// Copyright (C) 2012 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.change;

import static com.google.gerrit.extensions.client.ListChangesOption.ALL_COMMITS;
import static com.google.gerrit.extensions.client.ListChangesOption.ALL_REVISIONS;
import static com.google.gerrit.extensions.client.ListChangesOption.CHANGE_ACTIONS;
import static com.google.gerrit.extensions.client.ListChangesOption.CHECK;
import static com.google.gerrit.extensions.client.ListChangesOption.COMMIT_FOOTERS;
import static com.google.gerrit.extensions.client.ListChangesOption.CURRENT_ACTIONS;
import static com.google.gerrit.extensions.client.ListChangesOption.CURRENT_COMMIT;
import static com.google.gerrit.extensions.client.ListChangesOption.CURRENT_REVISION;
import static com.google.gerrit.extensions.client.ListChangesOption.DETAILED_ACCOUNTS;
import static com.google.gerrit.extensions.client.ListChangesOption.DETAILED_LABELS;
import static com.google.gerrit.extensions.client.ListChangesOption.LABELS;
import static com.google.gerrit.extensions.client.ListChangesOption.MESSAGES;
import static com.google.gerrit.extensions.client.ListChangesOption.REVIEWED;
import static com.google.gerrit.extensions.client.ListChangesOption.REVIEWER_UPDATES;
import static com.google.gerrit.extensions.client.ListChangesOption.SKIP_MERGEABLE;
import static com.google.gerrit.extensions.client.ListChangesOption.SUBMITTABLE;
import static com.google.gerrit.extensions.client.ListChangesOption.TRACKING_IDS;
import static com.google.gerrit.server.ChangeMessagesUtil.createChangeMessageInfo;
import static java.util.stream.Collectors.toList;

import com.google.common.base.Joiner;
import com.google.common.base.MoreObjects;
import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.common.data.SubmitRecord;
import com.google.gerrit.common.data.SubmitRecord.Status;
import com.google.gerrit.common.data.SubmitRequirement;
import com.google.gerrit.common.data.SubmitTypeRecord;
import com.google.gerrit.exceptions.StorageException;
import com.google.gerrit.extensions.api.changes.FixInput;
import com.google.gerrit.extensions.client.ListChangesOption;
import com.google.gerrit.extensions.client.ReviewerState;
import com.google.gerrit.extensions.common.AccountInfo;
import com.google.gerrit.extensions.common.ApprovalInfo;
import com.google.gerrit.extensions.common.ChangeInfo;
import com.google.gerrit.extensions.common.ChangeMessageInfo;
import com.google.gerrit.extensions.common.LabelInfo;
import com.google.gerrit.extensions.common.ProblemInfo;
import com.google.gerrit.extensions.common.ReviewerUpdateInfo;
import com.google.gerrit.extensions.common.RevisionInfo;
import com.google.gerrit.extensions.common.SubmitRequirementInfo;
import com.google.gerrit.extensions.common.TrackingIdInfo;
import com.google.gerrit.extensions.restapi.Url;
import com.google.gerrit.index.query.QueryResult;
import com.google.gerrit.mail.Address;
import com.google.gerrit.metrics.Description;
import com.google.gerrit.metrics.Description.Units;
import com.google.gerrit.metrics.MetricMaker;
import com.google.gerrit.metrics.Timer0;
import com.google.gerrit.reviewdb.client.Account;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.ChangeMessage;
import com.google.gerrit.reviewdb.client.PatchSet;
import com.google.gerrit.reviewdb.client.PatchSetApproval;
import com.google.gerrit.reviewdb.client.Project;
import com.google.gerrit.server.ChangeMessagesUtil;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.GpgException;
import com.google.gerrit.server.ReviewerByEmailSet;
import com.google.gerrit.server.ReviewerSet;
import com.google.gerrit.server.ReviewerStatusUpdate;
import com.google.gerrit.server.StarredChangesUtil;
import com.google.gerrit.server.account.AccountInfoComparator;
import com.google.gerrit.server.account.AccountLoader;
import com.google.gerrit.server.config.GerritServerConfig;
import com.google.gerrit.server.config.TrackingFooters;
import com.google.gerrit.server.index.change.ChangeField;
import com.google.gerrit.server.notedb.ChangeNotes;
import com.google.gerrit.server.notedb.ReviewerStateInternal;
import com.google.gerrit.server.patch.PatchListNotAvailableException;
import com.google.gerrit.server.permissions.ChangePermission;
import com.google.gerrit.server.permissions.PermissionBackend;
import com.google.gerrit.server.permissions.PermissionBackendException;
import com.google.gerrit.server.project.RemoveReviewerControl;
import com.google.gerrit.server.project.SubmitRuleOptions;
import com.google.gerrit.server.query.change.ChangeData;
import com.google.gerrit.server.query.change.ChangeData.ChangedLines;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.Singleton;
import com.google.inject.assistedinject.Assisted;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.function.Supplier;
import org.eclipse.jgit.lib.Config;

