java/com/google/gerrit/plugins/codeowners/backend/OnCodeOwnerApproval.java - plugins/code-owners - Git at Google

 // Copyright (C) 2020 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.plugins.codeowners.backend;

 import static com.google.common.base.Preconditions.checkState;
 import static com.google.common.collect.ImmutableMap.toImmutableMap;
 import static com.google.gerrit.plugins.codeowners.backend.CodeOwnersChangeMessageUtil.appendPaths;
 import static com.google.gerrit.server.update.context.RefUpdateContext.RefUpdateType.CHANGE_MODIFICATION;
 import static com.google.gerrit.server.update.context.RefUpdateContext.RefUpdateType.PLUGIN;

 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.extensions.common.ApprovalInfo;
 import com.google.gerrit.extensions.events.CommentAddedListener;
 import com.google.gerrit.metrics.Timer0;
 import com.google.gerrit.plugins.codeowners.backend.config.CodeOwnersPluginConfiguration;
 import com.google.gerrit.plugins.codeowners.backend.config.CodeOwnersPluginProjectConfigSnapshot;
 import com.google.gerrit.plugins.codeowners.backend.config.RequiredApproval;
 import com.google.gerrit.plugins.codeowners.metrics.CodeOwnerMetrics;
 import com.google.gerrit.server.ChangeMessagesUtil;
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.git.WorkQueue;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.restapi.change.OnPostReview;
 import com.google.gerrit.server.update.BatchUpdate;
 import com.google.gerrit.server.update.BatchUpdateOp;
 import com.google.gerrit.server.update.ChangeContext;
 import com.google.gerrit.server.update.RetryHelper;
 import com.google.gerrit.server.update.context.RefUpdateContext;
 import com.google.gerrit.server.util.AccountTemplateUtil;
 import com.google.gerrit.server.util.LabelVote;
 import com.google.gerrit.server.util.ManualRequestContext;
 import com.google.gerrit.server.util.OneOffRequestContext;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
 import java.nio.file.Path;
 import java.time.Instant;
 import java.util.Map;
 import java.util.Optional;

 /**
  * Callback that is invoked on post review and that extends the change message if a code owner
  * approval was changed.
  *
  * <p>If a code owner approval was added, removed or changed, include in the change message that is
  * being posted on vote, which of the files:
  *
  * <ul>
  *   <li>are approved now
  *   <li>are no longer approved
  *   <li>are still approved
  * </ul>
  */
 @Singleton
 class OnCodeOwnerApproval implements OnPostReview, CommentAddedListener {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();

   private static final String TAG_ADD_CODE_OWNER_APPROVAL =
       ChangeMessagesUtil.AUTOGENERATED_BY_GERRIT_TAG_PREFIX + "code-owners:addCodeOwnerApproval";

   private final WorkQueue workQueue;
   private final OneOffRequestContext oneOffRequestContext;
   private final CodeOwnersPluginConfiguration codeOwnersPluginConfiguration;
   private final CodeOwnerApprovalCheck codeOwnerApprovalCheck;
   private final CodeOwnerMetrics codeOwnerMetrics;
   private final ChangeNotes.Factory changeNotesFactory;
   private final ChangeMessagesUtil changeMessageUtil;
   private final Provider<CurrentUser> userProvider;
   private final RetryHelper retryHelper;

   @Inject
   OnCodeOwnerApproval(
       WorkQueue workQueue,
       OneOffRequestContext oneOffRequestContext,
       CodeOwnersPluginConfiguration codeOwnersPluginConfiguration,
       CodeOwnerApprovalCheck codeOwnerApprovalCheck,
       CodeOwnerMetrics codeOwnerMetrics,
       ChangeNotes.Factory changeNotesFactory,
       ChangeMessagesUtil changeMessageUtil,
       Provider<CurrentUser> userProvider,
       RetryHelper retryHelper) {
     this.workQueue = workQueue;
     this.oneOffRequestContext = oneOffRequestContext;
     this.codeOwnersPluginConfiguration = codeOwnersPluginConfiguration;
     this.codeOwnerApprovalCheck = codeOwnerApprovalCheck;
     this.codeOwnerMetrics = codeOwnerMetrics;
     this.changeNotesFactory = changeNotesFactory;
     this.changeMessageUtil = changeMessageUtil;
     this.userProvider = userProvider;
     this.retryHelper = retryHelper;
   }

