// Copyright (C) 2017 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.update;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.truth.Truth.assertThat;
import static com.google.gerrit.testing.GerritJUnit.assertThrows;
import static com.google.gerrit.testing.TestActionRefUpdateContext.openTestRefUpdateContext;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;

import com.github.rholder.retry.Attempt;
import com.github.rholder.retry.RetryException;
import com.github.rholder.retry.RetryListener;
import com.google.common.cache.Cache;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.entities.Account;
import com.google.gerrit.entities.Change;
import com.google.gerrit.entities.PatchSet;
import com.google.gerrit.entities.Project;
import com.google.gerrit.entities.RefNames;
import com.google.gerrit.entities.SubmissionId;
import com.google.gerrit.entities.SubmitRecord;
import com.google.gerrit.extensions.client.ReviewerState;
import com.google.gerrit.extensions.events.AttentionSetListener;
import com.google.gerrit.extensions.registration.DynamicSet;
import com.google.gerrit.extensions.restapi.ResourceConflictException;
import com.google.gerrit.git.LockFailureException;
import com.google.gerrit.git.RefUpdateUtil;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.GerritPersonIdent;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.InternalUser;
import com.google.gerrit.server.Sequences;
import com.google.gerrit.server.account.AccountManager;
import com.google.gerrit.server.account.AuthRequest;
import com.google.gerrit.server.change.AbandonOp;
import com.google.gerrit.server.change.AddReviewersOp;
import com.google.gerrit.server.change.ChangeInserter;
import com.google.gerrit.server.change.PatchSetInserter;
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.notedb.ReviewerStateInternal;
import com.google.gerrit.server.patch.DiffSummary;
import com.google.gerrit.server.patch.DiffSummaryKey;
import com.google.gerrit.server.update.RetryableAction.ActionType;
import com.google.gerrit.server.update.context.RefUpdateContext;
import com.google.gerrit.server.util.time.TimeUtil;
import com.google.gerrit.testing.InMemoryTestEnvironment;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.name.Named;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import org.eclipse.jgit.junit.TestRepository;
import org.eclipse.jgit.lib.BatchRefUpdate;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.PersonIdent;
import org.eclipse.jgit.lib.RefUpdate;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import org.junit.After;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.mockito.ArgumentCaptor;
import org.mockito.Captor;
import org.mockito.Mock;
import org.mockito.junit.MockitoJUnit;
import org.mockito.junit.MockitoRule;

public class BatchUpdateTest {
  private static final int MAX_UPDATES = 4;
  private static final int MAX_PATCH_SETS = 3;

  @Rule
  public InMemoryTestEnvironment testEnvironment =
      new InMemoryTestEnvironment(
          () -> {
            Config cfg = new Config();
            cfg.setInt("change", null, "maxFiles", 2);
            cfg.setInt("change", null, "maxPatchSets", MAX_PATCH_SETS);
            cfg.setInt("change", null, "maxUpdates", MAX_UPDATES);
            cfg.setString("index", null, "type", "fake");
            return cfg;
          });

  @Inject private BatchUpdate.Factory batchUpdateFactory;
  @Inject private ChangeInserter.Factory changeInserterFactory;
  @Inject private ChangeNotes.Factory changeNotesFactory;
  @Inject private GitRepositoryManager repoManager;
  @Inject private PatchSetInserter.Factory patchSetInserterFactory;
  @Inject private Provider<CurrentUser> user;
  @Inject private Sequences sequences;
  @Inject private AddReviewersOp.Factory addReviewersOpFactory;
  @Inject private DynamicSet<AttentionSetListener> attentionSetListeners;
  @Inject private AccountManager accountManager;
  @Inject private AuthRequest.Factory authRequestFactory;
  @Inject private IdentifiedUser.GenericFactory userFactory;
  @Inject private InternalUser.Factory internalUserFactory;
  @Inject private AbandonOp.Factory abandonOpFactory;
  @Inject @GerritPersonIdent private PersonIdent serverIdent;
  @Inject private RetryHelper retryHelper;

  @Rule public final MockitoRule mockito = MockitoJUnit.rule();

  @Captor ArgumentCaptor<AttentionSetListener.Event> attentionSetEventCaptor;
  @Mock private AttentionSetListener attentionSetListener;

  @Inject
  private @Named("diff_summary") Cache<DiffSummaryKey, DiffSummary> diffSummaryCache;

  private Project.NameKey project;
  private TestRepository<Repository> repo;

  private RefUpdateContext testRefUpdateContext;

  @Before
  public void setUp() throws Exception {
    project = Project.nameKey("test");