/**
 * Produces {@link ChangeInfo} (which is serialized to JSON afterwards) from {@link ChangeData}.
 *
 * <p>This is intended to be used on request scope, but may be used for converting multiple {@link
 * ChangeData} objects from different sources.
 */
public class ChangeJson {
  private static final FluentLogger logger = FluentLogger.forEnclosingClass();

  public static final SubmitRuleOptions SUBMIT_RULE_OPTIONS_LENIENT =
      ChangeField.SUBMIT_RULE_OPTIONS_LENIENT.toBuilder().build();

  public static final SubmitRuleOptions SUBMIT_RULE_OPTIONS_STRICT =
      ChangeField.SUBMIT_RULE_OPTIONS_STRICT.toBuilder().build();

  static final ImmutableSet<ListChangesOption> REQUIRE_LAZY_LOAD =
      ImmutableSet.of(
          ALL_COMMITS,
          ALL_REVISIONS,
          CHANGE_ACTIONS,
          CHECK,
          COMMIT_FOOTERS,
          CURRENT_ACTIONS,
          CURRENT_COMMIT,
          MESSAGES);

  @Singleton
  public static class Factory {
    private final AssistedFactory factory;

    @Inject
    Factory(AssistedFactory factory) {
      this.factory = factory;
    }

    public ChangeJson noOptions() {
      return create(ImmutableSet.of());
    }

    public ChangeJson create(Iterable<ListChangesOption> options) {
      return factory.create(options, Optional.empty());
    }

    public ChangeJson create(
        Iterable<ListChangesOption> options,
        PluginDefinedAttributesFactory pluginDefinedAttributesFactory) {
      return factory.create(options, Optional.of(pluginDefinedAttributesFactory));
    }

    public ChangeJson create(ListChangesOption first, ListChangesOption... rest) {
      return create(Sets.immutableEnumSet(first, rest));
    }
  }

  public interface AssistedFactory {
    ChangeJson create(
        Iterable<ListChangesOption> options,
        Optional<PluginDefinedAttributesFactory> pluginDefinedAttributesFactory);
  }

  @Singleton
  private static class Metrics {
    private final Timer0 toChangeInfoLatency;
    private final Timer0 toChangeInfosLatency;
    private final Timer0 formatQueryResultsLatency;

    @Inject
    Metrics(MetricMaker metricMaker) {
      toChangeInfoLatency =
          metricMaker.newTimer(
              "http/server/rest_api/change_json/to_change_info_latency",
              new Description("Latency for toChangeInfo invocations in ChangeJson")
                  .setCumulative()
                  .setUnit(Units.MILLISECONDS));
      toChangeInfosLatency =
          metricMaker.newTimer(
              "http/server/rest_api/change_json/to_change_infos_latency",
              new Description("Latency for toChangeInfos invocations in ChangeJson")
                  .setCumulative()
                  .setUnit(Units.MILLISECONDS));
      formatQueryResultsLatency =
          metricMaker.newTimer(
              "http/server/rest_api/change_json/format_query_results_latency",
              new Description("Latency for formatQueryResults invocations in ChangeJson")
                  .setCumulative()
                  .setUnit(Units.MILLISECONDS));
    }
  }

