// 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.restapi.change;

import static com.google.common.base.MoreObjects.firstNonNull;
import static com.google.gerrit.extensions.conditions.BooleanCondition.and;
import static com.google.gerrit.server.permissions.RefPermission.CREATE_CHANGE;

import com.google.common.flogger.FluentLogger;
import com.google.gerrit.entities.Account;
import com.google.gerrit.entities.Change;
import com.google.gerrit.entities.ChangeMessage;
import com.google.gerrit.entities.PatchSet;
import com.google.gerrit.entities.Project;
import com.google.gerrit.extensions.api.changes.NotifyHandling;
import com.google.gerrit.extensions.api.changes.RevertInput;
import com.google.gerrit.extensions.common.ChangeInfo;
import com.google.gerrit.extensions.restapi.ResourceConflictException;
import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
import com.google.gerrit.extensions.restapi.Response;
import com.google.gerrit.extensions.restapi.RestApiException;
import com.google.gerrit.extensions.webui.UiAction;
import com.google.gerrit.server.ApprovalsUtil;
import com.google.gerrit.server.ChangeMessagesUtil;
import com.google.gerrit.server.ChangeUtil;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.PatchSetUtil;
import com.google.gerrit.server.ReviewerSet;
import com.google.gerrit.server.change.ChangeInserter;
import com.google.gerrit.server.change.ChangeJson;
import com.google.gerrit.server.change.ChangeResource;
import com.google.gerrit.server.change.NotifyResolver;
import com.google.gerrit.server.extensions.events.ChangeReverted;
import com.google.gerrit.server.git.CommitUtil;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.mail.send.RevertedSender;
import com.google.gerrit.server.notedb.ChangeNotes;
import com.google.gerrit.server.notedb.ReviewerStateInternal;
import com.google.gerrit.server.notedb.Sequences;
import com.google.gerrit.server.permissions.PermissionBackend;
import com.google.gerrit.server.permissions.PermissionBackendException;
import com.google.gerrit.server.project.ContributorAgreementsChecker;
import com.google.gerrit.server.project.NoSuchChangeException;
import com.google.gerrit.server.project.NoSuchProjectException;
import com.google.gerrit.server.project.ProjectCache;
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.Context;
import com.google.gerrit.server.update.RetryHelper;
import com.google.gerrit.server.update.RetryingRestModifyView;
import com.google.gerrit.server.update.UpdateException;
import com.google.gerrit.server.util.time.TimeUtil;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import java.sql.Timestamp;
import java.util.HashSet;
import java.util.Set;
import org.eclipse.jgit.errors.ConfigInvalidException;
import org.eclipse.jgit.errors.RepositoryNotFoundException;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;

@Singleton
public class Revert extends RetryingRestModifyView<ChangeResource, RevertInput, ChangeInfo>
    implements UiAction<ChangeResource> {
  private static final FluentLogger logger = FluentLogger.forEnclosingClass();

  private final PermissionBackend permissionBackend;
  private final GitRepositoryManager repoManager;
  private final ChangeInserter.Factory changeInserterFactory;
  private final ChangeMessagesUtil cmUtil;
  private final Sequences seq;
  private final PatchSetUtil psUtil;
  private final RevertedSender.Factory revertedSenderFactory;
  private final ChangeJson.Factory json;
  private final ApprovalsUtil approvalsUtil;
  private final ChangeReverted changeReverted;
  private final ContributorAgreementsChecker contributorAgreements;
  private final ProjectCache projectCache;
  private final NotifyResolver notifyResolver;
  private final CommitUtil commitUtil;

  @Inject
  Revert(
      PermissionBackend permissionBackend,
      GitRepositoryManager repoManager,
      ChangeInserter.Factory changeInserterFactory,
      ChangeMessagesUtil cmUtil,
      RetryHelper retryHelper,
      Sequences seq,
      PatchSetUtil psUtil,
      RevertedSender.Factory revertedSenderFactory,
      ChangeJson.Factory json,
      ApprovalsUtil approvalsUtil,
      ChangeReverted changeReverted,
      ContributorAgreementsChecker contributorAgreements,
      ProjectCache projectCache,
      NotifyResolver notifyResolver,
      CommitUtil commitUtil) {
    super(retryHelper);
    this.permissionBackend = permissionBackend;
    this.repoManager = repoManager;
    this.changeInserterFactory = changeInserterFactory;
    this.cmUtil = cmUtil;
    this.seq = seq;
    this.psUtil = psUtil;
    this.revertedSenderFactory = revertedSenderFactory;
    this.json = json;
    this.approvalsUtil = approvalsUtil;
    this.changeReverted = changeReverted;
    this.contributorAgreements = contributorAgreements;
    this.projectCache = projectCache;
    this.notifyResolver = notifyResolver;
    this.commitUtil = commitUtil;
  }

  @Override
  public Response<ChangeInfo> applyImpl(
      BatchUpdate.Factory updateFactory, ChangeResource rsrc, RevertInput input)
      throws IOException, RestApiException, UpdateException, NoSuchChangeException,
          PermissionBackendException, NoSuchProjectException, ConfigInvalidException {
    Change change = rsrc.getChange();
    if (!change.isMerged()) {
      throw new ResourceConflictException("change is " + ChangeUtil.status(change));
    }

    contributorAgreements.check(rsrc.getProject(), rsrc.getUser());
    permissionBackend.user(rsrc.getUser()).ref(change.getDest()).check(CREATE_CHANGE);
    projectCache.checkedGet(rsrc.getProject()).checkStatePermitsWrite();