   @Override
   public Optional<String> getChangeMessageAddOn(
       Instant when,
       IdentifiedUser user,
       ChangeNotes changeNotes,
       PatchSet patchSet,
       Map<String, Short> oldApprovals,
       Map<String, Short> approvals) {
     CodeOwnersPluginProjectConfigSnapshot codeOwnersConfig =
         codeOwnersPluginConfiguration.getProjectConfig(changeNotes.getProjectName());
     int maxPathsInChangeMessage = codeOwnersConfig.getMaxPathsInChangeMessages();
     if (codeOwnersConfig.isDisabled(changeNotes.getChange().getDest().branch())
         || maxPathsInChangeMessage <= 0) {
       logger.atFine().log("skip extending the change message since message posting is disabled");
       return Optional.empty();
     }
     if (codeOwnersConfig.enableAsyncMessageOnCodeOwnerApproval()) {
       // To avoid adding latency to PostReview post the change message asynchronously from
       // #onCommentAdded(Event) after PostReview is done.
       logger.atFine().log(
           "skip extending the change message since async message posting is enabled");
       return Optional.empty();
     }

     // code owner approvals are only computed for the current patch set
     if (!changeNotes.getChange().currentPatchSetId().equals(patchSet.id())) {
       logger.atFine().log("skip extending the change message on non-current patch set");
       return Optional.empty();
     }

     RequiredApproval requiredApproval = codeOwnersConfig.getRequiredApproval();

     if (oldApprovals.get(requiredApproval.labelType().getName()) == null) {
       // If oldApprovals doesn't contain the label or if the labels value in it is null, the label
       // was not changed.
       // This means that the user only voted on unrelated labels.
       return Optional.empty();
     }

     logger.atFine().log("post change message synchronously");
     try (Timer0.Context ctx = codeOwnerMetrics.extendChangeMessageOnPostReview.start()) {
       return buildMessageForCodeOwnerApproval(
           user,
           changeNotes,
           patchSet,
           oldApprovals,
           approvals,
           requiredApproval,
           maxPathsInChangeMessage);
     } catch (Exception e) {
       Optional<? extends Exception> configurationError =
           CodeOwnersExceptionHook.getCauseOfConfigurationError(e);
       if (configurationError.isPresent()) {
         logger.atWarning().log(
             "Failed to post code-owners change message for code owner approval on change %s"
                 + " in project %s: %s",
             changeNotes.getChangeId(),
             changeNotes.getProjectName(),
             configurationError.get().getMessage());
       } else {
         logger.atSevere().withCause(e).log(
             "Failed to post code-owners change message for code owner approval on change %s"
                 + " in project %s.",
             changeNotes.getChangeId(), changeNotes.getProjectName());
       }
       return Optional.empty();
     }
   }

   @Override
   public void onCommentAdded(Event event) {
     Project.NameKey projectName = Project.nameKey(event.getChange().project);
     CodeOwnersPluginProjectConfigSnapshot codeOwnersConfig =
         codeOwnersPluginConfiguration.getProjectConfig(projectName);
     int maxPathsInChangeMessage = codeOwnersConfig.getMaxPathsInChangeMessages();
     if (codeOwnersConfig.isDisabled(event.getChange().branch) || maxPathsInChangeMessage <= 0) {
       logger.atFine().log("skip posting the change message since message posting is disabled");
       return;
     }
     if (!codeOwnersConfig.enableAsyncMessageOnCodeOwnerApproval()) {
       // The change message has already been synchronously extended by #getChangeMessageAddOn(...).
       logger.atFine().log(
           "skip posting the change message since async message posting is disabled");
       return;
     }

     // post change message asynchronously to avoid adding latency to PostReview
     logger.atFine().log("schedule asynchronous posting of the change message");

     CurrentUser user = userProvider.get();
     if (!user.isIdentifiedUser()) {
       // cannot compute owned paths for non-identified user
       logger.atFine().log(
           "skip posting the change message for non-identified user %s", user.getLoggableName());
       return;
     }

     Change.Id changeId = Change.id(event.getChange()._number);
     ChangeNotes changeNotes = changeNotesFactory.create(projectName, changeId);
     PatchSet.Id patchSetId = PatchSet.id(changeId, event.getRevision()._number);
     RequiredApproval requiredApproval = codeOwnersConfig.getRequiredApproval();

     // code owner approvals are only computed for the current patch set
     PatchSet currentPatchSet = changeNotes.getCurrentPatchSet();
     if (!currentPatchSet.id().equals(patchSetId)) {
       logger.atFine().log("skip posting the change message on non-current patch set");
       return;
     }

     if (event.getOldApprovals().get(requiredApproval.labelType().getName()) == null) {
       // If oldApprovals doesn't contain the label or if the labels value in it is null, the label
       // was not changed.
       // This means that the user only voted on unrelated labels.
       return;
     }