  private final Provider<CurrentUser> userProvider;
  private final PermissionBackend permissionBackend;
  private final ChangeData.Factory changeDataFactory;
  private final AccountLoader.Factory accountLoaderFactory;
  private final ImmutableSet<ListChangesOption> options;
  private final ChangeMessagesUtil cmUtil;
  private final Provider<ConsistencyChecker> checkerProvider;
  private final ActionJson actionJson;
  private final ChangeNotes.Factory notesFactory;
  private final LabelsJson labelsJson;
  private final RemoveReviewerControl removeReviewerControl;
  private final TrackingFooters trackingFooters;
  private final Metrics metrics;
  private final RevisionJson revisionJson;
  private final Optional<PluginDefinedAttributesFactory> pluginDefinedAttributesFactory;
  private final boolean excludeMergeableInChangeInfo;
  private final boolean lazyLoad;

  private AccountLoader accountLoader;
  private FixInput fix;

  @Inject
  ChangeJson(
      Provider<CurrentUser> user,
      PermissionBackend permissionBackend,
      ChangeData.Factory cdf,
      AccountLoader.Factory ailf,
      ChangeMessagesUtil cmUtil,
      Provider<ConsistencyChecker> checkerProvider,
      ActionJson actionJson,
      ChangeNotes.Factory notesFactory,
      LabelsJson.Factory labelsJsonFactory,
      RemoveReviewerControl removeReviewerControl,
      TrackingFooters trackingFooters,
      Metrics metrics,
      RevisionJson.Factory revisionJsonFactory,
      @GerritServerConfig Config cfg,
      @Assisted Iterable<ListChangesOption> options,
      @Assisted Optional<PluginDefinedAttributesFactory> pluginDefinedAttributesFactory) {
    this.userProvider = user;
    this.changeDataFactory = cdf;
    this.permissionBackend = permissionBackend;
    this.accountLoaderFactory = ailf;
    this.cmUtil = cmUtil;
    this.checkerProvider = checkerProvider;
    this.actionJson = actionJson;
    this.notesFactory = notesFactory;
    this.labelsJson = labelsJsonFactory.create(options);
    this.removeReviewerControl = removeReviewerControl;
    this.trackingFooters = trackingFooters;
    this.metrics = metrics;
    this.revisionJson = revisionJsonFactory.create(options);
    this.options = Sets.immutableEnumSet(options);
    this.excludeMergeableInChangeInfo =
        cfg.getBoolean("change", "api", "excludeMergeableInChangeInfo", false);
    this.lazyLoad = containsAnyOf(this.options, REQUIRE_LAZY_LOAD);
    this.pluginDefinedAttributesFactory = pluginDefinedAttributesFactory;

    logger.atFine().log("options = %s", options);
  }

  public ChangeJson fix(FixInput fix) {
    this.fix = fix;
    return this;
  }

  public ChangeInfo format(ChangeResource rsrc) {
    return format(changeDataFactory.create(rsrc.getNotes()));
  }

  public ChangeInfo format(Change change) {
    return format(changeDataFactory.create(change));
  }

  public ChangeInfo format(Project.NameKey project, Change.Id id) {
    return format(project, id, ChangeInfo::new);
  }

  public ChangeInfo format(ChangeData cd) {
    return format(cd, Optional.empty(), true, ChangeInfo::new);
  }

  public ChangeInfo format(RevisionResource rsrc) {
    ChangeData cd = changeDataFactory.create(rsrc.getNotes());
    return format(cd, Optional.of(rsrc.getPatchSet().getId()), true, ChangeInfo::new);
  }

  public List<List<ChangeInfo>> format(List<QueryResult<ChangeData>> in)
      throws PermissionBackendException {
    try (Timer0.Context ignored = metrics.formatQueryResultsLatency.start()) {
      accountLoader = accountLoaderFactory.create(has(DETAILED_ACCOUNTS));
      List<List<ChangeInfo>> res = new ArrayList<>(in.size());
      Map<Change.Id, ChangeInfo> cache = Maps.newHashMapWithExpectedSize(in.size());
      for (QueryResult<ChangeData> r : in) {
        List<ChangeInfo> infos = toChangeInfos(r.entities(), cache);
        if (!infos.isEmpty() && r.more()) {
          infos.get(infos.size() - 1)._moreChanges = true;
        }
        res.add(infos);
      }
      accountLoader.fill();
      return res;
    }
  }

