java/com/google/gerrit/server/CommentsUtil.java - gerrit/ - Git at Google

 // 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;

 import static com.google.common.base.MoreObjects.firstNonNull;
 import static com.google.common.base.Preconditions.checkArgument;
 import static java.util.Comparator.comparing;
 import static java.util.stream.Collectors.toCollection;
 import static java.util.stream.Collectors.toList;

 import com.google.common.collect.ComparisonChain;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Ordering;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.ChangeMessage;
 import com.google.gerrit.entities.Comment;
 import com.google.gerrit.entities.FixReplacement;
 import com.google.gerrit.entities.FixSuggestion;
 import com.google.gerrit.entities.HumanComment;
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.entities.RobotComment;
 import com.google.gerrit.exceptions.StorageException;
 import com.google.gerrit.extensions.client.Side;
 import com.google.gerrit.extensions.common.CommentInfo;
 import com.google.gerrit.extensions.common.FixReplacementInfo;
 import com.google.gerrit.extensions.common.FixSuggestionInfo;
 import com.google.gerrit.server.config.GerritServerId;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.notedb.ChangeUpdate;
 import com.google.gerrit.server.patch.DiffNotAvailableException;
 import com.google.gerrit.server.patch.DiffOperations;
 import com.google.gerrit.server.patch.DiffOptions;
 import com.google.gerrit.server.patch.filediff.FileDiffOutput;
 import com.google.gerrit.server.update.ChangeContext;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import java.io.IOException;
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;

 /** Utility functions to manipulate Comments. */
 @Singleton
 public class CommentsUtil {
   public static final Ordering<Comment> COMMENT_ORDER =
       new Ordering<>() {
         @Override
         public int compare(Comment c1, Comment c2) {
           return ComparisonChain.start()
               .compare(c1.key.filename, c2.key.filename)
               .compare(c1.key.patchSetId, c2.key.patchSetId)
               .compare(c1.side, c2.side)
               .compare(c1.lineNbr, c2.lineNbr)
               .compare(c1.writtenOn, c2.writtenOn)
               .result();
         }
       };

   public static final Ordering<CommentInfo> COMMENT_INFO_ORDER =
       new Ordering<>() {
         @Override
         public int compare(CommentInfo a, CommentInfo b) {
           return ComparisonChain.start()
               .compare(a.path, b.path, NULLS_FIRST)
               .compare(a.patchSet, b.patchSet, NULLS_FIRST)
               .compare(side(a), side(b))
               .compare(a.line, b.line, NULLS_FIRST)
               .compare(a.inReplyTo, b.inReplyTo, NULLS_FIRST)
               .compare(a.message, b.message)
               .compare(a.id, b.id)
               .result();
         }

         private int side(CommentInfo c) {
           return firstNonNull(c.side, Side.REVISION).ordinal();
         }
       };

   public static PatchSet.Id getCommentPsId(Change.Id changeId, Comment comment) {
     return PatchSet.id(changeId, comment.key.patchSetId);
   }

   @Nullable
   public static String extractMessageId(@Nullable String tag) {
     if (tag == null || !tag.startsWith("mailMessageId=")) {
       return null;
     }
     return tag.substring("mailMessageId=".length());
   }

   private static final Ordering<Comparable<?>> NULLS_FIRST = Ordering.natural().nullsFirst();

   private final DiffOperations diffOperations;
   private final GitRepositoryManager repoManager;
   private final String serverId;

   @Inject
   CommentsUtil(
       DiffOperations diffOperations,
       GitRepositoryManager repoManager,
       @GerritServerId String serverId) {
     this.diffOperations = diffOperations;
     this.repoManager = repoManager;
     this.serverId = serverId;
   }

   public HumanComment newHumanComment(
       ChangeNotes changeNotes,
       CurrentUser currentUser,
       Instant when,
       String path,
       PatchSet.Id psId,
       short side,
       String message,
       @Nullable Boolean unresolved,
       @Nullable String parentUuid,
       @Nullable List<FixSuggestion> fixSuggestions) {
     if (unresolved == null) {
       if (parentUuid == null) {
         // Default to false if comment is not descended from another.
         unresolved = false;
       } else {
         // Inherit unresolved value from inReplyTo comment if not specified.
         Comment.Key key = new Comment.Key(parentUuid, path, psId.get());
         Optional<HumanComment> parent = getPublishedHumanComment(changeNotes, key);