     @SuppressWarnings("unused")
     WorkQueue.Task<?> possiblyIgnoredError =
         (WorkQueue.Task<?>)
             workQueue
                 .getDefaultQueue()
                 .submit(
                     () -> {
                       try (ManualRequestContext ignored =
                           oneOffRequestContext.openAs(user.getAccountId())) {
                         postChangeMessage(
                             event.getWhen(),
                             user.asIdentifiedUser(),
                             changeNotes,
                             currentPatchSet,
                             mapApprovalInfosToVotingValues(event.getOldApprovals()),
                             mapApprovalInfosToVotingValues(event.getApprovals()),
                             requiredApproval,
                             maxPathsInChangeMessage);
                       }
                     });
   }

   private void postChangeMessage(
       Instant when,
       IdentifiedUser user,
       ChangeNotes changeNotes,
       PatchSet patchSet,
       Map<String, Short> oldApprovals,
       Map<String, Short> approvals,
       RequiredApproval requiredApproval,
       int maxPathsInChangeMessages) {
     try (Timer0.Context ctx = codeOwnerMetrics.addChangeMessageOnCodeOwnerApproval.start()) {
       retryHelper
           .changeUpdate(
               "addCodeOwnersMessageOnCodeOwnerApproval",
               updateFactory -> {
                 try (BatchUpdate batchUpdate =
                         updateFactory.create(changeNotes.getProjectName(), user, when);
                     RefUpdateContext pluginCtx = RefUpdateContext.open(PLUGIN);
                     RefUpdateContext changeCtx = RefUpdateContext.open(CHANGE_MODIFICATION)) {
                   batchUpdate.addOp(
                       changeNotes.getChangeId(),
                       new Op(
                           user,
                           changeNotes,
                           patchSet,
                           oldApprovals,
                           approvals,
                           requiredApproval,
                           maxPathsInChangeMessages));
                   batchUpdate.execute();
                 }
                 return null;
               })
           .call();
     } catch (Exception e) {
       Optional<? extends Exception> configurationError =
           CodeOwnersExceptionHook.getCauseOfConfigurationError(e);
       if (configurationError.isPresent()) {
         logger.atWarning().log(
             "Failed to post code-owners change message for code owner approval on change %s in"
                 + " project %s: %s",
             changeNotes.getChangeId(),
             changeNotes.getProjectName(),
             configurationError.get().getMessage());
       } else {
         logger.atSevere().withCause(e).log(
             "Failed to post code-owners change message for code owner approval on change %s in"
                 + " project %s.",
             changeNotes.getChangeId(), changeNotes.getProjectName());
       }
     }
   }

   private Optional<String> buildMessageForCodeOwnerApproval(
       IdentifiedUser user,
       ChangeNotes changeNotes,
       PatchSet patchSet,
       Map<String, Short> oldApprovals,
       Map<String, Short> approvals,
       RequiredApproval requiredApproval,
       int limit) {
     LabelVote newVote = getNewVote(requiredApproval, approvals);

     // limit + 1, so that we can show an indicator if there are more than <limit> files.
     ImmutableList<Path> ownedPaths =
         OwnedChangedFile.getOwnedPaths(
             codeOwnerApprovalCheck.getOwnedPaths(
                 changeNotes,
                 changeNotes.getCurrentPatchSet(),
                 user.getAccountId(),
                 /* start= */ 0,
                 limit + 1,
                 /* checkReviewers= */ false));

     if (ownedPaths.isEmpty()) {
       // the user doesn't own any of the modified paths
       return Optional.empty();
     }

     if (isIgnoredDueToSelfApproval(user, patchSet, requiredApproval)) {
       if (isCodeOwnerApprovalNewlyApplied(requiredApproval, oldApprovals, newVote)
           || isCodeOwnerApprovalUpOrDowngraded(requiredApproval, oldApprovals, newVote)) {
         return Optional.of(
             String.format(
                 "The vote %s is ignored as code-owner approval since the label doesn't allow"
                     + " self approval of the patch set uploader.",
                 newVote));
       }
       return Optional.empty();
     }

     boolean hasImplicitApprovalByUser =
         codeOwnersPluginConfiguration
                 .getProjectConfig(changeNotes.getProjectName())
                 .areImplicitApprovalsEnabled()
             && patchSet.uploader().equals(user.getAccountId());

     boolean noLongerExplicitlyApproved = false;
     StringBuilder message = new StringBuilder();
     if (isCodeOwnerApprovalNewlyApplied(requiredApproval, oldApprovals, newVote)) {
       if (hasImplicitApprovalByUser) {
         message.append(
             String.format(
                 "By voting %s the following files are now explicitly code-owner approved by %s:\n",
                 newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
       } else {
         message.append(
             String.format(
                 "By voting %s the following files are now code-owner approved by %s:\n",
                 newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
       }
     } else if (isCodeOwnerApprovalRemoved(requiredApproval, oldApprovals, newVote)) {
       if (newVote.value() == 0) {
         if (hasImplicitApprovalByUser) {
           noLongerExplicitlyApproved = true;
           message.append(
               String.format(
                   "By removing the %s vote the following files are no longer explicitly code-owner"
                       + " approved by %s:\n",
                   newVote.label(), AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
         } else {
           message.append(
               String.format(
                   "By removing the %s vote the following files are no longer code-owner approved"
                       + " by %s:\n",
                   newVote.label(), AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
         }
       } else {
         if (hasImplicitApprovalByUser) {
           noLongerExplicitlyApproved = true;
           message.append(
               String.format(
                   "By voting %s the following files are no longer explicitly code-owner approved by"
                       + " %s:\n",
                   newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
         } else {
           message.append(
               String.format(
                   "By voting %s the following files are no longer code-owner approved by %s:\n",
                   newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
         }
       }
     } else if (isCodeOwnerApprovalUpOrDowngraded(requiredApproval, oldApprovals, newVote)) {
       if (hasImplicitApprovalByUser) {
         message.append(
             String.format(
                 "By voting %s the following files are still explicitly code-owner approved by"
                     + " %s:\n",
                 newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
       } else {
         message.append(
             String.format(
                 "By voting %s the following files are still code-owner approved by %s:\n",
                 newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
       }
     } else {
       // non-approval was downgraded (e.g. -1 to -2)
       return Optional.empty();
     }

