/**
    * 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 com.google.common.base.Preconditions;
  import com.google.common.base.Predicate;
  import com.google.common.collect.Collections2;
  import com.google.common.collect.Lists;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.Random;
  
  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;
  
  /**
   * An abstract compaction policy that select files on seq id order.
   */
  @InterfaceAudience.Private
  public abstract class SortedCompactionPolicy extends CompactionPolicy {
  
    private static final Log LOG = LogFactory.getLog(SortedCompactionPolicy.class);
  
    public SortedCompactionPolicy(Configuration conf, StoreConfigInformation storeConfigInfo) {
      super(conf, storeConfigInfo);
    }
  
    public List<StoreFile> preSelectCompactionForCoprocessor(final Collection<StoreFile> candidates,
        final List<StoreFile> filesCompacting) {
      return getCurrentEligibleFiles(new ArrayList<StoreFile>(candidates), filesCompacting);
    }
  
    /**
     * @param candidateFiles candidate files, ordered from oldest to newest by seqId. We rely on
     *   DefaultStoreFileManager to sort the files by seqId to guarantee contiguous compaction based
     *   on seqId for data consistency.
     * @return subset copy of candidate list that meets compaction criteria
     */
    public CompactionRequest selectCompaction(Collection<StoreFile> candidateFiles,
        final List<StoreFile> filesCompacting, final boolean isUserCompaction,
        final boolean mayUseOffPeak, final boolean forceMajor) throws IOException {
      // Preliminary compaction subject to filters
      ArrayList<StoreFile> candidateSelection = new ArrayList<StoreFile>(candidateFiles);
      // Stuck and not compacting enough (estimate). It is not guaranteed that we will be
      // able to compact more if stuck and compacting, because ratio policy excludes some
      // non-compacting files from consideration during compaction (see getCurrentEligibleFiles).
      int futureFiles = filesCompacting.isEmpty() ? 0 : 1;
      boolean mayBeStuck = (candidateFiles.size() - filesCompacting.size() + futureFiles)
          >= storeConfigInfo.getBlockingFileCount();
  
      candidateSelection = getCurrentEligibleFiles(candidateSelection, filesCompacting);
      LOG.debug("Selecting compaction from " + candidateFiles.size() + " store files, " +
          filesCompacting.size() + " compacting, " + candidateSelection.size() +
          " eligible, " + storeConfigInfo.getBlockingFileCount() + " blocking");
  
      // If we can't have all files, we cannot do major anyway
      boolean isAllFiles = candidateFiles.size() == candidateSelection.size();
      if (!(forceMajor && isAllFiles)) {
        candidateSelection = skipLargeFiles(candidateSelection, mayUseOffPeak);
        isAllFiles = candidateFiles.size() == candidateSelection.size();
      }
  
      // Try a major compaction if this is a user-requested major compaction,
      // or if we do not have too many files to compact and this was requested as a major compaction
      boolean isTryingMajor = (forceMajor && isAllFiles && isUserCompaction)
          || (((forceMajor && isAllFiles) || shouldPerformMajorCompaction(candidateSelection))
            && (candidateSelection.size() < comConf.getMaxFilesToCompact()));
      // Or, if there are any references among the candidates.
      boolean isAfterSplit = StoreUtils.hasReferences(candidateSelection);
  
      CompactionRequest result = createCompactionRequest(candidateSelection,
        isTryingMajor || isAfterSplit, mayUseOffPeak, mayBeStuck);
  
      ArrayList<StoreFile> filesToCompact = Lists.newArrayList(result.getFiles());
      removeExcessFiles(filesToCompact, isUserCompaction, isTryingMajor);
      result.updateFiles(filesToCompact);
  
      isAllFiles = (candidateFiles.size() == filesToCompact.size());
      result.setOffPeak(!filesToCompact.isEmpty() && !isAllFiles && mayUseOffPeak);
      result.setIsMajor(isTryingMajor && isAllFiles, isAllFiles);
  
      return result;
    }
 
   protected abstract CompactionRequest createCompactionRequest(ArrayList<StoreFile>
     candidateSelection, boolean tryingMajor, boolean mayUseOffPeak, boolean mayBeStuck)
     throws IOException;
 
   /*
    * @param filesToCompact Files to compact. Can be null.
    * @return True if we should run a major compaction.
    */
   @Override
   public abstract boolean shouldPerformMajorCompaction(final Collection<StoreFile> filesToCompact)
     throws IOException;
 
   /**
    * Used calculation jitter
    */
   private final Random random = new Random();
 