         // If the comment was not found, it is descended from a robot comment, or the UUID is
         // invalid. Either way, we use the default.
         unresolved = parent.map(p -> p.unresolved).orElse(false);
       }
     }
     HumanComment c =
         new HumanComment(
             new Comment.Key(ChangeUtil.messageUuid(), path, psId.get()),
             currentUser.getAccountId(),
             when,
             side,
             message,
             serverId,
             unresolved);
     c.parentUuid = parentUuid;
     c.fixSuggestions = fixSuggestions;
     currentUser.updateRealAccountId(c::setRealAuthor);
     return c;
   }

   public RobotComment newRobotComment(
       ChangeContext ctx,
       String path,
       PatchSet.Id psId,
       short side,
       String message,
       String robotId,
       String robotRunId) {
     RobotComment c =
         new RobotComment(
             new Comment.Key(ChangeUtil.messageUuid(), path, psId.get()),
             ctx.getUser().getAccountId(),
             ctx.getWhen(),
             side,
             message,
             serverId,
             robotId,
             robotRunId);
     ctx.getUser().updateRealAccountId(c::setRealAuthor);
     return c;
   }

   public Optional<HumanComment> getPublishedHumanComment(ChangeNotes notes, Comment.Key key) {
     return publishedHumanCommentsByChange(notes).stream()
         .filter(c -> key.equals(c.key))
         .findFirst();
   }

   public Optional<HumanComment> getPublishedHumanComment(ChangeNotes notes, String uuid) {
     return publishedHumanCommentsByChange(notes).stream()
         .filter(c -> c.key.uuid.equals(uuid))
         .findFirst();
   }

   public List<HumanComment> publishedHumanCommentsByChange(ChangeNotes notes) {
     notes.load();
     return sort(Lists.newArrayList(notes.getHumanComments().values()));
   }

   public List<RobotComment> robotCommentsByChange(ChangeNotes notes) {
     notes.load();
     return sort(Lists.newArrayList(notes.getRobotComments().values()));
   }

   public Optional<RobotComment> getRobotComment(ChangeNotes notes, String uuid) {
     return robotCommentsByChange(notes).stream().filter(c -> c.key.uuid.equals(uuid)).findFirst();
   }

   public List<HumanComment> publishedByPatchSet(ChangeNotes notes, PatchSet.Id psId) {
     return commentsOnPatchSet(notes.load().getHumanComments().values(), psId);
   }

   public List<RobotComment> robotCommentsByPatchSet(ChangeNotes notes, PatchSet.Id psId) {
     return commentsOnPatchSet(notes.load().getRobotComments().values(), psId);
   }

   /**
    * This method populates the "changeMessageId" field of the comments parameter based on timestamp
    * matching. The comments objects will be modified.
    *
    * <p>Each comment will be matched to the nearest next change message in timestamp
    *
    * @param comments the list of comments
    * @param changeMessages list of change messages
    */
   public static void linkCommentsToChangeMessages(
       List<? extends CommentInfo> comments,
       List<ChangeMessage> changeMessages,
       boolean skipAutoGeneratedMessages) {

     // First sort by timestamp, then by authorId so that we could move on to the next change message
     // in case multiple accounts left comments at the same timestamp.
     ArrayList<ChangeMessage> sortedChangeMessages =
         changeMessages.stream()
             .sorted(
                 comparing(ChangeMessage::getWrittenOn)
                     .thenComparingInt(c -> c.getAuthor() == null ? 0 : c.getAuthor().get()))
             .collect(toCollection(ArrayList::new));

