package org.apache.helix;
   
   /*
    * 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.
   */
  
  import java.io.BufferedInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.UnsupportedEncodingException;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.TimeoutException;
  
  import org.apache.log4j.Logger;
  
  public class ExternalCommand
  {
    public static final String MODULE = ExternalCommand.class.getName();
    public static final Logger LOG = Logger.getLogger(MODULE);
  
    private final ProcessBuilder _processBuilder;
  
    private Process _process;
    private InputReader _out;
    private InputReader _err;
  
    private static class InputReader extends Thread
    {
      private static final int BUFFER_SIZE = 2048;
  
      private final InputStream _in;
      private final ByteArrayOutputStream _out;
      private boolean _running = false;
  
      InputReader(InputStream in)
      {
        _in = in;
        _out = new ByteArrayOutputStream();
      }
  
      @Override
      public void run()
      {
        _running = true;
  
        byte[] buf = new byte[BUFFER_SIZE];
        int n = 0;
        try
        {
          while((n = _in.read(buf)) != -1)
            _out.write(buf, 0, n);
        }
        catch(IOException e)
        {
          LOG.error("error while reading external command", e);
        }
  
        _running = false;
      }
  
      public byte[] getOutput()
      {
        if(_running)
          throw new IllegalStateException("wait for process to be completed");
  
        return _out.toByteArray();
      }
    }
    /**
  * Constructor */
    public ExternalCommand(ProcessBuilder processBuilder)
    {
      _processBuilder = processBuilder;
    }
  
    /**
  * After creating the command, you have to start it...
  *
  * @throws IOException
 */
   public void start() throws IOException
   {
     _process = _processBuilder.start();
     _out = new InputReader(new BufferedInputStream(_process.getInputStream()));
     _err = new InputReader(new BufferedInputStream(_process.getErrorStream()));
 
     _out.start();
     _err.start();
   }
 
   /**
 * @see ProcessBuilder
 */
   public Map<String, String> getEnvironment()
   {
     return _processBuilder.environment();
   }
 
   /**
 * @see ProcessBuilder
 */
   public File getWorkingDirectory()
   {
     return _processBuilder.directory();
   }
 
   /**
 * @see ProcessBuilder
 */
   public void setWorkingDirectory(File directory)
   {
     _processBuilder.directory(directory);
   }
 
   /**
 * @see ProcessBuilder
 */
   public boolean getRedirectErrorStream()
   {
     return _processBuilder.redirectErrorStream();
   }
 
   /**
 * @see ProcessBuilder
 */
   public void setRedirectErrorStream(boolean redirectErrorStream)
   {
     _processBuilder.redirectErrorStream(redirectErrorStream);
   }
 
   public byte[] getOutput() throws InterruptedException
   {
     waitFor();
     return _out.getOutput();
   }
 
   public byte[] getError() throws InterruptedException
   {
     waitFor();
     return _err.getOutput();
   }
 
   /**
 * Returns the output as a string.
 *
 * @param encoding
 * @return encoded string
 * @throws InterruptedException
 * @throws UnsupportedEncodingException
 */
   public String getStringOutput(String encoding) throws InterruptedException,
                                                         UnsupportedEncodingException
   {
     return new String(getOutput(), encoding);
   }
 
   /**
 * Returns the output as a string. Uses encoding "UTF-8".
 *
 * @return utf8 encoded string
 * @throws InterruptedException
 */
   public String getStringOutput() throws InterruptedException
   {
     try
     {
       return getStringOutput("UTF-8");
     }
     catch(UnsupportedEncodingException e)
     {
       // should not happen
       throw new RuntimeException(e);
     }
   }
 
   /**
 * Returns the error as a string.
 *
 * @param encoding
 * @return error as string
 * @throws InterruptedException
 * @throws UnsupportedEncodingException
 */
   public String getStringError(String encoding) throws InterruptedException,
                                                        UnsupportedEncodingException
   {
     return new String(getError(), encoding);
   }
 
   /**
 * Returns the error as a string. Uses encoding "UTF-8".
 *
 * @return error as string
 * @throws InterruptedException
 */
   public String getStringError() throws InterruptedException
   {
     try
     {
       return getStringError("UTF-8");
     }
     catch(UnsupportedEncodingException e)
     {
       // should not happen
       throw new RuntimeException(e);
     }
   }
 