    Repository inMemoryRepo = repoManager.createRepository(project);
    repo = new TestRepository<>(inMemoryRepo);
    // All tests here are low level. Open context here to avoid repeated code in multiple tests.
    testRefUpdateContext = openTestRefUpdateContext();
  }

  @After
  public void tearDown() {
    testRefUpdateContext.close();
  }

  @Test
  public void addRefUpdateFromFastForwardCommit() throws Exception {
    RevCommit masterCommit = repo.branch("master").commit().create();
    RevCommit branchCommit = repo.branch("branch").commit().parent(masterCommit).create();

    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addRepoOnlyOp(
          new RepoOnlyOp() {
            @Override
            public void updateRepo(RepoContext ctx) throws Exception {
              ctx.addRefUpdate(masterCommit.getId(), branchCommit.getId(), "refs/heads/master");
            }
          });
      bu.execute();
    }
    assertThat(repo.getRepository().exactRef("refs/heads/master").getObjectId())
        .isEqualTo(branchCommit.getId());
  }

  @Test
  public void batchUpdateThatChangeAttentionSetAsInternalUser() throws Exception {
    Change.Id id = createChangeWithUpdates(1);
    attentionSetListeners.add("test", attentionSetListener);

    Account.Id reviewer =
        accountManager.authenticate(authRequestFactory.createForUser("user")).getAccountId();

    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addOp(
          id,
          addReviewersOpFactory.create(
              ImmutableSet.of(reviewer), ImmutableList.of(), ReviewerState.REVIEWER, false));
      bu.execute();
    }

    try (BatchUpdate bu =
        batchUpdateFactory.create(project, internalUserFactory.create(), TimeUtil.now())) {
      bu.addOp(id, abandonOpFactory.create(null, "test abandon"));
      bu.execute();
    }

    verify(attentionSetListener, times(2)).onAttentionSetChanged(attentionSetEventCaptor.capture());
    AttentionSetListener.Event event = attentionSetEventCaptor.getAllValues().get(0);
    assertThat(event.getChange()._number).isEqualTo(id.get());
    assertThat(event.usersAdded()).containsExactly(reviewer.get());
    assertThat(event.usersRemoved()).isEmpty();

    event = attentionSetEventCaptor.getAllValues().get(1);
    assertThat(event.getChange()._number).isEqualTo(id.get());
    assertThat(event.usersAdded()).isEmpty();
    assertThat(event.usersRemoved()).containsExactly(reviewer.get());
  }

  @Test
  public void cannotExceedMaxUpdates() throws Exception {
    Change.Id id = createChangeWithUpdates(MAX_UPDATES);
    ObjectId oldMetaId = getMetaId(id);
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addOp(id, new AddMessageOp("Excessive update"));
      ResourceConflictException thrown = assertThrows(ResourceConflictException.class, bu::execute);
      assertThat(thrown)
          .hasMessageThat()
          .contains("Change " + id + " may not exceed " + MAX_UPDATES);
    }
    assertThat(getUpdateCount(id)).isEqualTo(MAX_UPDATES);
    assertThat(getMetaId(id)).isEqualTo(oldMetaId);
  }

  @Test
  public void cannotExceedMaxUpdatesCountingMultipleChangeUpdatesInSingleBatch() throws Exception {
    Change.Id id = createChangeWithPatchSets(2);

    ObjectId oldMetaId = getMetaId(id);
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addOp(id, new AddMessageOp("Update on PS1", PatchSet.id(id, 1)));
      bu.addOp(id, new AddMessageOp("Update on PS2", PatchSet.id(id, 2)));
      ResourceConflictException thrown = assertThrows(ResourceConflictException.class, bu::execute);
      assertThat(thrown)
          .hasMessageThat()
          .contains("Change " + id + " may not exceed " + MAX_UPDATES);
    }
    assertThat(getUpdateCount(id)).isEqualTo(MAX_UPDATES - 1);
    assertThat(getMetaId(id)).isEqualTo(oldMetaId);
  }

  @Test
  public void attentionSetUpdateEventsFiredForSeveralChangesInSingleBatch() throws Exception {
    Change.Id id1 = createChangeWithUpdates(1);
    Change.Id id2 = createChangeWithUpdates(1);
    attentionSetListeners.add("test", attentionSetListener);

    Account.Id reviewer1 =
        accountManager.authenticate(authRequestFactory.createForUser("user1")).getAccountId();
    Account.Id reviewer2 =
        accountManager.authenticate(authRequestFactory.createForUser("user2")).getAccountId();

