// 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.git.strategy;

import com.google.common.collect.ImmutableSet;
import com.google.gerrit.server.git.CodeReviewCommit;
import com.google.gerrit.server.git.IntegrationException;
import com.google.gerrit.server.git.MergeTip;

import org.eclipse.jgit.lib.PersonIdent;
import org.eclipse.jgit.revwalk.RevCommit;

import java.util.Collection;
import java.util.List;

public class MergeIfNecessary extends SubmitStrategy {
  MergeIfNecessary(SubmitStrategy.Arguments args) {
    super(args);
  }

  @Override
  protected MergeTip _run(CodeReviewCommit branchTip,
      Collection<CodeReviewCommit> toMerge) throws IntegrationException {
    List<CodeReviewCommit> sorted =
        args.mergeUtil.reduceToMinimalMerge(args.mergeSorter, toMerge);
    MergeTip mergeTip;
    if (branchTip == null) {
      // The branch is unborn. Take a fast-forward resolution to
      // create the branch.
      mergeTip = new MergeTip(sorted.get(0), toMerge);
      branchTip = sorted.remove(0);
    } else {
      mergeTip = new MergeTip(branchTip, toMerge);
      branchTip =
          args.mergeUtil.getFirstFastForward(branchTip, args.rw, sorted);
    }
    mergeTip.moveTipTo(branchTip, branchTip);

    // For every other commit do a pair-wise merge.
    while (!sorted.isEmpty()) {
      CodeReviewCommit mergedFrom = sorted.remove(0);
      PersonIdent serverIdent = args.serverIdent.get();
      PersonIdent caller = args.caller.newCommitterIdent(
          serverIdent.getWhen(), serverIdent.getTimeZone());
      branchTip =
          args.mergeUtil.mergeOneCommit(caller, serverIdent,
              args.repo, args.rw, args.inserter, args.canMergeFlag,
              args.destBranch, branchTip, mergedFrom);
      mergeTip.moveTipTo(branchTip, mergedFrom);
    }
    RevCommit initialTip = mergeTip.getInitialTip();
    args.mergeUtil.markCleanMerges(args.rw, args.canMergeFlag, branchTip,
        initialTip == null ? ImmutableSet.<RevCommit> of()
            : ImmutableSet.of(initialTip));
    setRefLogIdent();
    return mergeTip;
  }

  @Override
  public boolean dryRun(CodeReviewCommit mergeTip, CodeReviewCommit toMerge)
      throws IntegrationException {
    return args.mergeUtil.canFastForward(
          args.mergeSorter, mergeTip, args.rw, toMerge)
        || args.mergeUtil.canMerge(
          args.mergeSorter, args.repo, mergeTip, toMerge);
  }
}