// Copyright (C) 2016 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.base.MoreObjects;
import com.google.common.base.Strings;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.Iterables;
import com.google.gerrit.entities.BranchNameKey;
import com.google.gerrit.entities.Change;
import com.google.gerrit.entities.PatchSet;
import com.google.gerrit.entities.Project;
import com.google.gerrit.exceptions.GerritNoMergeBaseException;
import com.google.gerrit.exceptions.InvalidMergeStrategyException;
import com.google.gerrit.exceptions.MergeWithConflictsNotSupportedException;
import com.google.gerrit.extensions.client.ListChangesOption;
import com.google.gerrit.extensions.common.ChangeInfo;
import com.google.gerrit.extensions.common.MergeInput;
import com.google.gerrit.extensions.common.MergePatchSetInput;
import com.google.gerrit.extensions.restapi.AuthException;
import com.google.gerrit.extensions.restapi.BadRequestException;
import com.google.gerrit.extensions.restapi.MergeConflictException;
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.restapi.RestModifyView;
import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
import com.google.gerrit.server.ChangeUtil;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.GerritPersonIdent;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.PatchSetUtil;
import com.google.gerrit.server.change.ChangeFinder;
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.PatchSetInserter;
import com.google.gerrit.server.config.GerritServerConfig;
import com.google.gerrit.server.git.CodeReviewCommit;
import com.google.gerrit.server.git.CodeReviewCommit.CodeReviewRevWalk;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.git.MergeUtil;
import com.google.gerrit.server.git.MergeUtilFactory;
import com.google.gerrit.server.notedb.ChangeNotes;
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.permissions.RefPermission;
import com.google.gerrit.server.project.ProjectCache;
import com.google.gerrit.server.project.ProjectState;
import com.google.gerrit.server.restapi.project.CommitsCollection;
import com.google.gerrit.server.submit.MergeIdenticalTreeException;
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.Provider;
import com.google.inject.Singleton;
import java.io.IOException;
import java.time.Instant;
import java.time.ZoneId;
import java.util.List;
import java.util.Optional;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.PersonIdent;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.util.ChangeIdUtil;

@Singleton
public class CreateMergePatchSet implements RestModifyView<ChangeResource, MergePatchSetInput> {
  private final BatchUpdate.Factory updateFactory;
  private final GitRepositoryManager gitManager;
  private final CommitsCollection commits;
  private final ZoneId serverZoneId;
  private final Provider<CurrentUser> user;
  private final ChangeJson.Factory jsonFactory;
  private final PatchSetUtil psUtil;
  private final MergeUtilFactory mergeUtilFactory;
  private final PatchSetInserter.Factory patchSetInserterFactory;
  private final ProjectCache projectCache;
  private final ChangeFinder changeFinder;
  private final PermissionBackend permissionBackend;
  private final boolean useDiff3;

  @Inject
  CreateMergePatchSet(
      @GerritServerConfig Config cfg,
      BatchUpdate.Factory updateFactory,
      GitRepositoryManager gitManager,
      CommitsCollection commits,
      @GerritPersonIdent PersonIdent myIdent,
      Provider<CurrentUser> user,
      ChangeJson.Factory json,
      PatchSetUtil psUtil,
      MergeUtilFactory mergeUtilFactory,
      PatchSetInserter.Factory patchSetInserterFactory,
      ProjectCache projectCache,
      ChangeFinder changeFinder,
      PermissionBackend permissionBackend) {
    this.updateFactory = updateFactory;
    this.gitManager = gitManager;
    this.commits = commits;
    this.serverZoneId = myIdent.getZoneId();
    this.user = user;
    this.jsonFactory = json;
    this.psUtil = psUtil;
    this.mergeUtilFactory = mergeUtilFactory;
    this.patchSetInserterFactory = patchSetInserterFactory;
    this.projectCache = projectCache;
    this.changeFinder = changeFinder;
    this.permissionBackend = permissionBackend;
    this.useDiff3 =
        cfg.getBoolean(
            "change", /* subsection= */ null, "diff3ConflictView", /* defaultValue= */ false);
  }

