/*
 * 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.carbondata.processing.sort.sortdata;

import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

import org.apache.carbondata.common.logging.LogServiceFactory;
import org.apache.carbondata.core.constants.CarbonCommonConstants;
import org.apache.carbondata.core.util.CarbonThreadFactory;
import org.apache.carbondata.processing.sort.exception.CarbonSortKeyAndGroupByException;

import org.apache.log4j.Logger;

/**
 * It does mergesort intermediate files to big file.
 */
public class SortIntermediateFileMerger {

  private static final Logger LOGGER =
      LogServiceFactory.getLogService(SortIntermediateFileMerger.class.getName());

  private ExecutorService executorService;

  private List<File> procFiles;

  private SortParameters parameters;

  private final Object lockObject = new Object();

  private List<Future<Void>> mergerTask;

  public SortIntermediateFileMerger(SortParameters parameters) {
    this.parameters = parameters;
    // processed file list
    this.procFiles = new ArrayList<File>(CarbonCommonConstants.CONSTANT_SIZE_TEN);
    this.executorService = Executors.newFixedThreadPool(parameters.getNumberOfCores(),
        new CarbonThreadFactory("SafeIntermediateMergerPool:" + parameters.getTableName(),
                true));
    mergerTask = new ArrayList<>();
  }

  public void addFileToMerge(File sortTempFile) {
    // add sort temp filename to and arrayList. When the list size reaches 20 then
    // intermediate merging of sort temp files will be triggered
    synchronized (lockObject) {
      procFiles.add(sortTempFile);
      if (procFiles.size() >= parameters.getNumberOfIntermediateFileToBeMerged()) {
        File[] fileList = procFiles.toArray(new File[procFiles.size()]);
        this.procFiles = new ArrayList<>();
        startIntermediateMerging(fileList);
      }
    }
  }

  /**
   * Below method will be used to start the intermediate file merging
   *
   * @param intermediateFiles
   */
  private void startIntermediateMerging(File[] intermediateFiles) {
    int index = new Random().nextInt(parameters.getTempFileLocation().length);
    String chosenTempDir = parameters.getTempFileLocation()[index];
    File file = new File(chosenTempDir + File.separator + parameters.getTableName()
        + '_' + parameters.getRangeId() + '_' + System.nanoTime()
        + CarbonCommonConstants.MERGERD_EXTENSION);
    IntermediateFileMerger merger = new IntermediateFileMerger(parameters, intermediateFiles, file);
    if (LOGGER.isDebugEnabled()) {
      LOGGER.debug("Submitting request for intermediate merging number of files: "
              + intermediateFiles.length);
    }
    mergerTask.add(executorService.submit(merger));
  }

  public void finish() throws CarbonSortKeyAndGroupByException {
    try {
      executorService.shutdown();
      executorService.awaitTermination(2, TimeUnit.DAYS);
    } catch (InterruptedException e) {
      throw new CarbonSortKeyAndGroupByException("Problem while shutdown the server ", e);
    }
    procFiles.clear();
    procFiles = null;
    checkForFailure();
  }

  private void checkForFailure() throws CarbonSortKeyAndGroupByException {
    for (int i = 0; i < mergerTask.size(); i++) {
      try {
        mergerTask.get(i).get();
      } catch (InterruptedException | ExecutionException e) {
        LOGGER.error(e.getMessage(), e);
        throw new CarbonSortKeyAndGroupByException(e);
      }
    }
  }

  public void close() {
    if (!executorService.isShutdown()) {
      executorService.shutdownNow();
    }
  }

}
