1 files changed, 108 insertions, 0 deletions
diff --git a/src/Agent.Windows/Recovery/TaskResourceJournal.cs b/src/Agent.Windows/Recovery/TaskResourceJournal.cs
new file mode 100644
index 0000000..b638041
--- /dev/null
+++ b/src/Agent.Windows/Recovery/TaskResourceJournal.cs
@@ -0,0 +1,108 @@
+using System.Text.Json;
+
+namespace Agent.Windows.Recovery;
+
+public enum JournalEntryState { Prepared, Applied, Cleaned }
+
+public sealed class JournalEntry
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    public string Kind { get; set; } = string.Empty;
+    public string Target { get; set; } = string.Empty;
+    public JournalEntryState State { get; set; }
+    public Dictionary<string, string> Data { get; set; } = new(StringComparer.Ordinal);
+}
+
+public sealed class JournalDocument
+{
+    public int SchemaVersion { get; set; } = 1;
+    public Guid TaskId { get; set; }
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+    public List<JournalEntry> Entries { get; set; } = [];
+}
+
+public sealed class TaskResourceJournal
+{
+    private static readonly JsonSerializerOptions JsonOptions = new() { WriteIndented = true };
+    private readonly object _sync = new();
+    private readonly JournalDocument _document;
+
+    private TaskResourceJournal(string path, JournalDocument document) { Path = path; _document = document; }
+    public string Path { get; }
+    public Guid TaskId => _document.TaskId;
+    public IReadOnlyList<JournalEntry> Entries { get { lock (_sync) return _document.Entries.Select(Clone).ToArray(); } }
+
+    public static TaskResourceJournal Create(string journalDirectory, Guid taskId)
+    {
+        Directory.CreateDirectory(journalDirectory);
+        string path = System.IO.Path.Combine(journalDirectory, taskId.ToString("N") + ".journal.json");
+        if (File.Exists(path)) throw new InvalidOperationException($"Journal already exists for task '{taskId}'.");
+        var journal = new TaskResourceJournal(path, new JournalDocument { TaskId = taskId });
+        journal.Persist();
+        return journal;
+    }
+
+    public static TaskResourceJournal Open(string path)
+    {
+        JournalDocument document = JsonSerializer.Deserialize<JournalDocument>(File.ReadAllText(path), JsonOptions)
+            ?? throw new InvalidDataException($"Journal '{path}' is empty.");
+        if (document.SchemaVersion != 1 || document.TaskId == Guid.Empty) throw new InvalidDataException($"Journal '{path}' is invalid.");
+        return new(path, document);
+    }
+
+    public Guid Prepare(string kind, string target, IReadOnlyDictionary<string, string> data)
+    {
+        lock (_sync)
+        {
+            var entry = new JournalEntry { Kind = kind, Target = target, State = JournalEntryState.Prepared, Data = new(data, StringComparer.Ordinal) };
+            _document.Entries.Add(entry);
+            Persist();
+            return entry.Id;
+        }
+    }
+
+    public void MarkApplied(Guid entryId, IReadOnlyDictionary<string, string>? additionalData = null)
+    {
+        lock (_sync)
+        {
+            JournalEntry entry = Get(entryId);
+            if (entry.State != JournalEntryState.Prepared) throw new InvalidOperationException("Only prepared resources can be marked applied.");
+            if (additionalData is not null) foreach ((string key, string value) in additionalData) entry.Data[key] = value;
+            entry.State = JournalEntryState.Applied;
+            Persist();
+        }
+    }
+
+    public void MarkCleaned(Guid entryId)
+    {
+        lock (_sync)
+        {
+            JournalEntry entry = Get(entryId);
+            if (entry.State == JournalEntryState.Cleaned) return;
+            entry.State = JournalEntryState.Cleaned;
+            Persist();
+        }
+    }
+
+    public void CompleteAndDelete()
+    {
+        lock (_sync)
+        {
+            if (_document.Entries.Any(entry => entry.State != JournalEntryState.Cleaned)) throw new InvalidOperationException("Journal still contains live resources.");
+            File.Delete(Path);
+        }
+    }
+
+    private JournalEntry Get(Guid id) => _document.Entries.SingleOrDefault(entry => entry.Id == id) ?? throw new KeyNotFoundException($"Journal entry '{id}' not found.");
+    private void Persist()
+    {
+        string temporary = Path + ".tmp";
+        using (FileStream stream = new(temporary, FileMode.Create, FileAccess.Write, FileShare.None, 4096, FileOptions.WriteThrough))
+        {
+            JsonSerializer.Serialize(stream, _document, JsonOptions);
+            stream.Flush(flushToDisk: true);
+        }
+        File.Move(temporary, Path, overwrite: true);
+    }
+    private static JournalEntry Clone(JournalEntry source) => new() { Id = source.Id, Kind = source.Kind, Target = source.Target, State = source.State, Data = new(source.Data, StringComparer.Ordinal) };
+}