Add clickable mention and channel links to message content display

src/Decho/Views/MessageItemView.axaml.cs

@@ -1,5 +1,7 @@
+using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Documents;
+using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.Media;
 using Avalonia.Media.Imaging;
@@ -10,6 +12,8 @@ using Decho.ViewModels;
 using EchoHub.Core.DTOs;
 using EchoHub.Core.Models;
 
+using Romzetron.Avalonia;
+
 using System.Text.RegularExpressions;
 
 namespace Decho.Views;
@@ -17,6 +21,7 @@ namespace Decho.Views;
 public partial class MessageItemView : UserControl
 {
     private static readonly Regex MentionRegex = new(@"@(\w+)", RegexOptions.Compiled);
+    private static readonly Regex ChannelRegex = new(@"(?<!\w)#(\w+)", RegexOptions.Compiled);
     private CancellationTokenSource? _loadCts;
     private string? _loadedMessageId;
 
@@ -54,19 +59,51 @@ public partial class MessageItemView : UserControl
 
         tb.Inlines?.Clear();
 
+        var mentionMatches = MentionRegex.Matches(content).Cast<Match>();
+        var channelMatches = ChannelRegex.Matches(content).Cast<Match>();
+        var allMatches = mentionMatches.Concat(channelMatches)
+            .OrderBy(m => m.Index)
+            .ToList();
+
         int lastIndex = 0;
-        foreach (Match match in MentionRegex.Matches(content))
+        foreach (Match match in allMatches)
         {
             if (match.Index > lastIndex)
             {
                 tb.Inlines?.Add(new Run(content[lastIndex..match.Index]));
             }
 
-            tb.Inlines?.Add(new Run(match.Value)
+            bool isMention = match.Value[0] == '@';
+            var container = new InlineUIContainer
             {
-                Foreground = new SolidColorBrush(Color.Parse("#FEE75C")),
+                BaselineAlignment = BaselineAlignment.Center,
+            };
+            var label = new TextBlock
+            {
+                Text = match.Value,
                 FontWeight = FontWeight.Bold,
-            });
+                Cursor = new Cursor(StandardCursorType.Hand),
+                Padding = new Thickness(0),
+                LineHeight = double.NaN,
+            };
+
+            if (isMention)
+            {
+                string username = match.Groups[1].Value;
+                label.Margin = new Thickness(0, 0, 0, -2);
+                label.Foreground = ColorPalette.Yellow05;
+                label.PointerPressed += (_, args) => OnMentionPointerPressed(username, args);
+            }
+            else
+            {
+                string channelName = match.Groups[1].Value;
+                label.Margin = new Thickness(0, 0, 0, -2);
+                label.Foreground = ColorPalette.Blue05;
+                label.PointerPressed += (_, args) => OnChannelPointerPressed(channelName, args);
+            }
+
+            container.Child = label;
+            tb.Inlines?.Add(container);
 
             lastIndex = match.Index + match.Length;
         }
@@ -77,6 +114,64 @@ public partial class MessageItemView : UserControl
         }
     }
 
+    private async void OnMentionPointerPressed(string username, PointerPressedEventArgs e)
+    {
+        if (DataContext is not MessageViewModel msg)
+        {
+            return;
+        }
+
+        MainWindowViewModel? mainVm = this.GetMainWindowViewModel();
+        if (mainVm is null)
+        {
+            return;
+        }
+
+        string serverUrl = msg.ServerUrl ?? mainVm.Chat.CurrentServerUrl;
+        UserProfileDto? profile = await mainVm.ConnectionService.GetUserProfileAsync(serverUrl, username);
+        if (profile is null)
+        {
+            return;
+        }
+
+        ProfileWindow dialog = new ProfileWindow(profile);
+
+        if (TopLevel.GetTopLevel(this) is Window parent)
+        {
+            await dialog.ShowDialog(parent);
+        }
+    }
+
+    private void OnChannelPointerPressed(string channelName, PointerPressedEventArgs e)
+    {
+        if (DataContext is not MessageViewModel msg)
+        {
+            return;
+        }
+
+        MainWindowViewModel? mainVm = this.GetMainWindowViewModel();
+        if (mainVm is null)
+        {
+            return;
+        }
+
+        string serverUrl = msg.ServerUrl ?? mainVm.Chat.CurrentServerUrl;
+        ServerViewModel? serverVm = mainVm.Sidebar.GetServer(serverUrl);
+        if (serverVm is null)
+        {
+            return;
+        }
+
+        ChannelViewModel? channel = serverVm.Channels.FirstOrDefault(c =>
+            string.Equals(c.Name, channelName, StringComparison.OrdinalIgnoreCase));
+        if (channel is null)
+        {
+            return;
+        }
+
+        mainVm.Sidebar.SelectedChannel = channel;
+    }
+
     private async void OnAttachmentImageLoaded(object? sender, RoutedEventArgs e)
     {
         if (sender is not Image image)