     if (ownedPaths.size() <= limit) {
       appendPaths(message, ownedPaths.stream());
     } else {
       appendPaths(message, ownedPaths.stream().limit(limit));
       message.append("(more files)\n");
     }

     if (hasImplicitApprovalByUser && noLongerExplicitlyApproved) {
       message.append(
           String.format(
               "\nThe listed files are still implicitly approved by %s.\n",
               AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
     }

     return Optional.of(message.toString());
   }

   private boolean isIgnoredDueToSelfApproval(
       IdentifiedUser user, PatchSet patchSet, RequiredApproval requiredApproval) {
     return patchSet.uploader().equals(user.getAccountId())
         && requiredApproval.labelType().isIgnoreSelfApproval();
   }

   private boolean isCodeOwnerApprovalNewlyApplied(
       RequiredApproval requiredApproval, Map<String, Short> oldApprovals, LabelVote newVote) {
     String labelName = requiredApproval.labelType().getName();
     return oldApprovals.get(labelName) < requiredApproval.value()
         && newVote.value() >= requiredApproval.value();
   }

   private boolean isCodeOwnerApprovalRemoved(
       RequiredApproval requiredApproval, Map<String, Short> oldApprovals, LabelVote newVote) {
     String labelName = requiredApproval.labelType().getName();
     return oldApprovals.get(labelName) >= requiredApproval.value()
         && newVote.value() < requiredApproval.value();
   }

   private boolean isCodeOwnerApprovalUpOrDowngraded(
       RequiredApproval requiredApproval, Map<String, Short> oldApprovals, LabelVote newVote) {
     String labelName = requiredApproval.labelType().getName();
     return oldApprovals.get(labelName) >= requiredApproval.value()
         && newVote.value() >= requiredApproval.value();
   }

   private LabelVote getNewVote(RequiredApproval requiredApproval, Map<String, Short> approvals) {
     String labelName = requiredApproval.labelType().getName();
     checkState(
         approvals.containsKey(labelName),
         "expected that approval on label %s exists (approvals = %s)",
         labelName,
         approvals);
     return LabelVote.create(labelName, approvals.get(labelName));
   }

   private static ImmutableMap<String, Short> mapApprovalInfosToVotingValues(
       Map<String, ApprovalInfo> approvals) {
     return approvals.entrySet().stream()
         .collect(
             toImmutableMap(
                 Map.Entry::getKey,
                 e -> e.getValue().value != null ? e.getValue().value.shortValue() : null));
   }

   private class Op implements BatchUpdateOp {
     private final IdentifiedUser user;
     private final ChangeNotes changeNotes;
     private final PatchSet patchSet;
     private final Map<String, Short> oldApprovals;
     private final Map<String, Short> approvals;
     private final RequiredApproval requiredApproval;
     private final int limit;

     Op(
         IdentifiedUser user,
         ChangeNotes changeNotes,
         PatchSet patchSet,
         Map<String, Short> oldApprovals,
         Map<String, Short> approvals,
         RequiredApproval requiredApproval,
         int limit) {
       this.user = user;
       this.changeNotes = changeNotes;
       this.patchSet = patchSet;
       this.oldApprovals = oldApprovals;
       this.approvals = approvals;
       this.requiredApproval = requiredApproval;
       this.limit = limit;
     }

     @Override
     public boolean updateChange(ChangeContext ctx) throws Exception {
       Optional<String> message =
           buildMessageForCodeOwnerApproval(
               user, changeNotes, patchSet, oldApprovals, approvals, requiredApproval, limit);

       if (message.isEmpty()) {
         return false;
       }

       changeMessageUtil.setChangeMessage(ctx, message.get(), TAG_ADD_CODE_OWNER_APPROVAL);
       return true;
     }
   }
 }
	// Copyright (C) 2020 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.plugins.codeowners.backend;

