feat: implement rollback functionality with pre-update backup and recovery options | Rebase

src/EchoHub.Client/Services/UpdateBackupService.cs

@@ -0,0 +1,153 @@
+using System.Diagnostics;
+using System.IO.Compression;
+using System.Text.Json;
+
+using Serilog;
+
+namespace EchoHub.Client.Services;
+
+/// <summary>
+/// Manages pre-update backups and rollback restoration for the auto-updater.
+/// Backup location: ~/.echohub/update-backup/
+/// </summary>
+public static class UpdateBackupService
+{
+    private static readonly string BackupDir = Path.Combine(
+        Environment.GetFolderPath(Environment.SpecialFolder.UserProfile),
+        ".echohub", "update-backup");
+
+    private static readonly string BackupZipPath = Path.Combine(BackupDir, "backup.zip");
+    private static readonly string BackupInfoPath = Path.Combine(BackupDir, "backup-info.json");
+
+    /// <summary>
+    /// True if a backup exists from a recent update (set at startup).
+    /// </summary>
+    public static bool IsPostUpdate { get; set; }
+
+    /// <summary>
+    /// Creates a ZIP backup of the current app directory before an update.
+    /// Deletes any previous backup first. Uses fastest compression for speed.
+    /// </summary>
+    public static void CreateBackup()
+    {
+        var appDir = AppContext.BaseDirectory.TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
+        var version = UpdateChecker.CurrentVersion;
+
+        if (Directory.Exists(BackupDir))
+            Directory.Delete(BackupDir, true);
+
+        Directory.CreateDirectory(BackupDir);
+
+        Log.Information("Creating pre-update backup of {AppDir} (v{Version})", appDir, version);
+
+        ZipFile.CreateFromDirectory(appDir, BackupZipPath, CompressionLevel.Fastest, includeBaseDirectory: false);
+
+        var info = new BackupInfo(version, appDir, DateTimeOffset.UtcNow);
+        var json = JsonSerializer.Serialize(info, BackupJsonContext.Default.BackupInfo);
+        File.WriteAllText(BackupInfoPath, json);
+
+        Log.Information("Backup created at {BackupPath}", BackupZipPath);
+    }
+
+    /// <summary>
+    /// Returns true if a valid backup exists (both ZIP and metadata file present).
+    /// </summary>
+    public static bool BackupExists()
+        => File.Exists(BackupZipPath) && File.Exists(BackupInfoPath);
+
+    /// <summary>
+    /// Reads backup metadata. Returns null if no backup exists or metadata is unreadable.
+    /// </summary>
+    public static BackupInfo? GetBackupInfo()
+    {
+        if (!File.Exists(BackupInfoPath))
+            return null;
+
+        try
+        {
+            var json = File.ReadAllText(BackupInfoPath);
+            return JsonSerializer.Deserialize(json, BackupJsonContext.Default.BackupInfo);
+        }
+        catch (Exception ex)
+        {
+            Log.Warning(ex, "Failed to read backup metadata");
+            return null;
+        }
+    }
+
+    /// <summary>
+    /// Restores the backup ZIP to the app directory, then restarts the process.
+    /// This method does not return — it calls Environment.Exit(0).
+    /// </summary>
+    public static void RestoreBackup()
+    {
+        var info = GetBackupInfo()
+            ?? throw new InvalidOperationException("No backup metadata found");
+
+        var appDir = info.AppDirectory;
+        Log.Information("Restoring backup v{Version} to {AppDir}", info.Version, appDir);
+
+        // On Windows, rename the running executable so extraction can overwrite it
+        if (OperatingSystem.IsWindows())
+        {
+            var currentExe = Environment.ProcessPath;
+            if (!string.IsNullOrEmpty(currentExe) && File.Exists(currentExe))
+            {
+                var oldExe = currentExe + ".old";
+                if (File.Exists(oldExe))
+                    File.Delete(oldExe);
+                File.Move(currentExe, oldExe);
+            }
+        }
+
+        ZipFile.ExtractToDirectory(BackupZipPath, appDir, overwriteFiles: true);
+
+        // Restore execute permission on Unix
+        if (!OperatingSystem.IsWindows())
+        {
+            var exePath = Environment.ProcessPath
+                ?? Path.Combine(appDir, "EchoHub.Client");
+
+            if (File.Exists(exePath))
+            {
+                var mode = File.GetUnixFileMode(exePath);
+                File.SetUnixFileMode(exePath, mode | UnixFileMode.UserExecute);
+            }
+        }
+
+        // Start the restored version and exit
+        var processPath = Environment.ProcessPath
+            ?? Path.Combine(appDir, "EchoHub.Client");
+
+        Log.Information("Launching restored version v{Version}: {Path}", info.Version, processPath);
+        Process.Start(new ProcessStartInfo(processPath) { UseShellExecute = false });
+        Environment.Exit(0);
+    }
+
+    /// <summary>
+    /// Deletes the backup directory and all contents.
+    /// </summary>
+    public static void DeleteBackup()
+    {
+        if (!Directory.Exists(BackupDir))
+            return;
+
+        try
+        {
+            Directory.Delete(BackupDir, true);
+            Log.Information("Update backup deleted");
+        }
+        catch (Exception ex)
+        {
+            Log.Warning(ex, "Failed to delete update backup");
+        }
+    }
+}
+
+public record BackupInfo(
+    string Version,
+    string AppDirectory,
+    DateTimeOffset CreatedAt);
+
+[System.Text.Json.Serialization.JsonSerializable(typeof(BackupInfo))]
+internal partial class BackupJsonContext : System.Text.Json.Serialization.JsonSerializerContext;