     ArrayList<CommentInfo> sortedCommentInfos =
         comments.stream()
             .sorted(
                 comparing(CommentInfo::getUpdated)
                     .thenComparingInt(c -> c.author == null ? 0 : c.author._accountId))
             .collect(toCollection(ArrayList::new));

     int cmItr = 0;
     int lastMatch = 0;
     for (CommentInfo comment : sortedCommentInfos) {
       // Keep advancing the change message pointer until we associate the comment to the next change
       // message in timestamp
       while (cmItr < sortedChangeMessages.size()) {
         ChangeMessage cm = sortedChangeMessages.get(cmItr);
         if (isAfter(comment, cm)
             || !haveSameAuthor(cm, comment)
             || (skipAutoGeneratedMessages && isAutoGenerated(cm))) {
           cmItr += 1;
         } else {
           lastMatch = cmItr;
           break;
         }
       }
       if (cmItr < changeMessages.size()) {
         comment.changeMessageId = sortedChangeMessages.get(cmItr).getKey().uuid();
       } else {
         // In case of no match "cmItr" will never be less than "changeMessages" size, hence the
         // changeMessageId won't be set for any comment.
         //
         // Reset the search to the last succesful match, since we can't assume there will always be
         // a match between change messages and comments. This could be the case of imported changes.
         //
         // More details here: https://issues.gerritcodereview.com/issues/318079520
         cmItr = lastMatch;
       }
     }
   }

   private static boolean isAutoGenerated(ChangeMessage cm) {
     // Ignore Gerrit auto-generated messages, allowing to link against human change messages that
     // have an auto-generated tag
     return ChangeMessagesUtil.isAutogeneratedByGerrit(cm.getTag());
   }

   private static boolean isAfter(CommentInfo c, ChangeMessage cm) {
     return c.getUpdated().isAfter(cm.getWrittenOn());
   }

   private static boolean haveSameAuthor(ChangeMessage cm, CommentInfo comment) {
     return Objects.equals(
         Optional.ofNullable(cm.getAuthor()).map(a -> a.get()),
         Optional.ofNullable(comment.author).map(a -> a._accountId));
   }

   public void putHumanComments(
       ChangeUpdate update, Comment.Status status, Iterable<HumanComment> comments) {
     for (HumanComment c : comments) {
       update.putComment(status, c);
     }
   }

   public void putRobotComments(ChangeUpdate update, Iterable<RobotComment> comments) {
     for (RobotComment c : comments) {
       update.putRobotComment(c);
     }
   }

   public void deleteHumanComments(ChangeUpdate update, Iterable<HumanComment> comments) {
     for (HumanComment c : comments) {
       update.deleteComment(c);
     }
   }

   public void deleteCommentByRewritingHistory(
       ChangeUpdate update, Comment.Key commentKey, String newMessage) {
     update.deleteCommentByRewritingHistory(commentKey.uuid, newMessage);
   }

   private static <T extends Comment> List<T> commentsOnPatchSet(
       Collection<T> allComments, PatchSet.Id psId) {
     List<T> result = new ArrayList<>(allComments.size());
     for (T c : allComments) {
       if (c.key.patchSetId == psId.get()) {
         result.add(c);
       }
     }
     return sort(result);
   }

   public void setCommentCommitId(Comment c, Change change, PatchSet ps) {
     if (c.getCommitId() == null) {
       checkArgument(
           c.key.patchSetId == ps.id().get(),
           "cannot set commit ID for patch set %s on comment %s",
           ps.id(),
           c);

       // This code is very much down into our stack and shouldn't be used for validation. Hence,
       // don't throw an exception here if we can't find a commit for the indicated side but
       // simply use the all-null ObjectId.
       c.setCommitId(determineCommitId(change, ps, c.side).orElseGet(ObjectId::zeroId));
     }
   }

