Implemented confi snapshots

internal/controllogic/store.go

@@ -17,19 +17,25 @@ var ErrNotFound = errors.New("control logic graph not found")
 
 // Store persists control-logic graphs as a single JSON file in the storage dir.
 // Writes are atomic (tmp file + rename); all access is mutex-guarded.
+//
+// Git-style versioning: the live graph lives in controllogic.json (the current
+// revision), while every superseded revision is preserved as a backup file
+// {id}.vN.json under versionsDir. Promote/Fork build on these backups.
 type Store struct {
-	mu       sync.RWMutex
-	path     string
-	trashDir string
-	items    map[string]Graph
+	mu          sync.RWMutex
+	path        string
+	trashDir    string
+	versionsDir string
+	items       map[string]Graph
 }
 
 // NewStore opens (or initialises) the control-logic store under storageDir.
 func NewStore(storageDir string) (*Store, error) {
 	s := &Store{
-		path:     filepath.Join(storageDir, definitionsFile),
-		trashDir: filepath.Join(storageDir, "trash", "controllogic"),
-		items:    map[string]Graph{},
+		path:        filepath.Join(storageDir, definitionsFile),
+		trashDir:    filepath.Join(storageDir, "trash", "controllogic"),
+		versionsDir: filepath.Join(storageDir, "controllogic_versions"),
+		items:       map[string]Graph{},
 	}
 	if err := s.load(); err != nil {
 		return nil, err
@@ -94,14 +100,46 @@ func (s *Store) Get(id string) (Graph, error) {
 	return g, nil
 }
 
-// Save inserts or replaces a graph and persists the store.
+// Save inserts or replaces a graph and persists the store. When replacing an
+// existing graph the superseded revision is backed up as {id}.vN.json and the
+// new graph's Version is bumped; a brand-new graph starts at version 1.
 func (s *Store) Save(g Graph) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
+	if old, ok := s.items[g.ID]; ok {
+		oldV := old.Version
+		if oldV < 1 {
+			oldV = 1
+			old.Version = 1
+		}
+		if err := s.backupLocked(old); err != nil {
+			return fmt.Errorf("back up control logic revision: %w", err)
+		}
+		g.Version = oldV + 1
+	} else if g.Version < 1 {
+		g.Version = 1
+	}
 	s.items[g.ID] = g
 	return s.saveLocked()
 }
 
+// backupLocked writes a single graph revision to versionsDir as {id}.vN.json.
+// Caller must hold s.mu.
+func (s *Store) backupLocked(g Graph) error {
+	if err := os.MkdirAll(s.versionsDir, 0o755); err != nil {
+		return err
+	}
+	data, err := json.MarshalIndent(g, "", "  ")
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(s.versionPath(g.ID, g.Version), data, 0o644)
+}
+
+func (s *Store) versionPath(id string, version int) string {
+	return filepath.Join(s.versionsDir, fmt.Sprintf("%s.v%d.json", id, version))
+}
+
 // Delete removes a graph by id, first writing a copy into the trash folder so it
 // can be recovered if needed. The trash backup is best-effort: a failure to write
 // it does not prevent the delete (but is reported).