  @Override
  public Response<ChangeInfo> apply(ChangeResource rsrc, MergePatchSetInput in)
      throws IOException, RestApiException, UpdateException, PermissionBackendException {
    // Not allowed to create a new patch set if the current patch set is locked.
    psUtil.checkPatchSetNotLocked(rsrc.getNotes());

    rsrc.permissions().check(ChangePermission.ADD_PATCH_SET);
    if (in.author != null) {
      permissionBackend
          .currentUser()
          .project(rsrc.getProject())
          .ref(rsrc.getChange().getDest().branch())
          .check(RefPermission.FORGE_AUTHOR);
    }

    ProjectState projectState =
        projectCache.get(rsrc.getProject()).orElseThrow(illegalState(rsrc.getProject()));
    projectState.checkStatePermitsWrite();

    MergeInput merge = in.merge;
    if (merge == null || Strings.isNullOrEmpty(merge.source)) {
      throw new BadRequestException("merge.source must be non-empty");
    }
    if (in.author != null
        && (Strings.isNullOrEmpty(in.author.email) || Strings.isNullOrEmpty(in.author.name))) {
      throw new BadRequestException("Author must specify name and email");
    }
    in.baseChange = Strings.nullToEmpty(in.baseChange).trim();

    PatchSet ps = psUtil.current(rsrc.getNotes());
    Change change = rsrc.getChange();
    Project.NameKey project = change.getProject();
    BranchNameKey dest = change.getDest();
    try (Repository git = gitManager.openRepository(project);
        ObjectInserter oi = git.newObjectInserter();
        ObjectReader reader = oi.newReader();
        CodeReviewRevWalk rw = CodeReviewCommit.newRevWalk(reader)) {

      RevCommit sourceCommit = MergeUtil.resolveCommit(git, rw, merge.source);
      if (!commits.canRead(projectState, git, sourceCommit)) {
        throw new ResourceNotFoundException(
            "cannot find source commit: " + merge.source + " to merge.");
      }

      RevCommit currentPsCommit;
      ImmutableList<String> groups = null;
      if (!in.inheritParent && !in.baseChange.isEmpty()) {
        PatchSet basePS = findBasePatchSet(in.baseChange);
        currentPsCommit = rw.parseCommit(basePS.commitId());
        groups = basePS.groups();
      } else {
        currentPsCommit = rw.parseCommit(ps.commitId());
      }

      Instant now = TimeUtil.now();
      IdentifiedUser me = user.get().asIdentifiedUser();
      PersonIdent author =
          in.author == null
              ? me.newCommitterIdent(now, serverZoneId)
              : new PersonIdent(in.author.name, in.author.email, now, serverZoneId);
      RevCommit commit = rw.parseCommit(ps.commitId());
      PersonIdent committer =
          Optional.ofNullable(commit.getCommitterIdent())
              .map(
                  ident ->
                      me.newCommitterIdent(ident.getEmailAddress(), now, serverZoneId)
                          .orElseGet(() -> me.newCommitterIdent(now, serverZoneId)))
              .orElseGet(() -> me.newCommitterIdent(now, serverZoneId));
      CodeReviewCommit newCommit =
          createMergeCommit(
              in,
              projectState,
              dest,
              git,
              oi,
              rw,
              currentPsCommit,
              sourceCommit,
              author,
              committer,
              ObjectId.fromString(change.getKey().get().substring(1)));
      oi.flush();

      PatchSet.Id nextPsId = ChangeUtil.nextPatchSetId(ps.id());
      PatchSetInserter psInserter =
          patchSetInserterFactory.create(rsrc.getNotes(), nextPsId, newCommit);
      try (RefUpdateContext ctx = RefUpdateContext.open(CHANGE_MODIFICATION)) {
        try (BatchUpdate bu = updateFactory.create(project, me, now)) {
          bu.setRepository(git, rw, oi);
          bu.setNotify(NotifyResolver.Result.none());
          psInserter
              .setMessage(messageForChange(nextPsId, newCommit))
              .setWorkInProgress(!newCommit.getFilesWithGitConflicts().isEmpty())
              .setCheckAddPatchSetPermission(false);
          newCommit.getConflicts().ifPresent(psInserter::setConflicts);

          if (in.validationOptions != null) {
            ImmutableListMultimap.Builder<String, String> validationOptions =
                ImmutableListMultimap.builder();
            in.validationOptions
                .entrySet()
                .forEach(e -> validationOptions.put(e.getKey(), e.getValue()));
            psInserter.setValidationOptions(validationOptions.build());
          }

          if (groups != null) {
            psInserter.setGroups(groups);
          }
          bu.addOp(rsrc.getId(), psInserter);
          bu.execute();
        }
      }