   /**
    * Determines the SHA-1 of the commit referenced by the (change, patchset, side) triple.
    *
    * @param change the change to which the commit belongs
    * @param patchset the patchset to which the commit belongs
    * @param side the side indicating which commit of the patchset to take. 1 is the patchset commit,
    *     0 the parent commit (or auto-merge for changes representing merge commits); -x the xth
    *     parent commit of a merge commit
    * @return the commit SHA-1 or an empty {@link Optional} if the side isn't available for the given
    *     change/patchset
    * @throws StorageException if the SHA-1 is unavailable for an unknown reason
    */
   public Optional<ObjectId> determineCommitId(Change change, PatchSet patchset, short side) {
     if (Side.fromShort(side) == Side.PARENT) {
       if (side < 0) {
         int parentNumber = Math.abs(side);
         return resolveParentCommit(change.getProject(), patchset, parentNumber);
       }
       return Optional.ofNullable(resolveAutoMergeCommit(change, patchset));
     }
     return Optional.of(patchset.commitId());
   }

   private Optional<ObjectId> resolveParentCommit(
       Project.NameKey project, PatchSet patchset, int parentNumber) {
     try (Repository repository = repoManager.openRepository(project)) {
       RevCommit commit = repository.parseCommit(patchset.commitId());
       if (commit.getParentCount() < parentNumber) {
         return Optional.empty();
       }
       return Optional.of(commit.getParent(parentNumber - 1));
     } catch (IOException e) {
       throw new StorageException(e);
     }
   }

   @Nullable
   private ObjectId resolveAutoMergeCommit(Change change, PatchSet patchset) {
     try {
       // TODO(ghareeb): Adjust after the auto-merge code was moved out of the diff caches. Also
       // unignore the test in PortedCommentsIT.
       Map<String, FileDiffOutput> modifiedFiles =
           diffOperations.listModifiedFilesAgainstParent(
               change.getProject(), patchset.commitId(), /* parentNum= */ 0, DiffOptions.DEFAULTS);
       return modifiedFiles.isEmpty()
           ? null
           : modifiedFiles.values().iterator().next().oldCommitId();
     } catch (DiffNotAvailableException e) {
       throw new StorageException(e);
     }
   }

   public static <T extends Comment> List<T> sort(List<T> comments) {
     comments.sort(COMMENT_ORDER);
     return comments;
   }

   @Nullable
   public static ImmutableList<FixSuggestion> createFixSuggestionsFromInput(
       List<FixSuggestionInfo> fixSuggestionInfos) {
     if (fixSuggestionInfos == null) {
       return null;
     }

     ImmutableList.Builder<FixSuggestion> fixSuggestions =
         ImmutableList.builderWithExpectedSize(fixSuggestionInfos.size());
     for (FixSuggestionInfo fixSuggestionInfo : fixSuggestionInfos) {
       fixSuggestions.add(createFixSuggestionFromInput(fixSuggestionInfo));
     }
     return fixSuggestions.build();
   }

   public static FixSuggestion createFixSuggestionFromInput(FixSuggestionInfo fixSuggestionInfo) {
     List<FixReplacement> fixReplacements = toFixReplacements(fixSuggestionInfo.replacements);
     String fixId = ChangeUtil.messageUuid();
     return new FixSuggestion(fixId, fixSuggestionInfo.description, fixReplacements);
   }

   public static List<FixReplacement> toFixReplacements(
       List<FixReplacementInfo> fixReplacementInfos) {
     return fixReplacementInfos.stream().map(CommentsUtil::toFixReplacement).collect(toList());
   }

   public static FixReplacement toFixReplacement(FixReplacementInfo fixReplacementInfo) {
     Comment.Range range = new Comment.Range(fixReplacementInfo.range);
     return new FixReplacement(fixReplacementInfo.path, range, fixReplacementInfo.replacement);
   }
 }
	// 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;

	import static com.google.common.base.MoreObjects.firstNonNull;
	import static com.google.common.base.Preconditions.checkArgument;
	import static java.util.Comparator.comparing;
	import static java.util.stream.Collectors.toCollection;
	import static java.util.stream.Collectors.toList;