    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addOp(
          id1,
          addReviewersOpFactory.create(
              ImmutableSet.of(reviewer1), ImmutableList.of(), ReviewerState.REVIEWER, false));
      bu.addOp(
          id2,
          addReviewersOpFactory.create(
              ImmutableSet.of(reviewer2), ImmutableList.of(), ReviewerState.REVIEWER, false));
      bu.execute();
    }
    verify(attentionSetListener, times(2)).onAttentionSetChanged(attentionSetEventCaptor.capture());
    AttentionSetListener.Event event1 = attentionSetEventCaptor.getAllValues().get(0);
    assertThat(event1.getChange()._number).isEqualTo(id1.get());
    assertThat(event1.usersAdded()).containsExactly(reviewer1.get());
    assertThat(event1.usersRemoved()).isEmpty();

    AttentionSetListener.Event event2 = attentionSetEventCaptor.getAllValues().get(1);
    assertThat(event2.getChange()._number).isEqualTo(id2.get());
    assertThat(event2.usersRemoved()).isEmpty();
  }

  @Test
  public void exceedingMaxUpdatesAllowedWithCompleteNoOp() throws Exception {
    Change.Id id = createChangeWithUpdates(MAX_UPDATES);
    ObjectId oldMetaId = getMetaId(id);
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addOp(
          id,
          new BatchUpdateOp() {
            @Override
            public boolean updateChange(ChangeContext ctx) {
              return false;
            }
          });
      bu.execute();
    }
    assertThat(getUpdateCount(id)).isEqualTo(MAX_UPDATES);
    assertThat(getMetaId(id)).isEqualTo(oldMetaId);
  }

  @Test
  public void exceedingMaxUpdatesAllowedWithNoOpAfterPopulatingUpdate() throws Exception {
    Change.Id id = createChangeWithUpdates(MAX_UPDATES);
    ObjectId oldMetaId = getMetaId(id);
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addOp(
          id,
          new BatchUpdateOp() {
            @Override
            public boolean updateChange(ChangeContext ctx) {
              ctx.getUpdate(ctx.getChange().currentPatchSetId()).setChangeMessage("No-op");
              return false;
            }
          });
      bu.execute();
    }
    assertThat(getUpdateCount(id)).isEqualTo(MAX_UPDATES);
    assertThat(getMetaId(id)).isEqualTo(oldMetaId);
  }

  @Test
  public void exceedingMaxUpdatesAllowedWithSubmit() throws Exception {
    Change.Id id = createChangeWithUpdates(MAX_UPDATES);
    ObjectId oldMetaId = getMetaId(id);
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addOp(id, new SubmitOp());
      bu.execute();
    }
    assertThat(getUpdateCount(id)).isEqualTo(MAX_UPDATES + 1);
    assertThat(getMetaId(id)).isNotEqualTo(oldMetaId);
  }

  @Test
  public void exceedingMaxUpdatesAllowedWithSubmitAfterOtherOp() throws Exception {
    Change.Id id = createChangeWithPatchSets(2);
    ObjectId oldMetaId = getMetaId(id);
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addOp(id, new AddMessageOp("Message on PS1", PatchSet.id(id, 1)));
      bu.addOp(id, new SubmitOp());
      bu.execute();
    }
    assertThat(getUpdateCount(id)).isEqualTo(MAX_UPDATES + 1);
    assertThat(getMetaId(id)).isNotEqualTo(oldMetaId);
  }
  // Not possible to write a variant of this test that submits first and adds a message second in
  // the same batch, since submit always comes last.

  @Test
  public void exceedingMaxUpdatesAllowedWithAbandon() throws Exception {
    Change.Id id = createChangeWithUpdates(MAX_UPDATES);
    ObjectId oldMetaId = getMetaId(id);
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.addOp(
          id,
          new BatchUpdateOp() {
            @Override
            public boolean updateChange(ChangeContext ctx) {
              ChangeUpdate update = ctx.getUpdate(ctx.getChange().currentPatchSetId());
              update.setChangeMessage("Abandon");
              update.setStatus(Change.Status.ABANDONED);
              return true;
            }
          });
      bu.execute();
    }
    assertThat(getUpdateCount(id)).isEqualTo(MAX_UPDATES + 1);
    assertThat(getMetaId(id)).isNotEqualTo(oldMetaId);
  }

  @Test
  public void limitPatchSetCount_exceed() throws Exception {
    Change.Id changeId = createChangeWithPatchSets(MAX_PATCH_SETS);
    ObjectId oldMetaId = getMetaId(changeId);
    ChangeNotes notes = changeNotesFactory.create(project, changeId);
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      ObjectId commitId =
          repo.amend(notes.getCurrentPatchSet().commitId()).message("kaboom").create();
      bu.addOp(
          changeId,
          patchSetInserterFactory
              .create(notes, PatchSet.id(changeId, MAX_PATCH_SETS + 1), commitId)
              .setMessage("kaboom"));
      ResourceConflictException thrown = assertThrows(ResourceConflictException.class, bu::execute);
      assertThat(thrown)
          .hasMessageThat()
          .contains("Change " + changeId + " may not exceed " + MAX_PATCH_SETS + " patch sets");
    }
    assertThat(changeNotesFactory.create(project, changeId).getPatchSets()).hasSize(MAX_PATCH_SETS);
    assertThat(getMetaId(changeId)).isEqualTo(oldMetaId);
  }