  public List<ChangeInfo> format(Collection<ChangeData> in) throws PermissionBackendException {
    accountLoader = accountLoaderFactory.create(has(DETAILED_ACCOUNTS));
    ensureLoaded(in);
    List<ChangeInfo> out = new ArrayList<>(in.size());
    for (ChangeData cd : in) {
      out.add(format(cd, Optional.empty(), false, ChangeInfo::new));
    }
    accountLoader.fill();
    return out;
  }

  public <I extends ChangeInfo> I format(
      Project.NameKey project, Change.Id id, Supplier<I> changeInfoSupplier) {
    ChangeNotes notes;
    try {
      notes = notesFactory.createChecked(project, id);
    } catch (StorageException e) {
      if (!has(CHECK)) {
        throw e;
      }
      return checkOnly(changeDataFactory.create(project, id), changeInfoSupplier);
    }
    return format(changeDataFactory.create(notes), Optional.empty(), true, changeInfoSupplier);
  }

  private static Collection<SubmitRequirementInfo> requirementsFor(ChangeData cd) {
    Collection<SubmitRequirementInfo> reqInfos = new ArrayList<>();
    for (SubmitRecord submitRecord : cd.submitRecords(SUBMIT_RULE_OPTIONS_STRICT)) {
      if (submitRecord.requirements == null) {
        continue;
      }
      for (SubmitRequirement requirement : submitRecord.requirements) {
        reqInfos.add(requirementToInfo(requirement, submitRecord.status));
      }
    }
    return reqInfos;
  }

  private static SubmitRequirementInfo requirementToInfo(SubmitRequirement req, Status status) {
    return new SubmitRequirementInfo(status.name(), req.fallbackText(), req.type(), req.data());
  }

  private static void finish(ChangeInfo info) {
    info.id =
        Joiner.on('~')
            .join(Url.encode(info.project), Url.encode(info.branch), Url.encode(info.changeId));
  }

  private static boolean containsAnyOf(
      ImmutableSet<ListChangesOption> set, ImmutableSet<ListChangesOption> toFind) {
    return !Sets.intersection(toFind, set).isEmpty();
  }

  private <I extends ChangeInfo> I format(
      ChangeData cd,
      Optional<PatchSet.Id> limitToPsId,
      boolean fillAccountLoader,
      Supplier<I> changeInfoSupplier) {
    try {
      if (fillAccountLoader) {
        accountLoader = accountLoaderFactory.create(has(DETAILED_ACCOUNTS));
        I res = toChangeInfo(cd, limitToPsId, changeInfoSupplier);
        accountLoader.fill();
        return res;
      }
      return toChangeInfo(cd, limitToPsId, changeInfoSupplier);
    } catch (PatchListNotAvailableException
        | GpgException
        | IOException
        | PermissionBackendException
        | RuntimeException e) {
      if (!has(CHECK)) {
        Throwables.throwIfInstanceOf(e, StorageException.class);
        throw new StorageException(e);
      }
      return checkOnly(cd, changeInfoSupplier);
    }
  }

  private void ensureLoaded(Iterable<ChangeData> all) {
    if (lazyLoad) {
      ChangeData.ensureChangeLoaded(all);
      if (has(ALL_REVISIONS)) {
        ChangeData.ensureAllPatchSetsLoaded(all);
      } else if (has(CURRENT_REVISION) || has(MESSAGES)) {
        ChangeData.ensureCurrentPatchSetLoaded(all);
      }
      if (has(REVIEWED) && userProvider.get().isIdentifiedUser()) {
        ChangeData.ensureReviewedByLoadedForOpenChanges(all);
      }
      ChangeData.ensureCurrentApprovalsLoaded(all);
    } else {
      for (ChangeData cd : all) {
        cd.setLazyLoad(false);
      }
    }
  }

