/**
 *
 * 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.hadoop.hbase.regionserver.compactions;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.regionserver.StoreConfigInformation;
import org.apache.hadoop.hbase.regionserver.StoreFile;
import org.apache.hadoop.hbase.regionserver.StoreUtils;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;

/**
 * 
 * FIFO compaction policy selects only files which have all cells expired. 
 * The column family MUST have non-default TTL. One of the use cases for this 
 * policy is when we need to store raw data which will be post-processed later 
 * and discarded completely after quite short period of time. Raw time-series vs. 
 * time-based roll up aggregates and compacted time-series. We collect raw time-series
 * and store them into CF with FIFO compaction policy, periodically we run task 
 * which creates roll up aggregates and compacts time-series, the original raw data 
 * can be discarded after that.
 * 
 */
@InterfaceAudience.Private
public class FIFOCompactionPolicy extends ExploringCompactionPolicy {
  
  private static final Log LOG = LogFactory.getLog(FIFOCompactionPolicy.class);


  public FIFOCompactionPolicy(Configuration conf, StoreConfigInformation storeConfigInfo) {
    super(conf, storeConfigInfo);
  }

  @Override
  public CompactionRequest selectCompaction(Collection<StoreFile> candidateFiles,
      List<StoreFile> filesCompacting, boolean isUserCompaction, boolean mayUseOffPeak,
      boolean forceMajor) throws IOException {
    
    if(forceMajor){
      LOG.warn("Major compaction is not supported for FIFO compaction policy. Ignore the flag.");
    }
    boolean isAfterSplit = StoreUtils.hasReferences(candidateFiles);
    if(isAfterSplit){
      LOG.info("Split detected, delegate selection to the parent policy.");
      return super.selectCompaction(candidateFiles, filesCompacting, isUserCompaction, 
        mayUseOffPeak, forceMajor);
    }
    
    // Nothing to compact
    Collection<StoreFile> toCompact = getExpiredStores(candidateFiles, filesCompacting);
    CompactionRequest result = new CompactionRequest(toCompact);
    return result;
  }

  @Override
  public boolean shouldPerformMajorCompaction(Collection<StoreFile> filesToCompact)
    throws IOException {
    boolean isAfterSplit = StoreUtils.hasReferences(filesToCompact);
    if(isAfterSplit){
      LOG.info("Split detected, delegate to the parent policy.");
      return super.shouldPerformMajorCompaction(filesToCompact);
    }
    return false;
  }

  @Override
  public boolean needsCompaction(Collection<StoreFile> storeFiles, 
      List<StoreFile> filesCompacting) {  
    boolean isAfterSplit = StoreUtils.hasReferences(storeFiles);
    if(isAfterSplit){
      LOG.info("Split detected, delegate to the parent policy.");
      return super.needsCompaction(storeFiles, filesCompacting);
    }
    return hasExpiredStores(storeFiles);
  }

  private  boolean hasExpiredStores(Collection<StoreFile> files) {
    long currentTime = EnvironmentEdgeManager.currentTime();
    for(StoreFile sf: files){
      // Check MIN_VERSIONS is in HStore removeUnneededFiles
      Long maxTs = sf.getReader().getMaxTimestamp();
      long maxTtl = storeConfigInfo.getStoreFileTtl();
      if(maxTs == null 
          || maxTtl == Long.MAX_VALUE
          || (currentTime - maxTtl < maxTs)){
        continue; 
      } else{
        return true;
      }
    }
    return false;
  }

  private  Collection<StoreFile> getExpiredStores(Collection<StoreFile> files,
    Collection<StoreFile> filesCompacting) {
    long currentTime = EnvironmentEdgeManager.currentTime();
    Collection<StoreFile> expiredStores = new ArrayList<>();
    for(StoreFile sf: files){
      // Check MIN_VERSIONS is in HStore removeUnneededFiles
      Long maxTs = sf.getReader().getMaxTimestamp();
      long maxTtl = storeConfigInfo.getStoreFileTtl();
      if(maxTs == null 
          || maxTtl == Long.MAX_VALUE
          || (currentTime - maxTtl < maxTs)){
        continue; 
      } else if(filesCompacting == null || filesCompacting.contains(sf) == false){
        expiredStores.add(sf);
      }
    }
    return expiredStores;
  }
}