   /**
    * @param filesToCompact
    * @return When to run next major compaction
    */
   public long getNextMajorCompactTime(final Collection<StoreFile> filesToCompact) {
     // default = 24hrs
     long ret = comConf.getMajorCompactionPeriod();
     if (ret > 0) {
       // default = 20% = +/- 4.8 hrs
       double jitterPct = comConf.getMajorCompactionJitter();
       if (jitterPct > 0) {
         long jitter = Math.round(ret * jitterPct);
         // deterministic jitter avoids a major compaction storm on restart
         Integer seed = StoreUtils.getDeterministicRandomSeed(filesToCompact);
         if (seed != null) {
           // Synchronized to ensure one user of random instance at a time.
           double rnd = -1;
           synchronized (this) {
             this.random.setSeed(seed);
             rnd = this.random.nextDouble();
           }
           ret += jitter - Math.round(2L * jitter * rnd);
         } else {
           ret = 0; // If seed is null, then no storefiles == no major compaction
         }
       }
     }
     return ret;
   }
 
   /**
    * @param compactionSize Total size of some compaction
    * @return whether this should be a large or small compaction
    */
   @Override
   public boolean throttleCompaction(long compactionSize) {
     return compactionSize > comConf.getThrottlePoint();
   }
 
   public abstract boolean needsCompaction(final Collection<StoreFile> storeFiles,
     final List<StoreFile> filesCompacting);
 
   protected ArrayList<StoreFile> getCurrentEligibleFiles(ArrayList<StoreFile> candidateFiles,
       final List<StoreFile> filesCompacting) {
     // candidates = all storefiles not already in compaction queue
     if (!filesCompacting.isEmpty()) {
       // exclude all files older than the newest file we're currently
       // compacting. this allows us to preserve contiguity (HBASE-2856)
       StoreFile last = filesCompacting.get(filesCompacting.size() - 1);
       int idx = candidateFiles.indexOf(last);
       Preconditions.checkArgument(idx != -1);
       candidateFiles.subList(0, idx + 1).clear();
     }
     return candidateFiles;
   }
 
   /**
    * @param candidates pre-filtrate
    * @return filtered subset exclude all files above maxCompactSize
    *   Also save all references. We MUST compact them
    */
   protected ArrayList<StoreFile> skipLargeFiles(ArrayList<StoreFile> candidates,
     boolean mayUseOffpeak) {
     int pos = 0;
     while (pos < candidates.size() && !candidates.get(pos).isReference()
       && (candidates.get(pos).getReader().length() > comConf.getMaxCompactSize(mayUseOffpeak))) {
       ++pos;
     }
     if (pos > 0) {
       LOG.debug("Some files are too large. Excluding " + pos
           + " files from compaction candidates");
       candidates.subList(0, pos).clear();
     }
     return candidates;
   }
 
   /**
    * @param candidates pre-filtrate
    * @return filtered subset exclude all bulk load files if configured
    */
   protected ArrayList<StoreFile> filterBulk(ArrayList<StoreFile> candidates) {
     candidates.removeAll(Collections2.filter(candidates, new Predicate<StoreFile>() {
       @Override
       public boolean apply(StoreFile input) {
         return input.excludeFromMinorCompaction();
       }
     }));
     return candidates;
   }
 
   /**
    * @param candidates pre-filtrate
    */
   protected void removeExcessFiles(ArrayList<StoreFile> candidates,
       boolean isUserCompaction, boolean isMajorCompaction) {
     int excess = candidates.size() - comConf.getMaxFilesToCompact();
     if (excess > 0) {
       if (isMajorCompaction && isUserCompaction) {
         LOG.debug("Warning, compacting more than " + comConf.getMaxFilesToCompact()
             + " files because of a user-requested major compaction");
       } else {
         LOG.debug("Too many admissible files. Excluding " + excess
             + " files from compaction candidates");
         candidates.subList(comConf.getMaxFilesToCompact(), candidates.size()).clear();
       }
     }
   }
 
   /**
    * @param candidates pre-filtrate
    * @return filtered subset forget the compactionSelection if we don't have enough files
    */
   protected ArrayList<StoreFile> checkMinFilesCriteria(ArrayList<StoreFile> candidates,
     int minFiles) {
     if (candidates.size() < minFiles) {
       if (LOG.isDebugEnabled()) {
         LOG.debug("Not compacting files because we only have " + candidates.size()
             + " files ready for compaction. Need " + minFiles + " to initiate.");
       }
       candidates.clear();
     }
     return candidates;
   }
 }