Refactor ChangeNotes: Make superclass AbstractChangeNotes

There will be many similarities with how we will be reading into the
ChangeNotes from the traditional notedb ref for a change and how we
will be reading draft comments from the users ref in the all users
repository. Therefore, I made a super class for ChangeNotes,
AbstractChangeNotes, that extends VersionedMetaData so that I can
utilize those same methods and instance variables in the
DraftCommentsNotes (or whatever it's called). Additionally, there was
a method for reading comments from the tree of a commit inside the
ChangeNotes.Parser, so I extracted that into the CommentsInNotesUtil
so that I can reuse that method in the parser of DraftCommentsNotes
(or whatever it's called).

I had the option to either make the AbstractChangeNotes class a raw
type with the actual inheritor extending Notes and specifying its own
type or modify all callers to add an explicit cast to ChangeNotes
whenever they use load(). I think that the former is the cleaner
alternative, so that's what I did.

Finally, the parseComments() method wasn't using the argument it was
being passed so I got rid of that as well.

Change-Id: I88513bdeb7d0ca8e4aba52254f2c3ccc10bd2ce1

gerrit-server/src/main/java/com/google/gerrit/server/notedb/AbstractChangeNotes.java

@@ -0,0 +1,77 @@
+// Copyright (C) 2014 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.notedb;
+
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.git.VersionedMetaData;
+import com.google.gwtorm.server.OrmException;
+
+import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.eclipse.jgit.lib.Repository;
+
+import java.io.IOException;
+
+/** View of contents at a single ref related to some change. **/
+public abstract class AbstractChangeNotes<T> extends VersionedMetaData {
+  private boolean loaded;
+  protected final GitRepositoryManager repoManager;
+  private final Change change;
+
+  AbstractChangeNotes(GitRepositoryManager repoManager, Change change) {
+    this.repoManager = repoManager;
+    this.change = new Change(change);
+  }
+
+  public Change.Id getChangeId() {
+    return change.getId();
+  }
+
+  public Change getChange() {
+    return change;
+  }
+
+  public T load() throws OrmException {
+    if (!loaded) {
+      Repository repo;
+      try {
+        repo = repoManager.openRepository(getProjectName());
+      } catch (IOException e) {
+        throw new OrmException(e);
+      }
+      try {
+        load(repo);
+        loaded = true;
+      } catch (ConfigInvalidException | IOException e) {
+        throw new OrmException(e);
+      } finally {
+        repo.close();
+      }
+    }
+    return self();
+  }
+
+  /**
+   * @return the NameKey for the project where the notes should be stored,
+   *    which is not necessarily the same as the change's project.
+   */
+  protected abstract Project.NameKey getProjectName();
+
+  @SuppressWarnings("unchecked")
+  protected final T self() {
+    return (T) this;
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java

@@ -47,22 +47,18 @@ import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.PatchSet.Id;
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.reviewdb.client.PatchSetApproval.LabelId;
+import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.server.git.GitRepositoryManager;
-import com.google.gerrit.server.git.VersionedMetaData;
 import com.google.gerrit.server.util.LabelVote;
-import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.lib.CommitBuilder;
-import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.PersonIdent;
-import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
-import org.eclipse.jgit.notes.Note;
 import org.eclipse.jgit.notes.NoteMap;
 import org.eclipse.jgit.revwalk.FooterKey;
 import org.eclipse.jgit.revwalk.RevCommit;
@@ -81,7 +77,7 @@ import java.util.List;
 import java.util.Map;
 
 /** View of a single {@link Change} based on the log of its notes branch. */
-public class ChangeNotes extends VersionedMetaData {
+public class ChangeNotes extends AbstractChangeNotes<ChangeNotes> {
   private static final Ordering<PatchSetApproval> PSA_BY_TIME =
       Ordering.natural().onResultOf(
         new Function<PatchSetApproval, Timestamp>() {
@@ -170,7 +166,7 @@ public class ChangeNotes extends VersionedMetaData {
       this.changeId = change.getId();
       this.tip = tip;
       this.walk = walk;
-      this.repo = repoManager.openRepository(change.getProject());
+      this.repo = repoManager.openRepository(getProjectName(change));
       approvals = Maps.newHashMap();
       reviewers = Maps.newLinkedHashMap();
       submitRecords = Lists.newArrayListWithExpectedSize(1);
@@ -184,7 +180,7 @@ public class ChangeNotes extends VersionedMetaData {
       for (RevCommit commit : walk) {
         parse(commit);
       }
-      parseComments(walk.parseCommit(tip));
+      parseComments();
       pruneReviewers();
     }
 
@@ -323,32 +319,11 @@ public class ChangeNotes extends VersionedMetaData {
       changeMessages.put(psId, changeMessage);
     }
 