	import com.google.common.collect.ComparisonChain;
	import com.google.common.collect.ImmutableList;
	import com.google.common.collect.Lists;
	import com.google.common.collect.Ordering;
	import com.google.gerrit.common.Nullable;
	import com.google.gerrit.entities.Change;
	import com.google.gerrit.entities.ChangeMessage;
	import com.google.gerrit.entities.Comment;
	import com.google.gerrit.entities.FixReplacement;
	import com.google.gerrit.entities.FixSuggestion;
	import com.google.gerrit.entities.HumanComment;
	import com.google.gerrit.entities.PatchSet;
	import com.google.gerrit.entities.Project;
	import com.google.gerrit.entities.RobotComment;
	import com.google.gerrit.exceptions.StorageException;
	import com.google.gerrit.extensions.client.Side;
	import com.google.gerrit.extensions.common.CommentInfo;
	import com.google.gerrit.extensions.common.FixReplacementInfo;
	import com.google.gerrit.extensions.common.FixSuggestionInfo;
	import com.google.gerrit.server.config.GerritServerId;
	import com.google.gerrit.server.git.GitRepositoryManager;
	import com.google.gerrit.server.notedb.ChangeNotes;
	import com.google.gerrit.server.notedb.ChangeUpdate;
	import com.google.gerrit.server.patch.DiffNotAvailableException;
	import com.google.gerrit.server.patch.DiffOperations;
	import com.google.gerrit.server.patch.DiffOptions;
	import com.google.gerrit.server.patch.filediff.FileDiffOutput;
	import com.google.gerrit.server.update.ChangeContext;
	import com.google.inject.Inject;
	import com.google.inject.Singleton;
	import java.io.IOException;
	import java.time.Instant;
	import java.util.ArrayList;
	import java.util.Collection;
	import java.util.List;
	import java.util.Map;
	import java.util.Objects;
	import java.util.Optional;
	import org.eclipse.jgit.lib.ObjectId;
	import org.eclipse.jgit.lib.Repository;
	import org.eclipse.jgit.revwalk.RevCommit;

	/** Utility functions to manipulate Comments. */
	@Singleton
	public class CommentsUtil {
	public static final Ordering<Comment> COMMENT_ORDER =
	new Ordering<>() {
	@Override
	public int compare(Comment c1, Comment c2) {
	return ComparisonChain.start()
	.compare(c1.key.filename, c2.key.filename)
	.compare(c1.key.patchSetId, c2.key.patchSetId)
	.compare(c1.side, c2.side)
	.compare(c1.lineNbr, c2.lineNbr)
	.compare(c1.writtenOn, c2.writtenOn)
	.result();
	}
	};

	public static final Ordering<CommentInfo> COMMENT_INFO_ORDER =
	new Ordering<>() {
	@Override
	public int compare(CommentInfo a, CommentInfo b) {
	return ComparisonChain.start()
	.compare(a.path, b.path, NULLS_FIRST)
	.compare(a.patchSet, b.patchSet, NULLS_FIRST)
	.compare(side(a), side(b))
	.compare(a.line, b.line, NULLS_FIRST)
	.compare(a.inReplyTo, b.inReplyTo, NULLS_FIRST)
	.compare(a.message, b.message)
	.compare(a.id, b.id)
	.result();
	}

	private int side(CommentInfo c) {
	return firstNonNull(c.side, Side.REVISION).ordinal();
	}
	};

	public static PatchSet.Id getCommentPsId(Change.Id changeId, Comment comment) {
	return PatchSet.id(changeId, comment.key.patchSetId);
	}

	@Nullable
	public static String extractMessageId(@Nullable String tag) {
	if (tag == null \|\| !tag.startsWith("mailMessageId=")) {
	return null;
	}
	return tag.substring("mailMessageId=".length());
	}

	private static final Ordering<Comparable<?>> NULLS_FIRST = Ordering.natural().nullsFirst();

	private final DiffOperations diffOperations;
	private final GitRepositoryManager repoManager;
	private final String serverId;

