Autosave named scenes with revision and disk conflict safety

include/faset/authoring/service.hpp

@@ -25,7 +25,8 @@ class AuthoringService {
                   const Json& operations, const std::string& idempotency_key = "");
     Json undo(const std::string& document, std::uint64_t expected_revision);
     Json redo(const std::string& document, std::uint64_t expected_revision);
-    Json save(const std::string& document, const std::filesystem::path& relative = {});
+    Json save(const std::string& document, const std::filesystem::path& relative = {},
+              std::optional<std::uint64_t> expected_revision = std::nullopt);
     Json recovery_documents() const;
     Json recover(const std::string& document,
                  std::optional<std::uint64_t> expected_revision = std::nullopt);

include/faset/editor/autosave.hpp

@@ -0,0 +1,35 @@
+#pragma once
+
+#include <faset/core/json.hpp>
+#include <chrono>
+#include <functional>
+#include <map>
+#include <mutex>
+#include <string>
+
+namespace faset::editor {
+
+class AutosaveController {
+  public:
+    using Clock = std::chrono::steady_clock;
+    using SaveFn = std::function<Json(const std::string&, std::uint64_t)>;
+    explicit AutosaveController(SaveFn save);
+
+    // Called from the Editor event loop with an injected monotonic clock for
+    // deterministic tests. Only a named dirty scene becomes eligible to save.
+    void observe(const Json& documents, Clock::time_point now, bool enabled);
+    Json status() const;
+
+  private:
+    struct Entry {
+        std::uint64_t revision{};
+        std::string path, state = "saved", error;
+        Clock::time_point deadline{};
+    };
+    SaveFn save_;
+    mutable std::mutex mutex_;
+    std::map<std::string, Entry> entries_;
+    bool enabled_ = true;
+};
+
+} // namespace faset::editor

include/faset/editor/session.hpp

@@ -2,6 +2,7 @@
 #include <faset/assets/asset_pipeline.hpp>
 #include <faset/core/process.hpp>
 #include <faset/editor/build_service.hpp>
+#include <faset/editor/autosave.hpp>
 #include <faset/editor/commands.hpp>
 #include <faset/editor/plugins.hpp>
 #include <memory>
@@ -62,6 +63,8 @@ class Session {
     Commands commands_;
     assets::AssetPipeline assets_;
     BuildService builds_;
+    AutosaveController autosave_;
+    bool autosave_enabled_ = true;
     std::map<std::string, std::shared_ptr<ImportTask>> imports_;
     std::vector<std::jthread> workers_;
     std::vector<std::string> logs_;