	import static com.google.common.base.Preconditions.checkState;
	import static com.google.common.collect.ImmutableMap.toImmutableMap;
	import static com.google.gerrit.plugins.codeowners.backend.CodeOwnersChangeMessageUtil.appendPaths;
	import static com.google.gerrit.server.update.context.RefUpdateContext.RefUpdateType.CHANGE_MODIFICATION;
	import static com.google.gerrit.server.update.context.RefUpdateContext.RefUpdateType.PLUGIN;

	import com.google.common.collect.ImmutableList;
	import com.google.common.collect.ImmutableMap;
	import com.google.common.flogger.FluentLogger;
	import com.google.gerrit.entities.Change;
	import com.google.gerrit.entities.PatchSet;
	import com.google.gerrit.entities.Project;
	import com.google.gerrit.extensions.common.ApprovalInfo;
	import com.google.gerrit.extensions.events.CommentAddedListener;
	import com.google.gerrit.metrics.Timer0;
	import com.google.gerrit.plugins.codeowners.backend.config.CodeOwnersPluginConfiguration;
	import com.google.gerrit.plugins.codeowners.backend.config.CodeOwnersPluginProjectConfigSnapshot;
	import com.google.gerrit.plugins.codeowners.backend.config.RequiredApproval;
	import com.google.gerrit.plugins.codeowners.metrics.CodeOwnerMetrics;
	import com.google.gerrit.server.ChangeMessagesUtil;
	import com.google.gerrit.server.CurrentUser;
	import com.google.gerrit.server.IdentifiedUser;
	import com.google.gerrit.server.git.WorkQueue;
	import com.google.gerrit.server.notedb.ChangeNotes;
	import com.google.gerrit.server.restapi.change.OnPostReview;
	import com.google.gerrit.server.update.BatchUpdate;
	import com.google.gerrit.server.update.BatchUpdateOp;
	import com.google.gerrit.server.update.ChangeContext;
	import com.google.gerrit.server.update.RetryHelper;
	import com.google.gerrit.server.update.context.RefUpdateContext;
	import com.google.gerrit.server.util.AccountTemplateUtil;
	import com.google.gerrit.server.util.LabelVote;
	import com.google.gerrit.server.util.ManualRequestContext;
	import com.google.gerrit.server.util.OneOffRequestContext;
	import com.google.inject.Inject;
	import com.google.inject.Provider;
	import com.google.inject.Singleton;
	import java.nio.file.Path;
	import java.time.Instant;
	import java.util.Map;
	import java.util.Optional;

	/**
	* Callback that is invoked on post review and that extends the change message if a code owner
	* approval was changed.
	*
	* <p>If a code owner approval was added, removed or changed, include in the change message that is
	* being posted on vote, which of the files:
	*
	* <ul>
	* <li>are approved now
	* <li>are no longer approved
	* <li>are still approved
	* </ul>
	*/
	@Singleton
	class OnCodeOwnerApproval implements OnPostReview, CommentAddedListener {
	private static final FluentLogger logger = FluentLogger.forEnclosingClass();

	private static final String TAG_ADD_CODE_OWNER_APPROVAL =
	ChangeMessagesUtil.AUTOGENERATED_BY_GERRIT_TAG_PREFIX + "code-owners:addCodeOwnerApproval";

	private final WorkQueue workQueue;
	private final OneOffRequestContext oneOffRequestContext;
	private final CodeOwnersPluginConfiguration codeOwnersPluginConfiguration;
	private final CodeOwnerApprovalCheck codeOwnerApprovalCheck;
	private final CodeOwnerMetrics codeOwnerMetrics;
	private final ChangeNotes.Factory changeNotesFactory;
	private final ChangeMessagesUtil changeMessageUtil;
	private final Provider<CurrentUser> userProvider;
	private final RetryHelper retryHelper;

	@Inject
	OnCodeOwnerApproval(
	WorkQueue workQueue,
	OneOffRequestContext oneOffRequestContext,
	CodeOwnersPluginConfiguration codeOwnersPluginConfiguration,
	CodeOwnerApprovalCheck codeOwnerApprovalCheck,
	CodeOwnerMetrics codeOwnerMetrics,
	ChangeNotes.Factory changeNotesFactory,
	ChangeMessagesUtil changeMessageUtil,
	Provider<CurrentUser> userProvider,
	RetryHelper retryHelper) {
	this.workQueue = workQueue;
	this.oneOffRequestContext = oneOffRequestContext;
	this.codeOwnersPluginConfiguration = codeOwnersPluginConfiguration;
	this.codeOwnerApprovalCheck = codeOwnerApprovalCheck;
	this.codeOwnerMetrics = codeOwnerMetrics;
	this.changeNotesFactory = changeNotesFactory;
	this.changeMessageUtil = changeMessageUtil;
	this.userProvider = userProvider;
	this.retryHelper = retryHelper;
	}

