refactor: finalize backend streaming ownership

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-08-06 11:48:46 +02:00 · 2026-04-13 15:47:39 +02:00
parent 4e34d2abfc
commit 1fdb1c27d5
6 changed files with 365 additions and 84 deletions
@@ -0,0 +1,142 @@
+using System.Text;
+
+namespace Aryx.AgentHost.Services;
+
+internal readonly record struct TranscriptSegment(
+    string MessageId,
+    string AuthorName,
+    string Content,
+    bool IsFinalized = false)
+{
+    public static TranscriptSegment FromTuple((string MessageId, string AuthorName, string Content) segment)
+        => new(segment.MessageId, segment.AuthorName, segment.Content);
+
+    public void Deconstruct(out string messageId, out string authorName, out string content)
+    {
+        messageId = MessageId;
+        authorName = AuthorName;
+        content = Content;
+    }
+}
+
+internal sealed class StreamingTranscriptBuffer
+{
+    private readonly List<BufferedTranscriptSegment> _segments = [];
+
+    public int Count => _segments.Count;
+
+    public TranscriptSegment AppendDelta(
+        string messageId,
+        string authorName,
+        string delta)
+    {
+        _ = TryAppendDelta(messageId, authorName, delta, out TranscriptSegment segment);
+        return segment;
+    }
+
+    public bool TryAppendDelta(
+        string messageId,
+        string authorName,
+        string delta,
+        out TranscriptSegment segment)
+    {
+        BufferedTranscriptSegment bufferedSegment = GetOrCreateSegment(messageId, authorName);
+        bool contentChanged = bufferedSegment.TryAppendDelta(authorName, delta);
+        segment = bufferedSegment.ToSnapshot();
+        return contentChanged;
+    }
+
+    public bool TryApplySnapshot(
+        string messageId,
+        string authorName,
+        string content,
+        out TranscriptSegment segment)
+    {
+        BufferedTranscriptSegment bufferedSegment = GetOrCreateSegment(messageId, authorName);
+        bool visibleContentChanged = bufferedSegment.TryApplySnapshot(authorName, content);
+        segment = bufferedSegment.ToSnapshot();
+        return visibleContentChanged;
+    }
+
+    public IReadOnlyList<TranscriptSegment> Snapshot()
+    {
+        return _segments.Select(segment => segment.ToSnapshot()).ToList();
+    }
+
+    private BufferedTranscriptSegment GetOrCreateSegment(string messageId, string authorName)
+    {
+        BufferedTranscriptSegment? existing = _segments.LastOrDefault(segment => segment.MessageId == messageId);
+        if (existing is not null)
+        {
+            return existing;
+        }
+
+        BufferedTranscriptSegment created = new(messageId, authorName);
+        _segments.Add(created);
+        return created;
+    }
+
+    private sealed class BufferedTranscriptSegment
+    {
+        public BufferedTranscriptSegment(string messageId, string authorName)
+        {
+            MessageId = messageId;
+            AuthorName = authorName;
+        }
+
+        public string MessageId { get; }
+
+        public string AuthorName { get; private set; }
+
+        public bool IsFinalized { get; private set; }
+
+        public StringBuilder Content { get; } = new();
+
+        public bool TryAppendDelta(string authorName, string delta)
+        {
+            SetAuthorName(authorName);
+            if (IsFinalized || string.IsNullOrEmpty(delta))
+            {
+                return false;
+            }
+
+            string currentContent = Content.ToString();
+            string mergedContent = StreamingTextMerger.Merge(currentContent, delta);
+            if (string.Equals(currentContent, mergedContent, StringComparison.Ordinal))
+            {
+                return false;
+            }
+
+            SetContent(mergedContent);
+            return true;
+        }
+
+        public bool TryApplySnapshot(string authorName, string content)
+        {
+            SetAuthorName(authorName);
+            string normalizedContent = content ?? string.Empty;
+            string currentContent = Content.ToString();
+            bool visibleContentChanged = !string.Equals(currentContent, normalizedContent, StringComparison.Ordinal);
+
+            SetContent(normalizedContent);
+            IsFinalized = true;
+            return visibleContentChanged;
+        }
+
+        private void SetContent(string value)
+        {
+            Content.Clear();
+            Content.Append(value);
+        }
+
+        private void SetAuthorName(string value)
+        {
+            AuthorName = value;
+        }
+
+        public TranscriptSegment ToSnapshot()
+        {
+            return new TranscriptSegment(MessageId, AuthorName, Content.ToString(), IsFinalized);
+        }
+    }
+}