	@Inject
	CommentsUtil(
	DiffOperations diffOperations,
	GitRepositoryManager repoManager,
	@GerritServerId String serverId) {
	this.diffOperations = diffOperations;
	this.repoManager = repoManager;
	this.serverId = serverId;
	}

	public HumanComment newHumanComment(
	ChangeNotes changeNotes,
	CurrentUser currentUser,
	Instant when,
	String path,
	PatchSet.Id psId,
	short side,
	String message,
	@Nullable Boolean unresolved,
	@Nullable String parentUuid,
	@Nullable List<FixSuggestion> fixSuggestions) {
	if (unresolved == null) {
	if (parentUuid == null) {
	// Default to false if comment is not descended from another.
	unresolved = false;
	} else {
	// Inherit unresolved value from inReplyTo comment if not specified.
	Comment.Key key = new Comment.Key(parentUuid, path, psId.get());
	Optional<HumanComment> parent = getPublishedHumanComment(changeNotes, key);

	// If the comment was not found, it is descended from a robot comment, or the UUID is
	// invalid. Either way, we use the default.
	unresolved = parent.map(p -> p.unresolved).orElse(false);
	}
	}
	HumanComment c =
	new HumanComment(
	new Comment.Key(ChangeUtil.messageUuid(), path, psId.get()),
	currentUser.getAccountId(),
	when,
	side,
	message,
	serverId,
	unresolved);
	c.parentUuid = parentUuid;
	c.fixSuggestions = fixSuggestions;
	currentUser.updateRealAccountId(c::setRealAuthor);
	return c;
	}

	public RobotComment newRobotComment(
	ChangeContext ctx,
	String path,
	PatchSet.Id psId,
	short side,
	String message,
	String robotId,
	String robotRunId) {
	RobotComment c =
	new RobotComment(
	new Comment.Key(ChangeUtil.messageUuid(), path, psId.get()),
	ctx.getUser().getAccountId(),
	ctx.getWhen(),
	side,
	message,
	serverId,
	robotId,
	robotRunId);
	ctx.getUser().updateRealAccountId(c::setRealAuthor);
	return c;
	}

	public Optional<HumanComment> getPublishedHumanComment(ChangeNotes notes, Comment.Key key) {
	return publishedHumanCommentsByChange(notes).stream()
	.filter(c -> key.equals(c.key))
	.findFirst();
	}

	public Optional<HumanComment> getPublishedHumanComment(ChangeNotes notes, String uuid) {
	return publishedHumanCommentsByChange(notes).stream()
	.filter(c -> c.key.uuid.equals(uuid))
	.findFirst();
	}

	public List<HumanComment> publishedHumanCommentsByChange(ChangeNotes notes) {
	notes.load();
	return sort(Lists.newArrayList(notes.getHumanComments().values()));
	}

	public List<RobotComment> robotCommentsByChange(ChangeNotes notes) {
	notes.load();
	return sort(Lists.newArrayList(notes.getRobotComments().values()));
	}

	public Optional<RobotComment> getRobotComment(ChangeNotes notes, String uuid) {
	return robotCommentsByChange(notes).stream().filter(c -> c.key.uuid.equals(uuid)).findFirst();
	}

	public List<HumanComment> publishedByPatchSet(ChangeNotes notes, PatchSet.Id psId) {
	return commentsOnPatchSet(notes.load().getHumanComments().values(), psId);
	}

	public List<RobotComment> robotCommentsByPatchSet(ChangeNotes notes, PatchSet.Id psId) {
	return commentsOnPatchSet(notes.load().getRobotComments().values(), psId);
	}

	/**
	* This method populates the "changeMessageId" field of the comments parameter based on timestamp
	* matching. The comments objects will be modified.
	*
	* <p>Each comment will be matched to the nearest next change message in timestamp
	*
	* @param comments the list of comments
	* @param changeMessages list of change messages
	*/
	public static void linkCommentsToChangeMessages(
	List<? extends CommentInfo> comments,
	List<ChangeMessage> changeMessages,
	boolean skipAutoGeneratedMessages) {