-    private void parseComments(RevCommit commit)
+    private void parseComments()
         throws IOException, ConfigInvalidException, ParseException {
-      Ref sharedMeta = repo.getRef(ChangeNoteUtil.changeRefName(changeId));
+      commentNoteMap = CommentsInNotesUtil.parseCommentsFromNotes(repo,
-      if (sharedMeta != null) {
+          ChangeNoteUtil.changeRefName(changeId), walk, changeId,
-        RevCommit sharedBaseCommit = walk.parseCommit(sharedMeta.getObjectId());
+          commentsForBase, commentsForPs);
-        commentNoteMap =
-            NoteMap.read(walk.getObjectReader(), sharedBaseCommit);
-      }
-      Iterator<Note> notes = commentNoteMap.iterator();
-      while (notes.hasNext()) {
-        Note next = notes.next();
-        byte[] bytes = walk.getObjectReader().open(
-            next.getData(), Constants.OBJ_BLOB).getBytes();
-        List<PatchLineComment> result =
-            CommentsInNotesUtil.parseNote(bytes, changeId);
-        if ((result == null) || (result.isEmpty())) {
-          continue;
-        }
-        PatchSet.Id psId = result.get(0).getKey().getParentKey().getParentKey();
-        short side = result.get(0).getSide();
-        if (side == 0) {
-          commentsForBase.putAll(psId, result);
-        } else {
-          commentsForPs.putAll(psId, result);
-        }
-      }
     }
 
     private void parseApproval(PatchSet.Id psId, Account.Id accountId,
@@ -508,9 +483,6 @@ public class ChangeNotes extends VersionedMetaData {
     }
   }
 
-  private final GitRepositoryManager repoManager;
-  private final Change change;
-  private boolean loaded;
   private ImmutableListMultimap<PatchSet.Id, PatchSetApproval> approvals;
   private ImmutableSetMultimap<ReviewerState, Account.Id> reviewers;
   private ImmutableList<SubmitRecord> submitRecords;
@@ -521,37 +493,7 @@ public class ChangeNotes extends VersionedMetaData {
 
   @VisibleForTesting
   public ChangeNotes(GitRepositoryManager repoManager, Change change) {
-    this.repoManager = repoManager;
+    super(repoManager, change);
-    this.change = new Change(change);
-  }
-
-  // TODO(dborowitz): Wrap fewer exceptions if/when we kill gwtorm.
-  public ChangeNotes load() throws OrmException {
-    if (!loaded) {
-      Repository repo;
-      try {
-        repo = repoManager.openRepository(change.getProject());
-      } catch (IOException e) {
-        throw new OrmException(e);
-      }
-      try {
-        load(repo);
-        loaded = true;
-      } catch (ConfigInvalidException | IOException e) {
-        throw new OrmException(e);
-      } finally {
-        repo.close();
-      }
-    }
-    return this;
-  }
-
-  public Change.Id getChangeId() {
-    return change.getId();
-  }
-
-  public Change getChange() {
-    return change;
   }
 
   public ImmutableListMultimap<PatchSet.Id, PatchSetApproval> getApprovals() {
@@ -594,7 +536,7 @@ public class ChangeNotes extends VersionedMetaData {
 
   @Override
   protected String getRefName() {
-    return ChangeNoteUtil.changeRefName(change.getId());
+    return ChangeNoteUtil.changeRefName(getChangeId());
   }
 
   @Override
@@ -606,6 +548,7 @@ public class ChangeNotes extends VersionedMetaData {
     }
     RevWalk walk = new RevWalk(reader);
     try {
+      Change change = getChange();
       Parser parser = new Parser(change, rev, walk, repoManager);
       parser.parseAll();
 
@@ -649,4 +592,13 @@ public class ChangeNotes extends VersionedMetaData {
     throw new UnsupportedOperationException(
         getClass().getSimpleName() + " is read-only");
   }
+
+  private static Project.NameKey getProjectName(Change change) {
+    return change.getProject();
+  }
+
+  @Override
+  protected Project.NameKey getProjectName() {
+    return getProjectName(getChange());
+  }
 }

gerrit-server/src/main/java/com/google/gerrit/server/notedb/CommentsInNotesUtil.java

@@ -21,6 +21,7 @@ import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Lists;
+import com.google.common.collect.Multimap;
 import com.google.common.primitives.Ints;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
@@ -35,7 +36,14 @@ import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 
 import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.notes.Note;
+import org.eclipse.jgit.notes.NoteMap;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.util.GitDateFormatter;
 import org.eclipse.jgit.util.GitDateParser;
 import org.eclipse.jgit.util.MutableInteger;
@@ -68,6 +76,36 @@ public class CommentsInNotesUtil {
   private static final String REVISION = "Revision";
   private static final String UUID = "UUID";
 
+  public static NoteMap parseCommentsFromNotes(Repository repo, String refName,
+      RevWalk walk, Change.Id changeId,
+      Multimap<PatchSet.Id, PatchLineComment> commentsForBase,
+      Multimap<PatchSet.Id, PatchLineComment> commentsForPs)
+      throws IOException, ConfigInvalidException {
+    Ref ref = repo.getRef(refName);
+    if (ref == null) {
+      return null;
+    }
+    RevCommit commit = walk.parseCommit(ref.getObjectId());
+    NoteMap noteMap = NoteMap.read(walk.getObjectReader(), commit);
+
+    for (Note note: noteMap) {
+      byte[] bytes = walk.getObjectReader().open(
+          note.getData(), Constants.OBJ_BLOB).getBytes();
+      List<PatchLineComment> result = parseNote(bytes, changeId);
+      if ((result == null) || (result.isEmpty())) {
+        continue;
+      }
+      PatchSet.Id psId = result.get(0).getKey().getParentKey().getParentKey();
+      short side = result.get(0).getSide();
+      if (side == 0) {
+        commentsForBase.putAll(psId, result);
+      } else {
+        commentsForPs.putAll(psId, result);
+      }
+    }
+    return noteMap;
+  }
+
   public static List<PatchLineComment> parseNote(byte[] note,
       Change.Id changeId) throws ConfigInvalidException {
     List<PatchLineComment> result = Lists.newArrayList();