// Copyright (C) 2013 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.gerrit.server.project.ProjectCache.illegalState;
import static com.google.gerrit.server.update.context.RefUpdateContext.RefUpdateType.CHANGE_MODIFICATION;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import com.google.gerrit.entities.Change;
import com.google.gerrit.entities.PatchSet;
import com.google.gerrit.extensions.api.changes.RebaseInput;
import com.google.gerrit.extensions.client.ListChangesOption;
import com.google.gerrit.extensions.common.ChangeInfo;
import com.google.gerrit.extensions.restapi.ResourceConflictException;
import com.google.gerrit.extensions.restapi.Response;
import com.google.gerrit.extensions.restapi.RestApiException;
import com.google.gerrit.extensions.restapi.RestModifyView;
import com.google.gerrit.extensions.webui.UiAction;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.IdentifiedUser.ImpersonationPermissionMode;
import com.google.gerrit.server.PatchSetUtil;
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.change.RebaseChangeOp;
import com.google.gerrit.server.change.RebaseUtil;
import com.google.gerrit.server.change.RevisionResource;
import com.google.gerrit.server.git.CodeReviewCommit;
import com.google.gerrit.server.git.GitRepositoryManager;
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.ProjectCache;
import com.google.gerrit.server.update.BatchUpdate;
import com.google.gerrit.server.update.UpdateException;
import com.google.gerrit.server.update.context.RefUpdateContext;
import com.google.gerrit.server.util.time.TimeUtil;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevWalk;

@Singleton
public class Rebase
    implements RestModifyView<RevisionResource, RebaseInput>, UiAction<RevisionResource> {
  private static final ImmutableSet<ListChangesOption> OPTIONS =
      Sets.immutableEnumSet(ListChangesOption.CURRENT_REVISION, ListChangesOption.CURRENT_COMMIT);

  private final BatchUpdate.Factory updateFactory;
  private final GitRepositoryManager repoManager;
  private final RebaseUtil rebaseUtil;
  private final ChangeJson.Factory json;
  private final PermissionBackend permissionBackend;
  private final ProjectCache projectCache;
  private final PatchSetUtil patchSetUtil;
  private final RebaseMetrics rebaseMetrics;
  private final IdentifiedUser.GenericFactory userFactory;

  @Inject
  public Rebase(
      BatchUpdate.Factory updateFactory,
      GitRepositoryManager repoManager,
      RebaseUtil rebaseUtil,
      ChangeJson.Factory json,
      PermissionBackend permissionBackend,
      ProjectCache projectCache,
      PatchSetUtil patchSetUtil,
      RebaseMetrics rebaseMetrics,
      IdentifiedUser.GenericFactory userFactory) {
    this.updateFactory = updateFactory;
    this.repoManager = repoManager;
    this.rebaseUtil = rebaseUtil;
    this.json = json;
    this.permissionBackend = permissionBackend;
    this.projectCache = projectCache;
    this.patchSetUtil = patchSetUtil;
    this.rebaseMetrics = rebaseMetrics;
    this.userFactory = userFactory;
  }

  @Override
  public Response<ChangeInfo> apply(RevisionResource rsrc, RebaseInput input)
      throws UpdateException, RestApiException, IOException, PermissionBackendException {
    IdentifiedUser rebaseAsUser;
    if (input.onBehalfOfUploader && !rsrc.getPatchSet().uploader().equals(rsrc.getAccountId())) {
      rebaseAsUser =
          userFactory.runAs(
              /* remotePeer= */ null,
              rsrc.getPatchSet().uploader(),
              rsrc.getUser(),
              ImpersonationPermissionMode.THIS_USER);
      rsrc.permissions().check(ChangePermission.REBASE_ON_BEHALF_OF_UPLOADER);
      rebaseUtil.checkCanRebaseOnBehalfOf(rsrc, input);
    } else {
      rebaseAsUser = rsrc.getUser().asIdentifiedUser();
      input.onBehalfOfUploader = false;
      rsrc.permissions().check(ChangePermission.REBASE);
    }

    projectCache
        .get(rsrc.getProject())
        .orElseThrow(illegalState(rsrc.getProject()))
        .checkStatePermitsWrite();

