/**
 * 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.mapred.pipes;

import java.io.File;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.mapreduce.MRJobConfig;
import org.apache.hadoop.mapreduce.filecache.DistributedCache;
import org.apache.hadoop.fs.FileUtil;
import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.RecordReader;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.TaskAttemptID;
import org.apache.hadoop.mapred.TaskLog;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.hadoop.util.StringUtils;

/**
 * This class is responsible for launching and communicating with the child 
 * process.
 */
class Application<K1 extends WritableComparable, V1 extends Writable,
                  K2 extends WritableComparable, V2 extends Writable> {
  private static final Log LOG = LogFactory.getLog(Application.class.getName());
  private ServerSocket serverSocket;
  private Process process;
  private Socket clientSocket;
  private OutputHandler<K2, V2> handler;
  private DownwardProtocol<K1, V1> downlink;
  static final boolean WINDOWS
  = System.getProperty("os.name").startsWith("Windows");

  /**
   * Start the child process to handle the task for us.
   * @param conf the task's configuration
   * @param recordReader the fake record reader to update progress with
   * @param output the collector to send output to
   * @param reporter the reporter for the task
   * @param outputKeyClass the class of the output keys
   * @param outputValueClass the class of the output values
   * @throws IOException
   * @throws InterruptedException
   */
  Application(JobConf conf, 
              RecordReader<FloatWritable, NullWritable> recordReader, 
              OutputCollector<K2,V2> output, Reporter reporter,
              Class<? extends K2> outputKeyClass,
              Class<? extends V2> outputValueClass
              ) throws IOException, InterruptedException {
    serverSocket = new ServerSocket(0);
    Map<String, String> env = new HashMap<String,String>();
    // add TMPDIR environment variable with the value of java.io.tmpdir
    env.put("TMPDIR", System.getProperty("java.io.tmpdir"));
    env.put(Submitter.PORT, 
            Integer.toString(serverSocket.getLocalPort()));
    List<String> cmd = new ArrayList<String>();
    String interpretor = conf.get(Submitter.INTERPRETOR);
    if (interpretor != null) {
      cmd.add(interpretor);
    }

    String executable = DistributedCache.getLocalCacheFiles(conf)[0].toString();
    if (!new File(executable).canExecute()) {
      // LinuxTaskController sets +x permissions on all distcache files already.
      // In case of DefaultTaskController, set permissions here.
      FileUtil.chmod(executable, "u+x");
    }
    cmd.add(executable);
    // wrap the command in a stdout/stderr capture
    // we are starting map/reduce task of the pipes job. this is not a cleanup
    // attempt. 
    TaskAttemptID taskid = 
      TaskAttemptID.forName(conf.get(MRJobConfig.TASK_ATTEMPT_ID));
    File stdout = TaskLog.getTaskLogFile(taskid, false, TaskLog.LogName.STDOUT);
    File stderr = TaskLog.getTaskLogFile(taskid, false, TaskLog.LogName.STDERR);
    long logLength = TaskLog.getTaskLogLength(conf);
    cmd = TaskLog.captureOutAndError(null, cmd, stdout, stderr, logLength,
                                     false);

    process = runClient(cmd, env);
    clientSocket = serverSocket.accept();
    handler = new OutputHandler<K2, V2>(output, reporter, recordReader);
    K2 outputKey = (K2)
      ReflectionUtils.newInstance(outputKeyClass, conf);
    V2 outputValue = (V2) 
      ReflectionUtils.newInstance(outputValueClass, conf);
    downlink = new BinaryProtocol<K1, V1, K2, V2>(clientSocket, handler, 
                                  outputKey, outputValue, conf);
    downlink.start();
    downlink.setJobConf(conf);
  }

  /**
   * Get the downward protocol object that can send commands down to the
   * application.
   * @return the downlink proxy
   */
  DownwardProtocol<K1, V1> getDownlink() {
    return downlink;
  }

  /**
   * Wait for the application to finish
   * @return did the application finish correctly?
   * @throws Throwable
   */
  boolean waitForFinish() throws Throwable {
    downlink.flush();
    return handler.waitForFinish();
  }

  /**
   * Abort the application and wait for it to finish.
   * @param t the exception that signalled the problem
   * @throws IOException A wrapper around the exception that was passed in
   */
  void abort(Throwable t) throws IOException {
    LOG.info("Aborting because of " + StringUtils.stringifyException(t));
    try {
      downlink.abort();
      downlink.flush();
    } catch (IOException e) {
      // IGNORE cleanup problems
    }
    try {
      handler.waitForFinish();
    } catch (Throwable ignored) {
      process.destroy();
    }
    IOException wrapper = new IOException("pipe child exception");
    wrapper.initCause(t);
    throw wrapper;      
  }
  
  /**
   * Clean up the child procress and socket.
   * @throws IOException
   */
  void cleanup() throws IOException {
    serverSocket.close();
    try {
      downlink.close();
    } catch (InterruptedException ie) {
      Thread.currentThread().interrupt();
    }      
  }

  /**
   * Run a given command in a subprocess, including threads to copy its stdout
   * and stderr to our stdout and stderr.
   * @param command the command and its arguments
   * @param env the environment to run the process in
   * @return a handle on the process
   * @throws IOException
   */
  static Process runClient(List<String> command, 
                           Map<String, String> env) throws IOException {
    ProcessBuilder builder = new ProcessBuilder(command);
    if (env != null) {
      builder.environment().putAll(env);
    }
    Process result = builder.start();
    return result;
  }

}