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/service/export_service.go

@@ -0,0 +1,217 @@
+package service
+
+import (
+	"archive/zip"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"path/filepath"
+
+	"gorm.io/gorm"
+
+	datatype "github.com/pocket-id/pocket-id/backend/internal/model/types"
+	"github.com/pocket-id/pocket-id/backend/internal/storage"
+	"github.com/pocket-id/pocket-id/backend/internal/utils"
+)
+
+// ExportService handles exporting Pocket ID data into a ZIP archive.
+type ExportService struct {
+	db      *gorm.DB
+	storage storage.FileStorage
+}
+
+func NewExportService(db *gorm.DB, storage storage.FileStorage) *ExportService {
+	return &ExportService{
+		db:      db,
+		storage: storage,
+	}
+}
+
+// ExportToZip performs the full export process and writes the ZIP data to the given writer.
+func (s *ExportService) ExportToZip(ctx context.Context, w io.Writer) error {
+	dbData, err := s.extractDatabase()
+	if err != nil {
+		return err
+	}
+
+	return s.writeExportZipStream(ctx, w, dbData)
+}
+
+// extractDatabase reads all tables into a DatabaseExport struct
+func (s *ExportService) extractDatabase() (DatabaseExport, error) {
+	schema, err := utils.LoadDBSchemaTypes(s.db)
+	if err != nil {
+		return DatabaseExport{}, fmt.Errorf("failed to load schema types: %w", err)
+	}
+
+	version, err := s.schemaVersion()
+	if err != nil {
+		return DatabaseExport{}, err
+	}
+
+	out := DatabaseExport{
+		Provider: s.db.Name(),
+		Version:  version,
+		Tables:   map[string][]map[string]any{},
+		// These tables need to be inserted in a specific order because of foreign key constraints
+		// Not all tables are listed here, because not all tables are order-dependent
+		TableOrder: []string{"users", "user_groups", "oidc_clients"},
+	}
+
+	for table := range schema {
+		if table == "storage" || table == "schema_migrations" {
+			continue
+		}
+		err = s.dumpTable(table, schema[table], &out)
+		if err != nil {
+			return DatabaseExport{}, err
+		}
+	}
+
+	return out, nil
+}
+
+func (s *ExportService) schemaVersion() (uint, error) {
+	var version uint
+	if err := s.db.Raw("SELECT version FROM schema_migrations").Row().Scan(&version); err != nil {
+		return 0, fmt.Errorf("failed to query schema version: %w", err)
+	}
+	return version, nil
+}
+
+// dumpTable selects all rows from a table and appends them to out.Tables
+func (s *ExportService) dumpTable(table string, types utils.DBSchemaTableTypes, out *DatabaseExport) error {
+	rows, err := s.db.Raw("SELECT * FROM " + table).Rows()
+	if err != nil {
+		return fmt.Errorf("failed to read table %s: %w", table, err)
+	}
+	defer rows.Close()
+
+	cols, _ := rows.Columns()
+	if len(cols) != len(types) {
+		// Should never happen...
+		return fmt.Errorf("mismatched columns in table (%d) and schema (%d)", len(cols), len(types))
+	}
+
+	for rows.Next() {
+		vals := s.getScanValuesForTable(cols, types)
+		err = rows.Scan(vals...)
+		if err != nil {
+			return fmt.Errorf("failed to scan row in table %s: %w", table, err)
+		}
+
+		rowMap := make(map[string]any, len(cols))
+		for i, col := range cols {
+			rowMap[col] = vals[i]
+		}
+
+		// Skip the app lock row in the kv table
+		if table == "kv" {
+			if keyPtr, ok := rowMap["key"].(*string); ok && keyPtr != nil && *keyPtr == lockKey {
+				continue
+			}
+		}
+
+		out.Tables[table] = append(out.Tables[table], rowMap)
+	}
+
+	return rows.Err()
+}
+
+func (s *ExportService) getScanValuesForTable(cols []string, types utils.DBSchemaTableTypes) []any {
+	res := make([]any, len(cols))
+	for i, col := range cols {
+		// Store a pointer
+		// Note: don't create a helper function for this switch, because it would return type "any" and mess everything up
+		// If the column is nullable, we need a pointer to a pointer!
+		switch types[col].Name {
+		case "boolean", "bool":
+			var x bool
+			if types[col].Nullable {
+				res[i] = utils.Ptr(utils.Ptr(x))
+			} else {
+				res[i] = utils.Ptr(x)
+			}
+		case "blob", "bytea", "jsonb":
+			// Treat jsonb columns as binary too
+			var x []byte
+			if types[col].Nullable {
+				res[i] = utils.Ptr(utils.Ptr(x))
+			} else {
+				res[i] = utils.Ptr(x)
+			}
+		case "timestamp", "timestamptz", "timestamp with time zone", "datetime":
+			var x datatype.DateTime
+			if types[col].Nullable {
+				res[i] = utils.Ptr(utils.Ptr(x))
+			} else {
+				res[i] = utils.Ptr(x)
+			}
+		case "integer", "int", "bigint":
+			var x int64
+			if types[col].Nullable {
+				res[i] = utils.Ptr(utils.Ptr(x))
+			} else {
+				res[i] = utils.Ptr(x)
+			}
+		default:
+			// Treat everything else as a string (including the "numeric" type)
+			var x string
+			if types[col].Nullable {
+				res[i] = utils.Ptr(utils.Ptr(x))
+			} else {
+				res[i] = utils.Ptr(x)
+			}
+		}
+	}
+
+	return res
+}
+
+func (s *ExportService) writeExportZipStream(ctx context.Context, w io.Writer, dbData DatabaseExport) error {
+	zipWriter := zip.NewWriter(w)
+
+	// Add database.json
+	jsonWriter, err := zipWriter.Create("database.json")
+	if err != nil {
+		return fmt.Errorf("failed to create database.json in zip: %w", err)
+	}
+
+	jsonEncoder := json.NewEncoder(jsonWriter)
+	jsonEncoder.SetEscapeHTML(false)
+
+	if err := jsonEncoder.Encode(dbData); err != nil {
+		return fmt.Errorf("failed to encode database.json: %w", err)
+	}
+
+	// Add uploaded files
+	if err := s.addUploadsToZip(ctx, zipWriter); err != nil {
+		return err
+	}
+
+	return zipWriter.Close()
+}
+
+// addUploadsToZip adds all files from the storage to the ZIP archive under the "uploads/" directory
+func (s *ExportService) addUploadsToZip(ctx context.Context, zipWriter *zip.Writer) error {
+	return s.storage.Walk(ctx, "/", func(p storage.ObjectInfo) error {
+		zipPath := filepath.Join("uploads", p.Path)
+
+		w, err := zipWriter.Create(zipPath)
+		if err != nil {
+			return fmt.Errorf("failed to create zip entry for %s: %w", zipPath, err)
+		}
+
+		f, _, err := s.storage.Open(ctx, p.Path)
+		if err != nil {
+			return fmt.Errorf("failed to open file %s: %w", zipPath, err)
+		}
+		defer f.Close()
+
+		if _, err := io.Copy(w, f); err != nil {
+			return fmt.Errorf("failed to copy file %s into zip: %w", zipPath, err)
+		}
+		return nil
+	})
+}