/*
    * 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 java.util.*;
  import java.io.*;
  import org.apache.hadoop.chukwa.Chunk;
  import org.apache.hadoop.chukwa.ChunkImpl;
  import org.apache.hadoop.chukwa.datacollection.ChunkReceiver;
  import org.apache.log4j.Logger;
  import static org.apache.hadoop.chukwa.datacollection.adaptor.AdaptorShutdownPolicy.*;
  
  public class WriteaheadBuffered extends AbstractWrapper {
    Logger log = Logger.getLogger(WriteaheadBuffered.class);
    static final String BUF_DIR_OPT = "adaptor.writeaheadWrapper.dir";
    static  String BUF_DIR = "/tmp"; //1 MB
    static long COMPACT_AT = 1024 * 1024; //compact when it can free at least this much storage
    
    File outBuf;
    DataOutputStream outToDisk;
    long fSize, highestSentOffset;
    
    
    @Override
    public synchronized void add(Chunk event) throws InterruptedException {
      try {
        event.write(outToDisk);
        outToDisk.flush();
        fSize += event.getData().length;
        long seq = event.getSeqID();
        if(seq > highestSentOffset)
          highestSentOffset = seq;
      } catch(IOException e) {
        log.error(e);
      }
      dest.add(event);
    }
    
    @Override
    public void start(String adaptorID, String type, long offset,
        ChunkReceiver dest) throws AdaptorException {
      try {
        String dummyAdaptorID = adaptorID;
        this.dest = dest;
        
        outBuf = new File(BUF_DIR, adaptorID);
        long newOffset = offset;
        if(outBuf.length() > 0) {
          DataInputStream dis = new DataInputStream(new FileInputStream(outBuf));
          while(dis.available() > 0) {
            Chunk c = ChunkImpl.read(dis);
            fSize += c.getData().length;
            long seq = c.getSeqID();
            if(seq >offset) {
              dest.add(c);
              newOffset = seq;
            }
          }
          //send chunks that are outstanding        
          dis.close();
        }
        outToDisk = new DataOutputStream(new FileOutputStream(outBuf, true));
        
        inner.start(dummyAdaptorID, innerType, newOffset, this);
      } catch(IOException e) {
        throw new AdaptorException(e);
      } catch(InterruptedException e) {
        throw new AdaptorException(e);
      }
    }
    
    @Override
    public synchronized void committed(long l) {
  
      try {
        long bytesOutstanding = highestSentOffset - l;
        if(fSize - bytesOutstanding > COMPACT_AT) {
          fSize = 0;
          outToDisk.close();
          File outBufTmp = new File(outBuf.getAbsoluteFile(), outBuf.getName() + ".tmp");
          outBuf.renameTo(outBufTmp);
          outToDisk = new DataOutputStream(new FileOutputStream(outBuf, false));
          DataInputStream dis = new DataInputStream(new FileInputStream(outBufTmp));
          while(dis.available() > 0) {
           Chunk c = ChunkImpl.read(dis);
           if(c.getSeqID() > l) { //not yet committed
             c.write(outToDisk);
             fSize += c.getData().length;
           }
         }
         dis.close();
         outBufTmp.delete();
       }
     } catch(IOException e) {
       log.error(e);
       //should this be fatal?
     }
   }
   
   @Override
   public long shutdown(AdaptorShutdownPolicy p) throws AdaptorException {
     if(p != RESTARTING)
       outBuf.delete();    
     return inner.shutdown(p);
   }
 
 }