  private boolean has(ListChangesOption option) {
    return options.contains(option);
  }

  private List<ChangeInfo> toChangeInfos(
      List<ChangeData> changes, Map<Change.Id, ChangeInfo> cache) {
    try (Timer0.Context ignored = metrics.toChangeInfosLatency.start()) {
      List<ChangeInfo> changeInfos = new ArrayList<>(changes.size());
      for (int i = 0; i < changes.size(); i++) {
        // We can only cache and re-use an entity if it's not the last in the list. The last entity
        // may later get _moreChanges set. If it was cached or re-used, that setting would propagate
        // to the original entity yielding wrong results.
        // This problem has two sides where 'last in the list' has to be respected:
        // (1) Caching
        // (2) Reusing
        boolean isCacheable = i != changes.size() - 1;
        ChangeData cd = changes.get(i);
        ChangeInfo info = cache.get(cd.getId());
        if (info != null && isCacheable) {
          changeInfos.add(info);
          continue;
        }

        // Compute and cache if possible
        try {
          ensureLoaded(Collections.singleton(cd));
          info = format(cd, Optional.empty(), false, ChangeInfo::new);
          changeInfos.add(info);
          if (isCacheable) {
            cache.put(new Change.Id(info._number), info);
          }
        } catch (RuntimeException e) {
          logger.atWarning().withCause(e).log(
              "Omitting corrupt change %s from results", cd.getId());
        }
      }
      return changeInfos;
    }
  }

  private <I extends ChangeInfo> I checkOnly(ChangeData cd, Supplier<I> changeInfoSupplier) {
    ChangeNotes notes;
    try {
      notes = cd.notes();
    } catch (StorageException e) {
      String msg = "Error loading change";
      logger.atWarning().withCause(e).log(msg + " %s", cd.getId());
      I info = changeInfoSupplier.get();
      info._number = cd.getId().get();
      ProblemInfo p = new ProblemInfo();
      p.message = msg;
      info.problems = Lists.newArrayList(p);
      return info;
    }

    ConsistencyChecker.Result result = checkerProvider.get().check(notes, fix);
    I info = changeInfoSupplier.get();
    Change c = result.change();
    if (c != null) {
      info.project = c.getProject().get();
      info.branch = c.getDest().getShortName();
      info.topic = c.getTopic();
      info.changeId = c.getKey().get();
      info.subject = c.getSubject();
      info.status = c.getStatus().asChangeStatus();
      info.owner = new AccountInfo(c.getOwner().get());
      info.created = c.getCreatedOn();
      info.updated = c.getLastUpdatedOn();
      info._number = c.getId().get();
      info.problems = result.problems();
      info.isPrivate = c.isPrivate() ? true : null;
      info.workInProgress = c.isWorkInProgress() ? true : null;
      info.hasReviewStarted = c.hasReviewStarted();
      finish(info);
    } else {
      info._number = result.id().get();
      info.problems = result.problems();
    }
    return info;
  }

  private <I extends ChangeInfo> I toChangeInfo(
      ChangeData cd, Optional<PatchSet.Id> limitToPsId, Supplier<I> changeInfoSupplier)
      throws PatchListNotAvailableException, GpgException, PermissionBackendException, IOException {
    try (Timer0.Context ignored = metrics.toChangeInfoLatency.start()) {
      return toChangeInfoImpl(cd, limitToPsId, changeInfoSupplier);
    }
  }

  private <I extends ChangeInfo> I toChangeInfoImpl(
      ChangeData cd, Optional<PatchSet.Id> limitToPsId, Supplier<I> changeInfoSupplier)
      throws PatchListNotAvailableException, GpgException, PermissionBackendException, IOException {
    I out = changeInfoSupplier.get();
    CurrentUser user = userProvider.get();

    if (has(CHECK)) {
      out.problems = checkerProvider.get().check(cd.notes(), fix).problems();
      // If any problems were fixed, the ChangeData needs to be reloaded.
      for (ProblemInfo p : out.problems) {
        if (p.status == ProblemInfo.Status.FIXED) {
          cd = changeDataFactory.create(cd.project(), cd.getId());
          break;
        }
      }
    }