      ChangeJson json = jsonFactory.create(ListChangesOption.CURRENT_REVISION);
      ChangeInfo changeInfo = json.format(psInserter.getChange());
      changeInfo.containsGitConflicts =
          !newCommit.getFilesWithGitConflicts().isEmpty() ? true : null;
      return Response.ok(changeInfo);
    } catch (InvalidMergeStrategyException | MergeWithConflictsNotSupportedException e) {
      throw new BadRequestException(e.getMessage());
    }
  }

  private PatchSet findBasePatchSet(String baseChange)
      throws PermissionBackendException, UnprocessableEntityException {
    List<ChangeNotes> notes = changeFinder.find(baseChange);
    if (notes.size() != 1) {
      throw new UnprocessableEntityException("Base change not found: " + baseChange);
    }
    ChangeNotes change = Iterables.getOnlyElement(notes);
    try {
      permissionBackend.currentUser().change(change).check(ChangePermission.READ);
    } catch (AuthException e) {
      throw new UnprocessableEntityException("Read not permitted for " + baseChange, e);
    }
    return psUtil.current(change);
  }

  private CodeReviewCommit createMergeCommit(
      MergePatchSetInput in,
      ProjectState projectState,
      BranchNameKey dest,
      Repository git,
      ObjectInserter oi,
      CodeReviewRevWalk rw,
      RevCommit currentPsCommit,
      RevCommit sourceCommit,
      PersonIdent author,
      PersonIdent committer,
      ObjectId changeId)
      throws ResourceNotFoundException,
          MergeIdenticalTreeException,
          MergeConflictException,
          IOException,
          InvalidMergeStrategyException,
          GerritNoMergeBaseException {

    ObjectId parentCommit;
    if (in.inheritParent) {
      // inherit first parent from previous patch set
      parentCommit = currentPsCommit.getParent(0);
    } else if (!in.baseChange.isEmpty()) {
      parentCommit = currentPsCommit.getId();
    } else {
      // get the current branch tip of destination branch
      Ref destRef = git.getRefDatabase().exactRef(dest.branch());
      if (destRef != null) {
        parentCommit = destRef.getObjectId();
      } else {
        throw new ResourceNotFoundException("cannot find destination branch");
      }
    }
    RevCommit mergeTip = rw.parseCommit(parentCommit);

    String commitMsg;
    if (Strings.emptyToNull(in.subject) != null) {
      commitMsg = ChangeIdUtil.insertId(in.subject, changeId);
    } else {
      // reuse previous patch set commit message
      commitMsg = currentPsCommit.getFullMessage();
    }

    String mergeStrategy =
        MoreObjects.firstNonNull(
            Strings.emptyToNull(in.merge.strategy),
            mergeUtilFactory.create(projectState).mergeStrategyName());

    return MergeUtil.createMergeCommit(
        oi,
        git.getConfig(),
        mergeTip,
        sourceCommit,
        mergeStrategy,
        in.merge.allowConflicts,
        author,
        committer,
        commitMsg,
        rw,
        this.useDiff3);
  }

  private static String messageForChange(PatchSet.Id patchSetId, CodeReviewCommit commit) {
    StringBuilder stringBuilder =
        new StringBuilder(String.format("Uploaded patch set %s.", patchSetId.get()));

    if (!commit.getFilesWithGitConflicts().isEmpty()) {
      stringBuilder.append("\n\nThe following files contain Git conflicts:\n");
      commit.getFilesWithGitConflicts().stream()
          .sorted()
          .forEach(filePath -> stringBuilder.append("* ").append(filePath).append("\n"));
    }

    return stringBuilder.toString();
  }
}