporter.Core/Services/ExportService.TemplateModel.cs

@@ -27,45 +27,21 @@ namespace DiscordChatExporter.Core.Services
             }
 
             private IEnumerable<MessageGroup> GroupMessages(IEnumerable<Message> messages)
+                => messages.GroupAdjacentWhile((buffer, message) =>
                 {
-                // Group adjacent messages by timestamp and author
-                var buffer = new List<Message>();
-                foreach (var message in messages)
-                {
-                    // Group break condition
-                    var breakCondition =
-                        buffer.Any() &&
-                        (
-                            message.Author.Id != buffer.First().Author.Id || // when author changes
-                            (message.Timestamp - buffer.Last().Timestamp).TotalMinutes > 7 // when more than 7 minutes passed since last message
-                        );
-
-                    // If condition is true - flush buffer
-                    if (breakCondition)
-                    {
-                        var group = new MessageGroup(buffer.First().Author, buffer.First().Timestamp, buffer);
+                    // Break group if the author changed
+                    if (buffer.Last().Author.Id != message.Author.Id)
+                        return false;
 
-                        // Reset the buffer instead of clearing to avoid mutations on existing references
-                        buffer = new List<Message>();
+                    // Break group if last message was more than 7 minutes ago
+                    if ((message.Timestamp - buffer.Last().Timestamp).TotalMinutes > 7)
+                        return false;
 
-                        yield return group;
-                    }
-
-                    // Add message to buffer
-                    buffer.Add(message);
-                }
-
-                // Add what's remaining in buffer
-                if (buffer.Any())
-                {
-                    var group = new MessageGroup(buffer.First().Author, buffer.First().Timestamp, buffer);
-
-                    yield return group;
-                }
-            }
+                    return true;
+                }).Select(g => new MessageGroup(g.First().Author, g.First().Timestamp, g));
 
-            private string Format(IFormattable obj, string format) =>
-                obj.ToString(format, CultureInfo.InvariantCulture);
+            private string Format(IFormattable obj, string format)
+                => obj.ToString(format, CultureInfo.InvariantCulture);
 
             private string FormatDate(DateTime dateTime) => Format(dateTime, _dateFormat);
 

DiscordChatExporter.Core/Services/ExportService.cs

@@ -1,5 +1,7 @@
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
+using DiscordChatExporter.Core.Internal;
 using DiscordChatExporter.Core.Models;
 using Scriban;
 using Scriban.Runtime;
@@ -82,34 +84,6 @@ 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)
         {
@@ -121,7 +95,11 @@ namespace DiscordChatExporter.Core.Services
             // Otherwise split into partitions and export separately
             else
             {
-                var partitions = SplitIntoPartitions(chatLog, partitionLimit.Value);
+                // Create partitions by grouping up to X adjacent messages into separate chat logs
+                var partitions = chatLog.Messages.GroupAdjacentWhile(g => g.Count < partitionLimit.Value)
+                    .Select(g => new ChatLog(chatLog.Guild, chatLog.Channel, chatLog.From, chatLog.To, g, chatLog.Mentionables))
+                    .ToArray();
+
                 ExportChatLogPartitioned(partitions, filePath, format);
             }
         }