feat: add audio playback and file download features with corresponding UI updates

src/EchoHub.Client/AppOrchestrator.cs

@@ -22,6 +22,7 @@ public sealed class AppOrchestrator : IDisposable
     private readonly MainWindow _mainWindow;
     private readonly CommandHandler _commandHandler;
     private readonly NotificationSoundService _notificationSound;
+    private readonly AudioPlaybackService _audioPlayback = new();
 
     private EchoHubConnection? _connection;
     private ApiClient? _apiClient;
@@ -80,6 +81,8 @@ public sealed class AppOrchestrator : IDisposable
         _mainWindow.OnSavedServersRequested += HandleSavedServersRequested;
         _mainWindow.OnCreateChannelRequested += HandleCreateChannelRequested;
         _mainWindow.OnDeleteChannelRequested += HandleDeleteChannelRequested;
+        _mainWindow.OnAudioPlayRequested += HandleAudioPlayRequested;
+        _mainWindow.OnFileDownloadRequested += HandleFileDownloadRequested;
     }
 
     // ── Command Handler Wiring ─────────────────────────────────────────────
@@ -798,6 +801,40 @@ public sealed class AppOrchestrator : IDisposable
         }, "Failed to delete channel");
     }
 
+    private void HandleAudioPlayRequested(string attachmentUrl, string fileName)
+    {
+        if (!IsAuthenticated) return;
+
+        RunAsync(async () =>
+        {
+            InvokeUI(() => _mainWindow.AddSystemMessage(_mainWindow.CurrentChannel, $"Playing {fileName}..."));
+            var tempPath = await _apiClient!.DownloadFileToTempAsync(attachmentUrl, fileName);
+            await _audioPlayback.PlayAsync(tempPath);
+        }, "Failed to play audio");
+    }
+
+    private void HandleFileDownloadRequested(string attachmentUrl, string fileName)
+    {
+        if (!IsAuthenticated) return;
+
+        RunAsync(async () =>
+        {
+            InvokeUI(() => _mainWindow.AddSystemMessage(_mainWindow.CurrentChannel, $"Downloading {fileName}..."));
+            var tempPath = await _apiClient!.DownloadFileToTempAsync(attachmentUrl, fileName);
+
+            try
+            {
+                var psi = new System.Diagnostics.ProcessStartInfo(tempPath) { UseShellExecute = true };
+                System.Diagnostics.Process.Start(psi);
+            }
+            catch (Exception ex)
+            {
+                Log.Warning(ex, "Failed to open file with default app: {Path}", tempPath);
+                InvokeUI(() => _mainWindow.AddSystemMessage(_mainWindow.CurrentChannel, $"Downloaded to: {tempPath}"));
+            }
+        }, "Failed to download file");
+    }
+
     // ── Connection Event Wiring ────────────────────────────────────────────
 
     private void WireConnectionEvents(EchoHubConnection connection)

src/EchoHub.Client/Commands/CommandHandler.cs

@@ -339,7 +339,7 @@ public class CommandHandler
               /nick <name>                         - Set display name
               /color <#hex>                        - Set nickname color
               /theme <name>                        - Switch theme
-              /send <filepath or URL> [-s|-m|-l]      - Send a file or image (size: small/medium/large)
+              /send <filepath or URL> [-s|-m|-l]      - Send file/image/audio (size flag for images)
               /avatar <URL or filepath>             - Set your avatar
               /profile [username]                   - View a profile
               /servers                             - Open saved servers

src/EchoHub.Client/Services/ApiClient.cs

@@ -196,6 +196,23 @@ public sealed class ApiClient : IDisposable
         return await response.Content.ReadFromJsonAsync<MessageDto>();
     }
 
+    public async Task<string> DownloadFileToTempAsync(string relativeUrl, string fileName)
+    {
+        EnsureAuthenticated();
+        var response = await AuthenticatedGetAsync(relativeUrl);
+        await EnsureSuccessAsync(response);
+
+        var tempDir = Path.Combine(Path.GetTempPath(), "EchoHub");
+        Directory.CreateDirectory(tempDir);
+        var tempPath = Path.Combine(tempDir, $"{Guid.NewGuid():N}_{fileName}");
+
+        await using var stream = await response.Content.ReadAsStreamAsync();
+        await using var file = File.Create(tempPath);
+        await stream.CopyToAsync(file);
+
+        return tempPath;
+    }
+
     public async Task<ChannelDto?> CreateChannelAsync(string name, string? topic = null, bool isPublic = true)
     {
         EnsureAuthenticated();

src/EchoHub.Client/Services/AudioPlaybackService.cs

@@ -0,0 +1,39 @@
+using NetCoreAudio;
+using Serilog;
+
+namespace EchoHub.Client.Services;
+
+public class AudioPlaybackService
+{
+    private readonly Player _player = new();
+
+    public bool IsPlaying => _player.Playing;
+
+    public async Task PlayAsync(string filePath)
+    {
+        try
+        {
+            if (_player.Playing)
+                await _player.Stop();
+
+            await _player.Play(filePath);
+        }
+        catch (Exception ex)
+        {
+            Log.Warning(ex, "Failed to play audio file: {Path}", filePath);
+        }
+    }
+
+    public async Task StopAsync()
+    {
+        try
+        {
+            if (_player.Playing)
+                await _player.Stop();
+        }
+        catch (Exception ex)
+        {
+            Log.Warning(ex, "Failed to stop audio playback");
+        }
+    }
+}

src/EchoHub.Client/UI/ChatRenderer.cs

@@ -1,6 +1,7 @@
 using System.Collections;
 using System.Collections.Specialized;
 using System.Text.RegularExpressions;
+using EchoHub.Core.Models;
 using Terminal.Gui.Drawing;
 using Terminal.Gui.Text;
 using Terminal.Gui.Views;
@@ -22,6 +23,9 @@ public partial class ChatLine
     public int TextLength { get; }
     public Guid? MessageId { get; set; }
     public bool IsMention { get; set; }
+    public string? AttachmentUrl { get; set; }
+    public string? AttachmentFileName { get; set; }
+    public MessageType? Type { get; set; }
 
     public ChatLine(string plainText)
     {
@@ -217,6 +221,8 @@ public class ChatListSource : IListDataSource
         RaiseCollectionChanged();
     }
 