	// First sort by timestamp, then by authorId so that we could move on to the next change message
	// in case multiple accounts left comments at the same timestamp.
	ArrayList<ChangeMessage> sortedChangeMessages =
	changeMessages.stream()
	.sorted(
	comparing(ChangeMessage::getWrittenOn)
	.thenComparingInt(c -> c.getAuthor() == null ? 0 : c.getAuthor().get()))
	.collect(toCollection(ArrayList::new));

	ArrayList<CommentInfo> sortedCommentInfos =
	comments.stream()
	.sorted(
	comparing(CommentInfo::getUpdated)
	.thenComparingInt(c -> c.author == null ? 0 : c.author._accountId))
	.collect(toCollection(ArrayList::new));

	int cmItr = 0;
	int lastMatch = 0;
	for (CommentInfo comment : sortedCommentInfos) {
	// Keep advancing the change message pointer until we associate the comment to the next change
	// message in timestamp
	while (cmItr < sortedChangeMessages.size()) {
	ChangeMessage cm = sortedChangeMessages.get(cmItr);
	if (isAfter(comment, cm)
	\|\| !haveSameAuthor(cm, comment)
	\|\| (skipAutoGeneratedMessages && isAutoGenerated(cm))) {
	cmItr += 1;
	} else {
	lastMatch = cmItr;
	break;
	}
	}
	if (cmItr < changeMessages.size()) {
	comment.changeMessageId = sortedChangeMessages.get(cmItr).getKey().uuid();
	} else {
	// In case of no match "cmItr" will never be less than "changeMessages" size, hence the
	// changeMessageId won't be set for any comment.
	//
	// Reset the search to the last succesful match, since we can't assume there will always be
	// a match between change messages and comments. This could be the case of imported changes.
	//
	// More details here: https://issues.gerritcodereview.com/issues/318079520
	cmItr = lastMatch;
	}
	}
	}

	private static boolean isAutoGenerated(ChangeMessage cm) {
	// Ignore Gerrit auto-generated messages, allowing to link against human change messages that
	// have an auto-generated tag
	return ChangeMessagesUtil.isAutogeneratedByGerrit(cm.getTag());
	}

	private static boolean isAfter(CommentInfo c, ChangeMessage cm) {
	return c.getUpdated().isAfter(cm.getWrittenOn());
	}

	private static boolean haveSameAuthor(ChangeMessage cm, CommentInfo comment) {
	return Objects.equals(
	Optional.ofNullable(cm.getAuthor()).map(a -> a.get()),
	Optional.ofNullable(comment.author).map(a -> a._accountId));
	}

	public void putHumanComments(
	ChangeUpdate update, Comment.Status status, Iterable<HumanComment> comments) {
	for (HumanComment c : comments) {
	update.putComment(status, c);
	}
	}

	public void putRobotComments(ChangeUpdate update, Iterable<RobotComment> comments) {
	for (RobotComment c : comments) {
	update.putRobotComment(c);
	}
	}

	public void deleteHumanComments(ChangeUpdate update, Iterable<HumanComment> comments) {
	for (HumanComment c : comments) {
	update.deleteComment(c);
	}
	}

	public void deleteCommentByRewritingHistory(
	ChangeUpdate update, Comment.Key commentKey, String newMessage) {
	update.deleteCommentByRewritingHistory(commentKey.uuid, newMessage);
	}

	private static <T extends Comment> List<T> commentsOnPatchSet(
	Collection<T> allComments, PatchSet.Id psId) {
	List<T> result = new ArrayList<>(allComments.size());
	for (T c : allComments) {
	if (c.key.patchSetId == psId.get()) {
	result.add(c);
	}
	}
	return sort(result);
	}

	public void setCommentCommitId(Comment c, Change change, PatchSet ps) {
	if (c.getCommitId() == null) {
	checkArgument(
	c.key.patchSetId == ps.id().get(),
	"cannot set commit ID for patch set %s on comment %s",
	ps.id(),
	c);

