Move NoteDbSchemaVersionManager to c.g.g.server.schema package

Currently, NoteDbSchemaVersionManager class cannot access
NoteDbSchemaVersions.LATEST constant, and instead a hard coded value is
used. This approach is very error prone as recent schema migration 181
has shown. As mentioned in TODO comment, this class can now be easily
moved to c.g.g.server.schema package, and hard coded value can be
replaced with NoteDbSchemaVersions.LATEST constant.

Change-Id: I301c4f2c93bb0cf384574d358e110f770102ed4f

java/com/google/gerrit/server/schema/AllProjectsCreator.java

@@ -47,7 +47,6 @@ import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.meta.MetaDataUpdate;
 import com.google.gerrit.server.group.SystemGroupBackend;
-import com.google.gerrit.server.notedb.NoteDbSchemaVersionManager;
 import com.google.gerrit.server.notedb.RepoSequence;
 import com.google.gerrit.server.project.ProjectConfig;
 import com.google.gwtorm.server.OrmException;

java/com/google/gerrit/server/schema/NoteDbSchemaUpdater.java

@@ -25,7 +25,6 @@ import com.google.gerrit.server.Sequences;
 import com.google.gerrit.server.config.AllUsersName;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.git.GitRepositoryManager;
-import com.google.gerrit.server.notedb.NoteDbSchemaVersionManager;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import java.io.IOException;

java/com/google/gerrit/server/schema/NoteDbSchemaVersionCheck.java

@@ -17,7 +17,6 @@ package com.google.gerrit.server.schema;
 import com.google.gerrit.extensions.events.LifecycleListener;
 import com.google.gerrit.lifecycle.LifecycleModule;
 import com.google.gerrit.server.config.SitePaths;
-import com.google.gerrit.server.notedb.NoteDbSchemaVersionManager;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Module;

java/com/google/gerrit/server/schema/NoteDbSchemaVersionManager.java

@@ -0,0 +1,96 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.schema;
+
+import static com.google.gerrit.reviewdb.client.RefNames.REFS_VERSION;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.gerrit.server.config.AllProjectsName;
+import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.notedb.IntBlob;
+import com.google.gwtorm.server.OrmException;
+import java.io.IOException;
+import java.util.Optional;
+import javax.inject.Inject;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevWalk;
+
+public class NoteDbSchemaVersionManager {
+  private final AllProjectsName allProjectsName;
+  private final GitRepositoryManager repoManager;
+
+  @Inject
+  @VisibleForTesting
+  public NoteDbSchemaVersionManager(
+      AllProjectsName allProjectsName, GitRepositoryManager repoManager) {
+    // Can't inject GitReferenceUpdated here because it has dependencies that are not always
+    // available in this injector (e.g. during init). This is ok for now since no other ref updates
+    // during init are available to plugins, and there are not any other use cases for listening for
+    // updates to the version ref.
+    this.allProjectsName = allProjectsName;
+    this.repoManager = repoManager;
+  }
+
+  public int read() throws OrmException {
+    try (Repository repo = repoManager.openRepository(allProjectsName)) {
+      return IntBlob.parse(repo, REFS_VERSION).map(IntBlob::value).orElse(0);
+    } catch (IOException e) {
+      throw new OrmException("Failed to read " + REFS_VERSION, e);
+    }
+  }
+
+  public void init() throws IOException, OrmException {
+    try (Repository repo = repoManager.openRepository(allProjectsName);
+        RevWalk rw = new RevWalk(repo)) {
+      Optional<IntBlob> old = IntBlob.parse(repo, REFS_VERSION, rw);
+      if (old.isPresent()) {
+        throw new OrmException(
+            String.format(
+                "Expected no old version for %s, found %s", REFS_VERSION, old.get().value()));
+      }
+      IntBlob.store(
+          repo,
+          rw,
+          allProjectsName,
+          REFS_VERSION,
+          old.map(IntBlob::id).orElse(ObjectId.zeroId()),
+          NoteDbSchemaVersions.LATEST,
+          GitReferenceUpdated.DISABLED);
+    }
+  }
+
+  public void increment(int expectedOldVersion) throws IOException, OrmException {
+    try (Repository repo = repoManager.openRepository(allProjectsName);
+        RevWalk rw = new RevWalk(repo)) {
+      Optional<IntBlob> old = IntBlob.parse(repo, REFS_VERSION, rw);
+      if (old.isPresent() && old.get().value() != expectedOldVersion) {
+        throw new OrmException(
+            String.format(
+                "Expected old version %d for %s, found %d",
+                expectedOldVersion, REFS_VERSION, old.get().value()));
+      }
+      IntBlob.store(
+          repo,
+          rw,
+          allProjectsName,
+          REFS_VERSION,
+          old.map(IntBlob::id).orElse(ObjectId.zeroId()),
+          expectedOldVersion + 1,
+          GitReferenceUpdated.DISABLED);
+    }
+  }
+}