/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.phoenix.iterate;

import java.sql.SQLException;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.HRegionLocation;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.snapshot.SnapshotDescriptionUtils;
import org.apache.hadoop.hbase.snapshot.SnapshotManifest;
import org.apache.phoenix.compile.QueryPlan;
import org.apache.phoenix.compile.StatementContext;
import org.apache.phoenix.mapreduce.util.PhoenixConfigurationUtil;

import org.apache.phoenix.thirdparty.com.google.common.annotations.VisibleForTesting;
import org.apache.phoenix.thirdparty.com.google.common.base.Preconditions;
import org.apache.phoenix.thirdparty.com.google.common.collect.Lists;

import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.shaded.protobuf.generated.SnapshotProtos.SnapshotDescription;
import org.apache.hadoop.hbase.shaded.protobuf.generated.SnapshotProtos.SnapshotRegionManifest;

/**
 * Scan grouper that creates a scan group if a plan is row key ordered or if a scan crosses region
 * boundaries
 */
public class MapReduceParallelScanGrouper implements ParallelScanGrouper {

  private static final MapReduceParallelScanGrouper INSTANCE = new MapReduceParallelScanGrouper();

  public static MapReduceParallelScanGrouper getInstance() {
    return INSTANCE;
  }

  @VisibleForTesting
  MapReduceParallelScanGrouper() {
  }

  @Override
  public boolean shouldStartNewScan(QueryPlan plan, Scan lastScan, byte[] startKey,
    boolean crossesRegionBoundary) {
    return (!plan.isRowKeyOrdered() || crossesRegionBoundary) && lastScan != null;
  }

  @Override
  public List<HRegionLocation> getRegionBoundaries(StatementContext context, byte[] tableName)
    throws SQLException {
    String snapshotName;
    Configuration conf = context.getConnection().getQueryServices().getConfiguration();
    if ((snapshotName = getSnapshotName(conf)) != null) {
      return getRegionLocationsFromSnapshot(conf, snapshotName);
    } else {
      return context.getConnection().getQueryServices().getAllTableRegions(tableName,
        context.getStatement().getQueryTimeoutInMillis());
    }
  }

  /**
   * {@inheritDoc}.
   */
  @Override
  public List<HRegionLocation> getRegionBoundaries(StatementContext context, byte[] tableName,
    byte[] startRegionBoundaryKey, byte[] stopRegionBoundaryKey) throws SQLException {
    String snapshotName;
    Configuration conf = context.getConnection().getQueryServices().getConfiguration();
    if ((snapshotName = getSnapshotName(conf)) != null) {
      return getRegionLocationsFromSnapshot(conf, snapshotName);
    } else {
      return context.getConnection().getQueryServices().getTableRegions(tableName,
        startRegionBoundaryKey, stopRegionBoundaryKey,
        context.getStatement().getQueryTimeoutInMillis());
    }
  }

  private List<HRegionLocation> getRegionLocationsFromSnapshot(Configuration conf,
    String snapshotName) {
    try {
      Path rootDir = new Path(conf.get(HConstants.HBASE_DIR));
      FileSystem fs = rootDir.getFileSystem(conf);
      Path snapshotDir = SnapshotDescriptionUtils.getCompletedSnapshotDir(snapshotName, rootDir);
      SnapshotDescription snapshotDescription =
        SnapshotDescriptionUtils.readSnapshotInfo(fs, snapshotDir);
      SnapshotManifest manifest = SnapshotManifest.open(conf, fs, snapshotDir, snapshotDescription);
      return getRegionLocationsFromManifest(manifest);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Get list of region locations from SnapshotManifest BaseResultIterators assume that regions are
   * sorted using RegionInfo.COMPARATOR
   */
  private List<HRegionLocation> getRegionLocationsFromManifest(SnapshotManifest manifest) {
    List<SnapshotRegionManifest> regionManifests = manifest.getRegionManifests();
    Preconditions.checkNotNull(regionManifests);

    List<RegionInfo> regionInfos = Lists.newArrayListWithCapacity(regionManifests.size());
    List<HRegionLocation> hRegionLocations = Lists.newArrayListWithCapacity(regionManifests.size());

    for (SnapshotRegionManifest regionManifest : regionManifests) {
      RegionInfo regionInfo = ProtobufUtil.toRegionInfo(regionManifest.getRegionInfo());
      if (isValidRegion(regionInfo)) {
        regionInfos.add(regionInfo);
      }
    }

    regionInfos.sort(RegionInfo.COMPARATOR);

    for (RegionInfo regionInfo : regionInfos) {
      hRegionLocations.add(new HRegionLocation(regionInfo, null));
    }

    return hRegionLocations;
  }

  // Exclude offline split parent regions
  private boolean isValidRegion(RegionInfo hri) {
    if (hri.isOffline() && (hri.isSplit() || hri.isSplitParent())) {
      return false;
    }
    return true;
  }

  private String getSnapshotName(Configuration conf) {
    return conf.get(PhoenixConfigurationUtil.SNAPSHOT_NAME_KEY);
  }

}