  @Test
  public void limitFileCount_exceed() throws Exception {
    Change.Id changeId = createChangeWithUpdates(1);
    ChangeNotes notes = changeNotesFactory.create(project, changeId);

    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      ObjectId commitId =
          repo.amend(notes.getCurrentPatchSet().commitId())
              .add("bar.txt", "bar")
              .add("baz.txt", "baz")
              .add("boom.txt", "boom")
              .message("blah")
              .create();
      bu.addOp(
          changeId,
          patchSetInserterFactory
              .create(notes, PatchSet.id(changeId, 2), commitId)
              .setMessage("blah"));
      ResourceConflictException thrown = assertThrows(ResourceConflictException.class, bu::execute);
      assertThat(thrown)
          .hasMessageThat()
          .contains("Exceeding maximum number of files per change (3 > 2)");
    }
  }

  @Test
  public void limitFileCount_cacheKeyMatches() throws Exception {
    Change.Id changeId = createChangeWithUpdates(1);
    ChangeNotes notes = changeNotesFactory.create(project, changeId);

    int cacheSizeBefore = diffSummaryCache.asMap().size();

    // We don't want to depend on the test helper used above so we perform an explicit commit
    // here.
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      ObjectId commitId =
          repo.amend(notes.getCurrentPatchSet().commitId())
              .add("bar.txt", "bar")
              .add("baz.txt", "baz")
              .message("blah")
              .create();
      bu.addOp(
          changeId,
          patchSetInserterFactory
              .create(notes, PatchSet.id(changeId, 3), commitId)
              .setMessage("blah"));
      bu.execute();
    }

    // Assert that we only performed the diff computation once. This would e.g. catch
    // bugs/deviations in the computation of the cache key.
    assertThat(diffSummaryCache.asMap()).hasSize(cacheSizeBefore + 1);
  }

  @Test
  public void executeOpsWithDifferentUsers() throws Exception {
    Change.Id changeId = createChange();

    ObjectId oldHead = getMetaId(changeId);

    CurrentUser defaultUser = user.get();
    IdentifiedUser user1 =
        userFactory.create(
            accountManager.authenticate(authRequestFactory.createForUser("user1")).getAccountId());
    IdentifiedUser user2 =
        userFactory.create(
            accountManager.authenticate(authRequestFactory.createForUser("user2")).getAccountId());

    TestOp testOp1 = new TestOp().addReviewer(defaultUser.getAccountId());
    TestOp testOp2 = new TestOp().addReviewer(user1.getAccountId());
    TestOp testOp3 = new TestOp().addReviewer(user2.getAccountId());

    try (BatchUpdate bu = batchUpdateFactory.create(project, defaultUser, TimeUtil.now())) {
      bu.addOp(changeId, user1, testOp1);
      bu.addOp(changeId, user2, testOp2);
      bu.addOp(changeId, testOp3);
      bu.execute();

      PersonIdent refLogIdent = bu.getRefLogIdent().get();
      assertThat(refLogIdent.getName())
          .isEqualTo(
              String.format(
                  "account-%s|account-%s|account-%s",
                  defaultUser.asIdentifiedUser().getAccountId(),
                  user1.asIdentifiedUser().getAccountId(),
                  user2.asIdentifiedUser().getAccountId()));
      assertThat(refLogIdent.getEmailAddress())
          .isEqualTo(String.format("%s@unknown", refLogIdent.getName()));
    }

    assertThat(testOp1.updateRepoUser).isEqualTo(user1);
    assertThat(testOp1.updateChangeUser).isEqualTo(user1);
    assertThat(testOp1.postUpdateUser).isEqualTo(user1);

    assertThat(testOp2.updateRepoUser).isEqualTo(user2);
    assertThat(testOp2.updateChangeUser).isEqualTo(user2);
    assertThat(testOp2.postUpdateUser).isEqualTo(user2);

    assertThat(testOp3.updateRepoUser).isEqualTo(defaultUser);
    assertThat(testOp3.updateChangeUser).isEqualTo(defaultUser);
    assertThat(testOp3.postUpdateUser).isEqualTo(defaultUser);

