Basic echo implementation

Decho/App.axaml.cs

@@ -9,6 +9,8 @@ namespace Decho;
 
 public partial class App : Application
 {
+    private MainWindowViewModel? _viewModel;
+
     public override void Initialize()
     {
         AvaloniaXamlLoader.Load(this);
@@ -18,13 +20,18 @@ public partial class App : Application
     {
         if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
         {
+            _viewModel = new MainWindowViewModel();
+
             desktop.MainWindow = new MainWindow
             {
-                DataContext = new MainWindowViewModel(),
+                DataContext = _viewModel,
             };
+
+            _viewModel.SetMainWindow(desktop.MainWindow);
+
+            desktop.Exit += (_, _) => _viewModel.Dispose();
         }
 
         base.OnFrameworkInitializationCompleted();
     }
-
 }

Decho/Decho.csproj

@@ -3,6 +3,7 @@
     <OutputType>WinExe</OutputType>
     <TargetFramework>net10.0</TargetFramework>
     <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
     <ApplicationManifest>app.manifest</ApplicationManifest>
     <AvaloniaUseCompiledBindingsByDefault>true</AvaloniaUseCompiledBindingsByDefault>
   </PropertyGroup>
@@ -25,5 +26,15 @@
     <PackageReference Include="Projektanker.Icons.Avalonia.FontAwesome" Version="9.6.2" />
     <PackageReference Include="ReactiveUI.Avalonia" Version="11.3.8" />
     <PackageReference Include="Romzetron.Avalonia" Version="11.3.4" />
+    <PackageReference Include="Microsoft.AspNetCore.SignalR.Client" Version="10.0.3" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="10.0.3" />
+    <PackageReference Include="Serilog" Version="4.3.1" />
+    <PackageReference Include="Serilog.Settings.Configuration" Version="10.0.0" />
+    <PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\EchoHub\src\EchoHub.Client\EchoHub.Client.csproj" />
+    <ProjectReference Include="..\..\EchoHub\src\EchoHub.Core\EchoHub.Core.csproj" />
   </ItemGroup>
 </Project>

Decho/Models/ChannelModel.cs

@@ -4,16 +4,27 @@ namespace Decho.Models;
 
 public sealed class ChannelModel
 {
-    public ChannelModel(string id, string name, ObservableCollection<MessageModel> messages)
+    public ChannelModel(
+        string id,
+        string name,
+        ObservableCollection<MessageModel> messages,
+        string? topic = null,
+        bool isPublic = true)
     {
         Id = id;
         Name = name;
         Messages = messages;
+        Topic = topic;
+        IsPublic = isPublic;
     }
 
     public string Id { get; }
 
     public string Name { get; }
 
+    public string? Topic { get; set; }
+
+    public bool IsPublic { get; }
+
     public ObservableCollection<MessageModel> Messages { get; }
 }

Decho/Models/MessageModel.cs

@@ -1,15 +1,31 @@
-using System;
+using EchoHub.Core.Models;
 
 namespace Decho.Models;
 
 public sealed class MessageModel
 {
-    public MessageModel(string id, UserModel author, DateTimeOffset sentAt, string content)
+    public MessageModel(
+        string id,
+        UserModel author,
+        DateTimeOffset sentAt,
+        string content,
+        string channelName,
+        string? serverUrl = null,
+        MessageType type = MessageType.Text,
+        string? attachmentUrl = null,
+        string? attachmentFileName = null,
+        long? attachmentFileSize = null)
     {
         Id = id;
         Author = author;
         SentAt = sentAt;
         Content = content;
+        ChannelName = channelName;
+        ServerUrl = serverUrl;
+        Type = type;
+        AttachmentUrl = attachmentUrl;
+        AttachmentFileName = attachmentFileName;
+        AttachmentFileSize = attachmentFileSize;
     }
 
     public string Id { get; }
@@ -19,4 +35,16 @@ public sealed class MessageModel
     public DateTimeOffset SentAt { get; }
 
     public string Content { get; }
+
+    public string ChannelName { get; }
+
+    public string? ServerUrl { get; }
+
+    public MessageType Type { get; }
+
+    public string? AttachmentUrl { get; }
+
+    public string? AttachmentFileName { get; }
+
+    public long? AttachmentFileSize { get; }
 }

Decho/Models/ServerModel.cs

@@ -4,16 +4,35 @@ namespace Decho.Models;
 
 public sealed class ServerModel
 {
-    public ServerModel(string id, string name, ObservableCollection<ChannelModel> channels)
+    public ServerModel(
+        string id,
+        string name,
+        ObservableCollection<ChannelModel> channels,
+        string serverUrl = "",
+        bool isConnected = false,
+        bool isConnecting = false,
+        string? connectedUser = null)
     {
         Id = id;
         Name = name;
         Channels = channels;
+        ServerUrl = serverUrl;
+        IsConnected = isConnected;
+        IsConnecting = isConnecting;
+        ConnectedUser = connectedUser;
     }
 
     public string Id { get; }
 
     public string Name { get; }
 
+    public string ServerUrl { get; set; }
+
+    public bool IsConnected { get; set; }
+
+    public bool IsConnecting { get; set; }
+
+    public string? ConnectedUser { get; set; }
+
     public ObservableCollection<ChannelModel> Channels { get; }
 }

Decho/Models/UserModel.cs

@@ -1,14 +1,30 @@
+using EchoHub.Core.Models;
+
 namespace Decho.Models;
 
 public sealed class UserModel
 {
-    public UserModel(string id, string displayName)
+    public UserModel(
+        string id,
+        string displayName,
+        string? nicknameColor = null,
+        UserStatus status = UserStatus.Online,
+        string? statusMessage = null)
     {
         Id = id;
         DisplayName = displayName;
+        NicknameColor = nicknameColor;
+        Status = status;
+        StatusMessage = statusMessage;
     }
 
     public string Id { get; }
 
     public string DisplayName { get; }
+
+    public string? NicknameColor { get; set; }
+
+    public UserStatus Status { get; set; }
+
+    public string? StatusMessage { get; set; }
 }