    Change in = cd.change();
    out.project = in.getProject().get();
    out.branch = in.getDest().getShortName();
    out.topic = in.getTopic();
    out.assignee = in.getAssignee() != null ? accountLoader.get(in.getAssignee()) : null;
    out.hashtags = cd.hashtags();
    out.changeId = in.getKey().get();
    if (in.isNew()) {
      SubmitTypeRecord str = cd.submitTypeRecord();
      if (str.isOk()) {
        out.submitType = str.type;
      }
      if (!excludeMergeableInChangeInfo && !has(SKIP_MERGEABLE)) {
        out.mergeable = cd.isMergeable();
      }
      if (has(SUBMITTABLE)) {
        out.submittable = submittable(cd);
      }
    }
    Optional<ChangedLines> changedLines = cd.changedLines();
    if (changedLines.isPresent()) {
      out.insertions = changedLines.get().insertions;
      out.deletions = changedLines.get().deletions;
    }
    out.isPrivate = in.isPrivate() ? true : null;
    out.workInProgress = in.isWorkInProgress() ? true : null;
    out.hasReviewStarted = in.hasReviewStarted();
    out.subject = in.getSubject();
    out.status = in.getStatus().asChangeStatus();
    out.owner = accountLoader.get(in.getOwner());
    out.created = in.getCreatedOn();
    out.updated = in.getLastUpdatedOn();
    out._number = in.getId().get();
    out.totalCommentCount = cd.totalCommentCount();
    out.unresolvedCommentCount = cd.unresolvedCommentCount();

    if (user.isIdentifiedUser()) {
      Collection<String> stars = cd.stars(user.getAccountId());
      out.starred = stars.contains(StarredChangesUtil.DEFAULT_LABEL) ? true : null;
      if (!stars.isEmpty()) {
        out.stars = stars;
      }
    }

    if (in.isNew() && has(REVIEWED) && user.isIdentifiedUser()) {
      out.reviewed = cd.isReviewedBy(user.getAccountId()) ? true : null;
    }

    out.labels = labelsJson.labelsFor(accountLoader, cd, has(LABELS), has(DETAILED_LABELS));
    out.requirements = requirementsFor(cd);

    if (out.labels != null && has(DETAILED_LABELS)) {
      // If limited to specific patch sets but not the current patch set, don't
      // list permitted labels, since users can't vote on those patch sets.
      if (user.isIdentifiedUser()
          && (!limitToPsId.isPresent() || limitToPsId.get().equals(in.currentPatchSetId()))) {
        out.permittedLabels =
            !cd.change().isAbandoned()
                ? labelsJson.permittedLabels(user.getAccountId(), cd)
                : ImmutableMap.of();
      }

      out.reviewers = reviewerMap(cd.reviewers(), cd.reviewersByEmail(), false);
      out.pendingReviewers = reviewerMap(cd.pendingReviewers(), cd.pendingReviewersByEmail(), true);
      out.removableReviewers = removableReviewers(cd, out);
    }

    setSubmitter(cd, out);
    if (pluginDefinedAttributesFactory.isPresent()) {
      out.plugins = pluginDefinedAttributesFactory.get().create(cd);
    }
    out.revertOf = cd.change().getRevertOf() != null ? cd.change().getRevertOf().get() : null;

    if (has(REVIEWER_UPDATES)) {
      out.reviewerUpdates = reviewerUpdates(cd);
    }

    boolean needMessages = has(MESSAGES);
    boolean needRevisions = has(ALL_REVISIONS) || has(CURRENT_REVISION) || limitToPsId.isPresent();
    Map<PatchSet.Id, PatchSet> src;
    if (needMessages || needRevisions) {
      src = loadPatchSets(cd, limitToPsId);
    } else {
      src = null;
    }

    if (needMessages) {
      out.messages = messages(cd);
    }
    finish(out);