	@Override
	public Optional<String> getChangeMessageAddOn(
	Instant when,
	IdentifiedUser user,
	ChangeNotes changeNotes,
	PatchSet patchSet,
	Map<String, Short> oldApprovals,
	Map<String, Short> approvals) {
	CodeOwnersPluginProjectConfigSnapshot codeOwnersConfig =
	codeOwnersPluginConfiguration.getProjectConfig(changeNotes.getProjectName());
	int maxPathsInChangeMessage = codeOwnersConfig.getMaxPathsInChangeMessages();
	if (codeOwnersConfig.isDisabled(changeNotes.getChange().getDest().branch())
	\|\| maxPathsInChangeMessage <= 0) {
	logger.atFine().log("skip extending the change message since message posting is disabled");
	return Optional.empty();
	}
	if (codeOwnersConfig.enableAsyncMessageOnCodeOwnerApproval()) {
	// To avoid adding latency to PostReview post the change message asynchronously from
	// #onCommentAdded(Event) after PostReview is done.
	logger.atFine().log(
	"skip extending the change message since async message posting is enabled");
	return Optional.empty();
	}

	// code owner approvals are only computed for the current patch set
	if (!changeNotes.getChange().currentPatchSetId().equals(patchSet.id())) {
	logger.atFine().log("skip extending the change message on non-current patch set");
	return Optional.empty();
	}

	RequiredApproval requiredApproval = codeOwnersConfig.getRequiredApproval();

	if (oldApprovals.get(requiredApproval.labelType().getName()) == null) {
	// If oldApprovals doesn't contain the label or if the labels value in it is null, the label
	// was not changed.
	// This means that the user only voted on unrelated labels.
	return Optional.empty();
	}

	logger.atFine().log("post change message synchronously");
	try (Timer0.Context ctx = codeOwnerMetrics.extendChangeMessageOnPostReview.start()) {
	return buildMessageForCodeOwnerApproval(
	user,
	changeNotes,
	patchSet,
	oldApprovals,
	approvals,
	requiredApproval,
	maxPathsInChangeMessage);
	} catch (Exception e) {
	Optional<? extends Exception> configurationError =
	CodeOwnersExceptionHook.getCauseOfConfigurationError(e);
	if (configurationError.isPresent()) {
	logger.atWarning().log(
	"Failed to post code-owners change message for code owner approval on change %s"
	+ " in project %s: %s",
	changeNotes.getChangeId(),
	changeNotes.getProjectName(),
	configurationError.get().getMessage());
	} else {
	logger.atSevere().withCause(e).log(
	"Failed to post code-owners change message for code owner approval on change %s"
	+ " in project %s.",
	changeNotes.getChangeId(), changeNotes.getProjectName());
	}
	return Optional.empty();
	}
	}

	@Override
	public void onCommentAdded(Event event) {
	Project.NameKey projectName = Project.nameKey(event.getChange().project);
	CodeOwnersPluginProjectConfigSnapshot codeOwnersConfig =
	codeOwnersPluginConfiguration.getProjectConfig(projectName);
	int maxPathsInChangeMessage = codeOwnersConfig.getMaxPathsInChangeMessages();
	if (codeOwnersConfig.isDisabled(event.getChange().branch) \|\| maxPathsInChangeMessage <= 0) {
	logger.atFine().log("skip posting the change message since message posting is disabled");
	return;
	}
	if (!codeOwnersConfig.enableAsyncMessageOnCodeOwnerApproval()) {
	// The change message has already been synchronously extended by #getChangeMessageAddOn(...).
	logger.atFine().log(
	"skip posting the change message since async message posting is disabled");
	return;
	}

	// post change message asynchronously to avoid adding latency to PostReview
	logger.atFine().log("schedule asynchronous posting of the change message");

	CurrentUser user = userProvider.get();
	if (!user.isIdentifiedUser()) {
	// cannot compute owned paths for non-identified user
	logger.atFine().log(
	"skip posting the change message for non-identified user %s", user.getLoggableName());
	return;
	}

	Change.Id changeId = Change.id(event.getChange()._number);
	ChangeNotes changeNotes = changeNotesFactory.create(projectName, changeId);
	PatchSet.Id patchSetId = PatchSet.id(changeId, event.getRevision()._number);
	RequiredApproval requiredApproval = codeOwnersConfig.getRequiredApproval();

	// code owner approvals are only computed for the current patch set
	PatchSet currentPatchSet = changeNotes.getCurrentPatchSet();
	if (!currentPatchSet.id().equals(patchSetId)) {
	logger.atFine().log("skip posting the change message on non-current patch set");
	return;
	}

	if (event.getOldApprovals().get(requiredApproval.labelType().getName()) == null) {
	// If oldApprovals doesn't contain the label or if the labels value in it is null, the label
	// was not changed.
	// This means that the user only voted on unrelated labels.
	return;
	}

