From b6d3899b8119b170082611b471c2e2986083c135 Mon Sep 17 00:00:00 2001
From: Pierre-Olivier Mercier <nemunaire@nemunai.re>
Date: Tue, 29 Sep 2020 23:09:47 +0200
Subject: [PATCH] Prepare leveldb migrations

---
 storage/leveldb/database.go |  4 --
 storage/leveldb/updates.go  | 76 +++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 4 deletions(-)
 create mode 100644 storage/leveldb/updates.go

diff --git a/storage/leveldb/database.go b/storage/leveldb/database.go
index 31142e3..7b139b1 100644
--- a/storage/leveldb/database.go
+++ b/storage/leveldb/database.go
@@ -55,10 +55,6 @@ func NewLevelDBStorage(path string) (*LevelDBStorage, error) {
 	}
 }
 
-func (s *LevelDBStorage) DoMigration() error {
-	return nil
-}
-
 func (s *LevelDBStorage) Tidy() error {
 	for _, tidy := range []func() error{s.TidySessions, s.TidySources, s.TidyDomains, s.TidyZones} {
 		if err := tidy(); err != nil {
diff --git a/storage/leveldb/updates.go b/storage/leveldb/updates.go
new file mode 100644
index 0000000..3c3eaed
--- /dev/null
+++ b/storage/leveldb/updates.go
@@ -0,0 +1,76 @@
+// Copyright or © or Copr. happyDNS (2020)
+//
+// contact@happydns.org
+//
+// This software is a computer program whose purpose is to provide a modern
+// interface to interact with DNS systems.
+//
+// This software is governed by the CeCILL license under French law and abiding
+// by the rules of distribution of free software.  You can use, modify and/or
+// redistribute the software under the terms of the CeCILL license as
+// circulated by CEA, CNRS and INRIA at the following URL
+// "http://www.cecill.info".
+//
+// As a counterpart to the access to the source code and rights to copy, modify
+// and redistribute granted by the license, users are provided only with a
+// limited warranty and the software's author, the holder of the economic
+// rights, and the successive licensors have only limited liability.
+//
+// In this respect, the user's attention is drawn to the risks associated with
+// loading, using, modifying and/or developing or reproducing the software by
+// the user in light of its specific status of free software, that may mean
+// that it is complicated to manipulate, and that also therefore means that it
+// is reserved for developers and experienced professionals having in-depth
+// computer knowledge. Users are therefore encouraged to load and test the
+// software's suitability as regards their requirements in conditions enabling
+// the security of their systems and/or data to be ensured and, more generally,
+// to use and operate it in the same conditions as regards security.
+//
+// The fact that you are presently reading this means that you have had
+// knowledge of the CeCILL license and that you accept its terms.
+
+package database
+
+import ()
+
+type LevelDBMigrationFunc func(s *LevelDBStorage) error
+
+var migrations []LevelDBMigrationFunc = []LevelDBMigrationFunc{}
+
+func (s *LevelDBStorage) DoMigration() (err error) {
+	found := false
+
+	found, err = s.db.Has([]byte("version"), nil)
+	if err != nil {
+		return
+	}
+
+	var version int
+
+	if !found {
+		version = len(migrations)
+		err = s.put("version", version)
+		if err != nil {
+			return
+		}
+	}
+
+	err = s.get("version", &version)
+	if err != nil {
+		return
+	}
+
+	for v, migration := range migrations[version:] {
+		// Do the migration
+		if err = migration(s); err != nil {
+			return
+		}
+
+		// Save the step
+		if err = s.put("version", v+1); err != nil {
+			return
+		}
+	}
+
+	return nil
+}