/**
 * 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.mapred;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
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.fs.FSDataInputStream;
import org.apache.hadoop.fs.ChecksumFileSystem;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.LocalDirAllocator;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.io.RawComparator;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.mapred.IFile.Reader;
import org.apache.hadoop.mapred.IFile.Writer;
import org.apache.hadoop.util.PriorityQueue;
import org.apache.hadoop.util.Progress;
import org.apache.hadoop.util.Progressable;

class Merger {  
  private static final Log LOG = LogFactory.getLog(Merger.class);

  // Local directories
  private static LocalDirAllocator lDirAlloc = 
    new LocalDirAllocator("mapred.local.dir");

  public static <K extends Object, V extends Object>
  RawKeyValueIterator merge(Configuration conf, FileSystem fs,
                            Class<K> keyClass, Class<V> valueClass, 
                            CompressionCodec codec,
                            Path[] inputs, boolean deleteInputs, 
                            int mergeFactor, Path tmpDir,
                            RawComparator<K> comparator, Progressable reporter,
                            Counters.Counter readsCounter,
                            Counters.Counter writesCounter)
  throws IOException {
    return 
      new MergeQueue<K, V>(conf, fs, inputs, deleteInputs, codec, comparator, 
                           reporter).merge(keyClass, valueClass,
                                           mergeFactor, tmpDir,
                                           readsCounter, writesCounter);
  }
  
  public static <K extends Object, V extends Object>
  RawKeyValueIterator merge(Configuration conf, FileSystem fs,
                                   Class<K> keyClass, Class<V> valueClass,
                                   CompressionCodec codec,
                                   List<Segment<K, V>> segments, 
                                   int mergeFactor, Path tmpDir,
                                   RawComparator<K> comparator, Progressable reporter,
                                   Counters.Counter readsCounter,
                                   Counters.Counter writesCounter)
      throws IOException {
    return new MergeQueue<K, V>(conf, fs, segments, comparator, reporter,
        false, codec).merge(keyClass, valueClass,
            mergeFactor, tmpDir,
            readsCounter, writesCounter);

  }

  public static <K extends Object, V extends Object>
  RawKeyValueIterator merge(Configuration conf, FileSystem fs, 
                            Class<K> keyClass, Class<V> valueClass, 
                            List<Segment<K, V>> segments, 
                            int mergeFactor, Path tmpDir,
                            RawComparator<K> comparator, Progressable reporter,
                            Counters.Counter readsCounter,
                            Counters.Counter writesCounter)
      throws IOException {
    return merge(conf, fs, keyClass, valueClass, segments, mergeFactor, tmpDir,
                 comparator, reporter, false, readsCounter, writesCounter);
  }

  public static <K extends Object, V extends Object>
  RawKeyValueIterator merge(Configuration conf, FileSystem fs,
                            Class<K> keyClass, Class<V> valueClass,
                            List<Segment<K, V>> segments,
                            int mergeFactor, Path tmpDir,
                            RawComparator<K> comparator, Progressable reporter,
                            boolean sortSegments,
                            Counters.Counter readsCounter,
                            Counters.Counter writesCounter)
      throws IOException {
    return new MergeQueue<K, V>(conf, fs, segments, comparator, reporter,
                           sortSegments).merge(keyClass, valueClass,
                                               mergeFactor, tmpDir,
                                               readsCounter, writesCounter);
  }

  static <K extends Object, V extends Object>
    RawKeyValueIterator merge(Configuration conf, FileSystem fs,
                            Class<K> keyClass, Class<V> valueClass,
                            List<Segment<K, V>> segments,
                            int mergeFactor, int inMemSegments, Path tmpDir,
                            RawComparator<K> comparator, Progressable reporter,
                            boolean sortSegments,
                            Counters.Counter readsCounter,
                            Counters.Counter writesCounter)
      throws IOException {
    return new MergeQueue<K, V>(conf, fs, segments, comparator, reporter,
                           sortSegments).merge(keyClass, valueClass,
                                               mergeFactor, inMemSegments,