Decho/Services/ConnectionService.cs

@@ -0,0 +1,509 @@
+using System.Collections.ObjectModel;
+using EchoHub.Client.Config;
+using EchoHub.Client.Services;
+using EchoHub.Client.Commands;
+using EchoHub.Core.Constants;
+using EchoHub.Core.DTOs;
+using EchoHub.Core.Models;
+using Decho.Models;
+
+namespace Decho.Services;
+
+public sealed class ConnectionService : IDisposable
+{
+    private readonly Dictionary<string, ServerConnection> _connections = new(StringComparer.OrdinalIgnoreCase);
+
+    public event Action<ServerModel>? ServerAdded;
+    public event Action<string>? ServerRemoved;
+    public event Action<ServerModel>? ServerStateChanged;
+    public event Action<string, ChannelModel>? ChannelAdded;
+    public event Action<string, string>? ChannelRemoved;
+    public event Action<string, MessageModel>? MessageReceived;
+    public event Action<string, string, string?>? UserJoined;
+    public event Action<string, string>? UserLeft;
+    public event Action<string, string>? ErrorOccurred;
+
+    internal IReadOnlyDictionary<string, ServerConnection> Connections => _connections;
+
+    internal ServerConnection? GetConnection(string serverUrl) =>
+        _connections.TryGetValue(serverUrl, out var conn) ? conn : null;
+
+    public async Task<ServerModel> ConnectAsync(string serverUrl, string username, string password, bool isRegister, bool rememberMe)
+    {
+        var conn = new ConnectionManager();
+
+        var dialogResult = new EchoHub.Client.UI.Dialogs.ConnectDialogResult(
+            serverUrl, username, password, isRegister, rememberMe, null);
+
+        ConnectResult result;
+        try
+        {
+            result = await conn.ConnectAsync(dialogResult, _ => { });
+        }
+        catch
+        {
+            await conn.DisposeAsync();
+            throw;
+        }
+
+        var login = result.Login;
+        var userModel = new UserModel(login.Username, login.DisplayName ?? login.Username,
+            login.NicknameColor);
+
+        var channels = new ObservableCollection<ChannelModel>();
+        var serverModel = new ServerModel(
+            Guid.NewGuid().ToString("N"),
+            new Uri(serverUrl).Host,
+            channels,
+            serverUrl,
+            isConnected: true,
+            connectedUser: login.Username);
+
+        var serverEntry = new ServerConnection(conn, conn.Api!, serverModel, userModel);
+
+        foreach (var ch in result.Channels)
+        {
+            var channelModel = ChannelModelFromDto(ch);
+            channels.Add(channelModel);
+        }
+
+        WireConnectionEvents(serverEntry, conn);
+
+        _connections[serverUrl] = serverEntry;
+        SaveRefreshToken(serverUrl, rememberMe);
+        ServerAdded?.Invoke(serverModel);
+
+        return serverModel;
+    }
+
+    public async Task ConnectWithSavedTokenAsync(string serverUrl, string username, string refreshToken, bool rememberMe)
+    {
+        var conn = new ConnectionManager();
+
+        var dialogResult = new EchoHub.Client.UI.Dialogs.ConnectDialogResult(
+            serverUrl, username, "", false, rememberMe, refreshToken);
+
+        ConnectResult result;
+        try
+        {
+            result = await conn.ConnectAsync(dialogResult, _ => { });
+        }
+        catch
+        {
+            await conn.DisposeAsync();
+            throw;
+        }
+
+        var login = result.Login;
+        var userModel = new UserModel(login.Username, login.DisplayName ?? login.Username, login.NicknameColor);
+
+        var channels = new ObservableCollection<ChannelModel>();
+        var serverModel = new ServerModel(
+            Guid.NewGuid().ToString("N"),
+            new Uri(serverUrl).Host,
+            channels,
+            serverUrl,
+            isConnected: true,
+            connectedUser: login.Username);
+
+        var serverEntry = new ServerConnection(conn, conn.Api!, serverModel, userModel);
+
+        foreach (var ch in result.Channels)
+        {
+            var channelModel = ChannelModelFromDto(ch);
+            channels.Add(channelModel);
+        }
+
+        WireConnectionEvents(serverEntry, conn);
+
+        _connections[serverUrl] = serverEntry;
+        SaveRefreshToken(serverUrl, rememberMe);
+        ServerAdded?.Invoke(serverModel);
+    }
+
+    private void SaveRefreshToken(string serverUrl, bool rememberMe)
+    {
+        if (!rememberMe) return;
+        if (!_connections.TryGetValue(serverUrl, out var entry)) return;
+        var token = entry.ApiClient.RefreshToken;
+        if (string.IsNullOrEmpty(token)) return;
+
+        var config = ConfigManager.Load();
+        var saved = config.SavedServers.FirstOrDefault(s =>
+            string.Equals(s.Url, serverUrl, StringComparison.OrdinalIgnoreCase));
+        if (saved is null)
+        {
+            saved = new SavedServer
+            {
+                Name = new Uri(serverUrl).Host,
+                Url = serverUrl,
+                Username = entry.User.Id,
+                RememberMe = true,
+                LastConnected = DateTimeOffset.Now,
+            };
+            config.SavedServers.Add(saved);
+        }
+
+        saved.RefreshToken = token;
+        saved.LastConnected = DateTimeOffset.Now;
+        ConfigManager.Save(config);
+    }
+
+    public async Task DisconnectAsync(string serverUrl)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+
+        entry.Server.IsConnected = false;
+        entry.Server.IsConnecting = false;
+        ServerStateChanged?.Invoke(entry.Server);
+
+        await entry.Manager.CleanupAsync();
+        entry.ApiClient.Dispose();
+        await entry.Manager.DisposeAsync();
+
+        _connections.Remove(serverUrl);
+        ServerRemoved?.Invoke(serverUrl);
+    }
+
+    public async Task SendMessageAsync(string serverUrl, string channelName, string content)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            throw new InvalidOperationException("Not connected to server");
+
+        await entry.Manager.SendMessageAsync(channelName, content);
+    }
+
+    public async Task<List<MessageModel>> JoinChannelAsync(string serverUrl, string channelName)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            throw new InvalidOperationException("Not connected to server");
+
+        if (entry.Manager.TrackChannel(channelName))
+        {
+            var history = await entry.Manager.JoinChannelAsync(channelName);
+            return history.Select(m => MessageModelFromDto(m, entry)).ToList();
+        }
+
+        var existing = await entry.Manager.GetHistoryAsync(channelName);
+        return existing.Select(m => MessageModelFromDto(m, entry)).ToList();
+    }
+
+    public async Task LeaveChannelAsync(string serverUrl, string channelName)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.Manager.LeaveChannelAsync(channelName);
+    }
+
+    public async Task<List<MessageModel>> GetHistoryAsync(string serverUrl, string channelName, int count = HubConstants.DefaultHistoryCount, int offset = 0)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return [];
+
+        var history = await entry.Manager.GetHistoryAsync(channelName, count, offset);
+        return history.Select(m => MessageModelFromDto(m, entry)).ToList();
+    }
+
+    public async Task<List<UserPresenceDto>> GetOnlineUsersAsync(string serverUrl, string channelName)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return [];
+        return await entry.Manager.GetOnlineUsersAsync(channelName);
+    }
+
+    public async Task UpdateStatusAsync(string serverUrl, UserStatus status, string? statusMessage)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.Manager.UpdateStatusAsync(status, statusMessage);
+        entry.User.Status = status;
+        entry.User.StatusMessage = statusMessage;
+    }
+
+    public async Task<ChannelDto?> CreateChannelAsync(string serverUrl, string name, string? topic, bool isPublic)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return null;
+        return await entry.ApiClient.CreateChannelAsync(name, topic, isPublic);
+    }
+
+    public async Task DeleteChannelAsync(string serverUrl, string channelName)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.DeleteChannelAsync(channelName);
+        entry.Manager.UntrackChannel(channelName);
+    }
+
+    public async Task KickUserAsync(string serverUrl, string username, string? reason)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.KickUserAsync(username, reason);
+    }
+
+    public async Task BanUserAsync(string serverUrl, string username, string? reason)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.BanUserAsync(username, reason);
+    }
+
+    public async Task UnbanUserAsync(string serverUrl, string username)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.UnbanUserAsync(username);
+    }
+
+    public async Task MuteUserAsync(string serverUrl, string username, int? durationMinutes)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.MuteUserAsync(username, durationMinutes);
+    }
+
+    public async Task UnmuteUserAsync(string serverUrl, string username)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.UnmuteUserAsync(username);
+    }
+
+    public async Task AssignRoleAsync(string serverUrl, string username, ServerRole role)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.AssignRoleAsync(username, role);
+    }
+
+    public async Task NukeChannelAsync(string serverUrl, string channelName)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.NukeChannelAsync(channelName);
+    }
+
+    public async Task UpdateProfileAsync(string serverUrl, string? displayName, string? bio, string? nickColor)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.UpdateProfileAsync(new UpdateProfileRequest(displayName, bio, nickColor));
+    }
+
+    public async Task SetAvatarAsync(string serverUrl, string target)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await AvatarHelper.UploadAsync(entry.ApiClient, target);
+    }
+
+    public async Task SendUrlAsync(string serverUrl, string channelName, string url, string? size)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+        await entry.ApiClient.SendUrlAsync(channelName, url, size);
+    }
+
+    public async Task UploadFileAsync(string serverUrl, string channelName, string filePath, string? size)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+
+        await using var stream = File.OpenRead(filePath);
+        var fileName = Path.GetFileName(filePath);
+        await entry.ApiClient.UploadFileAsync(channelName, stream, fileName, size);
+    }
+
+    public void UpdateChannelTopic(string serverUrl, string channelName, string? topic)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+
+        var channel = entry.Server.Channels.FirstOrDefault(c =>
+            string.Equals(c.Name, channelName, StringComparison.OrdinalIgnoreCase));
+        if (channel is not null)
+            channel.Topic = topic;
+    }
+
+    public void AddChannelToList(string serverUrl, ChannelDto channelDto)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+
+        var model = ChannelModelFromDto(channelDto);
+        entry.Server.Channels.Add(model);
+        ChannelAdded?.Invoke(serverUrl, model);
+    }
+
+    public void RemoveChannelFromList(string serverUrl, string channelName)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return;
+
+        var channel = entry.Server.Channels.FirstOrDefault(c =>
+            string.Equals(c.Name, channelName, StringComparison.OrdinalIgnoreCase));
+        if (channel is not null)
+        {
+            entry.Server.Channels.Remove(channel);
+            ChannelRemoved?.Invoke(serverUrl, channelName);
+        }
+    }
+
+    public ClientConfig LoadConfig() => ConfigManager.Load();
+
+    public void SaveConfig(ClientConfig config) => ConfigManager.Save(config);
+
+    public void SaveServerToConfig(SavedServer server) => ConfigManager.SaveServer(server);
+
+    public void RemoveServerFromConfig(string url) => ConfigManager.RemoveServer(url);
+
+    public CommandHandler CreateCommandHandler() => new();
+
+    public bool IsCommand(string input) => input.StartsWith('/');
+
+    public string? GetRefreshToken(string serverUrl)
+    {
+        return _connections.TryGetValue(serverUrl, out var entry)
+            ? entry.ApiClient.RefreshToken
+            : null;
+    }
+
+    public async Task<string?> DownloadAttachmentAsync(string serverUrl, string relativeUrl, string fileName)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return null;
+        try
+        {
+            return await entry.ApiClient.DownloadFileToTempAsync(relativeUrl, fileName);
+        }
+        catch
+        {
+            return null;
+        }
+    }
+
+    public async Task<byte[]?> DownloadImageBytesAsync(string serverUrl, string relativeUrl)
+    {
+        if (!_connections.TryGetValue(serverUrl, out var entry))
+            return null;
+        return await entry.ApiClient.DownloadBytesAsync(relativeUrl);
+    }
+
+    public string? GetCurrentUsername(string serverUrl)
+    {
+        return _connections.TryGetValue(serverUrl, out var entry)
+            ? entry.User.DisplayName
+            : null;
+    }
+
+    public void Dispose()
+    {
+        foreach (var (_, entry) in _connections)
+        {
+            entry.ApiClient.Dispose();
+        }
+        _connections.Clear();
+    }
+
+    private void WireConnectionEvents(ServerConnection entry, ConnectionManager conn)
+    {
+        conn.MessageReceived += message =>
+        {
+            var msg = MessageModelFromDto(message, entry);
+            MessageReceived?.Invoke(entry.Server.ServerUrl, msg);
+        };
+
+        conn.UserJoined += (channelName, username, presence) =>
+        {
+            UserJoined?.Invoke(entry.Server.ServerUrl, channelName, username);
+        };
+
+        conn.UserLeft += (channelName, username) =>
+        {
+            UserLeft?.Invoke(entry.Server.ServerUrl, channelName);
+        };
+
+        conn.UserStatusChanged += presence =>
+        {
+            entry.User.Status = presence.Status;
+            entry.User.StatusMessage = presence.StatusMessage;
+        };
+
+        conn.ChannelUpdated += channel =>
+        {
+            var existing = entry.Server.Channels.FirstOrDefault(c =>
+                string.Equals(c.Name, channel.Name, StringComparison.OrdinalIgnoreCase));
+            if (existing is not null)
+            {
+                existing.Topic = channel.Topic;
+            }
+        };
+
+        conn.ForceDisconnected += reason =>
+        {
+            entry.Server.IsConnected = false;
+            ServerStateChanged?.Invoke(entry.Server);
+            ErrorOccurred?.Invoke(entry.Server.ServerUrl, reason);
+        };
+
+        conn.Error += error =>
+        {
+            ErrorOccurred?.Invoke(entry.Server.ServerUrl, error);
+        };
+
+        conn.ConnectionStatusChanged += status =>
+        {
+            entry.Server.IsConnected = status == "Connected";
+            entry.Server.IsConnecting = status is "Connecting..." or "Authenticating...";
+            ServerStateChanged?.Invoke(entry.Server);
+        };
+    }
+
+    internal static ChannelModel ChannelModelFromDto(ChannelDto dto)
+    {
+        return new ChannelModel(
+            dto.Id.ToString(),
+            dto.Name,
+            new ObservableCollection<MessageModel>(),
+            dto.Topic,
+            dto.IsPublic);
+    }
+
+    internal static MessageModel MessageModelFromDto(MessageDto dto, ServerConnection entry)
+    {
+        var author = new UserModel(
+            dto.SenderUsername,
+            dto.SenderUsername,
+            dto.SenderNicknameColor);
+
+        return new MessageModel(
+            dto.Id.ToString("N"),
+            author,
+            dto.SentAt,
+            dto.Content,
+            dto.ChannelName,
+            entry.Server.ServerUrl,
+            dto.Type,
+            dto.AttachmentUrl,
+            dto.AttachmentFileName,
+            dto.AttachmentFileSize);
+    }
+}
+
+internal sealed class ServerConnection
+{
+    internal ConnectionManager Manager { get; }
+    public ApiClient ApiClient { get; }
+    public ServerModel Server { get; }
+    public UserModel User { get; }
+
+    internal ServerConnection(ConnectionManager manager, ApiClient apiClient, ServerModel server, UserModel user)
+    {
+        Manager = manager;
+        ApiClient = apiClient;
+        Server = server;
+        User = user;
+    }
+}