    // This block must come after the ChangeInfo is mostly populated, since
    // it will be passed to ActionVisitors as-is.
    if (needRevisions) {
      out.revisions = revisionJson.getRevisions(accountLoader, cd, src, limitToPsId, out);
      if (out.revisions != null) {
        for (Map.Entry<String, RevisionInfo> entry : out.revisions.entrySet()) {
          if (entry.getValue().isCurrent) {
            out.currentRevision = entry.getKey();
            break;
          }
        }
      }
    }

    if (has(CURRENT_ACTIONS) || has(CHANGE_ACTIONS)) {
      actionJson.addChangeActions(out, cd.notes());
    }

    if (has(TRACKING_IDS)) {
      ListMultimap<String, String> set = trackingFooters.extract(cd.commitFooters());
      out.trackingIds =
          set.entries().stream()
              .map(e -> new TrackingIdInfo(e.getKey(), e.getValue()))
              .collect(toList());
    }

    return out;
  }

  private Map<ReviewerState, Collection<AccountInfo>> reviewerMap(
      ReviewerSet reviewers, ReviewerByEmailSet reviewersByEmail, boolean includeRemoved) {
    Map<ReviewerState, Collection<AccountInfo>> reviewerMap = new HashMap<>();
    for (ReviewerStateInternal state : ReviewerStateInternal.values()) {
      if (!includeRemoved && state == ReviewerStateInternal.REMOVED) {
        continue;
      }
      Collection<AccountInfo> reviewersByState = toAccountInfo(reviewers.byState(state));
      reviewersByState.addAll(toAccountInfoByEmail(reviewersByEmail.byState(state)));
      if (!reviewersByState.isEmpty()) {
        reviewerMap.put(state.asReviewerState(), reviewersByState);
      }
    }
    return reviewerMap;
  }

  private Collection<ReviewerUpdateInfo> reviewerUpdates(ChangeData cd) {
    List<ReviewerStatusUpdate> reviewerUpdates = cd.reviewerUpdates();
    List<ReviewerUpdateInfo> result = new ArrayList<>(reviewerUpdates.size());
    for (ReviewerStatusUpdate c : reviewerUpdates) {
      ReviewerUpdateInfo change = new ReviewerUpdateInfo();
      change.updated = c.date();
      change.state = c.state().asReviewerState();
      change.updatedBy = accountLoader.get(c.updatedBy());
      change.reviewer = accountLoader.get(c.reviewer());
      result.add(change);
    }
    return result;
  }

  private boolean submittable(ChangeData cd) {
    return SubmitRecord.allRecordsOK(cd.submitRecords(SUBMIT_RULE_OPTIONS_STRICT));
  }

  private void setSubmitter(ChangeData cd, ChangeInfo out) {
    Optional<PatchSetApproval> s = cd.getSubmitApproval();
    if (!s.isPresent()) {
      return;
    }
    out.submitted = s.get().getGranted();
    out.submitter = accountLoader.get(s.get().getAccountId());
  }

  private Collection<ChangeMessageInfo> messages(ChangeData cd) {
    List<ChangeMessage> messages = cmUtil.byChange(cd.notes());
    if (messages.isEmpty()) {
      return Collections.emptyList();
    }

    List<ChangeMessageInfo> result = Lists.newArrayListWithCapacity(messages.size());
    for (ChangeMessage message : messages) {
      result.add(createChangeMessageInfo(message, accountLoader));
    }
    return result;
  }

  private Collection<AccountInfo> removableReviewers(ChangeData cd, ChangeInfo out)
      throws PermissionBackendException {
    // Although this is called removableReviewers, this method also determines
    // which CCs are removable.
    //
    // For reviewers, we need to look at each approval, because the reviewer
    // should only be considered removable if *all* of their approvals can be
    // removed. First, add all reviewers with *any* removable approval to the
    // "removable" set. Along the way, if we encounter a non-removable approval,
    // add the reviewer to the "fixed" set. Before we return, remove all members
    // of "fixed" from "removable", because not all of their approvals can be
    // removed.
    Collection<LabelInfo> labels = out.labels.values();
    Set<Account.Id> fixed = Sets.newHashSetWithExpectedSize(labels.size());
    Set<Account.Id> removable = Sets.newHashSetWithExpectedSize(labels.size());

