/*
    * 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.giraph.utils;
  
  import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
  
  import java.util.concurrent.atomic.AtomicInteger;
  
  import org.apache.giraph.conf.FloatConfOption;
  import org.apache.giraph.conf.GiraphConstants;
  import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration;
  import org.apache.giraph.conf.IntConfOption;
  
  /**
   * Wraps a list of byte array outputs and provides convenient
   * utilities on top of it
   */
  public class ExtendedByteArrayOutputBuffer {
    /**
     * This option sets the capacity of an
     * {@link org.apache.giraph.utils.ExtendedDataOutput} instance created in
     * {@link org.apache.giraph.utils.ExtendedByteArrayOutputBuffer}
     */
    public static final IntConfOption CAPACITY_OF_DATAOUT_IN_BUFFER =
        new IntConfOption("giraph.capacityOfDataOutInBuffer",
            1024 * GiraphConstants.ONE_KB,
            "Set the capacity of dataoutputs in dataout buffer");
  
    /**
     * This option sets the maximum fraction of a
     * {@link org.apache.giraph.utils.ExtendedDataOutput} instance (stored in
     * {@link org.apache.giraph.utils.ExtendedByteArrayOutputBuffer})
     * that can be filled
     */
    public static final FloatConfOption FILLING_THRESHOLD_OF_DATAOUT_IN_BUFFER =
        new FloatConfOption("giraph.fillingThresholdOfDataoutInBuffer", 0.98f,
            "Set the maximum fraction of dataoutput capacity allowed to fill");
  
    /** Maximum size allowed for one byte array output */
    private final int maxBufSize;
    /** Stop writing to buffer after threshold has been reached */
    private final int threshold;
    /** Giraph configuration */
    private final ImmutableClassesGiraphConfiguration<?, ? , ?> config;
  
    /** Map of index => byte array outputs */
    private final Int2ObjectOpenHashMap<ExtendedDataOutput>
    bytearrayOutputs = new Int2ObjectOpenHashMap<>();
    /** Size of byte array outputs map */
    private final AtomicInteger mapSize = new AtomicInteger(0);
    /** Thread local variable to get hold of a byte array output stream */
    private final ThreadLocal<IndexAndDataOut> threadLocal =
      new ThreadLocal<IndexAndDataOut>() {
        @Override
        protected IndexAndDataOut initialValue() {
          return newIndexAndDataOutput();
        }
      };
  
    /**
     * Constructor
     *
     * @param config configuration
     */
    public ExtendedByteArrayOutputBuffer(
      ImmutableClassesGiraphConfiguration<?, ?, ?> config) {
      this.config = config;
  
      maxBufSize = CAPACITY_OF_DATAOUT_IN_BUFFER.get(config);
      threshold = (int) (FILLING_THRESHOLD_OF_DATAOUT_IN_BUFFER.get(config) *
        maxBufSize);
    }
  
    /**
     * Return threadLocal indexAndDataOutput instance
     *
     * @return threadLocal indexAndDataOutput instance
     */
    public IndexAndDataOut getIndexAndDataOut() {
      IndexAndDataOut indexAndDataOut = threadLocal.get();
      if (indexAndDataOut.dataOutput.getPos() >= threshold) {
        indexAndDataOut = newIndexAndDataOutput();
        threadLocal.set(indexAndDataOut);
     }
     return indexAndDataOut;
   }
 
   /**
    * Get dataoutput from bytearrayOutputs
    *
    * @param index index in bytearrayOutputs
    * @return extendeddataoutput at given index
    */
   public ExtendedDataOutput getDataOutput(int index) {
     return bytearrayOutputs.get(index);
   }
 
   /**
    * Holder for index &amp; DataOutput objects
    */
   public static class IndexAndDataOut {
     /** Index */
     private final int index;
     /** Dataouput instance */
     private final ExtendedDataOutput dataOutput;
 
     /**
      * Constructor
      *
      * @param index index in bytearrayOutputs
      * @param dataOutput dataoutput
      */
     public IndexAndDataOut(int index, ExtendedDataOutput dataOutput) {
       this.index = index;
       this.dataOutput = dataOutput;
     }
 
     public int getIndex() {
       return index;
     }
 
     public ExtendedDataOutput getDataOutput() {
       return dataOutput;
     }
   }
 
   /**
    * Create a new IndexAndDataOutput instance
    * @return new IndexAndDataOutput instance
    */
   private IndexAndDataOut newIndexAndDataOutput() {
     int index = mapSize.getAndIncrement();
     ExtendedDataOutput output = config.createExtendedDataOutput(
         maxBufSize);
     synchronized (bytearrayOutputs) {
       bytearrayOutputs.put(index, output);
     }
     return new IndexAndDataOut(index, output);
   }
 }