Decho/ViewModels/ChannelViewModel.cs

@@ -18,11 +18,40 @@ public sealed class ChannelViewModel : ViewModelBase
 
     public string Name => Model.Name;
 
+    public string? Topic
+    {
+        get => Model.Topic;
+        set
+        {
+            if (Model.Topic != value)
+            {
+                Model.Topic = value;
+                this.RaisePropertyChanged();
+                this.RaisePropertyChanged(nameof(HasTopic));
+            }
+        }
+    }
+
+    public bool HasTopic => !string.IsNullOrWhiteSpace(Topic);
+
+    public bool IsPublic => Model.IsPublic;
+
     public ObservableCollection<MessageViewModel> Messages { get; }
 
+    public void ClearMessages()
+    {
+        Model.Messages.Clear();
+        Messages.Clear();
+    }
+
     public void AddMessage(MessageModel message)
     {
         Model.Messages.Add(message);
         Messages.Add(new MessageViewModel(message));
     }
-}
+
+    public void AddMessageViewModel(MessageViewModel messageViewModel)
+    {
+        Messages.Add(messageViewModel);
+    }
+}

Decho/ViewModels/ChatViewModel.cs

@@ -1,4 +1,9 @@
+using System;
 using System.Collections.ObjectModel;
+using System.Threading.Tasks;
+
+using EchoHub.Client.Commands;
+using ReactiveUI;
 
 namespace Decho.ViewModels;
 
@@ -6,10 +11,15 @@ public sealed class ChatViewModel : ViewModelBase
 {
     private ObservableCollection<MessageViewModel> _messages = new();
     private string _channelTitle = "Select a channel";
+    private string? _channelTopic;
+    private bool _hasTopic;
+    private string _currentServerUrl = string.Empty;
+    private string _currentChannelName = string.Empty;
 
     public ChatViewModel()
     {
         Composer = new MessageComposerViewModel();
+        Composer.CommandRequested += HandleCommandAsync;
     }
 
     public ObservableCollection<MessageViewModel> Messages
@@ -24,18 +34,76 @@ public sealed class ChatViewModel : ViewModelBase
         private set => this.RaiseAndSetIfChanged(ref _channelTitle, value);
     }
 
+    public string? ChannelTopic
+    {
+        get => _channelTopic;
+        set
+        {
+            this.RaiseAndSetIfChanged(ref _channelTopic, value);
+            this.RaisePropertyChanged(nameof(HasTopic));
+        }
+    }
+
+    public bool HasTopic
+    {
+        get => _hasTopic;
+        private set => this.RaiseAndSetIfChanged(ref _hasTopic, value);
+    }
+
     public MessageComposerViewModel Composer { get; }
 
-    public void SetChannel(ChannelViewModel? channel)
+    public string CurrentServerUrl => _currentServerUrl;
+    public string CurrentChannelName => _currentChannelName;
+
+    public event Func<string, Task<string?>>? CommandRequested;
+
+    public void SetChannel(ChannelViewModel? channel, string serverUrl = "")
     {
         if (channel is null)
         {
             Messages = new ObservableCollection<MessageViewModel>();
             ChannelTitle = "Select a channel";
+            ChannelTopic = null;
+            HasTopic = false;
+            _currentChannelName = string.Empty;
+            _currentServerUrl = string.Empty;
+            Composer.SetServer(string.Empty);
             return;
         }
 
         Messages = channel.Messages;
         ChannelTitle = "#" + channel.Name;
+        ChannelTopic = channel.Topic;
+        HasTopic = channel.HasTopic;
+        _currentChannelName = channel.Name;
+        _currentServerUrl = serverUrl;
+        Composer.SetServer(serverUrl);
     }
-}
+
+    public void SetComposerCommandHandler(CommandHandler handler)
+    {
+        Composer.SetCommandHandler(handler);
+    }
+
+    public void AddMessage(MessageViewModel message)
+    {
+        Messages.Add(message);
+    }
+
+    public void ClearMessages()
+    {
+        Messages = new ObservableCollection<MessageViewModel>();
+        ChannelTitle = "Select a channel";
+        ChannelTopic = null;
+        HasTopic = false;
+    }
+
+    private async Task<string?> HandleCommandAsync(string commandText)
+    {
+        if (CommandRequested is not null)
+        {
+            return await CommandRequested(commandText);
+        }
+        return null;
+    }
+}

Decho/ViewModels/MainWindowViewModel.cs

@@ -1,16 +1,35 @@
 using System;
-using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reactive;
+using System.Reactive.Concurrency;
 using System.Reactive.Linq;
+using System.Threading.Tasks;
+
+using Avalonia.Controls;
+using Avalonia.Controls.ApplicationLifetimes;
 
 using Decho.Models;
+using Decho.Services;
+
+using EchoHub.Client.Commands;
+using EchoHub.Client.Config;
+using EchoHub.Core.Constants;
+using EchoHub.Core.DTOs;
+using EchoHub.Core.Models;
+
 using ReactiveUI;
 
 namespace Decho.ViewModels;
 
 public sealed class MainWindowViewModel : ViewModelBase
 {
-    private readonly UserModel _currentUser;
+    private readonly ConnectionService _connectionService;
+    private readonly CommandHandler _commandHandler;
+    private string _statusText = "Ready";
+    private bool _isConnected;
+    private Window? _mainWindow;
 
     public string Title { get; } = "Decho";
 
@@ -18,82 +37,842 @@ public sealed class MainWindowViewModel : ViewModelBase
 
     public ChatViewModel Chat { get; }
 
+    public string StatusText
+    {
+        get => _statusText;
+        set => this.RaiseAndSetIfChanged(ref _statusText, value);
+    }
+
+    public bool IsConnected
+    {
+        get => _isConnected;
+        set => this.RaiseAndSetIfChanged(ref _isConnected, value);
+    }
+
+    public ConnectionService ConnectionService => _connectionService;
+
+    public ReactiveCommand<Unit, Unit> AddServerCommand { get; }
+
     public MainWindowViewModel()
     {
-        _currentUser = new UserModel("user-1", "You");
+        _connectionService = new ConnectionService();
+        _commandHandler = _connectionService.CreateCommandHandler();
 
-        var servers = SeedServers();
-        Sidebar = new SidebarViewModel(servers);
+        Sidebar = new SidebarViewModel();
         Chat = new ChatViewModel();
 
-        Sidebar.WhenAnyValue(x => x.SelectedChannel)
-            .Subscribe(channel => Chat.SetChannel(channel));
+        AddServerCommand = ReactiveCommand.Create(AddServer);
 
         Chat.Composer.SendRequested += HandleSendRequested;
+        Chat.Composer.CommandRequested += HandleCommandAsync;
+        Chat.Composer.FileUploadRequested += HandleFileUploadRequested;
 
-        if (Sidebar.SelectedChannel is not null)
-            Chat.SetChannel(Sidebar.SelectedChannel);
+        WireCommandHandlerEvents();
+        WireConnectionServiceEvents();
+
+        Sidebar.WhenAnyValue(x => x.SelectedChannel)
+            .Subscribe(channel => HandleChannelSelected(channel));
+
+        _ = InitializeSavedServersAsync();
     }
 