    Change.Id revertId = revert(updateFactory, rsrc.getNotes(), rsrc.getUser(), input);
    return Response.ok(json.noOptions().format(rsrc.getProject(), revertId));
  }

  private Change.Id revert(
      BatchUpdate.Factory updateFactory, ChangeNotes notes, CurrentUser user, RevertInput input)
      throws IOException, RestApiException, UpdateException, ConfigInvalidException {
    Change.Id changeIdToRevert = notes.getChangeId();
    PatchSet.Id patchSetId = notes.getChange().currentPatchSetId();
    PatchSet patch = psUtil.get(notes, patchSetId);
    if (patch == null) {
      throw new ResourceNotFoundException(changeIdToRevert.toString());
    }

    Project.NameKey project = notes.getProjectName();
    try (Repository git = repoManager.openRepository(project);
        ObjectInserter oi = git.newObjectInserter();
        ObjectReader reader = oi.newReader();
        RevWalk revWalk = new RevWalk(reader)) {

      Timestamp now = TimeUtil.nowTs();
      ObjectId generatedChangeId = Change.generateChangeId();
      Change changeToRevert = notes.getChange();
      ObjectId revertCommitId =
          commitUtil.createRevertCommit(
              input.message, notes, user, generatedChangeId, now, oi, revWalk);

      RevCommit revertCommit = revWalk.parseCommit(revertCommitId);

      Change.Id changeId = Change.id(seq.nextChangeId());
      NotifyResolver.Result notify =
          notifyResolver.resolve(
              firstNonNull(input.notify, NotifyHandling.ALL), input.notifyDetails);

      ChangeInserter ins =
          changeInserterFactory
              .create(changeId, revertCommit, notes.getChange().getDest().branch())
              .setTopic(input.topic == null ? changeToRevert.getTopic() : input.topic.trim());
      ins.setMessage("Uploaded patch set 1.");

      ReviewerSet reviewerSet = approvalsUtil.getReviewers(notes);

      Set<Account.Id> reviewers = new HashSet<>();
      reviewers.add(changeToRevert.getOwner());
      reviewers.addAll(reviewerSet.byState(ReviewerStateInternal.REVIEWER));
      reviewers.remove(user.getAccountId());
      Set<Account.Id> ccs = new HashSet<>(reviewerSet.byState(ReviewerStateInternal.CC));
      ccs.remove(user.getAccountId());
      ins.setReviewersAndCcs(reviewers, ccs);
      ins.setRevertOf(changeIdToRevert);

      try (BatchUpdate bu = updateFactory.create(project, user, now)) {
        bu.setRepository(git, revWalk, oi);
        bu.setNotify(notify);
        bu.insertChange(ins);
        bu.addOp(changeId, new NotifyOp(changeToRevert, ins));
        bu.addOp(changeToRevert.getId(), new PostRevertedMessageOp(generatedChangeId));
        bu.execute();
      }
      return changeId;
    } catch (RepositoryNotFoundException e) {
      throw new ResourceNotFoundException(changeIdToRevert.toString(), e);
    }
  }

  @Override
  public UiAction.Description getDescription(ChangeResource rsrc) {
    Change change = rsrc.getChange();
    boolean projectStatePermitsWrite = false;
    try {
      projectStatePermitsWrite = projectCache.checkedGet(rsrc.getProject()).statePermitsWrite();
    } catch (IOException e) {
      logger.atSevere().withCause(e).log(
          "Failed to check if project state permits write: %s", rsrc.getProject());
    }
    return new UiAction.Description()
        .setLabel("Revert")
        .setTitle("Revert the change")
        .setVisible(
            and(
                change.isMerged() && projectStatePermitsWrite,
                permissionBackend
                    .user(rsrc.getUser())
                    .ref(change.getDest())
                    .testCond(CREATE_CHANGE)));
  }

  private class NotifyOp implements BatchUpdateOp {
    private final Change change;
    private final ChangeInserter ins;

    NotifyOp(Change change, ChangeInserter ins) {
      this.change = change;
      this.ins = ins;
    }

    @Override
    public void postUpdate(Context ctx) throws Exception {
      changeReverted.fire(change, ins.getChange(), ctx.getWhen());
      try {
        RevertedSender cm = revertedSenderFactory.create(ctx.getProject(), change.getId());
        cm.setFrom(ctx.getAccountId());
        cm.setNotify(ctx.getNotify(change.getId()));
        cm.send();
      } catch (Exception err) {
        logger.atSevere().withCause(err).log(
            "Cannot send email for revert change %s", change.getId());
      }
    }
  }

  private class PostRevertedMessageOp implements BatchUpdateOp {
    private final ObjectId computedChangeId;

    PostRevertedMessageOp(ObjectId computedChangeId) {
      this.computedChangeId = computedChangeId;
    }

    @Override
    public boolean updateChange(ChangeContext ctx) {
      Change change = ctx.getChange();
      PatchSet.Id patchSetId = change.currentPatchSetId();
      ChangeMessage changeMessage =
          ChangeMessagesUtil.newMessage(
              ctx,
              "Created a revert of this change as I" + computedChangeId.name(),
              ChangeMessagesUtil.TAG_REVERT);
      cmUtil.addChangeMessage(ctx.getUpdate(patchSetId), changeMessage);
      return true;
    }
  }
}