    // Verify that we got one meta commit per op.
    RevCommit metaCommitForTestOp3 = repo.getRepository().parseCommit(getMetaId(changeId));
    assertThat(metaCommitForTestOp3.getAuthorIdent().getEmailAddress())
        .isEqualTo(String.format("%s@gerrit", defaultUser.getAccountId()));
    assertThat(metaCommitForTestOp3.getFullMessage())
        .startsWith(
            "Update patch set 1\n"
                + "\n"
                + "Patch-set: 1\n"
                + String.format(
                    "Reviewer: Gerrit User %s <%s@gerrit>\n",
                    user2.getAccountId(), user2.getAccountId())
                + "Attention:");

    RevCommit metaCommitForTestOp2 =
        repo.getRepository().parseCommit(metaCommitForTestOp3.getParent(0));
    assertThat(metaCommitForTestOp2.getAuthorIdent().getEmailAddress())
        .isEqualTo(String.format("%s@gerrit", user2.getAccountId()));
    assertThat(metaCommitForTestOp2.getFullMessage())
        .startsWith(
            "Update patch set 1\n"
                + "\n"
                + "Patch-set: 1\n"
                + String.format(
                    "Reviewer: Gerrit User %s <%s@gerrit>\n",
                    user1.getAccountId(), user1.getAccountId())
                + "Attention:");

    RevCommit metaCommitForTestOp1 =
        repo.getRepository().parseCommit(metaCommitForTestOp2.getParent(0));
    assertThat(metaCommitForTestOp1.getAuthorIdent().getEmailAddress())
        .isEqualTo(String.format("%s@gerrit", user1.getAccountId()));
    assertThat(metaCommitForTestOp1.getFullMessage())
        .isEqualTo(
            "Update patch set 1\n"
                + "\n"
                + "Patch-set: 1\n"
                + String.format(
                    "Reviewer: Gerrit User %s <%s@gerrit>\n",
                    defaultUser.getAccountId(), defaultUser.getAccountId()));

    assertThat(metaCommitForTestOp1.getParent(0)).isEqualTo(oldHead);
  }

  @Test
  public void executeOpsWithSameUser() throws Exception {
    Change.Id changeId = createChange();

    ObjectId oldHead = getMetaId(changeId);

    CurrentUser defaultUser = user.get();
    IdentifiedUser user1 =
        userFactory.create(
            accountManager.authenticate(authRequestFactory.createForUser("user1")).getAccountId());
    IdentifiedUser user2 =
        userFactory.create(
            accountManager.authenticate(authRequestFactory.createForUser("user2")).getAccountId());

    TestOp testOp1 = new TestOp().addReviewer(user1.getAccountId());
    TestOp testOp2 = new TestOp().addReviewer(user2.getAccountId());

    try (BatchUpdate bu = batchUpdateFactory.create(project, defaultUser, TimeUtil.now())) {
      bu.addOp(changeId, defaultUser, testOp1);
      bu.addOp(changeId, testOp2);
      bu.execute();

      PersonIdent refLogIdent = bu.getRefLogIdent().get();
      PersonIdent defaultUserRefLogIdent = defaultUser.asIdentifiedUser().newRefLogIdent();
      assertThat(refLogIdent.getName()).isEqualTo(defaultUserRefLogIdent.getName());
      assertThat(refLogIdent.getEmailAddress()).isEqualTo(defaultUserRefLogIdent.getEmailAddress());
    }

    assertThat(testOp1.updateRepoUser).isEqualTo(defaultUser);
    assertThat(testOp1.updateChangeUser).isEqualTo(defaultUser);
    assertThat(testOp1.postUpdateUser).isEqualTo(defaultUser);

    assertThat(testOp2.updateRepoUser).isEqualTo(defaultUser);
    assertThat(testOp2.updateChangeUser).isEqualTo(defaultUser);
    assertThat(testOp2.postUpdateUser).isEqualTo(defaultUser);

    // Verify that we got a single meta commit (updates of both ops squashed into one commit).
    RevCommit metaCommit = repo.getRepository().parseCommit(getMetaId(changeId));
    assertThat(metaCommit.getAuthorIdent().getEmailAddress())
        .isEqualTo(String.format("%s@gerrit", defaultUser.getAccountId()));
    assertThat(metaCommit.getFullMessage())
        .startsWith(
            "Update patch set 1\n"
                + "\n"
                + "Patch-set: 1\n"
                + String.format(
                    "Reviewer: Gerrit User %s <%s@gerrit>\n",
                    user1.getAccountId(), user1.getAccountId())
                + String.format(
                    "Reviewer: Gerrit User %s <%s@gerrit>\n",
                    user2.getAccountId(), user2.getAccountId())
                + "Attention:");

    assertThat(metaCommit.getParent(0)).isEqualTo(oldHead);
  }

  @Test
  public void lockFailureOnConcurrentUpdate() throws Exception {
    Change.Id changeId = createChange();
    ObjectId metaId = getMetaId(changeId);