-    private void HandleSendRequested(string text)
+    public void SetMainWindow(Window window)
     {
-        if (Sidebar.SelectedChannel is null)
+        _mainWindow = window;
+    }
+
+    private void AddServer()
+    {
+        var placeholderServer = new ServerModel(
+            Guid.NewGuid().ToString("N"),
+            "New Server",
+            new ObservableCollection<ChannelModel>(),
+            isConnected: false);
+
+        var serverVm = new ServerViewModel(placeholderServer);
+        serverVm.ConnectRequested += async () => await HandleServerConnectRequested(serverVm);
+        serverVm.DisconnectRequested += async () => await HandleServerDisconnectRequested(serverVm);
+
+        Sidebar.Servers.Add(serverVm);
+        StatusText = "Click Connect on the server to get started";
+    }
+
+    private void WireCommandHandlerEvents()
+    {
+        _commandHandler.OnSetStatus += async (status, message) =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+            await _connectionService.UpdateStatusAsync(serverUrl, status, message);
+        };
+
+        _commandHandler.OnSetTheme += themeName =>
+        {
+            return Task.CompletedTask;
+        };
+
+        _commandHandler.OnJoinChannel += async channelName =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+
+            var channel = await _connectionService.JoinChannelAsync(serverUrl, channelName);
+            EnsureChannelInList(serverUrl, channelName);
+            var channelModel = FindChannel(serverUrl, channelName);
+            if (channelModel is not null)
+            {
+                var channelVm = Sidebar.GetServer(serverUrl)?.Channels
+                    .FirstOrDefault(c => c.Name == channelName);
+                if (channelVm is not null)
+                {
+                    foreach (var msg in channel)
+                        channelVm.AddMessage(msg);
+                }
+            }
+        };
+
+        _commandHandler.OnLeaveChannel += async () =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            var channel = Chat.CurrentChannelName;
+            if (string.IsNullOrEmpty(serverUrl) || string.IsNullOrEmpty(channel)) return;
+
+            if (channel == HubConstants.DefaultChannel) return;
+            await _connectionService.LeaveChannelAsync(serverUrl, channel);
+        };
+
+        _commandHandler.OnListUsers += async () =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            var channel = Chat.CurrentChannelName;
+            if (string.IsNullOrEmpty(serverUrl) || string.IsNullOrEmpty(channel)) return;
+
+            var users = await _connectionService.GetOnlineUsersAsync(serverUrl, channel);
+            var userList = string.Join(", ", users.Select(u => u.DisplayName ?? u.Username));
+            StatusText = $"Online in #{channel}: {userList}";
+        };
+
+        _commandHandler.OnSetTopic += async topic =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            var channel = Chat.CurrentChannelName;
+            if (string.IsNullOrEmpty(serverUrl) || string.IsNullOrEmpty(channel)) return;
+
+            await _connectionService.UpdateProfileAsync(serverUrl, null, null, null);
+            _connectionService.UpdateChannelTopic(serverUrl, channel, topic);
+            Chat.ChannelTopic = topic;
+        };
+
+        _commandHandler.OnKickUser += async (username, reason) =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+            await _connectionService.KickUserAsync(serverUrl, username, reason);
+        };
+
+        _commandHandler.OnBanUser += async (username, reason) =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+            await _connectionService.BanUserAsync(serverUrl, username, reason);
+        };
+
+        _commandHandler.OnUnbanUser += async username =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+            await _connectionService.UnbanUserAsync(serverUrl, username);
+        };
+
+        _commandHandler.OnMuteUser += async (username, duration) =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+            await _connectionService.MuteUserAsync(serverUrl, username, duration);
+        };
+
+        _commandHandler.OnUnmuteUser += async username =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+            await _connectionService.UnmuteUserAsync(serverUrl, username);
+        };
+
+        _commandHandler.OnAssignRole += async (username, roleStr) =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+
+            var role = roleStr.ToLowerInvariant() switch
+            {
+                "admin" => ServerRole.Admin,
+                "mod" => ServerRole.Mod,
+                _ => ServerRole.Member,
+            };
+            await _connectionService.AssignRoleAsync(serverUrl, username, role);
+        };
+
+        _commandHandler.OnNukeChannel += async () =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            var channel = Chat.CurrentChannelName;
+            if (string.IsNullOrEmpty(serverUrl) || string.IsNullOrEmpty(channel)) return;
+            await _connectionService.NukeChannelAsync(serverUrl, channel);
+        };
+
+        _commandHandler.OnTestSound += () => Task.CompletedTask;
+
+        _commandHandler.OnQuit += () =>
+        {
+            if (_mainWindow is not null)
+                Avalonia.Threading.Dispatcher.UIThread.Post(() => _mainWindow.Close());
+            return Task.CompletedTask;
+        };
+
+        _commandHandler.OnHelp += () => Task.CompletedTask;
+
+        _commandHandler.OnSendFile += async (target, size) =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            var channel = Chat.CurrentChannelName;
+            if (string.IsNullOrEmpty(serverUrl) || string.IsNullOrEmpty(channel)) return;
+
+            try
+            {
+                if (Uri.TryCreate(target, UriKind.Absolute, out var uri)
+                    && (uri.Scheme == "http" || uri.Scheme == "https"))
+                {
+                    await _connectionService.SendUrlAsync(serverUrl, channel, target, size);
+                }
+                else
+                {
+                    await _connectionService.UploadFileAsync(serverUrl, channel, target, size);
+                }
+            }
+            catch (Exception ex)
+            {
+                StatusText = $"Send failed: {ex.Message}";
+            }
+        };
+
+        _commandHandler.OnSetNick += async displayName =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+            await _connectionService.UpdateProfileAsync(serverUrl, displayName, null, null);
+        };
+
+        _commandHandler.OnSetColor += async color =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+            await _connectionService.UpdateProfileAsync(serverUrl, null, null, color);
+        };
+
+        _commandHandler.OnSetAvatar += async target =>
+        {
+            var serverUrl = GetCurrentServerUrl();
+            if (string.IsNullOrEmpty(serverUrl)) return;
+            await _connectionService.SetAvatarAsync(serverUrl, target);
+        };
+
+        _commandHandler.OnOpenProfile += async username =>
+        {
+            StatusText = $"Profile: {username ?? "self"}";
+        };
+
+        _commandHandler.OnOpenServers += () =>
+        {
+            var config = _connectionService.LoadConfig();
+            var servers = string.Join("\n", config.SavedServers.Select(s =>
+                $"{s.Name} ({s.Url}) - {s.Username ?? "?"}"));
+            StatusText = servers;
+            return Task.CompletedTask;
+        };
+    }
+
+    private void WireConnectionServiceEvents()
+    {
+        _connectionService.ServerAdded += server =>
+        {
+            var serverVm = new ServerViewModel(server);
+            serverVm.ConnectRequested += () => HandleServerConnectRequested(serverVm);
+            serverVm.DisconnectRequested += () => HandleServerDisconnectRequested(serverVm);
+            serverVm.WhenAnyValue(s => s.SelectedChannel)
+                .Where(channel => channel is not null)
+                .Subscribe(channel => Sidebar.SelectedChannel = channel!);
+
+            Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+            {
+                var existing = Sidebar.GetServer(server.ServerUrl);
+                if (existing is not null)
+                    Sidebar.Servers.Remove(existing);
+                Sidebar.Servers.Add(serverVm);
+                StatusText = $"Connected to {server.Name}";
+                IsConnected = true;
+            });
+        };
+
+        _connectionService.ServerRemoved += serverUrl =>
+        {
+            Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+            {
+                Sidebar.RemoveServer(serverUrl);
+                if (Sidebar.Servers.Count == 0)
+                {
+                    IsConnected = false;
+                    Chat.ClearMessages();
+                    StatusText = "Ready";
+                }
+            });
+        };
+
+        _connectionService.ServerStateChanged += server =>
+        {
+            Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+            {
+                var serverVm = Sidebar.GetServer(server.ServerUrl);
+                if (serverVm is not null)
+                {
+                    serverVm.SyncFromModel();
+                    if (!server.IsConnected)
+                        StatusText = $"Disconnected from {server.Name}";
+                }
+            });
+        };
+
+        _connectionService.MessageReceived += (serverUrl, message) =>
+        {
+            Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+            {
+                var channelVm = FindChannelViewModel(serverUrl, message.ChannelName);
+                if (channelVm is not null)
+                {
+                    channelVm.AddMessage(message);
+                }
+            });
+        };
+
+        _connectionService.ChannelAdded += (serverUrl, channel) =>
+        {
+            Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+            {
+                EnsureChannelInList(serverUrl, channel.Name);
+            });
+        };
+
+        _connectionService.ErrorOccurred += (serverUrl, error) =>
+        {
+            Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+            {
+                StatusText = $"Error: {error}";
+            });
+        };
+    }
+
+    private async Task<string?> HandleCommandAsync(string commandText)
+    {
+        var result = await _commandHandler.HandleAsync(commandText);
+        if (result.Message is not null && !result.IsError)
+        {
+            Chat.AddMessage(new MessageViewModel(new MessageModel(
+                Guid.NewGuid().ToString("N"),
+                new UserModel("system", "System"),
+                DateTimeOffset.Now,
+                result.Message,
+                Chat.CurrentChannelName,
+                Chat.CurrentServerUrl)));
+        }
+        return result.Message;
+    }
+
+    private void HandleSendRequested(string serverUrl, string text)
+    {
+        if (string.IsNullOrEmpty(Chat.CurrentChannelName))
             return;
 
-        var message = new MessageModel(
-            Guid.NewGuid().ToString("N"),
-            _currentUser,
-            DateTimeOffset.Now,
-            text);
+            if (_commandHandler.IsCommand(text))
+            {
+                _ = HandleCommandAsync(text);
+                return;
+            }
 
-        Sidebar.SelectedChannel.AddMessage(message);
+        Task.Run(async () =>
+        {
+            try
+            {
+                await _connectionService.SendMessageAsync(serverUrl, Chat.CurrentChannelName, text);
+            }
+            catch (Exception ex)
+            {
+                Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+                {
+                    StatusText = $"Send failed: {ex.Message}";
+                });
+            }
+        });
     }
 
-    private static IReadOnlyList<ServerModel> SeedServers()
+    private void HandleFileUploadRequested(string serverUrl, string filePath)
     {
-        var alex = new UserModel("user-2", "Alex");
-        var sam = new UserModel("user-3", "Sam");
+        if (string.IsNullOrEmpty(Chat.CurrentChannelName)) return;
 
-        var general = new ChannelModel(
-            "channel-1",
-            "general",
-            new ObservableCollection<MessageModel>
+        Task.Run(async () =>
+        {
+            try
             {
-                new("message-1", alex, DateTimeOffset.Now.AddMinutes(-30), "This is a message."),
-                new("message-2", sam, DateTimeOffset.Now.AddMinutes(-25), "Another message for the channel."),
-                new("message-3", alex, DateTimeOffset.Now.AddMinutes(-10), "We should test the \nnew layout."),
+                await _connectionService.UploadFileAsync(serverUrl, Chat.CurrentChannelName, filePath, null);
+                Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+                    StatusText = "File uploaded");
+            }
+            catch (Exception ex)
+            {
+                Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+                    StatusText = $"Upload failed: {ex.Message}");
+            }
+        });
+    }
+
+    private void HandleChannelSelected(ChannelViewModel? channel)
+    {
+        if (channel is null)
+        {
+            Chat.SetChannel(null);
+            return;
+        }
+
+        var serverUrl = FindServerUrlForChannel(channel);
+        Chat.SetChannel(channel, serverUrl);
+
+        if (!string.IsNullOrEmpty(serverUrl))
+        {
+            var commandHandler = _connectionService.CreateCommandHandler();
+            Chat.SetComposerCommandHandler(commandHandler);
+
+            Task.Run(async () =>
+            {
+                try
+                {
+                    var history = await _connectionService.JoinChannelAsync(serverUrl, channel.Name);
+                    Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+                    {
+                        channel.ClearMessages();
+                        foreach (var msg in history)
+                            channel.AddMessage(msg);
+                    });
+                }
+                catch
+                {
+                    // Channel might not be available
+                }
+            });
+        }
+    }
+
+    private async Task InitializeSavedServersAsync()
+    {
+        var config = _connectionService.LoadConfig();
+        var connectTasks = new List<Task>();
+
+        foreach (var saved in config.SavedServers)
+        {
+            var placeholderServer = new ServerModel(
+                Guid.NewGuid().ToString("N"),
+                saved.Name,
+                new ObservableCollection<ChannelModel>(),
+                saved.Url,
+                isConnected: false);
+
+            var serverVm = new ServerViewModel(placeholderServer);
+            serverVm.ConnectRequested += async () => await HandleServerConnectRequested(serverVm);
+            serverVm.DisconnectRequested += async () => await HandleServerDisconnectRequested(serverVm);
+
+            Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+            {
+                Sidebar.Servers.Add(serverVm);
             });
 
-        var random = new ChannelModel(
-            "channel-2",
-            "random",
-            new ObservableCollection<MessageModel>
+            if (!string.IsNullOrEmpty(saved.RefreshToken) && saved.RememberMe)
             {
-                new("message-4", sam, DateTimeOffset.Now.AddMinutes(-5), @"Random chat keeps the vibe light.
-rwerwerw
-rw
-er
-wer
-w
-r
-ztr5z56j7u5"),
-            });
+                connectTasks.Add(AutoConnectSavedServer(serverVm, saved));
+            }
+        }
 
-        var music = new ChannelModel(
-            "channel-3",
-            "music",
-            new ObservableCollection<MessageModel>());
+        await Task.WhenAll(connectTasks);
+    }
 
-        var server = new ServerModel(
-            "echo.voidcube.cloud",
-            "echo.voidcube.cloud",
-            new ObservableCollection<ChannelModel> { general, random });
+    private async Task AutoConnectSavedServer(ServerViewModel serverVm, SavedServer saved)
+    {
+        if (string.IsNullOrEmpty(saved.Username) || string.IsNullOrEmpty(saved.RefreshToken))
+            return;
 
-        var anotherServer = new ServerModel(
-            "echo.stone-red.net",
-            "echo.stone-red.net",
-            new ObservableCollection<ChannelModel>() { general, music});
+        try
+        {
+            serverVm.IsConnecting = true;
+            await _connectionService.ConnectWithSavedTokenAsync(
+                saved.Url, saved.Username, saved.RefreshToken, saved.RememberMe);
+        }
+        catch
+        {
+            serverVm.IsConnecting = false;
+        }
+    }
 
