/*
    *  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.mina.filter.errorgenerating;
  
  import java.util.Random;
  
  import org.apache.mina.core.buffer.IoBuffer;
  import org.apache.mina.core.filterchain.IoFilter;
  import org.apache.mina.core.filterchain.IoFilterAdapter;
  import org.apache.mina.core.session.IoSession;
  import org.apache.mina.core.write.DefaultWriteRequest;
  import org.apache.mina.core.write.WriteRequest;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * An {@link IoFilter} implementation generating random bytes and PDU modification in
   * your communication streams.
   * It's quite simple to use :
   * <code>ErrorGeneratingFilter egf = new ErrorGeneratingFilter();</code>
   * For activate the change of some bytes in your {@link IoBuffer}, for a probability of 200 out
   * of 1000 {@link IoBuffer} processed :
   * <code>egf.setChangeByteProbability(200);</code>
   * For activate the insertion of some bytes in your {@link IoBuffer}, for a
   * probability of 200 out of 1000 :
   * <code>egf.setInsertByteProbability(200);</code>
   * And for the removing of some bytes :
   * <code>egf.setRemoveByteProbability(200);</code>
   * You can activate the error generation for write or read with the
   * following methods :
   * <code>egf.setManipulateReads(true);
   * egf.setManipulateWrites(true); </code>
   * 
   * @author The Apache MINA Project (dev@mina.apache.org)
   * @org.apache.xbean.XBean
   */
  public class ErrorGeneratingFilter extends IoFilterAdapter {
      private int removeByteProbability = 0;
  
      private int insertByteProbability = 0;
  
      private int changeByteProbability = 0;
  
      private int removePduProbability = 0;
  
      private int duplicatePduProbability = 0;
  
      private int resendPduLasterProbability = 0;
  
      private int maxInsertByte = 10;
  
      private boolean manipulateWrites = false;
  
      private boolean manipulateReads = false;
  
      private Random rng = new Random();
  
      final private Logger logger = LoggerFactory
              .getLogger(ErrorGeneratingFilter.class);
  
      @Override
      public void filterWrite(NextFilter nextFilter, IoSession session,
              WriteRequest writeRequest) throws Exception {
          if (manipulateWrites) {
              // manipulate bytes
              if (writeRequest.getMessage() instanceof IoBuffer) {
                  manipulateIoBuffer(session, (IoBuffer) writeRequest
                          .getMessage());
                  IoBuffer buffer = insertBytesToNewIoBuffer(session,
                          (IoBuffer) writeRequest.getMessage());
                  if (buffer != null) {
                      writeRequest = new DefaultWriteRequest(buffer, writeRequest
                              .getFuture(), writeRequest.getDestination());
                  }
                  // manipulate PDU
              } else {
                  if (duplicatePduProbability > rng.nextInt()) {
                      nextFilter.filterWrite(session, writeRequest);
                  }
                  
                  if (resendPduLasterProbability > rng.nextInt()) {
                     // store it somewhere and trigger a write execution for
                     // later
                     // TODO
                 }
                 if (removePduProbability > rng.nextInt()) {
                     return;
                 }
             }
         }
         nextFilter.filterWrite(session, writeRequest);
     }
 
     @Override
     public void messageReceived(NextFilter nextFilter, IoSession session,
             Object message) throws Exception {
         if (manipulateReads) {
             if (message instanceof IoBuffer) {
                 // manipulate bytes
                 manipulateIoBuffer(session, (IoBuffer) message);
                 IoBuffer buffer = insertBytesToNewIoBuffer(session,
                         (IoBuffer) message);
                 if (buffer != null) {
                     message = buffer;
                 }
             } else {
                 // manipulate PDU
                 // TODO
             }
         }
         nextFilter.messageReceived(session, message);
     }
 
     private IoBuffer insertBytesToNewIoBuffer(IoSession session, IoBuffer buffer) {
         if (insertByteProbability > rng.nextInt(1000)) {
             logger.info(buffer.getHexDump());
             // where to insert bytes ?
             int pos = rng.nextInt(buffer.remaining()) - 1;
 
             // how many byte to insert ?
             int count = rng.nextInt(maxInsertByte-1)+1;
 
             IoBuffer newBuff = IoBuffer.allocate(buffer.remaining() + count);
             for (int i = 0; i < pos; i++)
                 newBuff.put(buffer.get());
             for (int i = 0; i < count; i++) {
                 newBuff.put((byte) (rng.nextInt(256)));
             }
             while (buffer.remaining() > 0) {
                 newBuff.put(buffer.get());
             }
             newBuff.flip();
 
             logger.info("Inserted " + count + " bytes.");
             logger.info(newBuff.getHexDump());
             return newBuff;
         }
         return null;
     }
 
     private void manipulateIoBuffer(IoSession session, IoBuffer buffer) {
         if (removeByteProbability > rng.nextInt(1000)) {
             logger.info(buffer.getHexDump());
             // where to remove bytes ?
             int pos = rng.nextInt(buffer.remaining());
             // how many byte to remove ?
             int count = rng.nextInt(buffer.remaining() - pos) + 1;
             if (count == buffer.remaining())
                 count = buffer.remaining() - 1;
 
