Added backups of all data, restorable on another computer (#1008)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Tools/DataBackup/DataRestoreFormat.cs

@@ -0,0 +1,76 @@
+namespace AIStudio.Tools.DataBackup;
+
+/// <summary>
+/// How a prepared restore waits for the next start, which applies it.
+/// </summary>
+/// <remarks>
+/// This is the contract between the app, which prepares a restore, and the runtime, which applies it
+/// before the app starts again, when no file is in use:
+/// <list type="bullet">
+/// <item>Below the data folder and below the configuration folder, PENDING_DIRECTORY holds what the
+/// backup brings for that folder, in the layout of that folder. Staging lies on the same disk as its
+/// target, so the runtime can move every element into place instead of copying it.</item>
+/// <item>The plan, PLAN_FILE_NAME in the pending directory of the data folder, names the elements to
+/// replace, cf. DataRestorePlan.</item>
+/// <item>READY_FILE_NAME in the same directory comes last. Without it, the restore was not prepared
+/// completely, and the runtime leaves everything as it is.</item>
+/// </list>
+/// What the runtime adds, cf. runtime/src/data_restore.rs:
+/// <list type="bullet">
+/// <item>PREVIOUS_DIRECTORY, below both folders, keeps what the restore replaced. The app removes it
+/// once it loaded the restored settings.</item>
+/// <item>JOURNAL_FILE_NAME in the pending directory of the data folder lists every move. While it lies
+/// next to READY_FILE_NAME, the runtime moves everything back at the next start, so the app never
+/// removes a pending directory which holds READY_FILE_NAME.</item>
+/// <item>RESULT_FILE_NAME in the data folder tells the app how the restore ended, cf. DataRestoreReport.</item>
+/// </list>
+/// Keep in sync with the runtime, which applies the restore.
+/// </remarks>
+public static class DataRestoreFormat
+{
+    /// <summary>
+    /// The version of the plan this version of AI Studio writes.
+    /// </summary>
+    public const int PLAN_FORMAT_VERSION = 1;
+
+    /// <summary>
+    /// The directory, below the data folder and below the configuration folder, which holds what a
+    /// prepared restore brings for that folder.
+    /// </summary>
+    public const string PENDING_DIRECTORY = ".restore-pending/";
+
+    /// <summary>
+    /// The plan of the restore, in the pending directory of the data folder.
+    /// </summary>
+    public const string PLAN_FILE_NAME = "restore.json";
+
+    /// <summary>
+    /// Marks a restore as prepared completely, in the pending directory of the data folder.
+    /// </summary>
+    public const string READY_FILE_NAME = "READY";
+
+    /// <summary>
+    /// The directory, below the data folder and below the configuration folder, which keeps what the
+    /// runtime replaced, in the layout of that folder.
+    /// </summary>
+    public const string PREVIOUS_DIRECTORY = ".restore-previous/";
+
+    /// <summary>
+    /// How the runtime applied a restore, in the data folder.
+    /// </summary>
+    public const string RESULT_FILE_NAME = ".restore-result.json";
+
+    /// <summary>
+    /// The journal of the runtime, in the pending directory of the data folder. Next to READY_FILE_NAME,
+    /// it tells that the runtime has not finished a restore: it moves it back at the next start.
+    /// </summary>
+    public const string JOURNAL_FILE_NAME = "journal.json";
+
+    /// <summary>
+    /// The path of one of the directories above, below the given folder.
+    /// </summary>
+    /// <param name="folder">The data or the configuration folder.</param>
+    /// <param name="directory">PENDING_DIRECTORY or PREVIOUS_DIRECTORY.</param>
+    /// <returns>The path of the directory.</returns>
+    public static string DirectoryIn(string folder, string directory) => Path.Join(folder, directory.TrimEnd(DataBackupContents.SEPARATOR));
+}