+    public ChatLine? GetLine(int index) => index >= 0 && index < _lines.Count ? _lines[index] : null;
+
     public bool IsMarked(int item) => false;
     public void SetMark(int item, bool value) { }
     public IList ToList() => _lines.Select(l => l.ToString()).ToList();
@@ -465,6 +471,8 @@ public static partial class ChatColors
     public static readonly Attribute EmbedTitleAttr = new(Color.White, Color.Black);
     public static readonly Attribute EmbedDescAttr = new(new Color(160, 160, 160), Color.Black);
     public static readonly Attribute EmbedUrlAttr = new(new Color(100, 100, 100), Color.Black);
+    public static readonly Attribute AudioAttr = new(new Color(180, 100, 255), Color.Black);
+    public static readonly Attribute FileAttr = new(new Color(100, 180, 255), Color.Black);
 
     /// <summary>
     /// Split text around @mentions, giving each @word the MentionTextAttr accent color.

src/EchoHub.Client/UI/MainWindow.cs

@@ -113,6 +113,16 @@ public sealed class MainWindow : Runnable
     /// </summary>
     public event Action? OnDeleteChannelRequested;
 
+    /// <summary>
+    /// Fired when the user activates (Enter/click) an audio message. Parameters: attachmentUrl, fileName.
+    /// </summary>
+    public event Action<string, string>? OnAudioPlayRequested;
+
+    /// <summary>
+    /// Fired when the user activates (Enter/click) a file message. Parameters: attachmentUrl, fileName.
+    /// </summary>
+    public event Action<string, string>? OnFileDownloadRequested;
+
     public MainWindow(IApplication app)
     {
         _app = app;
@@ -175,6 +185,7 @@ public sealed class MainWindow : Runnable
             Height = Dim.Fill()
         };
         _messageList.Source = new ChatListSource();
+        _messageList.Accepting += OnMessageListAccepting;
         _chatFrame.Add(_messageList);
         Add(_chatFrame);
 
@@ -360,6 +371,31 @@ public sealed class MainWindow : Runnable
         }
     }
 
+    private void OnMessageListAccepting(object? sender, CommandEventArgs e)
+    {
+        if (_messageList.Source is not ChatListSource source)
+            return;
+
+        var index = _messageList.SelectedItem;
+        if (!index.HasValue || index.Value < 0 || index.Value >= source.Count)
+            return;
+
+        var line = source.GetLine(index.Value);
+        if (line?.AttachmentUrl is null || line.AttachmentFileName is null)
+            return;
+
+        if (line.Type == MessageType.Audio)
+        {
+            OnAudioPlayRequested?.Invoke(line.AttachmentUrl, line.AttachmentFileName);
+            e.Handled = true;
+        }
+        else if (line.Type == MessageType.File)
+        {
+            OnFileDownloadRequested?.Invoke(line.AttachmentUrl, line.AttachmentFileName);
+            e.Handled = true;
+        }
+    }
+
     private void OnInputKeyDown(object? sender, Key e)
     {
         if (e.KeyCode == TabKey.KeyCode)
@@ -900,10 +936,24 @@ public sealed class MainWindow : Runnable
                 }
                 break;
 
+            case MessageType.Audio:
+                var audioName = message.AttachmentFileName ?? "unknown";
+                var audioLine = BuildChatLineColored(time, senderName, senderColor,
+                    $" \u266a [Audio: {audioName}] (Enter to play)", ChatColors.AudioAttr);
+                audioLine.AttachmentUrl = message.AttachmentUrl;
+                audioLine.AttachmentFileName = audioName;
+                audioLine.Type = MessageType.Audio;
+                lines.Add(audioLine);
+                break;
+
             case MessageType.File:
                 var fileName = message.AttachmentFileName ?? "unknown";
-                var fileContent = !string.IsNullOrWhiteSpace(message.Content) ? $" {message.Content}" : "";
-                lines.Add(BuildChatLine(time, senderName, senderColor, $" [File: {fileName}]{fileContent}"));
+                var fileLine = BuildChatLineColored(time, senderName, senderColor,
+                    $" [File: {fileName}] (Enter to download)", ChatColors.FileAttr);
+                fileLine.AttachmentUrl = message.AttachmentUrl;
+                fileLine.AttachmentFileName = fileName;
+                fileLine.Type = MessageType.File;
+                lines.Add(fileLine);
                 break;
 
             case MessageType.Text:
@@ -962,6 +1012,20 @@ public sealed class MainWindow : Runnable
         return new ChatLine(segments);
     }
 
+    /// <summary>
+    /// Build a chat line with a colored suffix (used for audio/file indicators).
+    /// </summary>
+    private static ChatLine BuildChatLineColored(string time, string senderName, Attribute? senderColor, string suffix, Attribute suffixColor)
+    {
+        var segments = new List<ChatSegment>
+        {
+            new($"[{time}] ", ChatColors.TimestampAttr),
+            new(senderName, senderColor),
+            new(suffix, suffixColor)
+        };
+        return new ChatLine(segments);
+    }
+
     /// <summary>
     /// Build a chat line with @mention highlighting in the suffix text.
     /// </summary>