Support attaching existing Restic repositories

internal/restic/restic.go

@@ -414,7 +414,7 @@ func resticError(message string, commandErr error) error {
 	case strings.Contains(lower, "wrong password") || strings.Contains(lower, "no key found"):
 		return errors.New("authentication: wrong repository password. Enter the original Restic password under Edit and select Test")
 	case strings.Contains(lower, "repository does not exist") || strings.Contains(lower, "is there a repository at the following location?"):
-		return errors.New("repository: destination is not initialized; open Repositories and select Initialize once")
+		return errors.New("repository: Am konfigurierten Ziel wurde keine Restic-config gefunden. Für ein vorhandenes Repository den exakten Repository-Ordner eintragen; nur ein wirklich neues, leeres Ziel initialisieren")
 	default:
 		message = strings.TrimSpace(strings.TrimPrefix(message, "Fatal:"))
 		return fmt.Errorf("restic: %s: %w", message, commandErr)

internal/restic/restic_test.go

@@ -298,6 +298,13 @@ func TestResticErrorExplainsCiphertextVerification(t *testing.T) {
 	}
 }
 
+func TestResticErrorExplainsMissingExistingRepositoryPath(t *testing.T) {
+	err := resticError("Fatal: repository does not exist", fmt.Errorf("exit status 10"))
+	if !strings.Contains(err.Error(), "exakten Repository-Ordner") || !strings.Contains(err.Error(), "wirklich neues") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
 func TestRunnerPausesResumesAndCancelsProcessGroup(t *testing.T) {
 	dir := t.TempDir()
 	ticksPath := filepath.Join(dir, "ticks")

internal/service/repository_test.go

@@ -0,0 +1,41 @@
+package service
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestValidateExistingRepositoryPathAcceptsRepositoryRoot(t *testing.T) {
+	root := t.TempDir()
+	if err := os.WriteFile(filepath.Join(root, "config"), []byte("restic"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	if err := validateExistingRepositoryPath(root); err != nil {
+		t.Fatalf("repository root rejected: %v", err)
+	}
+}
+
+func TestValidateExistingRepositoryPathSuggestsDirectChild(t *testing.T) {
+	root := t.TempDir()
+	repository := filepath.Join(root, "server-backup")
+	if err := os.Mkdir(repository, 0700); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(repository, "config"), []byte("restic"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	err := validateExistingRepositoryPath(root)
+	if err == nil || !strings.Contains(err.Error(), repository) {
+		t.Fatalf("missing repository suggestion: %v", err)
+	}
+}
+
+func TestValidateExistingRepositoryPathExplainsMissingConfig(t *testing.T) {
+	root := t.TempDir()
+	err := validateExistingRepositoryPath(root)
+	if err == nil || !strings.Contains(err.Error(), "config, data, index, keys und snapshots") {
+		t.Fatalf("missing layout guidance: %v", err)
+	}
+}

internal/service/service.go

@@ -262,10 +262,43 @@ func (s *Service) TestRepository(ctx context.Context, repoID string, initialize
 	if initialize {
 		return s.restic.Init(ctx, mounted.Repository)
 	}
+	if mounted.Repository.Type != model.RepositorySFTP {
+		if err := validateExistingRepositoryPath(mounted.Repository.Location); err != nil {
+			return err
+		}
+	}
 	_, err = s.restic.Snapshots(ctx, mounted.Repository)
 	return err
 }
 
+func validateExistingRepositoryPath(location string) error {
+	configPath := filepath.Join(location, "config")
+	if info, err := os.Stat(configPath); err == nil && !info.IsDir() {
+		return nil
+	}
+	entries, readErr := os.ReadDir(location)
+	if readErr != nil {
+		return fmt.Errorf("repository: Repository-Ordner %q kann nicht gelesen werden: %w", location, readErr)
+	}
+	candidates := make([]string, 0, 3)
+	for _, entry := range entries {
+		if !entry.IsDir() {
+			continue
+		}
+		candidate := filepath.Join(location, entry.Name())
+		if info, err := os.Stat(filepath.Join(candidate, "config")); err == nil && !info.IsDir() {
+			candidates = append(candidates, candidate)
+			if len(candidates) == 3 {
+				break
+			}
+		}
+	}
+	if len(candidates) > 0 {
+		return fmt.Errorf("repository: Im gewählten Ordner liegt keine Restic-config. Verwende direkt den Repository-Ordner: %s", strings.Join(candidates, ", "))
+	}
+	return fmt.Errorf("repository: Im gewählten Ordner %q wurde keine Restic-config gefunden. Ein vorhandenes Repository muss direkt auf den Ordner zeigen, der config, data, index, keys und snapshots enthält", location)
+}
+
 func (s *Service) UnlockRepository(ctx context.Context, repoID string) error {
 	repo, ok := s.repository(repoID)
 	if !ok {