    ChangeNotes notes = changeNotesFactory.create(project, changeId);
    assertThat(notes.getChange().getStatus()).isEqualTo(Change.Status.NEW);

    AtomicBoolean doneBackgroundUpdate = new AtomicBoolean(false);

    // Create a listener that updates the change meta ref concurrently on the first attempt.
    BatchUpdateListener listener =
        new BatchUpdateListener() {
          @Override
          public BatchRefUpdate beforeUpdateRefs(BatchRefUpdate bru) {
            try (RevWalk rw = new RevWalk(repo.getRepository())) {
              RevCommit old = rw.parseCommit(metaId);
              RevCommit commit =
                  repo.commit()
                      .parent(old)
                      .author(serverIdent)
                      .committer(serverIdent)
                      .setTopLevelTree(old.getTree())
                      .message("Concurrent Update\n\nPatch-Set: 1")
                      .create();
              RefUpdate ru = repo.getRepository().updateRef(RefNames.changeMetaRef(changeId));
              ru.setExpectedOldObjectId(metaId);
              ru.setNewObjectId(commit);
              ru.update();
              RefUpdateUtil.checkResult(ru);
              doneBackgroundUpdate.set(true);
            } catch (Exception e) {
              // Ignore. If an exception happens doneBackgroundUpdate is false and we fail later
              // when doneBackgroundUpdate is checked.
            }
            return bru;
          }
        };

    // Do a batch update, expect that it fails with LOCK_FAILURE due to the concurrent update.
    assertThat(doneBackgroundUpdate.get()).isFalse();
    UpdateException exception =
        assertThrows(
            UpdateException.class,
            () -> {
              try (BatchUpdate bu =
                  batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
                bu.addOp(changeId, abandonOpFactory.create(null, "abandon"));
                bu.execute(listener);
              }
            });
    assertThat(exception).hasCauseThat().isInstanceOf(LockFailureException.class);
    assertThat(doneBackgroundUpdate.get()).isTrue();

    // Check that the change was not updated.
    notes = changeNotesFactory.create(project, changeId);
    assertThat(notes.getChange().getStatus()).isEqualTo(Change.Status.NEW);
  }

  @Test
  public void useRetryHelperToRetryOnLockFailure() throws Exception {
    Change.Id changeId = createChange();
    ObjectId metaId = getMetaId(changeId);

    ChangeNotes notes = changeNotesFactory.create(project, changeId);
    assertThat(notes.getChange().getStatus()).isEqualTo(Change.Status.NEW);

    AtomicBoolean doneBackgroundUpdate = new AtomicBoolean(false);

    // Create a listener that updates the change meta ref concurrently on the first attempt.
    BatchUpdateListener listener =
        new BatchUpdateListener() {
          @Override
          public BatchRefUpdate beforeUpdateRefs(BatchRefUpdate bru) {
            if (!doneBackgroundUpdate.getAndSet(true)) {
              try (RevWalk rw = new RevWalk(repo.getRepository())) {
                RevCommit old = rw.parseCommit(metaId);
                RevCommit commit =
                    repo.commit()
                        .parent(old)
                        .author(serverIdent)
                        .committer(serverIdent)
                        .setTopLevelTree(old.getTree())
                        .message("Concurrent Update\n\nPatch-Set: 1")
                        .create();
                RefUpdate ru = repo.getRepository().updateRef(RefNames.changeMetaRef(changeId));
                ru.setExpectedOldObjectId(metaId);
                ru.setNewObjectId(commit);
                ru.update();
                RefUpdateUtil.checkResult(ru);
              } catch (Exception e) {
                // Ignore. If an exception happens doneBackgroundUpdate is false and we fail later
                // when doneBackgroundUpdate is checked.
              }
            }
            return bru;
          }
        };

    // Do a batch update, expect that it succeeds due to retrying despite the LOCK_FAILURE on the
    // first attempt.
    assertThat(doneBackgroundUpdate.get()).isFalse();

    @SuppressWarnings("unused")
    var unused =
        retryHelper
            .changeUpdate(
                "batchUpdate",
                updateFactory -> {
                  try (BatchUpdate bu = updateFactory.create(project, user.get(), TimeUtil.now())) {
                    bu.addOp(changeId, abandonOpFactory.create(null, "abandon"));
                    bu.execute(listener);
                  }
                  return null;
                })
            .call();

    // Check that the concurrent update was done.
    assertThat(doneBackgroundUpdate.get()).isTrue();

