/*
    * Copyright 2007, 2008 Ange Optimization ApS
    *
    * Licensed 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 eu.simuline.octave.util;
  
  import java.io.IOException;
  import java.io.Reader;
  import java.io.Writer;
  
  import eu.simuline.octave.exception.OctaveIOException;
  import eu.simuline.octave.exception.OctaveInterruptedException;
  
  import org.apache.commons.logging.LogFactory;
  import org.apache.commons.logging.Log;
  
  /**
   * A Thread that moves data from a Reader to a Writer. 
   * 
   * @author Kim Hansen
   */
  public final class ReaderWriterPipeThread extends Thread {
  
      private static final Log LOG = LogFactory
  	.getLog(ReaderWriterPipeThread.class);
  
      @SuppressWarnings("checkstyle:magicnumber")
      private static final char[] BUF = new char[4 * 1024];
   
      private final Reader reader;
  
      private Writer writer;
  
      /**
       * Will create a thread that reads from reader and writes to write 
       * until reader reaches EOF. 
       * Then the thread will close. 
       * Remember to join() this thread before closing reader or writer.
       * 
       * @param reader
       * @param writer
       *    may be null TBC: does this make sense? 
       * @return Returns the new thread
       */
      public static ReaderWriterPipeThread instantiate(final Reader reader, 
  						     final Writer writer) {
          final ReaderWriterPipeThread readerWriterPipeThread = 
  	    new ReaderWriterPipeThread(reader, writer);
          readerWriterPipeThread.setName(Thread.currentThread().getName() 
  				       + "-javaoctave-"
  				       + ReaderWriterPipeThread.class
  				       .getSimpleName());
  	readerWriterPipeThread
  	    .setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
  		    public void uncaughtException(Thread th, Throwable ex) {
  			System.out.println("Uncaught : " + ex + 
  					   " of thread " + th.getName());
  		    }
  		});
          readerWriterPipeThread.start();
          return readerWriterPipeThread;
      }
  
      /**
       * 
       * @param reader
       * @param writer
       *    may be null TBC: does this make sense? 
       */
      private ReaderWriterPipeThread(final Reader reader, final Writer writer) {
          this.reader = reader;
          this.writer = writer;
      }
  
      @Override
      public void run() {
          while (!interrupted()) {
              int len;
              try {
                  len = this.reader.read(BUF);
              } catch (final IOException e) {
                  LOG.error("Error when reading from reader", e);
                  throw new OctaveIOException(e);
              }
              if (len == -1) {
                  break;
              }
              try {
                 synchronized (this) {
                     if (this.writer != null) {
                 	this.writer.write(BUF, 0, len);
                 	this.writer.flush();
                     }
                 }
             } catch (final IOException e) {
                 LOG.error("Error when writing to writer", e);
                 throw new OctaveIOException(e);
             }
         }
         LOG.debug("ReaderWriterPipeThread finished without error");
     }
 
     /**
      * @param writer
      *    the writer to set
      *    This may be null TBC 
      */
     public void setWriter(final Writer writer) {
         synchronized (this) {
             this.writer = writer;
         }
     }
 
     /**
      * Close the thread.
      */
     public void close() {
         interrupt();
         try {
             join();
         } catch (final InterruptedException e) {
             throw new OctaveInterruptedException(e);
         }
     }
 
 }