Serialize restore recovery and rebase manifest paths

internal/app/restore_recovery.go

@@ -0,0 +1,63 @@
+package app
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
+	"gitea.maximumdirect.net/eric/narratio/internal/fileops"
+)
+
+type restoreMarker struct {
+	StartedAt time.Time `json:"started_at"`
+}
+
+func writeRestoreMarker(paths artifacts.SessionPaths) error {
+	marker := restoreMarker{StartedAt: nowUTC()}
+	data, err := json.Marshal(marker)
+	if err != nil {
+		return fmt.Errorf("encode recovery marker: %w", err)
+	}
+	if err := fileops.WriteFileAtomic(paths.RestoreMarkerPath, data, fileops.WorkspaceFileMode); err != nil {
+		return fmt.Errorf("write recovery marker: %w", err)
+	}
+	return nil
+}
+
+func clearRestoreMarker(paths artifacts.SessionPaths) error {
+	if strings.TrimSpace(paths.RestoreMarkerPath) == "" {
+		return fmt.Errorf("recovery marker path is required")
+	}
+	if err := os.Remove(paths.RestoreMarkerPath); err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("remove recovery marker: %w", err)
+	}
+	return nil
+}
+
+func requireCompleteRestore(paths artifacts.SessionPaths) error {
+	if strings.TrimSpace(paths.RestoreMarkerPath) == "" {
+		return fmt.Errorf("restore recovery marker path is required")
+	}
+	info, err := os.Lstat(paths.RestoreMarkerPath)
+	if os.IsNotExist(err) {
+		return nil
+	}
+	if err != nil {
+		return fmt.Errorf("check restore recovery marker: %w", err)
+	}
+	if !info.Mode().IsRegular() {
+		return fmt.Errorf("restore recovery marker is not a regular file; rerun session restore")
+	}
+	data, err := os.ReadFile(paths.RestoreMarkerPath)
+	if err != nil {
+		return fmt.Errorf("read restore recovery marker: %w", err)
+	}
+	var marker restoreMarker
+	if err := json.Unmarshal(data, &marker); err != nil || marker.StartedAt.IsZero() {
+		return fmt.Errorf("restore recovery marker is invalid; rerun session restore")
+	}
+	return fmt.Errorf("restore is incomplete; rerun session restore before running pipeline stages")
+}