    // Check that the BatchUpdate updated the change.
    notes = changeNotesFactory.create(project, changeId);
    assertThat(notes.getChange().getStatus()).isEqualTo(Change.Status.ABANDONED);
  }

  @Test
  public void noRetryingOnOuterLevelIfRetryingWasAlreadyDoneOnInnerLevel() throws Exception {
    Change.Id changeId = createChange();

    ChangeNotes notes = changeNotesFactory.create(project, changeId);
    assertThat(notes.getChange().getStatus()).isEqualTo(Change.Status.NEW);

    AtomicBoolean backgroundFailure = new AtomicBoolean(false);

    // Create a listener that updates the change meta ref concurrently on all attempts.
    BatchUpdateListener listener =
        new BatchUpdateListener() {
          @Override
          public BatchRefUpdate beforeUpdateRefs(BatchRefUpdate bru) {
            try (RevWalk rw = new RevWalk(repo.getRepository())) {
              String changeMetaRef = RefNames.changeMetaRef(changeId);
              ObjectId metaId = repo.getRepository().exactRef(changeMetaRef).getObjectId();
              RevCommit old = rw.parseCommit(metaId);
              RevCommit commit =
                  repo.commit()
                      .parent(old)
                      .author(serverIdent)
                      .committer(serverIdent)
                      .setTopLevelTree(old.getTree())
                      .message("Concurrent Update\n\nPatch-Set: 1")
                      .create();
              RefUpdate ru = repo.getRepository().updateRef(changeMetaRef);
              ru.setExpectedOldObjectId(metaId);
              ru.setNewObjectId(commit);
              ru.update();
              RefUpdateUtil.checkResult(ru);
            } catch (Exception e) {
              backgroundFailure.set(true);
            }

            return bru;
          }
        };

    AtomicInteger innerRetryOnExceptionCounter = new AtomicInteger();
    AtomicInteger outerRetryOnExceptionCounter = new AtomicInteger();
    UpdateException exception =
        assertThrows(
            UpdateException.class,
            () ->
                // Outer level retrying. We expect that no retrying is happens here because retrying
                // is already done on the inner level.
                retryHelper
                    .action(
                        ActionType.CHANGE_UPDATE,
                        "batchUpdate",
                        () ->
                            // Inner level retrying. We expect that retrying happens here.
                            retryHelper
                                .changeUpdate(
                                    "batchUpdate",
                                    updateFactory -> {
                                      try (BatchUpdate bu =
                                          updateFactory.create(
                                              project, user.get(), TimeUtil.now())) {
                                        bu.addOp(
                                            changeId, abandonOpFactory.create(null, "abandon"));
                                        bu.execute(listener);
                                      }
                                      return null;
                                    })
                                .listener(
                                    new RetryListener() {
                                      @Override
                                      public <V> void onRetry(Attempt<V> attempt) {
                                        if (attempt.hasException()) {
                                          @SuppressWarnings("unused")
                                          var unused =
                                              innerRetryOnExceptionCounter.incrementAndGet();
                                        }
                                      }
                                    })
                                .call())
                    // give it enough time to potentially retry multiple times when each retry also
                    // does retrying
                    .defaultTimeoutMultiplier(5)
                    .listener(
                        new RetryListener() {
                          @Override
                          public <V> void onRetry(Attempt<V> attempt) {
                            if (attempt.hasException()) {
                              @SuppressWarnings("unused")
                              var unused = outerRetryOnExceptionCounter.incrementAndGet();
                            }
                          }
                        })
                    .call());
    assertThat(backgroundFailure.get()).isFalse();

    // Check that retrying was done on the inner level.
    assertThat(innerRetryOnExceptionCounter.get()).isGreaterThan(1);

    // Check that there was no retrying on the outer level since retrying was already done on the
    // inner level.
    // We expect 1 because RetryListener#onRetry is invoked before the rejection predicate and stop
    // strategies are applied (i.e. before RetryHelper decides whether retrying should be done).
    assertThat(outerRetryOnExceptionCounter.get()).isEqualTo(1);

    assertThat(exception).hasCauseThat().isInstanceOf(RetryException.class);
    assertThat(exception.getCause()).hasCauseThat().isInstanceOf(UpdateException.class);
    assertThat(exception.getCause().getCause())
        .hasCauseThat()
        .isInstanceOf(LockFailureException.class);

