User Data Export and import (#967)

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/967
Co-authored-by: konrad <k@knt.li>
Co-committed-by: konrad <k@knt.li>

pkg/utils/write_to_zip.go

@@ -0,0 +1,63 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-2021 Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public Licensee as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public Licensee for more details.
+//
+// You should have received a copy of the GNU Affero General Public Licensee
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package utils
+
+import (
+	"archive/zip"
+	"fmt"
+	"io"
+	"strconv"
+)
+
+// Change to deflate to gain better compression
+// see http://golang.org/pkg/archive/zip/#pkg-constants
+const CompressionUsed = zip.Deflate
+
+func WriteBytesToZip(filename string, data []byte, writer *zip.Writer) (err error) {
+	header := &zip.FileHeader{
+		Name:   filename,
+		Method: CompressionUsed,
+	}
+	w, err := writer.CreateHeader(header)
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(data)
+	return
+}
+
+// WriteFilesToZip writes a bunch of files from the db to a zip file. It exprects a map with the file id
+// as key and its content as io.ReadCloser.
+func WriteFilesToZip(files map[int64]io.ReadCloser, wr *zip.Writer) (err error) {
+	for fid, file := range files {
+		header := &zip.FileHeader{
+			Name:   "files/" + strconv.FormatInt(fid, 10),
+			Method: CompressionUsed,
+		}
+		w, err := wr.CreateHeader(header)
+		if err != nil {
+			return err
+		}
+		_, err = io.Copy(w, file)
+		if err != nil {
+			return fmt.Errorf("error writing file %d: %s", fid, err)
+		}
+		_ = file.Close()
+	}
+
+	return nil
+}