/*
    * 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.chukwa.datacollection.adaptor;
  
  import static org.apache.hadoop.chukwa.datacollection.adaptor.AdaptorShutdownPolicy.RESTARTING;
  import java.util.*;
  import org.apache.hadoop.chukwa.Chunk;
  import org.apache.hadoop.chukwa.datacollection.ChunkReceiver;
  
  public class MemBuffered extends AbstractWrapper {
    
    static final String BUF_SIZE_OPT = "adaptor.memBufWrapper.size";
    static final int DEFAULT_BUF_SIZE = 1024*1024; //1 MB
    
    //true by default. If you were willing to discard data, you didn't need Mem Buffers
    static boolean BLOCK_WHEN_FULL = true;
    
    static class MemBuf {
      long dataSizeBytes;
      final long maxDataSize;
      final ArrayDeque<Chunk> chunks;
      
      public MemBuf(long maxDataSize) {
        dataSizeBytes = 0;
        this.maxDataSize = maxDataSize;
        chunks = new ArrayDeque<Chunk>();
      }
      
      synchronized void add(Chunk c) throws InterruptedException{
        int len = c.getData().length;
        if(BLOCK_WHEN_FULL)
          while(len + dataSizeBytes > maxDataSize)
            wait();
        else
          chunks.remove();
        dataSizeBytes += len;
        chunks.add(c);
      }
      
      synchronized void removeUpTo(long l) {
  
        long bytesFreed = 0;
        while(!chunks.isEmpty()) {
          Chunk c = chunks.getFirst();
          if(c.getSeqID() > l)
            chunks.addFirst(c);
          else
            bytesFreed += c.getData().length;
        }
        
        if(bytesFreed > 0) {
          dataSizeBytes -= bytesFreed;
          notifyAll();
        }
      }
      
    }
  
    static Map<String, MemBuf> buffers;
    static {
      buffers = new HashMap<String, MemBuf>();
    }
    
    MemBuf myBuffer;
    
    @Override
    public void add(Chunk event) throws InterruptedException {
      myBuffer.add(event);
      dest.add(event);
    }
    
    @Override
    public void start(String adaptorID, String type, long offset,
        ChunkReceiver dest) throws AdaptorException {
      try {
        String dummyAdaptorID = adaptorID;
        this.adaptorID = adaptorID;
        this.dest = dest;
        
        long bufSize = manager.getConfiguration().getInt(BUF_SIZE_OPT, DEFAULT_BUF_SIZE);
        synchronized(buffers) {
          myBuffer = buffers.get(adaptorID);
          if(myBuffer == null) {
            myBuffer = new MemBuf(bufSize);
           buffers.put(adaptorID, myBuffer);
         }
       }
 
       //Drain buffer into output queue
       long offsetToStartAt = offset;
       for(Chunk c:myBuffer.chunks) {
         dest.add(c);
         long seq = c.getSeqID();
         if(seq > offsetToStartAt)
           offsetToStartAt = seq;
       }
       
       inner.start(dummyAdaptorID, innerType, offsetToStartAt, this);
     } catch(InterruptedException e) {
      throw new AdaptorException(e);
     }
   }
   
   @Override
   public void committed(long l) {
     myBuffer.removeUpTo(l);
   }
   
   @Override
   public long shutdown(AdaptorShutdownPolicy p) throws AdaptorException {
     if(p != RESTARTING)
       buffers.remove(adaptorID);    
     return inner.shutdown(p);
   }
 
 
 }