Preloading and better parsing for UpdateViewModel

StabilityMatrix.Avalonia/ViewModels/Dialogs/UpdateViewModel.cs

@@ -2,10 +2,12 @@
 using System.Diagnostics;
 using System.IO;
 using System.Net.Http;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using AsyncAwaitBestPractices;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
+using Semver;
 using StabilityMatrix.Avalonia.ViewModels.Base;
 using StabilityMatrix.Avalonia.Views.Dialogs;
 using StabilityMatrix.Core.Attributes;
@@ -24,6 +26,8 @@ public partial class UpdateViewModel : ContentDialogViewModelBase
     private readonly IHttpClientFactory httpClientFactory;
     private readonly IUpdateHelper updateHelper;
 
+    private bool isLoaded;
+
     [ObservableProperty]
     private bool isUpdateAvailable;
 
@@ -60,31 +64,36 @@ public partial class UpdateViewModel : ContentDialogViewModelBase
         updateHelper.StartCheckingForUpdates().SafeFireAndForget();
     }
 
-    public override async Task OnLoadedAsync()
+    /// <summary>
+    /// Formats changelog markdown including up to the current version
+    /// </summary>
+    internal static string? FormatChangelog(string markdown, SemVersion currentVersion)
+    {
+        var pattern = $@"(##[\s\S]+?)(?:## v{currentVersion.WithoutPrereleaseOrMetadata()})";
+
+        var match = Regex.Match(markdown, pattern);
+
+        return match.Success ? match.Groups[1].Value.TrimEnd() : null;
+    }
+
+    public async Task Preload()
     {
         if (UpdateInfo is null)
             return;
 
-        UpdateText =
-            $"Stability Matrix v{UpdateInfo.Version} is now available! You currently have v{Compat.AppVersion}. Would you like to update now?";
-
-        var client = httpClientFactory.CreateClient();
+        using var client = httpClientFactory.CreateClient();
         var response = await client.GetAsync(UpdateInfo.ChangelogUrl);
         if (response.IsSuccessStatusCode)
         {
-            ReleaseNotes = await response.Content.ReadAsStringAsync();
+            var changelog = await response.Content.ReadAsStringAsync();
 
             // Formatting for new changelog format
             // https://keepachangelog.com/en/1.1.0/
             if (UpdateInfo.ChangelogUrl.EndsWith(".md", StringComparison.OrdinalIgnoreCase))
             {
-                // Skip until the first occurrence of "##"
-                const string delimiter = "##";
-                var startIndex = ReleaseNotes.IndexOf(delimiter, StringComparison.Ordinal);
-                if (startIndex != -1)
-                {
-                    ReleaseNotes = ReleaseNotes[startIndex..];
-                }
+                ReleaseNotes =
+                    FormatChangelog(changelog, UpdateInfo.Version)
+                    ?? "## Unable to format release notes";
             }
         }
         else
@@ -93,6 +102,27 @@ public partial class UpdateViewModel : ContentDialogViewModelBase
         }
     }
 
+    public override async Task OnLoadedAsync()
+    {
+        if (UpdateInfo is null)
+            return;
+
+        UpdateText =
+            $"Stability Matrix v{UpdateInfo.Version} is now available! You currently have v{Compat.AppVersion}. Would you like to update now?";
+
+        if (!isLoaded)
+        {
+            await Preload();
+        }
+    }
+
+    /// <inheritdoc />
+    public override void OnUnloaded()
+    {
+        base.OnUnloaded();
+        isLoaded = false;
+    }
+
     [RelayCommand]
     private async Task InstallUpdate()
     {