   /**
 * Properly waits until everything is complete: joins on the thread that
 * reads the output, joins on the thread that reads the error and finally
 * wait for the process to be finished.
 * @return the status code of the process.
 *
 * @throws InterruptedException
 */
   public int waitFor() throws InterruptedException
   {
     if(_process == null)
       throw new IllegalStateException("you must call start first");
 
     _out.join();
     _err.join();
     return _process.waitFor();
   }
 
   /**
 * Properly waits until everything is complete: joins on the thread that
 * reads the output, joins on the thread that reads the error and finally
 * wait for the process to be finished.
 * If the process has not completed before the timeout, throws a
 * {@link TimeoutException}
 * @return the status code of the process.
 *
 * @throws TimeoutException
 * @throws InterruptedException
 */
   public int waitFor(long timeout) throws InterruptedException, TimeoutException
   {
     if(_process == null)
       throw new IllegalStateException("you must call start first");
 
 //    Chronos c = new Chronos();
     _out.join(timeout);
 //    timeout -= c.tick();
     if (timeout <= 0)
       throw new TimeoutException("Wait timed out");
     _err.join(timeout);
 //    timeout -= c.tick();
     if (timeout <= 0)
       throw new TimeoutException("Wait timed out");
 
     // there is no timeout in this API, not much we can do here
     // waiting on the other two threads should give us some safety
     return _process.waitFor();
   }
 
   public int exitValue()
   {
     if(_process == null)
       throw new IllegalStateException("you must call start first");
 
     return _process.exitValue();
   }
 
   public void destroy()
   {
     if(_process == null)
       throw new IllegalStateException("you must call start first");
 
     _process.destroy();
   }
 
   /**
 * Creates an external process from the command. It is not started and you have to call
 * start on it!
 *
 * @param commands the command to execute
 * @return the process */
   public static ExternalCommand create(String... commands)
   {
     ExternalCommand ec = new ExternalCommand(new ProcessBuilder(commands));
     return ec;
   }
 
   /**
 * Creates an external process from the command. It is not started and you have to call
 * start on it!
 *
 * @param commands the command to execute
 * @return the process */
   public static ExternalCommand create(List<String> commands)
   {
     ExternalCommand ec = new ExternalCommand(new ProcessBuilder(commands));
     return ec;
   }
 
   /**
 * Creates an external process from the command. The command is executed.
 *
 * @param commands the commands to execute
 * @return the process
 * @throws IOException if there is an error */
   public static ExternalCommand start(String... commands) throws IOException
   {
     ExternalCommand ec = new ExternalCommand(new ProcessBuilder(commands));
     ec.start();
     return ec;
   }
 
   /**
 * Executes the external command in the given working directory and waits for it to be
 * finished.
 *
 * @param workingDirectory the root directory from where to run the command
 * @param command the command to execute (should be relative to the working directory
 * @param args the arguments to the command
 * @return the process */
   public static ExternalCommand execute(File workingDirectory,
                                         String command,
                                         String... args)
       throws IOException, InterruptedException
   {
     try
     {
       return executeWithTimeout(workingDirectory, command, 0, args);
     }
     catch (TimeoutException e)
     {
       // Can't happen!
       throw new IllegalStateException(MODULE + ".execute: Unexpected timeout occurred!");
     }
   }
 
 /**
 * Executes the external command in the given working directory and waits (until timeout
 * is elapsed) for it to be finished.
 *
 * @param workingDirectory
 * the root directory from where to run the command
 * @param command
 * the command to execute (should be relative to the working directory
 * @param timeout
 * the maximum amount of time to wait for this external command (in ms). If
 * this value is less than or equal to 0, timeout is ignored
 * @param args
 * the arguments to the command
 * @return the process
 */
   public static ExternalCommand executeWithTimeout(File workingDirectory,
                                                    String command,
                                                    long timeout,
                                                    String... args)
       throws IOException, InterruptedException, TimeoutException
   {
     List<String> arguments = new ArrayList<String>(args.length + 1);
 
     arguments.add(new File(workingDirectory, command).getAbsolutePath());
     arguments.addAll(Arrays.asList(args));
 
     ExternalCommand cmd = ExternalCommand.create(arguments);
 
     cmd.setWorkingDirectory(workingDirectory);
 
     cmd.setRedirectErrorStream(true);
 
     cmd.start();
 
     /* Use timeout if it is a valid value! */
     if (timeout <= 0)
       cmd.waitFor();
     else
       cmd.waitFor(timeout);
 
     if (LOG.isDebugEnabled())
       LOG.debug(cmd.getStringOutput());
 
     return cmd;
   }
 }