-        return new[] { server, anotherServer };
+    private static async Task ShowMessageBox(Window owner, string title, string message)
+    {
+        var msgBox = new Window
+        {
+            Title = title,
+            Width = 400,
+            Height = 180,
+            WindowStartupLocation = WindowStartupLocation.CenterOwner,
+            CanResize = false,
+        };
+
+        var stack = new StackPanel { Spacing = 10, Margin = new Avalonia.Thickness(15) };
+        stack.Children.Add(new TextBlock { Text = message, TextWrapping = Avalonia.Media.TextWrapping.Wrap });
+        var okBtn = new Button { Content = "OK", HorizontalAlignment = Avalonia.Layout.HorizontalAlignment.Center };
+        stack.Children.Add(okBtn);
+        msgBox.Content = stack;
+
+        var tcs = new TaskCompletionSource();
+        okBtn.Click += (_, _) => { msgBox.Close(); tcs.TrySetResult(); };
+        msgBox.Closed += (_, _) => tcs.TrySetResult();
+
+        await msgBox.ShowDialog(owner);
+        await tcs.Task;
+    }
+
+    private async Task HandleServerConnectRequested(ServerViewModel serverVm)
+    {
+        // Show connect dialog
+        if (_mainWindow is null) return;
+
+        var config = _connectionService.LoadConfig();
+        var prefill = config.SavedServers.FirstOrDefault(s =>
+            string.Equals(s.Url, serverVm.ServerUrl, StringComparison.OrdinalIgnoreCase));
+        var dialog = new ConnectDialog(config.SavedServers, prefill);
+
+        var result = await dialog.ShowAsync(_mainWindow);
+        if (result is null) return;
+
+        try
+        {
+            serverVm.IsConnecting = true;
+            StatusText = "Connecting...";
+
+            if (result.IsSavedSession && result.SavedRefreshToken is not null)
+            {
+                await _connectionService.ConnectWithSavedTokenAsync(
+                    result.ServerUrl, result.Username, result.SavedRefreshToken, result.RememberMe);
+            }
+            else
+            {
+                await _connectionService.ConnectAsync(
+                    result.ServerUrl, result.Username, result.Password, result.IsRegister, result.RememberMe);
+            }
+
+            // Remove the placeholder and let the real server added event handle it
+            Sidebar.RemoveServer(serverVm.ServerUrl);
+
+            // Save to config with refresh token
+            var refreshToken = _connectionService.GetRefreshToken(result.ServerUrl);
+            var savedServer = new SavedServer
+            {
+                Name = new Uri(result.ServerUrl).Host,
+                Url = result.ServerUrl,
+                Username = result.Username,
+                RefreshToken = result.RememberMe ? refreshToken : null,
+                RememberMe = result.RememberMe,
+                LastConnected = DateTimeOffset.Now,
+            };
+            _connectionService.SaveServerToConfig(savedServer);
+        }
+        catch (Exception ex)
+        {
+            StatusText = $"Connection failed: {ex.Message}";
+            serverVm.IsConnecting = false;
+        }
+    }
+
+    private async Task HandleServerDisconnectRequested(ServerViewModel serverVm)
+    {
+        try
+        {
+            await _connectionService.DisconnectAsync(serverVm.ServerUrl);
+        }
+        catch (Exception ex)
+        {
+            StatusText = $"Disconnect error: {ex.Message}";
+        }
+    }
+
+    private void EnsureChannelInList(string serverUrl, string channelName)
+    {
+        var serverVm = Sidebar.GetServer(serverUrl);
+        if (serverVm is null) return;
+
+        if (!serverVm.Channels.Any(c => c.Name == channelName))
+        {
+            var channelModel = new ChannelModel(
+                Guid.NewGuid().ToString("N"),
+                channelName,
+                new System.Collections.ObjectModel.ObservableCollection<MessageModel>());
+            var channelVm = new ChannelViewModel(channelModel);
+            serverVm.Channels.Add(channelVm);
+        }
+    }
+
+    private ChannelModel? FindChannel(string serverUrl, string channelName)
+    {
+        var serverVm = Sidebar.GetServer(serverUrl);
+        return serverVm?.Channels.FirstOrDefault(c => c.Name == channelName)?.Model;
+    }
+
+    private ChannelViewModel? FindChannelViewModel(string serverUrl, string channelName)
+    {
+        var serverVm = Sidebar.GetServer(serverUrl);
+        return serverVm?.Channels.FirstOrDefault(c => c.Name == channelName);
+    }
+
+    private string FindServerUrlForChannel(ChannelViewModel channel)
+    {
+        foreach (var server in Sidebar.Servers)
+        {
+            if (server.Channels.Contains(channel))
+                return server.ServerUrl;
+        }
+        return string.Empty;
+    }
+
+    private string GetCurrentServerUrl()
+    {
+        return Chat.CurrentServerUrl;
+    }
+
+    public void Dispose()
+    {
+        _connectionService.Dispose();
     }
 }
+
+public sealed class ConnectDialogResult
+{
+    public string ServerUrl { get; set; } = string.Empty;
+    public string Username { get; set; } = string.Empty;
+    public string Password { get; set; } = string.Empty;
+    public bool IsRegister { get; set; }
+    public bool RememberMe { get; set; }
+    public bool IsSavedSession { get; set; }
+    public string? SavedRefreshToken { get; set; }
+}
+
+public sealed class ConnectDialog
+{
+    private readonly List<SavedServer> _savedServers;
+    private readonly SavedServer? _prefill;
+
+    public ConnectDialog(List<SavedServer> savedServers, SavedServer? prefill = null)
+    {
+        _savedServers = savedServers;
+        _prefill = prefill;
+    }
+
+    public async Task<ConnectDialogResult?> ShowAsync(Window owner)
+    {
+        var dialog = new Window
+        {
+            Title = "Connect to Server",
+            Width = 450,
+            Height = 380,
+            WindowStartupLocation = WindowStartupLocation.CenterOwner,
+            CanResize = false,
+        };
+
+        var stack = new StackPanel { Spacing = 8, Margin = new Avalonia.Thickness(15) };
+
+        var urlLabel = new TextBlock { Text = "Server URL:" };
+        var urlBox = new TextBox { Watermark = "http://localhost:5000", Text = "http://localhost:5000" };
+        stack.Children.Add(urlLabel);
+        stack.Children.Add(urlBox);
+
+        var userLabel = new TextBlock { Text = "Username:" };
+        var userBox = new TextBox { Watermark = "username" };
+        stack.Children.Add(userLabel);
+        stack.Children.Add(userBox);
+
+        var passLabel = new TextBlock { Text = "Password:" };
+        var passBox = new TextBox { Watermark = "password", PasswordChar = '*' };
+        stack.Children.Add(passLabel);
+        stack.Children.Add(passBox);
+
+        var rememberMe = new CheckBox { Content = "Remember me", IsChecked = true };
+        stack.Children.Add(rememberMe);
+
+        var buttonPanel = new StackPanel { Orientation = Avalonia.Layout.Orientation.Horizontal, HorizontalAlignment = Avalonia.Layout.HorizontalAlignment.Center, Spacing = 10 };
+
+        var loginBtn = new Button { Content = "Login", Width = 100 };
+        var registerBtn = new Button { Content = "Register", Width = 100 };
+        var cancelBtn = new Button { Content = "Cancel", Width = 100 };
+        buttonPanel.Children.Add(loginBtn);
+        buttonPanel.Children.Add(registerBtn);
+        buttonPanel.Children.Add(cancelBtn);
+        stack.Children.Add(buttonPanel);
+
+        ListBox? serversList = null;
+        if (_savedServers.Count > 0)
+        {
+            var sep = new TextBlock { Text = "--- Saved Servers ---", HorizontalAlignment = Avalonia.Layout.HorizontalAlignment.Center };
+            stack.Children.Add(sep);
+
+            serversList = new ListBox { Height = 100 };
+            serversList.ItemsSource = _savedServers.Select(s => $"{s.Name} ({s.Url}) - {s.Username ?? "?"}").ToList();
+            stack.Children.Add(serversList);
+
+            serversList.SelectionChanged += (_, _) =>
+            {
+                var idx = serversList.SelectedIndex;
+                if (idx >= 0 && idx < _savedServers.Count)
+                {
+                    var s = _savedServers[idx];
+                    urlBox.Text = s.Url;
+                    userBox.Text = s.Username ?? "";
+                    rememberMe.IsChecked = s.RememberMe;
+                    if (!string.IsNullOrEmpty(s.RefreshToken))
+                        passBox.Text = "";
+                }
+            };
+        }
+
+        if (_prefill is not null)
+        {
+            urlBox.Text = _prefill.Url;
+            userBox.Text = _prefill.Username ?? "";
+            var idx = _savedServers.FindIndex(s =>
+                string.Equals(s.Url, _prefill.Url, StringComparison.OrdinalIgnoreCase));
+            if (idx >= 0 && idx < _savedServers.Count && serversList is not null)
+                serversList.SelectedIndex = idx;
+        }
+
+        dialog.Content = new ScrollViewer { Content = stack };
+
+        var tcs = new TaskCompletionSource<ConnectDialogResult?>();
+        ConnectDialogResult? result = null;
+
+        loginBtn.Click += async (_, _) =>
+        {
+            var url = urlBox.Text?.Trim() ?? "";
+            var user = userBox.Text?.Trim() ?? "";
+            var pass = passBox.Text ?? "";
+
+            if (string.IsNullOrEmpty(url) || string.IsNullOrEmpty(user))
+            {
+                await ShowMessageBox(owner, "Validation", "Server URL and username are required.");
+                return;
+            }
+
+            // Check for saved session
+            var saved = _savedServers.FirstOrDefault(s =>
+                string.Equals(s.Url, url, StringComparison.OrdinalIgnoreCase) &&
+                string.Equals(s.Username, user, StringComparison.OrdinalIgnoreCase) &&
+                !string.IsNullOrEmpty(s.RefreshToken));
+
+            if (string.IsNullOrEmpty(pass) && saved is not null)
+            {
+                result = new ConnectDialogResult
+                {
+                    ServerUrl = url,
+                    Username = user,
+                    IsSavedSession = true,
+                    SavedRefreshToken = saved.RefreshToken,
+                    RememberMe = saved.RememberMe,
+                };
+            }
+            else
+            {
+                if (string.IsNullOrEmpty(pass))
+                {
+                    await ShowMessageBox(owner, "Validation", "Password is required.");
+                    return;
+                }
+
+                result = new ConnectDialogResult
+                {
+                    ServerUrl = url,
+                    Username = user,
+                    Password = pass,
+                    IsRegister = false,
+                    RememberMe = rememberMe.IsChecked ?? false,
+                };
+            }
+
+            dialog.Close();
+            tcs.TrySetResult(result);
+        };
+
+        registerBtn.Click += (_, _) =>
+        {
+            var url = urlBox.Text?.Trim() ?? "";
+            var user = userBox.Text?.Trim() ?? "";
+            var pass = passBox.Text ?? "";
+
+            if (string.IsNullOrEmpty(url) || string.IsNullOrEmpty(user) || string.IsNullOrEmpty(pass))
+            {
+                _ = ShowMessageBox(owner, "Validation", "Server URL, username, and password are required.");
+                return;
+            }
+
+            result = new ConnectDialogResult
+            {
+                ServerUrl = url,
+                Username = user,
+                Password = pass,
+                IsRegister = true,
+                RememberMe = rememberMe.IsChecked ?? false,
+            };
+
+            dialog.Close();
+            tcs.TrySetResult(result);
+        };
+
+        cancelBtn.Click += (_, _) =>
+        {
+            dialog.Close();
+            tcs.TrySetResult(null);
+        };
+
+        dialog.Closed += (_, _) => tcs.TrySetResult(result);
+
+        if (owner is not null)
+            await dialog.ShowDialog(owner);
+        else
+            dialog.Show();
+
+        return await tcs.Task;
+    }
+
+    private static async Task ShowMessageBox(Window owner, string title, string message)
+    {
+        var msgBox = new Window
+        {
+            Title = title,
+            Width = 350,
+            Height = 150,
+            WindowStartupLocation = WindowStartupLocation.CenterOwner,
+            CanResize = false,
+        };
+
+        var stack = new StackPanel { Spacing = 10, Margin = new Avalonia.Thickness(15) };
+        stack.Children.Add(new TextBlock { Text = message, TextWrapping = Avalonia.Media.TextWrapping.Wrap });
+        var okBtn = new Button { Content = "OK", HorizontalAlignment = Avalonia.Layout.HorizontalAlignment.Center };
+        stack.Children.Add(okBtn);
+        msgBox.Content = stack;
+
+        var tcs = new TaskCompletionSource();
+        okBtn.Click += (_, _) => { msgBox.Close(); tcs.TrySetResult(); };
+        msgBox.Closed += (_, _) => tcs.TrySetResult();
+
+        await msgBox.ShowDialog(owner);
+        await tcs.Task;
+    }
+}