    Change change = rsrc.getChange();
    try (RefUpdateContext ctx = RefUpdateContext.open(CHANGE_MODIFICATION)) {
      try (Repository repo = repoManager.openRepository(change.getProject());
          ObjectInserter oi = repo.newObjectInserter();
          ObjectReader reader = oi.newReader();
          RevWalk rw = CodeReviewCommit.newRevWalk(reader);
          BatchUpdate bu =
              updateFactory.create(change.getProject(), rebaseAsUser, TimeUtil.now())) {
        rebaseUtil.verifyRebasePreconditions(rw, rsrc.getNotes(), rsrc.getPatchSet());

        RebaseChangeOp rebaseOp =
            rebaseUtil.getRebaseOp(
                rw,
                rsrc,
                input,
                rebaseUtil.parseOrFindBaseRevision(repo, rw, permissionBackend, rsrc, input, true),
                rebaseAsUser);

        // TODO(dborowitz): Why no notification? This seems wrong; dig up blame.
        bu.setNotify(NotifyResolver.Result.none());
        bu.setRepository(repo, rw, oi);
        bu.addOp(change.getId(), rebaseOp);
        bu.execute();

        rebaseMetrics.countRebase(input.onBehalfOfUploader, input.allowConflicts);

        ChangeInfo changeInfo = json.create(OPTIONS).format(change.getProject(), change.getId());
        changeInfo.containsGitConflicts =
            !rebaseOp.getRebasedCommit().getFilesWithGitConflicts().isEmpty() ? true : null;
        return Response.ok(changeInfo);
      }
    }
  }

  @Override
  public UiAction.Description getDescription(RevisionResource rsrc) throws IOException {
    UiAction.Description description =
        new UiAction.Description()
            .setLabel("Rebase")
            .setTitle("Rebase onto tip of branch or parent change.")
            .setVisible(false);

    Change change = rsrc.getChange();
    if (!(change.isNew() && rsrc.isCurrent())) {
      return description;
    }
    if (!projectCache
        .get(rsrc.getProject())
        .orElseThrow(illegalState(rsrc.getProject()))
        .statePermitsWrite()) {
      return description;
    }
    if (patchSetUtil.isPatchSetLocked(rsrc.getNotes())) {
      return description;
    }

    boolean enabled = false;
    try (Repository repo = repoManager.openRepository(change.getDest().project());
        RevWalk rw = new RevWalk(repo)) {
      if (RebaseUtil.hasAtLeastOneParent(rw, rsrc.getPatchSet())) {
        enabled = rebaseUtil.canRebase(rsrc.getPatchSet(), change.getDest(), repo, rw);
      }
    }

    boolean canRebase = rsrc.permissions().testOrFalse(ChangePermission.REBASE);
    boolean canRebaseOnBehalfOfUploader =
        rsrc.permissions().testOrFalse(ChangePermission.REBASE_ON_BEHALF_OF_UPLOADER);
    if (canRebase || canRebaseOnBehalfOfUploader) {
      return description
          .setOption("rebase", canRebase)
          .setOption("rebase_on_behalf_of_uploader", canRebaseOnBehalfOfUploader)
          .setEnabled(enabled)
          .setVisible(true);
    }

    return description;
  }

  public static class CurrentRevision implements RestModifyView<ChangeResource, RebaseInput> {
    private final PatchSetUtil psUtil;
    private final Rebase rebase;

    @Inject
    CurrentRevision(PatchSetUtil psUtil, Rebase rebase) {
      this.psUtil = psUtil;
      this.rebase = rebase;
    }

    @Override
    public Response<ChangeInfo> apply(ChangeResource rsrc, RebaseInput input)
        throws RestApiException, UpdateException, IOException, PermissionBackendException {
      PatchSet ps = psUtil.current(rsrc.getNotes());
      if (ps == null) {
        throw new ResourceConflictException("current revision is missing");
      }
      return Response.ok(rebase.apply(new RevisionResource(rsrc, ps), input).value());
    }
  }
}