	@SuppressWarnings("unused")
	WorkQueue.Task<?> possiblyIgnoredError =
	(WorkQueue.Task<?>)
	workQueue
	.getDefaultQueue()
	.submit(
	() -> {
	try (ManualRequestContext ignored =
	oneOffRequestContext.openAs(user.getAccountId())) {
	postChangeMessage(
	event.getWhen(),
	user.asIdentifiedUser(),
	changeNotes,
	currentPatchSet,
	mapApprovalInfosToVotingValues(event.getOldApprovals()),
	mapApprovalInfosToVotingValues(event.getApprovals()),
	requiredApproval,
	maxPathsInChangeMessage);
	}
	});
	}

	private void postChangeMessage(
	Instant when,
	IdentifiedUser user,
	ChangeNotes changeNotes,
	PatchSet patchSet,
	Map<String, Short> oldApprovals,
	Map<String, Short> approvals,
	RequiredApproval requiredApproval,
	int maxPathsInChangeMessages) {
	try (Timer0.Context ctx = codeOwnerMetrics.addChangeMessageOnCodeOwnerApproval.start()) {
	retryHelper
	.changeUpdate(
	"addCodeOwnersMessageOnCodeOwnerApproval",
	updateFactory -> {
	try (BatchUpdate batchUpdate =
	updateFactory.create(changeNotes.getProjectName(), user, when);
	RefUpdateContext pluginCtx = RefUpdateContext.open(PLUGIN);
	RefUpdateContext changeCtx = RefUpdateContext.open(CHANGE_MODIFICATION)) {
	batchUpdate.addOp(
	changeNotes.getChangeId(),
	new Op(
	user,
	changeNotes,
	patchSet,
	oldApprovals,
	approvals,
	requiredApproval,
	maxPathsInChangeMessages));
	batchUpdate.execute();
	}
	return null;
	})
	.call();
	} catch (Exception e) {
	Optional<? extends Exception> configurationError =
	CodeOwnersExceptionHook.getCauseOfConfigurationError(e);
	if (configurationError.isPresent()) {
	logger.atWarning().log(
	"Failed to post code-owners change message for code owner approval on change %s in"
	+ " project %s: %s",
	changeNotes.getChangeId(),
	changeNotes.getProjectName(),
	configurationError.get().getMessage());
	} else {
	logger.atSevere().withCause(e).log(
	"Failed to post code-owners change message for code owner approval on change %s in"
	+ " project %s.",
	changeNotes.getChangeId(), changeNotes.getProjectName());
	}
	}
	}

	private Optional<String> buildMessageForCodeOwnerApproval(
	IdentifiedUser user,
	ChangeNotes changeNotes,
	PatchSet patchSet,
	Map<String, Short> oldApprovals,
	Map<String, Short> approvals,
	RequiredApproval requiredApproval,
	int limit) {
	LabelVote newVote = getNewVote(requiredApproval, approvals);

	// limit + 1, so that we can show an indicator if there are more than <limit> files.
	ImmutableList<Path> ownedPaths =
	OwnedChangedFile.getOwnedPaths(
	codeOwnerApprovalCheck.getOwnedPaths(
	changeNotes,
	changeNotes.getCurrentPatchSet(),
	user.getAccountId(),
	/* start= */ 0,
	limit + 1,
	/* checkReviewers= */ false));

	if (ownedPaths.isEmpty()) {
	// the user doesn't own any of the modified paths
	return Optional.empty();
	}

	if (isIgnoredDueToSelfApproval(user, patchSet, requiredApproval)) {
	if (isCodeOwnerApprovalNewlyApplied(requiredApproval, oldApprovals, newVote)
	\|\| isCodeOwnerApprovalUpOrDowngraded(requiredApproval, oldApprovals, newVote)) {
	return Optional.of(
	String.format(
	"The vote %s is ignored as code-owner approval since the label doesn't allow"
	+ " self approval of the patch set uploader.",
	newVote));
	}
	return Optional.empty();
	}

	boolean hasImplicitApprovalByUser =
	codeOwnersPluginConfiguration
	.getProjectConfig(changeNotes.getProjectName())
	.areImplicitApprovalsEnabled()
	&& patchSet.uploader().equals(user.getAccountId());

