feat: add clipboard image handling for pasting and staging attachments

src/EchoHub.Client/AppOrchestrator.cs

@@ -35,6 +35,10 @@ public sealed class AppOrchestrator : IDisposable
     private readonly HashSet<string> _channelsLoadingMore = new(StringComparer.OrdinalIgnoreCase);
     private readonly List<string> _stagedAttachments = [];
 
+    // Temp PNGs created for clipboard-image pastes; deleted once their message is sent
+    // (or the staging tray is cleared) so pasted screenshots don't pile up in %TEMP%.
+    private readonly HashSet<string> _tempPastedFiles = [];
+
     // E2E channels whose unlock prompt the user cancelled — don't nag on every reselect.
     // Cleared on connect/reconnect; an explicit /join or a send attempt re-offers the prompt.
     private readonly HashSet<string> _declinedUnlocks = new(StringComparer.OrdinalIgnoreCase);
@@ -94,6 +98,8 @@ public sealed class AppOrchestrator : IDisposable
         _mainWindow.OnDisconnectRequested += HandleDisconnect;
         _mainWindow.OnLogoutRequested += HandleLogout;
         _mainWindow.OnMessageSubmitted += HandleMessageSubmitted;
+        _mainWindow.OnFilesStaged += HandleFilesStaged;
+        _mainWindow.OnImagePasted += HandleImagePasted;
         _mainWindow.OnChannelSelected += HandleChannelSelected;
         _mainWindow.OnProfileRequested += HandleProfileRequested;
         _mainWindow.OnStatusRequested += HandleStatusRequested;
@@ -221,11 +227,89 @@ public sealed class AppOrchestrator : IDisposable
 
     private Task HandleCmdClearAttachments()
     {
+        var temps = _stagedAttachments.Where(_tempPastedFiles.Contains).ToList();
+        _tempPastedFiles.ExceptWith(temps);
+        CleanupPastedTempFiles(temps);
+
         _stagedAttachments.Clear();
         InvokeUI(RefreshStagingTray);
         return Task.CompletedTask;
     }
 
+    /// <summary>
+    /// Stages a batch of local files (multi-file paste or drag-and-drop) as attachments of the
+    /// next message. Runs synchronously on the UI thread — unlike routing each file through a
+    /// fire-and-forget /send command, a 10-file paste can't race the staging list.
+    /// </summary>
+    private void HandleFilesStaged(string channel, IReadOnlyList<string> files)
+    {
+        if (!_conn.IsAuthenticated || !_conn.IsConnected)
+            return;
+
+        var slotsLeft = HubConstants.MaxAttachmentsPerMessage - _stagedAttachments.Count;
+        _stagedAttachments.AddRange(files.Take(Math.Max(0, slotsLeft)));
+
+        if (files.Count > slotsLeft)
+            _mainWindow.ShowError($"You can attach at most {HubConstants.MaxAttachmentsPerMessage} files per message.");
+
+        RefreshStagingTray();
+    }
+
+    /// <summary>
+    /// Stages an image pasted as raw clipboard data (copied from a browser, a screenshot tool,
+    /// or an image editor). The PNG is written to a per-paste temp folder so it flows through
+    /// the same path-based staging/encryption pipeline as regular files, and the temp file is
+    /// deleted once the message is sent.
+    /// </summary>
+    private void HandleImagePasted(string channel, byte[] png)
+    {
+        if (!_conn.IsAuthenticated || !_conn.IsConnected)
+            return;
+
+        if (_stagedAttachments.Count >= HubConstants.MaxAttachmentsPerMessage)
+        {
+            _mainWindow.ShowError($"You can attach at most {HubConstants.MaxAttachmentsPerMessage} files per message.");
+            return;
+        }
+
+        try
+        {
+            // A unique folder per paste keeps the Discord-style "image.png" display name
+            // while letting several pasted images coexist in one message.
+            var dir = Path.Combine(Path.GetTempPath(), "EchoHub", "pasted", Guid.NewGuid().ToString("N")[..8]);
+            Directory.CreateDirectory(dir);
+            var path = Path.Combine(dir, "image.png");
+            File.WriteAllBytes(path, png);
+
+            _tempPastedFiles.Add(path);
+            _stagedAttachments.Add(path);
+            RefreshStagingTray();
+        }
+        catch (Exception ex)
+        {
+            Log.Error(ex, "Staging a pasted clipboard image failed");
+            _mainWindow.ShowError($"Pasting image failed: {ex.Message}");
+        }
+    }
+
+    /// <summary>Best-effort removal of pasted-image temp files and their per-paste folders.</summary>
+    private static void CleanupPastedTempFiles(IReadOnlyList<string> files)
+    {
+        foreach (var file in files)
+        {
+            try
+            {
+                File.Delete(file);
+                if (Path.GetDirectoryName(file) is { } dir)
+                    Directory.Delete(dir);
+            }
+            catch (Exception ex)
+            {
+                Log.Debug(ex, "Could not delete pasted-image temp file {File}", file);
+            }
+        }
+    }
+
     /// <summary>
     /// Opens the ASCII-art size picker (no argument) or sets it directly from "s"/"m"/"l" (or
     /// small/medium/large). The choice is a persistent preference applied to attached images.
@@ -307,17 +391,29 @@ public sealed class AppOrchestrator : IDisposable
             _stagedAttachments.Clear();
             InvokeUI(RefreshStagingTray);
 
-            var hasRoomKey = _conn.RoomKeys.TryGetKey(channel, out var roomKey);
+            // Pasted clipboard images live in temp files; once this send owns them they are
+            // deleted whether the upload succeeds or fails (the tray is already cleared).
+            var tempFiles = staged.Where(_tempPastedFiles.Contains).ToList();
+            _tempPastedFiles.ExceptWith(tempFiles);
 
-            var outgoing = new List<OutgoingAttachment>();
-            foreach (var path in staged)
-                outgoing.Add(await BuildOutgoingAttachmentAsync(path, hasRoomKey ? roomKey : null, size));
+            try
+            {
+                var hasRoomKey = _conn.RoomKeys.TryGetKey(channel, out var roomKey);
 
-            var wireContent = hasRoomKey && !string.IsNullOrEmpty(content)
-                ? RoomCrypto.EncryptText(content, roomKey)
-                : content;
+                var outgoing = new List<OutgoingAttachment>();
+                foreach (var path in staged)
+                    outgoing.Add(await BuildOutgoingAttachmentAsync(path, hasRoomKey ? roomKey : null, size));
 
-            await _conn.Api!.SendMessageWithAttachmentsAsync(channel, wireContent, outgoing, size);
+                var wireContent = hasRoomKey && !string.IsNullOrEmpty(content)
+                    ? RoomCrypto.EncryptText(content, roomKey)
+                    : content;
+
+                await _conn.Api!.SendMessageWithAttachmentsAsync(channel, wireContent, outgoing, size);
+            }
+            finally
+            {
+                CleanupPastedTempFiles(tempFiles);
+            }
         }, "Send failed");
     }