	// This code is very much down into our stack and shouldn't be used for validation. Hence,
	// don't throw an exception here if we can't find a commit for the indicated side but
	// simply use the all-null ObjectId.
	c.setCommitId(determineCommitId(change, ps, c.side).orElseGet(ObjectId::zeroId));
	}
	}

	/**
	* Determines the SHA-1 of the commit referenced by the (change, patchset, side) triple.
	*
	* @param change the change to which the commit belongs
	* @param patchset the patchset to which the commit belongs
	* @param side the side indicating which commit of the patchset to take. 1 is the patchset commit,
	* 0 the parent commit (or auto-merge for changes representing merge commits); -x the xth
	* parent commit of a merge commit
	* @return the commit SHA-1 or an empty {@link Optional} if the side isn't available for the given
	* change/patchset
	* @throws StorageException if the SHA-1 is unavailable for an unknown reason
	*/
	public Optional<ObjectId> determineCommitId(Change change, PatchSet patchset, short side) {
	if (Side.fromShort(side) == Side.PARENT) {
	if (side < 0) {
	int parentNumber = Math.abs(side);
	return resolveParentCommit(change.getProject(), patchset, parentNumber);
	}
	return Optional.ofNullable(resolveAutoMergeCommit(change, patchset));
	}
	return Optional.of(patchset.commitId());
	}

	private Optional<ObjectId> resolveParentCommit(
	Project.NameKey project, PatchSet patchset, int parentNumber) {
	try (Repository repository = repoManager.openRepository(project)) {
	RevCommit commit = repository.parseCommit(patchset.commitId());
	if (commit.getParentCount() < parentNumber) {
	return Optional.empty();
	}
	return Optional.of(commit.getParent(parentNumber - 1));
	} catch (IOException e) {
	throw new StorageException(e);
	}
	}

	@Nullable
	private ObjectId resolveAutoMergeCommit(Change change, PatchSet patchset) {
	try {
	// TODO(ghareeb): Adjust after the auto-merge code was moved out of the diff caches. Also
	// unignore the test in PortedCommentsIT.
	Map<String, FileDiffOutput> modifiedFiles =
	diffOperations.listModifiedFilesAgainstParent(
	change.getProject(), patchset.commitId(), /* parentNum= */ 0, DiffOptions.DEFAULTS);
	return modifiedFiles.isEmpty()
	? null
	: modifiedFiles.values().iterator().next().oldCommitId();
	} catch (DiffNotAvailableException e) {
	throw new StorageException(e);
	}
	}

	public static <T extends Comment> List<T> sort(List<T> comments) {
	comments.sort(COMMENT_ORDER);
	return comments;
	}

	@Nullable
	public static ImmutableList<FixSuggestion> createFixSuggestionsFromInput(
	List<FixSuggestionInfo> fixSuggestionInfos) {
	if (fixSuggestionInfos == null) {
	return null;
	}

	ImmutableList.Builder<FixSuggestion> fixSuggestions =
	ImmutableList.builderWithExpectedSize(fixSuggestionInfos.size());
	for (FixSuggestionInfo fixSuggestionInfo : fixSuggestionInfos) {
	fixSuggestions.add(createFixSuggestionFromInput(fixSuggestionInfo));
	}
	return fixSuggestions.build();
	}

	public static FixSuggestion createFixSuggestionFromInput(FixSuggestionInfo fixSuggestionInfo) {
	List<FixReplacement> fixReplacements = toFixReplacements(fixSuggestionInfo.replacements);
	String fixId = ChangeUtil.messageUuid();
	return new FixSuggestion(fixId, fixSuggestionInfo.description, fixReplacements);
	}

	public static List<FixReplacement> toFixReplacements(
	List<FixReplacementInfo> fixReplacementInfos) {
	return fixReplacementInfos.stream().map(CommentsUtil::toFixReplacement).collect(toList());
	}

	public static FixReplacement toFixReplacement(FixReplacementInfo fixReplacementInfo) {
	Comment.Range range = new Comment.Range(fixReplacementInfo.range);
	return new FixReplacement(fixReplacementInfo.path, range, fixReplacementInfo.replacement);
	}
	}