	boolean noLongerExplicitlyApproved = false;
	StringBuilder message = new StringBuilder();
	if (isCodeOwnerApprovalNewlyApplied(requiredApproval, oldApprovals, newVote)) {
	if (hasImplicitApprovalByUser) {
	message.append(
	String.format(
	"By voting %s the following files are now explicitly code-owner approved by %s:\n",
	newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
	} else {
	message.append(
	String.format(
	"By voting %s the following files are now code-owner approved by %s:\n",
	newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
	}
	} else if (isCodeOwnerApprovalRemoved(requiredApproval, oldApprovals, newVote)) {
	if (newVote.value() == 0) {
	if (hasImplicitApprovalByUser) {
	noLongerExplicitlyApproved = true;
	message.append(
	String.format(
	"By removing the %s vote the following files are no longer explicitly code-owner"
	+ " approved by %s:\n",
	newVote.label(), AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
	} else {
	message.append(
	String.format(
	"By removing the %s vote the following files are no longer code-owner approved"
	+ " by %s:\n",
	newVote.label(), AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
	}
	} else {
	if (hasImplicitApprovalByUser) {
	noLongerExplicitlyApproved = true;
	message.append(
	String.format(
	"By voting %s the following files are no longer explicitly code-owner approved by"
	+ " %s:\n",
	newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
	} else {
	message.append(
	String.format(
	"By voting %s the following files are no longer code-owner approved by %s:\n",
	newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
	}
	}
	} else if (isCodeOwnerApprovalUpOrDowngraded(requiredApproval, oldApprovals, newVote)) {
	if (hasImplicitApprovalByUser) {
	message.append(
	String.format(
	"By voting %s the following files are still explicitly code-owner approved by"
	+ " %s:\n",
	newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
	} else {
	message.append(
	String.format(
	"By voting %s the following files are still code-owner approved by %s:\n",
	newVote, AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
	}
	} else {
	// non-approval was downgraded (e.g. -1 to -2)
	return Optional.empty();
	}

	if (ownedPaths.size() <= limit) {
	appendPaths(message, ownedPaths.stream());
	} else {
	appendPaths(message, ownedPaths.stream().limit(limit));
	message.append("(more files)\n");
	}

	if (hasImplicitApprovalByUser && noLongerExplicitlyApproved) {
	message.append(
	String.format(
	"\nThe listed files are still implicitly approved by %s.\n",
	AccountTemplateUtil.getAccountTemplate(user.getAccountId())));
	}

	return Optional.of(message.toString());
	}

	private boolean isIgnoredDueToSelfApproval(
	IdentifiedUser user, PatchSet patchSet, RequiredApproval requiredApproval) {
	return patchSet.uploader().equals(user.getAccountId())
	&& requiredApproval.labelType().isIgnoreSelfApproval();
	}

	private boolean isCodeOwnerApprovalNewlyApplied(
	RequiredApproval requiredApproval, Map<String, Short> oldApprovals, LabelVote newVote) {
	String labelName = requiredApproval.labelType().getName();
	return oldApprovals.get(labelName) < requiredApproval.value()
	&& newVote.value() >= requiredApproval.value();
	}

	private boolean isCodeOwnerApprovalRemoved(
	RequiredApproval requiredApproval, Map<String, Short> oldApprovals, LabelVote newVote) {
	String labelName = requiredApproval.labelType().getName();
	return oldApprovals.get(labelName) >= requiredApproval.value()
	&& newVote.value() < requiredApproval.value();
	}

	private boolean isCodeOwnerApprovalUpOrDowngraded(
	RequiredApproval requiredApproval, Map<String, Short> oldApprovals, LabelVote newVote) {
	String labelName = requiredApproval.labelType().getName();
	return oldApprovals.get(labelName) >= requiredApproval.value()
	&& newVote.value() >= requiredApproval.value();
	}

	private LabelVote getNewVote(RequiredApproval requiredApproval, Map<String, Short> approvals) {
	String labelName = requiredApproval.labelType().getName();
	checkState(
	approvals.containsKey(labelName),
	"expected that approval on label %s exists (approvals = %s)",
	labelName,
	approvals);
	return LabelVote.create(labelName, approvals.get(labelName));
	}

	private static ImmutableMap<String, Short> mapApprovalInfosToVotingValues(
	Map<String, ApprovalInfo> approvals) {
	return approvals.entrySet().stream()
	.collect(
	toImmutableMap(
	Map.Entry::getKey,
	e -> e.getValue().value != null ? e.getValue().value.shortValue() : null));
	}

	private class Op implements BatchUpdateOp {
	private final IdentifiedUser user;
	private final ChangeNotes changeNotes;
	private final PatchSet patchSet;
	private final Map<String, Short> oldApprovals;
	private final Map<String, Short> approvals;
	private final RequiredApproval requiredApproval;
	private final int limit;

	Op(
	IdentifiedUser user,
	ChangeNotes changeNotes,
	PatchSet patchSet,
	Map<String, Short> oldApprovals,
	Map<String, Short> approvals,
	RequiredApproval requiredApproval,
	int limit) {
	this.user = user;
	this.changeNotes = changeNotes;
	this.patchSet = patchSet;
	this.oldApprovals = oldApprovals;
	this.approvals = approvals;
	this.requiredApproval = requiredApproval;
	this.limit = limit;
	}

	@Override
	public boolean updateChange(ChangeContext ctx) throws Exception {
	Optional<String> message =
	buildMessageForCodeOwnerApproval(
	user, changeNotes, patchSet, oldApprovals, approvals, requiredApproval, limit);

	if (message.isEmpty()) {
	return false;
	}

	changeMessageUtil.setChangeMessage(ctx, message.get(), TAG_ADD_CODE_OWNER_APPROVAL);
	return true;
	}
	}
	}