    // Check if the user has the permission to remove a reviewer. This means we can bypass the
    // testRemoveReviewer check for a specific reviewer in the loop saving potentially many
    // permission checks.
    boolean canRemoveAnyReviewer =
        permissionBackendForChange(userProvider.get(), cd).test(ChangePermission.REMOVE_REVIEWER);
    for (LabelInfo label : labels) {
      if (label.all == null) {
        continue;
      }
      for (ApprovalInfo ai : label.all) {
        Account.Id id = new Account.Id(ai._accountId);

        if (canRemoveAnyReviewer
            || removeReviewerControl.testRemoveReviewer(
                cd, userProvider.get(), id, MoreObjects.firstNonNull(ai.value, 0))) {
          removable.add(id);
        } else {
          fixed.add(id);
        }
      }
    }

    // CCs are simpler than reviewers. They are removable if the ChangeControl
    // would permit a non-negative approval by that account to be removed, in
    // which case add them to removable. We don't need to add unremovable CCs to
    // "fixed" because we only visit each CC once here.
    Collection<AccountInfo> ccs = out.reviewers.get(ReviewerState.CC);
    if (ccs != null) {
      for (AccountInfo ai : ccs) {
        if (ai._accountId != null) {
          Account.Id id = new Account.Id(ai._accountId);
          if (canRemoveAnyReviewer
              || removeReviewerControl.testRemoveReviewer(cd, userProvider.get(), id, 0)) {
            removable.add(id);
          }
        }
      }
    }

    // Subtract any reviewers with non-removable approvals from the "removable"
    // set. This also subtracts any CCs that for some reason also hold
    // unremovable approvals.
    removable.removeAll(fixed);

    List<AccountInfo> result = Lists.newArrayListWithCapacity(removable.size());
    for (Account.Id id : removable) {
      result.add(accountLoader.get(id));
    }
    // Reviewers added by email are always removable
    for (Collection<AccountInfo> infos : out.reviewers.values()) {
      for (AccountInfo info : infos) {
        if (info._accountId == null) {
          result.add(info);
        }
      }
    }
    return result;
  }

  private Collection<AccountInfo> toAccountInfo(Collection<Account.Id> accounts) {
    return accounts.stream()
        .map(accountLoader::get)
        .sorted(AccountInfoComparator.ORDER_NULLS_FIRST)
        .collect(toList());
  }

  private Collection<AccountInfo> toAccountInfoByEmail(Collection<Address> addresses) {
    return addresses.stream()
        .map(a -> new AccountInfo(a.getName(), a.getEmail()))
        .sorted(AccountInfoComparator.ORDER_NULLS_FIRST)
        .collect(toList());
  }

  private Map<PatchSet.Id, PatchSet> loadPatchSets(
      ChangeData cd, Optional<PatchSet.Id> limitToPsId) {
    Collection<PatchSet> src;
    if (has(ALL_REVISIONS) || has(MESSAGES)) {
      src = cd.patchSets();
    } else {
      PatchSet ps;
      if (limitToPsId.isPresent()) {
        ps = cd.patchSet(limitToPsId.get());
        if (ps == null) {
          throw new StorageException("missing patch set " + limitToPsId.get());
        }
      } else {
        ps = cd.currentPatchSet();
        if (ps == null) {
          throw new StorageException("missing current patch set for change " + cd.getId());
        }
      }
      src = Collections.singletonList(ps);
    }
    Map<PatchSet.Id, PatchSet> map = Maps.newHashMapWithExpectedSize(src.size());
    for (PatchSet patchSet : src) {
      map.put(patchSet.getId(), patchSet);
    }
    return map;
  }

  /**
   * @return {@link com.google.gerrit.server.permissions.PermissionBackend.ForChange} constructed
   *     from either an index-backed or a database-backed {@link ChangeData} depending on {@code
   *     lazyload}.
   */
  private PermissionBackend.ForChange permissionBackendForChange(CurrentUser user, ChangeData cd) {
    PermissionBackend.WithUser withUser = permissionBackend.user(user);
    return lazyLoad
        ? withUser.change(cd)
        : withUser.indexedChange(cd, notesFactory.createFromIndexedChange(cd.change()));
  }
}