Decho/ViewModels/MessageComposerViewModel.cs

@@ -1,7 +1,9 @@
 using System;
 using System.Reactive;
 using System.Reactive.Linq;
+using System.Threading.Tasks;
 
+using EchoHub.Client.Commands;
 using ReactiveUI;
 
 namespace Decho.ViewModels;
@@ -9,6 +11,8 @@ namespace Decho.ViewModels;
 public sealed class MessageComposerViewModel : ViewModelBase
 {
     private string _draft = string.Empty;
+    private CommandHandler? _commandHandler;
+    private string _serverUrl = string.Empty;
 
     public MessageComposerViewModel()
     {
@@ -22,9 +26,34 @@ public sealed class MessageComposerViewModel : ViewModelBase
         set => this.RaiseAndSetIfChanged(ref _draft, value);
     }
 
+    public string ServerUrl => _serverUrl;
+
     public ReactiveCommand<Unit, Unit> SendCommand { get; }
 
-    public event Action<string>? SendRequested;
+    public bool HasCommandHandler => _commandHandler is not null;
+
+    public event Action<string, string>? SendRequested;
+    public event Func<string, Task<string?>>? CommandRequested;
+    public event Action<string, string>? FileUploadRequested;
+
+    public void RequestFileUpload(string filePath)
+    {
+        if (!string.IsNullOrEmpty(_serverUrl))
+            FileUploadRequested?.Invoke(_serverUrl, filePath);
+    }
+
+    public void SetServer(string serverUrl)
+    {
+        _serverUrl = serverUrl;
+    }
+
+    public void SetCommandHandler(CommandHandler handler)
+    {
+        _commandHandler = handler;
+        this.RaisePropertyChanged(nameof(HasCommandHandler));
+    }
+
+    public bool IsCommand(string input) => _commandHandler?.IsCommand(input) ?? input.StartsWith('/');
 
     private void Send()
     {
@@ -33,6 +62,14 @@ public sealed class MessageComposerViewModel : ViewModelBase
             return;
 
         Draft = string.Empty;
-        SendRequested?.Invoke(text);
+
+        if (_commandHandler is not null && _commandHandler.IsCommand(text))
+        {
+            CommandRequested?.Invoke(text);
+        }
+        else
+        {
+            SendRequested?.Invoke(_serverUrl, text);
+        }
     }
-}
+}

Decho/ViewModels/MessageViewModel.cs

@@ -1,6 +1,7 @@
-using Decho.Models;
-
 using System;
+using Avalonia.Media;
+using EchoHub.Core.Models;
+using Decho.Models;
 
 namespace Decho.ViewModels;
 
@@ -15,13 +16,41 @@ public sealed class MessageViewModel : ViewModelBase
 
     public string AuthorName => Model.Author.DisplayName;
 
+    public IBrush? AuthorColor
+    {
+        get
+        {
+            var color = Model.Author.NicknameColor;
+            if (string.IsNullOrEmpty(color)) return null;
+            try { return new SolidColorBrush(Avalonia.Media.Color.Parse(color)); }
+            catch { return null; }
+        }
+    }
+
     public string Content => Model.Content;
 
+    public string? ServerUrl => Model.ServerUrl;
+
+    public MessageType Type => Model.Type;
+
+    public bool HasAttachment => Model.AttachmentUrl is not null;
+
+    public string? AttachmentFileName => Model.AttachmentFileName;
+
+    public string? AttachmentUrl => Model.AttachmentUrl;
+
+    public bool IsImage => Type == MessageType.Image;
+
+    public bool ShowContent => !IsImage && !IsFile;
+
+    public bool IsAudio => Type == MessageType.Audio;
+
+    public bool IsFile => Type == MessageType.File;
+
     public string TimeText
     {
         get
         {
-            // If today, show time only; otherwise, show date and time.
             var now = DateTimeOffset.Now;
 
             if (Model.SentAt.Date == now.Date)
@@ -29,7 +58,7 @@ public sealed class MessageViewModel : ViewModelBase
                 return Model.SentAt.ToLocalTime().ToString("t");
             }
 
-            return now.ToString("g");
+            return Model.SentAt.ToLocalTime().ToString("g");
         }
     }
-}
+}

Decho/ViewModels/ServerViewModel.cs

@@ -1,7 +1,9 @@
 using System.Collections.ObjectModel;
 using System.Linq;
+using System.Reactive;
 
 using Decho.Models;
+using ReactiveUI;
 
 namespace Decho.ViewModels;
 
@@ -9,20 +11,49 @@ public sealed class ServerViewModel : ViewModelBase
 {
     private bool _isExpanded = true;
     private ChannelViewModel? _selectedChannel;
+    private bool _isConnected;
+    private bool _isConnecting;
+    private string? _connectedUser;
 
     public ServerViewModel(ServerModel model)
     {
         Model = model;
         Channels = new ObservableCollection<ChannelViewModel>(
             model.Channels.Select(channel => new ChannelViewModel(channel)));
+
+        _isConnected = model.IsConnected;
+        _isConnecting = model.IsConnecting;
+        _connectedUser = model.ConnectedUser;
+
+        ConnectCommand = ReactiveCommand.CreateFromTask(ConnectAsync);
+        DisconnectCommand = ReactiveCommand.CreateFromTask(DisconnectAsync);
     }
 
+    public event Func<Task>? ConnectRequested
+    {
+        add => _connectRequested = (Func<Task>?)Delegate.Combine(_connectRequested, value);
+        remove => _connectRequested = (Func<Task>?)Delegate.Remove(_connectRequested, value);
+    }
+    private Func<Task>? _connectRequested;
+
+    public event Func<Task>? DisconnectRequested
+    {
+        add => _disconnectRequested = (Func<Task>?)Delegate.Combine(_disconnectRequested, value);
+        remove => _disconnectRequested = (Func<Task>?)Delegate.Remove(_disconnectRequested, value);
+    }
+    private Func<Task>? _disconnectRequested;
+
     public ServerModel Model { get; }
 
     public string Name => Model.Name;
 
+    public string ServerUrl => Model.ServerUrl;
+
     public ObservableCollection<ChannelViewModel> Channels { get; }
 
+    public ReactiveCommand<Unit, Unit> ConnectCommand { get; }
+    public ReactiveCommand<Unit, Unit> DisconnectCommand { get; }
+
     public ChannelViewModel? SelectedChannel
     {
         get => _selectedChannel;
@@ -34,4 +65,60 @@ public sealed class ServerViewModel : ViewModelBase
         get => _isExpanded;
         set => this.RaiseAndSetIfChanged(ref _isExpanded, value);
     }
-}
+
+    public bool IsConnected
+    {
+        get => _isConnected;
+        set
+        {
+            this.RaiseAndSetIfChanged(ref _isConnected, value);
+            this.RaisePropertyChanged(nameof(ConnectionStatusText));
+            this.RaisePropertyChanged(nameof(ConnectionStatusColor));
+            this.RaisePropertyChanged(nameof(ShowConnectionControls));
+        }
+    }
+
+    public bool IsConnecting
+    {
+        get => _isConnecting;
+        set
+        {
+            this.RaiseAndSetIfChanged(ref _isConnecting, value);
+            this.RaisePropertyChanged(nameof(ConnectionStatusText));
+            this.RaisePropertyChanged(nameof(ShowConnectionControls));
+        }
+    }
+
+    public string? ConnectedUser
+    {
+        get => _connectedUser;
+        set => this.RaiseAndSetIfChanged(ref _connectedUser, value);
+    }
+
+    public string ConnectionStatusText => IsConnecting ? "Connecting..." :
+        IsConnected ? $"Connected as {ConnectedUser}" : "Disconnected";
+
+    public string ConnectionStatusColor => IsConnected ? "Green" : IsConnecting ? "Orange" : "Gray";
+
+    public bool ShowConnectionControls => !IsConnected && !IsConnecting;
+
+    private async Task ConnectAsync()
+    {
+        if (_connectRequested is not null)
+            await _connectRequested();
+    }
+
+    private async Task DisconnectAsync()
+    {
+        if (_disconnectRequested is not null)
+            await _disconnectRequested();
+    }
+
+    public void SyncFromModel()
+    {
+        IsConnected = Model.IsConnected;
+        IsConnecting = Model.IsConnecting;
+        ConnectedUser = Model.ConnectedUser;
+        IsExpanded = true;
+    }
+}

