feat: add CLI command for importing and exporting Pocket ID data (#998)

Co-authored-by: Alessandro (Ale) Segala <43508+ItalyPaleAle@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

backend/internal/cmds/export.go

@@ -0,0 +1,70 @@
+package cmds
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/pocket-id/pocket-id/backend/internal/bootstrap"
+	"github.com/pocket-id/pocket-id/backend/internal/service"
+	"github.com/spf13/cobra"
+)
+
+type exportFlags struct {
+	Path string
+}
+
+func init() {
+	var flags exportFlags
+
+	exportCmd := &cobra.Command{
+		Use:   "export",
+		Short: "Exports all data of Pocket ID into a ZIP file",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return runExport(cmd.Context(), flags)
+		},
+	}
+
+	exportCmd.Flags().StringVarP(&flags.Path, "path", "p", "pocket-id-export.zip", "Path to the ZIP file to export the data to, or '-' to write to stdout")
+
+	rootCmd.AddCommand(exportCmd)
+}
+
+// runExport orchestrates the export flow
+func runExport(ctx context.Context, flags exportFlags) error {
+	db, err := bootstrap.NewDatabase()
+	if err != nil {
+		return fmt.Errorf("failed to connect to database: %w", err)
+	}
+
+	storage, err := bootstrap.InitStorage(ctx, db)
+	if err != nil {
+		return fmt.Errorf("failed to initialize storage: %w", err)
+	}
+
+	exportService := service.NewExportService(db, storage)
+
+	var w io.Writer
+	if flags.Path == "-" {
+		w = os.Stdout
+	} else {
+		file, err := os.Create(flags.Path)
+		if err != nil {
+			return fmt.Errorf("failed to create export file: %w", err)
+		}
+		defer file.Close()
+
+		w = file
+	}
+
+	if err := exportService.ExportToZip(ctx, w); err != nil {
+		return fmt.Errorf("failed to export data: %w", err)
+	}
+
+	if flags.Path != "-" {
+		fmt.Printf("Exported data to %s\n", flags.Path)
+	}
+
+	return nil
+}