// 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.googlesource.gerrit.plugins.reviewnotes;

import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.MultimapBuilder;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.Project;
import com.google.gerrit.reviewdb.server.ReviewDb;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.notedb.ChangeNotes;
import com.google.gerrit.sshd.SshCommand;
import com.google.gwtorm.server.OrmException;
import com.google.gwtorm.server.SchemaFactory;
import com.google.inject.Inject;

import org.eclipse.jgit.api.errors.ConcurrentRefUpdateException;
import org.eclipse.jgit.errors.RepositoryNotFoundException;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.lib.TextProgressMonitor;
import org.eclipse.jgit.lib.ThreadSafeProgressMonitor;
import org.kohsuke.args4j.Option;

import java.io.IOException;
import java.util.List;
import java.util.Map;

/** Export review notes for all submitted changes in all projects. */
public class ExportReviewNotes extends SshCommand {
  @Option(name = "--threads", usage = "Number of concurrent threads to run")
  private int threads = 2;

  @Inject
  private GitRepositoryManager gitManager;

  @Inject
  private SchemaFactory<ReviewDb> database;

  @Inject
  private CreateReviewNotes.Factory reviewNotesFactory;

  @Inject
  private ChangeNotes.Factory notesFactory;

  private ListMultimap<Project.NameKey, ChangeNotes> changes;
  private ThreadSafeProgressMonitor monitor;

  @Override
  protected void run() throws Failure, InterruptedException {
    if (threads <= 0) {
      threads = 1;
    }

    changes = mergedChanges();

    monitor = new ThreadSafeProgressMonitor(new TextProgressMonitor(stdout));
    monitor.beginTask("Scanning merged changes", changes.size());
    monitor.startWorkers(threads);
    for (int tid = 0; tid < threads; tid++) {
      new Worker().start();
    }
    monitor.waitForCompletion();
    monitor.endTask();
  }

  private ListMultimap<Project.NameKey, ChangeNotes> mergedChanges() {
    try (ReviewDb db = database.open()) {
      return MultimapBuilder.hashKeys().arrayListValues()
          .build(notesFactory.create(db, new Predicate<ChangeNotes>() {
            @Override
            public boolean apply(ChangeNotes notes) {
              return notes.getChange().getStatus() == Change.Status.MERGED;
            }
          }));
    } catch (OrmException | IOException e) {
      stderr.println("Cannot read changes from database " + e.getMessage());
      return ImmutableListMultimap.of();
    }
  }

  private void export(ReviewDb db, Project.NameKey project,
      List<ChangeNotes> notes) throws IOException, OrmException {
    try (Repository git = gitManager.openRepository(project)) {
      CreateReviewNotes crn = reviewNotesFactory.create(db, project, git);
      crn.createNotes(notes, monitor);
      crn.commitNotes();
    } catch (RepositoryNotFoundException e) {
      stderr.println("Unable to open project: " + project.get());
    } catch (ConcurrentRefUpdateException e) {
      stderr.println(e.getMessage());
    }
  }

  private Map.Entry<Project.NameKey, List<ChangeNotes>> next() {
    synchronized (changes) {
      if (changes.isEmpty()) {
        return null;
      }

      final Project.NameKey name = changes.keySet().iterator().next();
      final List<ChangeNotes> list = changes.removeAll(name);
      return new Map.Entry<Project.NameKey, List<ChangeNotes>>() {
        @Override
        public Project.NameKey getKey() {
          return name;
        }

        @Override
        public List<ChangeNotes> getValue() {
          return list;
        }

        @Override
        public List<ChangeNotes> setValue(List<ChangeNotes> value) {
          throw new UnsupportedOperationException();
        }
      };
    }
  }

  private class Worker extends Thread {
    @Override
    public void run() {
      try (ReviewDb db = database.open()) {
        for (;;) {
          Map.Entry<Project.NameKey, List<ChangeNotes>> next = next();
          if (next != null) {
            try {
              export(db, next.getKey(), next.getValue());
            } catch (OrmException | IOException e) {
              stderr.println(e.getMessage());
            }
          } else {
            break;
          }
        }
      } catch (OrmException e) {
        stderr.println(e.getMessage());
      } finally {
        monitor.endWorker();
      }
    }
  }
}