// 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.googlesource.gerrit.plugins.branchnetwork.data;

import com.google.gerrit.entities.Project.NameKey;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import com.googlesource.gerrit.plugins.branchnetwork.data.json.Commit;
import com.googlesource.gerrit.plugins.branchnetwork.data.json.Head;
import com.googlesource.gerrit.plugins.branchnetwork.data.json.Parent;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revplot.PlotCommit;
import org.eclipse.jgit.revplot.PlotCommitList;
import org.eclipse.jgit.revplot.PlotLane;
import org.eclipse.jgit.revplot.PlotWalk;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevCommitList;
import org.eclipse.jgit.revwalk.RevSort;

@Singleton
public class JGitFacade {
  private final GitRepositoryManager repoManager;

  @Inject
  public JGitFacade(GitRepositoryManager repoManager) {
    this.repoManager = repoManager;
  }

  public List<Commit> logData(String repository) throws IOException {
    final Repository repo = repoManager.openRepository(NameKey.parse(repository));
    final PlotWalk walk = new PlotWalk(repo);
    try {

      List<Head> heads = getHeadsForRepository(repo);
      for (Head head : heads) {
        ObjectId headId = repo.resolve(head.getId());
        walk.markStart(walk.parseCommit(headId));
      }

      walk.sort(RevSort.COMMIT_TIME_DESC, true);

      PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
      pcl.source(walk);
      pcl.fillTo(Integer.MAX_VALUE);
      Collections.reverse(pcl);

      List<Commit> commits = new LinkedList<Commit>();
      final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

      Map<String, Commit> commitsById = new HashMap<String, Commit>(pcl.size());
      for (int i = 0; i < pcl.size(); i++) {
        PlotCommit<PlotLane> pc = pcl.get(i);
        Commit commit = new Commit();

        commit.setAuthor(pc.getAuthorIdent().getName());
        commit.setDate(sdf.format(pc.getAuthorIdent().getWhen()));
        commit.setId(pc.getId().getName());
        commit.setEmail(pc.getAuthorIdent().getEmailAddress());
        commit.setMessage(pc.getFullMessage());
        if (pc.getLane() != null) {
          commit.setSpace(1 + pc.getLane().getPosition());
        } else {
          commit.setSpace(1);
        }
        commit.setTime(i);

        for (RevCommit parentRC : pc.getParents()) {
          Commit parentCommit = commitsById.get(parentRC.getId().getName());
          assert parentCommit != null;
          Parent parent = new Parent();
          parent.setId(parentCommit.getId());
          parent.setTime(parentCommit.getTime());
          parent.setSpace(parentCommit.getSpace());
          commit.addParent(parent);
        }

        commitsById.put(commit.getId(), commit);
        commits.add(commit);
      }

      return commits;
    } finally {
      walk.dispose();
      repo.close();
    }
  }

  public List<String> getDatesForRepository(String repoName) throws IOException {
    List<String> dates = new LinkedList<String>();

    Repository repo = repoManager.openRepository(NameKey.parse(repoName));
    final PlotWalk walk = new PlotWalk(repo);

    try {
      List<Head> heads = getHeadsForRepository(repo);
      for (Head head : heads) {
        ObjectId headId = repo.resolve(head.getId());
        walk.markStart(walk.parseCommit(headId));
      }

      walk.sort(RevSort.COMMIT_TIME_DESC, true);
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
      RevCommitList<RevCommit> rcl = new RevCommitList<RevCommit>();
      rcl.source(walk);
      rcl.fillTo(Integer.MAX_VALUE);

      for (RevCommit rc : rcl) {
        dates.add(sdf.format(rc.getCommitterIdent().getWhen()));
      }
      Collections.reverse(dates);

      return dates;
    } finally {
      repo.close();
      walk.dispose();
    }
  }

  public List<Head> getHeadsForRepository(String repoName) throws IOException {
    Repository repo = repoManager.openRepository(NameKey.parse(repoName));
    try {
      return getHeadsForRepository(repo);
    } finally {
      repo.close();
    }
  }

  private List<Head> getHeadsForRepository(Repository repo) throws IOException {
    Map<String, Ref> headRefs = repo.getRefDatabase().getRefs(Constants.R_HEADS);

    List<Head> heads = new LinkedList<Head>();
    for (String headName : headRefs.keySet()) {
      Head head = new Head();
      head.setName(headName);
      head.setId(headRefs.get(headName).getObjectId().getName());
      heads.add(head);
    }

    return heads;
  }

  public int getBranchesPlotLanesCount(String repoName) throws IOException {
    try (Repository repo = repoManager.openRepository(NameKey.parse(repoName));
        PlotWalk walk = new PlotWalk(repo); ) {
      ObjectId headId = repo.resolve(Constants.HEAD);
      if (headId == null) return 0;

      walk.markStart(walk.parseCommit(headId));
      PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
      pcl.source(walk);
      pcl.fillTo(Integer.MAX_VALUE);

      int maxLane = 1;
      for (PlotCommit<PlotLane> pc : pcl) {
        if (pc.getLane() != null) {
          int lane = 1 + pc.getLane().getPosition();
          if (lane > maxLane) maxLane = lane;
        }
      }

      return maxLane;
    }
  }
}