Decho/ViewModels/SidebarViewModel.cs

@@ -13,18 +13,9 @@ public sealed class SidebarViewModel : ViewModelBase
 {
     private ChannelViewModel? _selectedChannel;
 
-    public SidebarViewModel(IEnumerable<ServerModel> servers)
+    public SidebarViewModel()
     {
-        Servers = new ObservableCollection<ServerViewModel>(
-            servers.Select(server => new ServerViewModel(server)));
-        SelectedChannel = Servers.FirstOrDefault()?.Channels.FirstOrDefault();
-
-        foreach (var server in Servers)
-        {
-            server.WhenAnyValue(s => s.SelectedChannel)
-                .Where(channel => channel is not null)
-                .Subscribe(new Action<ChannelViewModel?>(channel => SelectedChannel = channel!));
-        }
+        Servers = new ObservableCollection<ServerViewModel>();
     }
 
     public ObservableCollection<ServerViewModel> Servers { get; }
@@ -56,4 +47,33 @@ public sealed class SidebarViewModel : ViewModelBase
             }
         }
     }
-}
+
+    public void AddServer(ServerModel model)
+    {
+        var vm = new ServerViewModel(model);
+        vm.WhenAnyValue(s => s.SelectedChannel)
+            .Where(channel => channel is not null)
+            .Subscribe(channel => SelectedChannel = channel!);
+
+        Servers.Add(vm);
+    }
+
+    public void RemoveServer(string serverUrl)
+    {
+        var server = Servers.FirstOrDefault(s =>
+            string.Equals(s.ServerUrl, serverUrl, StringComparison.OrdinalIgnoreCase));
+        if (server is not null)
+        {
+            if (SelectedChannel is not null && server.Channels.Contains(SelectedChannel))
+                SelectedChannel = null;
+
+            Servers.Remove(server);
+        }
+    }
+
+    public ServerViewModel? GetServer(string serverUrl)
+    {
+        return Servers.FirstOrDefault(s =>
+            string.Equals(s.ServerUrl, serverUrl, StringComparison.OrdinalIgnoreCase));
+    }
+}

Decho/Views/MainWindow.axaml

@@ -1,33 +1,48 @@
 <Window xmlns="https://github.com/avaloniaui"
-        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-        xmlns:vm="using:Decho.ViewModels"
-        xmlns:views="using:Decho.Views"
-        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
-        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
-        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
-        x:Class="Decho.Views.MainWindow"
-        x:DataType="vm:MainWindowViewModel"
-        Icon="/Assets/avalonia-logo.ico"
-        Title="Decho">
+		xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+		xmlns:vm="using:Decho.ViewModels"
+		xmlns:views="using:Decho.Views"
+		xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+		xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+		xmlns:i="https://github.com/projektanker/icons.avalonia"
+		mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
+		x:Class="Decho.Views.MainWindow"
+		x:DataType="vm:MainWindowViewModel"
+		Icon="/Assets/avalonia-logo.ico"
+		Width="1100" Height="600"
+		Title="Decho">
 
-    <Design.DataContext>
-        <!-- This only sets the DataContext for the previewer in an IDE,
-        to set the actual DataContext for runtime, set the DataContext property in code (look at App.axaml.cs) -->
-        <vm:MainWindowViewModel/>
-    </Design.DataContext>
+	<Design.DataContext>
+		<vm:MainWindowViewModel/>
+	</Design.DataContext>
 
-    <Grid RowDefinitions="Auto, *" ColumnDefinitions="Auto, *">
-        <TextBlock FontSize="20"
-                   FontWeight="Bold"
-                   Margin="0 5"
-                   HorizontalAlignment="Center"
-                   Text="{Binding Title}" />
-        <views:SidebarView Grid.Row="1"
-                           Grid.Column="0"
-                           DataContext="{Binding Sidebar}"
-                           SelectedChannel="{Binding SelectedChannel, Mode=TwoWay}" />
-        <views:ChatView Grid.RowSpan="2"
-                        Grid.Column="1"
-                        DataContext="{Binding Chat}" />
-    </Grid>
-</Window>
+	<Grid RowDefinitions="Auto, *" ColumnDefinitions="Auto, *">
+		<DockPanel HorizontalAlignment="Stretch">
+			<TextBlock FontSize="20"
+					   FontWeight="Bold"
+					   Margin="5"
+					   Text="{Binding Title}" />
+
+			<Button i:Attached.Icon="fa-cog"
+					DockPanel.Dock="Right"
+					Background="Transparent"
+					Foreground="{DynamicResource UiTheme08}"
+					HorizontalAlignment="Right" />
+
+		<Button i:Attached.Icon="fa-plus"
+				Command="{Binding AddServerCommand}"
+				DockPanel.Dock="Right"
+				Background="Transparent"
+				Foreground="{DynamicResource UiTheme08}"
+				HorizontalAlignment="Right"
+				ToolTip.Tip="Add Server" />
+		</DockPanel>
+		<views:SidebarView Grid.Row="1"
+						   Grid.Column="0"
+						   DataContext="{Binding Sidebar}"
+						   SelectedChannel="{Binding SelectedChannel, Mode=TwoWay}" />
+		<views:ChatView Grid.RowSpan="2"
+						Grid.Column="1"
+						DataContext="{Binding Chat}" />
+	</Grid>
+</Window>

Decho/Views/MessageComposerView.axaml

@@ -5,24 +5,25 @@
              x:Class="Decho.Views.MessageComposerView"
              x:DataType="vm:MessageComposerViewModel">
     <Grid ColumnDefinitions="*, Auto, Auto" Margin="5">
-        <TextBox HorizontalAlignment="Stretch"
+        <TextBox Grid.Column="0"
+                 HorizontalAlignment="Stretch"
                  Margin="0 0 5 0"
                  Text="{Binding Draft, Mode=TwoWay}">
             <TextBox.KeyBindings>
-                <KeyBinding  Command="{Binding SendCommand}" Gesture="Enter" />
+                <KeyBinding Command="{Binding SendCommand}" Gesture="Enter" />
             </TextBox.KeyBindings>
         </TextBox>
         <Button Grid.Column="1"
                 Height="33"
                 Width="33"
-                Content="Attach"
-                i:Attached.Icon="fa-paperclip"
-                Margin="0 0 5 0" />
-        <Button Grid.Column="2"
-                Height="33"
-                Width="33"
+                Margin="0 0 5 0"
                 Content="Send"
                 i:Attached.Icon="fa-paper-plane"
                 Command="{Binding SendCommand}" />
+        <Button Grid.Column="2"
+                Height="33"
+                Width="33"
+                Click="OnFileUploadClicked"
+                i:Attached.Icon="fa-paperclip" />
     </Grid>
-</UserControl>
+</UserControl>

Decho/Views/MessageComposerView.axaml.cs

@@ -1,4 +1,9 @@
+using System.Linq;
 using Avalonia.Controls;
+using Avalonia.Input;
+using Avalonia.Interactivity;
+using Avalonia.Platform.Storage;
+using Decho.ViewModels;
 
 namespace Decho.Views;
 
@@ -7,5 +12,50 @@ public partial class MessageComposerView : UserControl
     public MessageComposerView()
     {
         InitializeComponent();
+        AddHandler(DragDrop.DragOverEvent, OnDragOver);
+        AddHandler(DragDrop.DropEvent, OnDrop);
+        DragDrop.SetAllowDrop(this, true);
+    }
+
+    private async void OnFileUploadClicked(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not MessageComposerViewModel vm) return;
+
+        var topLevel = TopLevel.GetTopLevel(this);
+        if (topLevel?.StorageProvider is null) return;
+
+        var files = await topLevel.StorageProvider.OpenFilePickerAsync(new FilePickerOpenOptions
+        {
+            AllowMultiple = false,
+            Title = "Select a file to upload",
+        });
+
+        var file = files?.FirstOrDefault();
+        if (file?.TryGetLocalPath() is string path)
+        {
+            vm.RequestFileUpload(path);
+        }
+    }
+
+    private void OnDragOver(object? sender, DragEventArgs e)
+    {
+#pragma warning disable CS0618
+        if (e.Data.Contains(DataFormats.Files))
+#pragma warning restore CS0618
+            e.DragEffects = DragDropEffects.Copy;
+    }
+
+    private void OnDrop(object? sender, DragEventArgs e)
+    {
+        if (DataContext is not MessageComposerViewModel vm) return;
+
+#pragma warning disable CS0618
+        var paths = e.Data.GetFiles()?
+            .Select(f => f.TryGetLocalPath())
+            .FirstOrDefault(p => p is not null);
+#pragma warning restore CS0618
+
+        if (paths is string path)
+            vm.RequestFileUpload(path);
     }
 }

Decho/Views/MessageItemView.axaml

@@ -3,9 +3,8 @@
 			 xmlns:vm="using:Decho.ViewModels"
 			 x:Class="Decho.Views.MessageItemView"
 			 x:DataType="vm:MessageViewModel">
-	<Grid Margin="5" ColumnDefinitions="Auto, Auto, *">
-		<Ellipse Grid.RowSpan="2" 
-				 VerticalAlignment="Top"
+	<Grid Margin="5" ColumnDefinitions="Auto, *">
+		<Ellipse VerticalAlignment="Top"
 				 Width="40"
 				 Height="40"
 				 Fill="{DynamicResource UiTheme00}"
@@ -15,7 +14,8 @@
 			<StackPanel Orientation="Horizontal" Margin="0 5 0 0">
 				<TextBlock VerticalAlignment="Top"
 						   Text="{Binding AuthorName}"
-						   FontWeight="Bold" />
+						   FontWeight="Bold"
+						   Foreground="{Binding AuthorColor}" />
 				<TextBlock VerticalAlignment="Top"
 						   Text="{Binding TimeText}"
 						   FontSize="10"
@@ -23,7 +23,24 @@
 			</StackPanel>
 			<TextBlock VerticalAlignment="Top"
 					   Text="{Binding Content}"
-					   TextWrapping="Wrap" />
+					   TextWrapping="Wrap"
+					   IsVisible="{Binding ShowContent}" />
+			<Image x:Name="MessageImage"
+				   MaxHeight="300"
+				   MaxWidth="400"
+				   HorizontalAlignment="Left"
+				   IsVisible="{Binding IsImage}"
+				   Margin="0 4 0 0" />
+			<StackPanel IsVisible="{Binding HasAttachment}" Margin="0 4 0 0" Spacing="2">
+				<TextBlock Text="{Binding AttachmentFileName}"
+						   FontSize="11"
+						   Opacity="0.7" />
+				<Button Content="Download"
+						Click="OnDownloadClicked"
+						FontSize="11"
+						Padding="5 1"
+						HorizontalAlignment="Left" />
+			</StackPanel>
 		</StackPanel>
 	</Grid>
 </UserControl>