             IoBuffer newBuff = IoBuffer.allocate(buffer.remaining() - count);
             for (int i = 0; i < pos; i++)
                 newBuff.put(buffer.get());
 
             buffer.skip(count); // hole
             while (newBuff.remaining() > 0)
                 newBuff.put(buffer.get());
             newBuff.flip();
             // copy the new buffer in the old one
             buffer.rewind();
             buffer.put(newBuff);
             buffer.flip();
             logger.info("Removed " + count + " bytes at position " + pos + ".");
             logger.info(buffer.getHexDump());
         }
         if (changeByteProbability > rng.nextInt(1000)) {
             logger.info(buffer.getHexDump());
             // how many byte to change ?
             int count = rng.nextInt(buffer.remaining() - 1) + 1;
 
             byte[] values = new byte[count];
             rng.nextBytes(values);
             for (int i = 0; i < values.length; i++) {
                 int pos = rng.nextInt(buffer.remaining());
                 buffer.put(pos, values[i]);
             }
             logger.info("Modified " + count + " bytes.");
             logger.info(buffer.getHexDump());
         }
     }
 
     public int getChangeByteProbability() {
         return changeByteProbability;
     }
     
     /**
      * Set the probability for the change byte error.
      * If this probability is > 0 the filter will modify a random number of byte
      * of the processed {@link IoBuffer}.
      * @param changeByteProbability probability of modifying an IoBuffer out of 1000 processed {@link IoBuffer} 
      */
     public void setChangeByteProbability(int changeByteProbability) {
         this.changeByteProbability = changeByteProbability;
     }
 
     public int getDuplicatePduProbability() {
         return duplicatePduProbability;
     }
     
     /**
      * not functional ATM
      * @param duplicatePduProbability
      */
     public void setDuplicatePduProbability(int duplicatePduProbability) {
         this.duplicatePduProbability = duplicatePduProbability;
     }
 
     public int getInsertByteProbability() {
         return insertByteProbability;
     }
 
     /**
      * Set the probability for the insert byte error.
      * If this probability is > 0 the filter will insert a random number of byte
      * in the processed {@link IoBuffer}.
      * @param changeByteProbability probability of inserting in IoBuffer out of 1000 processed {@link IoBuffer} 
      */
     public void setInsertByteProbability(int insertByteProbability) {
         this.insertByteProbability = insertByteProbability;
     }
 
     public boolean isManipulateReads() {
         return manipulateReads;
     }
 
     /**
      * Set to true if you want to apply error to the read {@link IoBuffer}
      * @param manipulateReads
      */
     public void setManipulateReads(boolean manipulateReads) {
         this.manipulateReads = manipulateReads;
     }
 
     public boolean isManipulateWrites() {
         return manipulateWrites;
     }
 
     /**
      * Set to true if you want to apply error to the written {@link IoBuffer}
      * @param manipulateWrites
      */
     public void setManipulateWrites(boolean manipulateWrites) {
         this.manipulateWrites = manipulateWrites;
     }
 
     public int getRemoveByteProbability() {
         return removeByteProbability;
     }
 
     /**
      * Set the probability for the remove byte error.
      * If this probability is > 0 the filter will remove a random number of byte
      * in the processed {@link IoBuffer}.
      * @param changeByteProbability probability of modifying an {@link IoBuffer} out of 1000 processed IoBuffer 
      */
     public void setRemoveByteProbability(int removeByteProbability) {
         this.removeByteProbability = removeByteProbability;
     }
 
     public int getRemovePduProbability() {
         return removePduProbability;
     }
 
     /**
      * not functional ATM
      * @param removePduProbability
      */
     public void setRemovePduProbability(int removePduProbability) {
         this.removePduProbability = removePduProbability;
     }
 
     public int getResendPduLasterProbability() {
         return resendPduLasterProbability;
     }
     /**
      * not functional ATM
      * @param resendPduLasterProbability
      */
     public void setResendPduLasterProbability(int resendPduLasterProbability) {
         this.resendPduLasterProbability = resendPduLasterProbability;
     }
 
     public int getMaxInsertByte() {
         return maxInsertByte;
     }
 
     /**
      * Set the maximum number of byte the filter can insert in a {@link IoBuffer}.
      * The default value is 10.
      * @param maxInsertByte maximum bytes inserted in a {@link IoBuffer} 
      */
     public void setMaxInsertByte(int maxInsertByte) {
         this.maxInsertByte = maxInsertByte;
     }
 }