// Copyright (C) 2015 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.restapi.change;

import static com.google.common.collect.ImmutableList.toImmutableList;
import static com.google.gerrit.extensions.api.changes.SubmittedTogetherOption.NON_VISIBLE_CHANGES;
import static com.google.gerrit.extensions.api.changes.SubmittedTogetherOption.TOPIC_CLOSURE;
import static java.util.Collections.reverseOrder;

import com.google.common.collect.ImmutableList;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.entities.Change;
import com.google.gerrit.exceptions.StorageException;
import com.google.gerrit.extensions.api.changes.SubmittedTogetherInfo;
import com.google.gerrit.extensions.api.changes.SubmittedTogetherOption;
import com.google.gerrit.extensions.client.ListChangesOption;
import com.google.gerrit.extensions.restapi.AuthException;
import com.google.gerrit.extensions.restapi.BadRequestException;
import com.google.gerrit.extensions.restapi.ResourceConflictException;
import com.google.gerrit.extensions.restapi.Response;
import com.google.gerrit.extensions.restapi.RestReadView;
import com.google.gerrit.server.change.ChangeJson;
import com.google.gerrit.server.change.ChangeResource;
import com.google.gerrit.server.change.WalkSorter;
import com.google.gerrit.server.change.WalkSorter.PatchSetData;
import com.google.gerrit.server.permissions.PermissionBackendException;
import com.google.gerrit.server.query.change.ChangeData;
import com.google.gerrit.server.query.change.InternalChangeQuery;
import com.google.gerrit.server.submit.ChangeSet;
import com.google.gerrit.server.submit.MergeSuperSet;
import com.google.inject.Inject;
import com.google.inject.Provider;
import java.io.IOException;
import java.util.Collections;
import java.util.Comparator;
import java.util.EnumSet;
import java.util.List;
import java.util.Set;
import org.kohsuke.args4j.Option;

public class SubmittedTogether implements RestReadView<ChangeResource> {
  private static final FluentLogger logger = FluentLogger.forEnclosingClass();

  private final EnumSet<SubmittedTogetherOption> options =
      EnumSet.noneOf(SubmittedTogetherOption.class);

  private final EnumSet<ListChangesOption> jsonOpt =
      EnumSet.of(ListChangesOption.CURRENT_REVISION, ListChangesOption.SUBMITTABLE);

  private static final Comparator<ChangeData> COMPARATOR =
      Comparator.comparing(ChangeData::project)
          .thenComparing(cd -> cd.getId().get(), reverseOrder());

  private final ChangeJson.Factory json;
  private final Provider<InternalChangeQuery> queryProvider;
  private final Provider<MergeSuperSet> mergeSuperSet;
  private final Provider<WalkSorter> sorter;

  @Option(name = "-o", usage = "Output options")
  void addOption(String option) {
    for (ListChangesOption o : ListChangesOption.values()) {
      if (o.name().equalsIgnoreCase(option)) {
        jsonOpt.add(o);
        return;
      }
    }

    for (SubmittedTogetherOption o : SubmittedTogetherOption.values()) {
      if (o.name().equalsIgnoreCase(option)) {
        options.add(o);
        return;
      }
    }

    throw new IllegalArgumentException("option not recognized: " + option);
  }

  @Inject
  SubmittedTogether(
      ChangeJson.Factory json,
      Provider<InternalChangeQuery> queryProvider,
      Provider<MergeSuperSet> mergeSuperSet,
      Provider<WalkSorter> sorter) {
    this.json = json;
    this.queryProvider = queryProvider;
    this.mergeSuperSet = mergeSuperSet;
    this.sorter = sorter;
  }

  public SubmittedTogether addListChangesOption(Set<ListChangesOption> o) {
    jsonOpt.addAll(o);
    return this;
  }

  public SubmittedTogether addSubmittedTogetherOption(Set<SubmittedTogetherOption> o) {
    options.addAll(o);
    return this;
  }

  @Override
  public Response<Object> apply(ChangeResource resource)
      throws AuthException, BadRequestException, ResourceConflictException, IOException,
          PermissionBackendException {
    SubmittedTogetherInfo info = applyInfo(resource);
    if (options.isEmpty()) {
      return Response.ok(info.changes);
    }
    return Response.ok(info);
  }

  public SubmittedTogetherInfo applyInfo(ChangeResource resource)
      throws AuthException, IOException, PermissionBackendException {
    Change c = resource.getChange();
    try {
      List<ChangeData> cds;
      int hidden;

      if (c.isNew()) {
        ChangeSet cs =
            mergeSuperSet
                .get()
                .completeChangeSet(c, resource.getUser(), options.contains(TOPIC_CLOSURE));
        cds = ensureRequiredDataIsLoaded(cs.changes().asList());
        hidden = cs.nonVisibleChanges().size();
      } else if (c.isMerged()) {
        cds = queryProvider.get().bySubmissionId(c.getSubmissionId());
        hidden = 0;
      } else {
        cds = Collections.emptyList();
        hidden = 0;
      }

      if (hidden != 0 && !options.contains(NON_VISIBLE_CHANGES)) {
        throw new AuthException("change would be submitted with a change that you cannot see");
      }

      cds = sort(cds, hidden);
      SubmittedTogetherInfo info = new SubmittedTogetherInfo();
      info.changes = json.create(jsonOpt).format(cds);
      info.nonVisibleChanges = hidden;
      return info;
    } catch (StorageException | IOException e) {
      logger.atSevere().withCause(e).log("Error on getting a ChangeSet");
      throw e;
    }
  }

  private ImmutableList<ChangeData> sort(List<ChangeData> cds, int hidden) throws IOException {
    if (cds.size() <= 1 && hidden == 0) {
      // Skip sorting for singleton lists, to avoid WalkSorter opening the
      // repo just to fill out the commit field in PatchSetData.
      return ImmutableList.of();
    }

    long numProjectsDistinct = cds.stream().map(ChangeData::project).distinct().count();
    long numProjects = cds.stream().map(ChangeData::project).count();

    if (numProjects == numProjectsDistinct || numProjectsDistinct > 5) {
      // We either have only a single change per project which means that WalkSorter won't make a
      // difference compared to our index-backed sort, or we are looking at more than 5 projects
      // which would make WalkSorter too expensive for this call.
      return cds.stream().sorted(COMPARATOR).collect(toImmutableList());
    }

    // Perform more expensive walk-sort.
    ImmutableList.Builder<ChangeData> sorted = ImmutableList.builderWithExpectedSize(cds.size());
    for (PatchSetData psd : sorter.get().sort(cds)) {
      sorted.add(psd.data());
    }
    return sorted.build();
  }

  private static List<ChangeData> ensureRequiredDataIsLoaded(List<ChangeData> cds) {
    // TODO(hiesel): Instead of calling these manually, either implement a helper that brings a
    // database-backed change on-par with an index-backed change in terms of the populated fields in
    // ChangeData or check if any of the ChangeDatas was loaded from the database and allow
    // lazyloading if so.
    for (ChangeData cd : cds) {
      cd.submitRecords(ChangeJson.SUBMIT_RULE_OPTIONS_LENIENT);
      cd.submitRecords(ChangeJson.SUBMIT_RULE_OPTIONS_STRICT);
      cd.currentPatchSet();
    }
    return cds;
  }
}