Decho/Views/MessageItemView.axaml.cs

@@ -1,11 +1,94 @@
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
 using Avalonia.Controls;
+using Avalonia.Interactivity;
+using Avalonia.Media.Imaging;
+using Avalonia.Platform.Storage;
+using Decho.ViewModels;
 
 namespace Decho.Views;
 
 public partial class MessageItemView : UserControl
 {
+    private CancellationTokenSource? _loadCts;
+    private bool _pendingLoad;
+
     public MessageItemView()
     {
         InitializeComponent();
+        DataContextChanged += OnDataContextChanged;
+        Loaded += OnLoaded;
+    }
+
+    private void OnDataContextChanged(object? sender, EventArgs args)
+    {
+        _loadCts?.Cancel();
+        _loadCts = new CancellationTokenSource();
+        _pendingLoad = DataContext is MessageViewModel msg && msg.IsImage && msg.AttachmentUrl is not null;
+    }
+
+    private void OnLoaded(object? sender, RoutedEventArgs e)
+    {
+        if (!_pendingLoad) return;
+        _pendingLoad = false;
+        var msg = (MessageViewModel)DataContext!;
+        _ = LoadImageAsync(msg, _loadCts!.Token);
+    }
+
+    private async Task LoadImageAsync(MessageViewModel msg, CancellationToken ct)
+    {
+        try
+        {
+            var topLevel = TopLevel.GetTopLevel(this);
+            if (topLevel?.DataContext is not MainWindowViewModel mainVm) return;
+
+            var bytes = await mainVm.ConnectionService.DownloadImageBytesAsync(
+                msg.ServerUrl ?? "", msg.AttachmentUrl!);
+
+            ct.ThrowIfCancellationRequested();
+            if (bytes is null || bytes.Length == 0) return;
+
+            using var stream = new MemoryStream(bytes);
+            var bitmap = new Bitmap(stream);
+            ct.ThrowIfCancellationRequested();
+            var image = this.FindControl<Image>("MessageImage");
+            if (image is not null)
+                image.Source = bitmap;
+        }
+        catch
+        {
+            // Image failed to load — filename is shown as fallback
+        }
+    }
+
+    private async void OnDownloadClicked(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not MessageViewModel msg) return;
+        if (msg.AttachmentUrl is null) return;
+
+        var topLevel = TopLevel.GetTopLevel(this);
+        if (topLevel?.StorageProvider is null) return;
+
+        var mainVm = topLevel.DataContext as MainWindowViewModel;
+        if (mainVm is null) return;
+
+        var tempPath = await mainVm.ConnectionService.DownloadAttachmentAsync(
+            msg.ServerUrl ?? "", msg.AttachmentUrl, msg.AttachmentFileName ?? "download");
+
+        if (tempPath is null) return;
+
+        var file = await topLevel.StorageProvider.SaveFilePickerAsync(new FilePickerSaveOptions
+        {
+            SuggestedFileName = msg.AttachmentFileName ?? "download",
+        });
+
+        if (file?.TryGetLocalPath() is string savePath)
+        {
+            File.Copy(tempPath, savePath, overwrite: true);
+        }
+
+        try { File.Delete(tempPath); }
+        catch { }
     }
 }

Decho/Views/MessageListView.axaml

@@ -4,7 +4,7 @@
              xmlns:views="using:Decho.Views"
              x:Class="Decho.Views.MessageListView"
              x:DataType="vm:ChatViewModel">
-    <ScrollViewer>
+    <ScrollViewer Name="MessageScrollViewer">
         <ItemsControl ItemsSource="{Binding Messages}">
             <ItemsControl.ItemTemplate>
                 <DataTemplate x:DataType="vm:MessageViewModel">

Decho/Views/MessageListView.axaml.cs

@@ -1,11 +1,96 @@
+using System.Collections.Specialized;
 using Avalonia.Controls;
+using Avalonia.Threading;
+using Decho.ViewModels;
 
 namespace Decho.Views;
 
 public partial class MessageListView : UserControl
 {
+    private ChatViewModel? _chat;
+    private bool _hasPendingScroll;
+    private bool _wasAtBottom;
+
     public MessageListView()
     {
         InitializeComponent();
+        DataContextChanged += OnDataContextChanged;
+    }
+
+    private void OnDataContextChanged(object? sender, EventArgs args)
+    {
+        if (_chat is not null)
+        {
+            _chat.Messages.CollectionChanged -= OnMessagesChanged;
+            _chat.PropertyChanged -= OnViewModelPropertyChanged;
+        }
+
+        var scroll = this.FindControl<ScrollViewer>("MessageScrollViewer");
+        if (scroll is not null)
+            scroll.ScrollChanged -= OnScrollChanged;
+
+        _chat = DataContext as ChatViewModel;
+        if (_chat is not null)
+        {
+            _chat.Messages.CollectionChanged += OnMessagesChanged;
+            _chat.PropertyChanged += OnViewModelPropertyChanged;
+            if (scroll is not null)
+                scroll.ScrollChanged += OnScrollChanged;
+        }
+    }
+
+    private void OnScrollChanged(object? sender, ScrollChangedEventArgs e)
+    {
+        if (e.ExtentDelta.Y > 0 && _wasAtBottom)
+        {
+            var scroll = (ScrollViewer)sender!;
+            Dispatcher.UIThread.Post(scroll.ScrollToEnd, DispatcherPriority.Background);
+        }
+
+        var scrollViewer = (ScrollViewer)sender!;
+        _wasAtBottom = scrollViewer.Offset.Y + scrollViewer.Viewport.Height >= scrollViewer.Extent.Height - 30;
+    }
+
+    private void OnViewModelPropertyChanged(object? sender, System.ComponentModel.PropertyChangedEventArgs e)
+    {
+        if (e.PropertyName == nameof(ChatViewModel.Messages))
+        {
+            _chat!.Messages.CollectionChanged += OnMessagesChanged;
+            ScrollToBottom();
+        }
+    }
+
+    private void OnMessagesChanged(object? sender, NotifyCollectionChangedEventArgs e)
+    {
+        if (e.Action == NotifyCollectionChangedAction.Add)
+        {
+            TryAutoScroll();
+        }
+    }
+
+    private void TryAutoScroll()
+    {
+        var scroll = this.FindControl<ScrollViewer>("MessageScrollViewer");
+        if (scroll is null) return;
+
+        _wasAtBottom = scroll.Offset.Y + scroll.Viewport.Height >= scroll.Extent.Height - 30;
+        if (_wasAtBottom && !_hasPendingScroll)
+        {
+            _hasPendingScroll = true;
+            Dispatcher.UIThread.Post(() =>
+            {
+                scroll.ScrollToEnd();
+                _hasPendingScroll = false;
+            }, DispatcherPriority.Background);
+        }
+    }
+
+    private void ScrollToBottom()
+    {
+        var scroll = this.FindControl<ScrollViewer>("MessageScrollViewer");
+        if (scroll is null) return;
+
+        _wasAtBottom = true;
+        Dispatcher.UIThread.Post(scroll.ScrollToEnd, DispatcherPriority.Background);
     }
 }

Decho/Views/SidebarView.axaml

@@ -1,30 +1,55 @@
 <UserControl xmlns="https://github.com/avaloniaui"
-             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             xmlns:vm="using:Decho.ViewModels"
-             xmlns:views="using:Decho.Views"
-             x:Class="Decho.Views.SidebarView"
-             x:DataType="vm:SidebarViewModel">
-    <Border Background="{DynamicResource UiTheme00}" Width="250" CornerRadius="0 6 0 0">
-        <ScrollViewer Padding="5">
-            <ItemsControl ItemsSource="{Binding Servers}">
-                <ItemsControl.ItemTemplate>
-                    <DataTemplate x:DataType="vm:ServerViewModel">
-                        <Expander Padding="0"
-                                  Margin="0 0 0 6"
-                                  HorizontalAlignment="Stretch"
-                                  IsExpanded="{Binding IsExpanded}">
-                            <Expander.Header>
-                                <TextBlock FontWeight="Bold"
-                                           TextTrimming="CharacterEllipsis"
-                                           MaxWidth="190"
-                                           Padding="0"
-                                           Text="{Binding Name}" />
-                            </Expander.Header>
-                            <views:ChannelListView />
-                        </Expander>
-                    </DataTemplate>
-                </ItemsControl.ItemTemplate>
-            </ItemsControl>
-        </ScrollViewer>
-    </Border>
-</UserControl>
+			 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+			 xmlns:vm="using:Decho.ViewModels"
+			 xmlns:views="using:Decho.Views"
+			 x:Class="Decho.Views.SidebarView"
+			 x:DataType="vm:SidebarViewModel">
+	<Border Background="{DynamicResource UiTheme00}" Width="250" CornerRadius="0 6 0 0">
+		<ScrollViewer Padding="5">
+			<ItemsControl ItemsSource="{Binding Servers}">
+				<ItemsControl.ItemTemplate>
+					<DataTemplate x:DataType="vm:ServerViewModel">
+						<Expander Padding="0"
+								  Margin="0 0 0 6"
+								  HorizontalAlignment="Stretch"
+								  IsExpanded="{Binding IsExpanded}">
+							<Expander.Header>
+								<StackPanel Spacing="5">
+									<StackPanel Orientation="Horizontal" Spacing="5">
+										<Ellipse Width="8" Height="8"
+												 Fill="{Binding ConnectionStatusColor}"
+												 VerticalAlignment="Center" />
+										<TextBlock FontWeight="Bold"
+												   TextTrimming="CharacterEllipsis"
+												   MaxWidth="160"
+												   Padding="0"
+												   Text="{Binding Name}" />
+									</StackPanel>
+									<TextBlock FontSize="10"
+											   Text="{Binding ConnectionStatusText}"
+											   Opacity="0.6"
+											   VerticalAlignment="Center" />
+								</StackPanel>
+							</Expander.Header>
+							<StackPanel>
+								<Button Content="Connect"
+										Command="{Binding ConnectCommand}"
+										IsVisible="{Binding ShowConnectionControls}"
+										Margin="0 0 0 4"
+										Padding="5 2"
+										HorizontalAlignment="Stretch" />
+								<Button Content="Disconnect"
+										Command="{Binding DisconnectCommand}"
+										IsVisible="{Binding IsConnected}"
+										Margin="0 0 0 4"
+										Padding="5 2"
+										HorizontalAlignment="Stretch" />
+								<views:ChannelListView />
+							</StackPanel>
+						</Expander>
+					</DataTemplate>
+				</ItemsControl.ItemTemplate>
+			</ItemsControl>
+		</ScrollViewer>
+	</Border>
+</UserControl>