    // Check that the change was not updated.
    notes = changeNotesFactory.create(project, changeId);
    assertThat(notes.getChange().getStatus()).isEqualTo(Change.Status.NEW);
  }

  private Change.Id createChange() throws Exception {
    Change.Id id = Change.id(sequences.nextChangeId());
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.insertChange(
          changeInserterFactory.create(
              id, repo.commit().message("Change").insertChangeId().create(), "refs/heads/master"));
      bu.execute();
    }
    return id;
  }

  private Change.Id createChangeWithUpdates(int totalUpdates) throws Exception {
    checkArgument(totalUpdates > 0);
    checkArgument(totalUpdates <= MAX_UPDATES);
    Change.Id id = Change.id(sequences.nextChangeId());
    try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
      bu.insertChange(
          changeInserterFactory.create(
              id, repo.commit().message("Change").insertChangeId().create(), "refs/heads/master"));
      bu.execute();
    }
    assertThat(getUpdateCount(id)).isEqualTo(1);
    for (int i = 2; i <= totalUpdates; i++) {
      try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
        bu.addOp(id, new AddMessageOp("Update " + i));
        bu.execute();
      }
    }
    assertThat(getUpdateCount(id)).isEqualTo(totalUpdates);
    return id;
  }

  private Change.Id createChangeWithPatchSets(int patchSets) throws Exception {
    checkArgument(patchSets >= 2);
    Change.Id id = createChangeWithUpdates(MAX_UPDATES - 2);
    ChangeNotes notes = changeNotesFactory.create(project, id);
    for (int i = 2; i <= patchSets; ++i) {
      try (BatchUpdate bu = batchUpdateFactory.create(project, user.get(), TimeUtil.now())) {
        ObjectId commitId =
            repo.amend(notes.getCurrentPatchSet().commitId()).message("PS" + i).create();
        bu.addOp(
            id,
            patchSetInserterFactory
                .create(notes, PatchSet.id(id, i), commitId)
                .setMessage("Add PS" + i));
        bu.execute();
      }
    }
    return id;
  }

  private static class AddMessageOp implements BatchUpdateOp {
    private final String message;
    @Nullable private final PatchSet.Id psId;

    AddMessageOp(String message) {
      this(message, null);
    }

    AddMessageOp(String message, PatchSet.Id psId) {
      this.message = message;
      this.psId = psId;
    }

    @Override
    public boolean updateChange(ChangeContext ctx) throws Exception {
      PatchSet.Id psIdToUpdate = psId;
      if (psIdToUpdate == null) {
        psIdToUpdate = ctx.getChange().currentPatchSetId();
      } else {
        checkState(
            ctx.getNotes().getPatchSets().containsKey(psIdToUpdate),
            "%s not in %s",
            psIdToUpdate,
            ctx.getNotes().getPatchSets().keySet());
      }
      ctx.getUpdate(psIdToUpdate).setChangeMessage(message);
      return true;
    }
  }

  private int getUpdateCount(Change.Id changeId) {
    return changeNotesFactory.create(project, changeId).getUpdateCount();
  }

  private ObjectId getMetaId(Change.Id changeId) throws Exception {
    return repo.getRepository().exactRef(RefNames.changeMetaRef(changeId)).getObjectId();
  }

  private static class SubmitOp implements BatchUpdateOp {
    @Override
    public boolean updateChange(ChangeContext ctx) throws Exception {
      SubmitRecord sr = new SubmitRecord();
      sr.status = SubmitRecord.Status.OK;
      SubmitRecord.Label cr = new SubmitRecord.Label();
      cr.status = SubmitRecord.Label.Status.OK;
      cr.appliedBy = ctx.getAccountId();
      cr.label = "Code-Review";
      sr.labels = ImmutableList.of(cr);
      ChangeUpdate update = ctx.getUpdate(ctx.getChange().currentPatchSetId());
      update.merge(new SubmissionId(ctx.getChange()), ImmutableList.of(sr));
      update.setChangeMessage("Submitted");
      return true;
    }
  }

  private static class TestOp implements BatchUpdateOp {
    CurrentUser updateRepoUser;
    CurrentUser updateChangeUser;
    CurrentUser postUpdateUser;

    private List<Account.Id> reviewersToAdd = new ArrayList<>();

    TestOp addReviewer(Account.Id accountId) {
      reviewersToAdd.add(accountId);
      return this;
    }

    @Override
    public void updateRepo(RepoContext ctx) {
      updateRepoUser = ctx.getUser();
    }

    @Override
    public boolean updateChange(ChangeContext ctx) {
      updateChangeUser = ctx.getUser();

      reviewersToAdd.forEach(
          accountId ->
              ctx.getUpdate(ctx.getChange().currentPatchSetId())
                  .putReviewer(accountId, ReviewerStateInternal.REVIEWER));
      return true;
    }

    @Override
    public void postUpdate(PostUpdateContext ctx) {
      postUpdateUser = ctx.getUser();
    }
  }
}