GODT-2034: Basic vault migration ability (proof of concept)

internal/vault/migrate.go

@@ -0,0 +1,47 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package vault
+
+import "fmt"
+
+type Version int
+
+const (
+	v2_3_x Version = iota
+	v2_4_x
+	v2_5_x
+
+	Current = v2_5_x
+)
+
+// upgrade migrates the vault from the given version to the next version.
+func upgrade(v Version, b []byte) ([]byte, error) {
+	switch v {
+	case v2_3_x:
+		return upgrade_2_3_x(b)
+
+	case v2_4_x:
+		return upgrade_2_4_x(b)
+
+	case Current:
+		return nil, fmt.Errorf("already at current version %d", Current)
+
+	default:
+		return nil, fmt.Errorf("unknown version %d", v)
+	}
+}