/*
 * 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.dolphinscheduler.common.shell;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Map;
import java.util.Set;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicBoolean;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/** 
 * A base class for running a Unix command.
 * 
 * <code>AbstractShell</code> can be used to run unix commands like <code>du</code> or
 * <code>df</code>. It also offers facilities to gate commands by 
 * time-intervals.
 */
public abstract class AbstractShell {
  
  private static final Logger logger = LoggerFactory.getLogger(AbstractShell.class);
  


  /**
   * Time after which the executing script would be timedout
   */
  protected long timeOutInterval = 0L;
  /**
   * If or not script timed out
   */
  private AtomicBoolean timedOut;

  /**
   * refresh interval in msec
    */
  private long interval;

  /**
   * last time the command was performed
   */
  private long lastTime;

  /**
   * env for the command execution
   */
  private Map<String, String> environment;
  private File dir;

  /**
   * sub process used to execute the command
   */
  private Process process;
  private int exitCode;

  /**
   * If or not script finished executing
   */
  private volatile AtomicBoolean completed;
  
  public AbstractShell() {
    this(0L);
  }
  
  /**
   * @param interval the minimum duration to wait before re-executing the 
   *        command.
   */
  public AbstractShell(long interval ) {
    this.interval = interval;
    this.lastTime = (interval<0) ? 0 : -interval;
  }


  
  /**
   * set the environment for the command
   * @param env Mapping of environment variables
   */
  protected void setEnvironment(Map<String, String> env) {
    this.environment = env;
  }

  /**
   * set the working directory
   * @param dir The directory where the command would be executed
   */
  protected void setWorkingDirectory(File dir) {
    this.dir = dir;
  }

  /**
   * check to see if a command needs to be executed and execute if needed
   * @throws IOException errors
   */
  protected void run() throws IOException {
    if (lastTime + interval > System.currentTimeMillis()) {
      return;
    }
    // reset for next run
    exitCode = 0;
    runCommand();
  }

  
  /**
   * Run a command   actual work
   */
  private void runCommand() throws IOException {
    ProcessBuilder builder = new ProcessBuilder(getExecString());
    Timer timeOutTimer = null;
    ShellTimeoutTimerTask timeoutTimerTask = null;
    timedOut = new AtomicBoolean(false);
    completed = new AtomicBoolean(false);
    
    if (environment != null) {
      builder.environment().putAll(this.environment);
    }
    if (dir != null) {
      builder.directory(this.dir);
    }
    
    process = builder.start();
    ProcessContainer.putProcess(process);

    if (timeOutInterval > 0) {
      timeOutTimer = new Timer();
      timeoutTimerTask = new ShellTimeoutTimerTask(
          this);
      //One time scheduling.
      timeOutTimer.schedule(timeoutTimerTask, timeOutInterval);
    }
    final BufferedReader errReader = 
            new BufferedReader(
                    new InputStreamReader(process.getErrorStream()));
    BufferedReader inReader =
            new BufferedReader(
                    new InputStreamReader(process.getInputStream()));
    final StringBuilder errMsg = new StringBuilder();
    
    // read error and input streams as this would free up the buffers
    // free the error stream buffer
    Thread errThread = new Thread() {
      @Override
      public void run() {
        try {
          String line = errReader.readLine();
          while((line != null) && !isInterrupted()) {
            errMsg.append(line);
            errMsg.append(System.getProperty("line.separator"));
            line = errReader.readLine();
          }
        } catch(IOException ioe) {
          logger.warn("Error reading the error stream", ioe);
        }
      }
    };
    Thread inThread = new Thread() {
      @Override
      public void run() {
        try {
          parseExecResult(inReader);
        } catch (IOException ioe) {
          logger.warn("Error reading the in stream", ioe);
        }
        super.run();
      }
    };
    try {
      errThread.start();
      inThread.start();
    } catch (IllegalStateException ise) { }
    try {
      // parse the output
      exitCode = process.waitFor();
      try {
        // make sure that the error and in thread exits
        errThread.join();
        inThread.join();
      } catch (InterruptedException ie) {
        logger.warn("Interrupted while reading the error and in stream", ie);
      }
      completed.set(true);
      //the timeout thread handling
      //taken care in finally block
      if (exitCode != 0 || errMsg.length() > 0) {
        throw new ExitCodeException(exitCode, errMsg.toString());
      }
    } catch (InterruptedException ie) {
      throw new IOException(ie.toString());
    } finally {
      if ((timeOutTimer!=null) && !timedOut.get()) {
        timeOutTimer.cancel();
      }
      // close the input stream
      try {
        inReader.close();
      } catch (IOException ioe) {
        logger.warn("Error while closing the input stream", ioe);
      }
      if (!completed.get()) {
        errThread.interrupt();
      }
      try {
        errReader.close();
      } catch (IOException ioe) {
        logger.warn("Error while closing the error stream", ioe);
      }
      ProcessContainer.removeProcess(process);
      process.destroy();
      lastTime = System.currentTimeMillis();
    }
  }

  /**
   *
   * @return an array containing the command name and its parameters
   */
  protected abstract String[] getExecString();
  
  /**
   * Parse the execution result
   * @param lines lines
   * @throws IOException errors
   */
  protected abstract void parseExecResult(BufferedReader lines)
  throws IOException;

  /**
   * get the current sub-process executing the given command
   * @return process executing the command
   */
  public Process getProcess() {
    return process;
  }

  /** get the exit code 
   * @return the exit code of the process
   */
  public int getExitCode() {
    return exitCode;
  }

  /**
   * Set if the command has timed out.
   * 
   */
  private void setTimedOut() {
    this.timedOut.set(true);
  }
  


  /**
   * Timer which is used to timeout scripts spawned off by shell.
   */
  private static class ShellTimeoutTimerTask extends TimerTask {

    private AbstractShell shell;

    public ShellTimeoutTimerTask(AbstractShell shell) {
      this.shell = shell;
    }

    @Override
    public void run() {
      Process p = shell.getProcess();
      try {
        p.exitValue();
      } catch (Exception e) {
        //Process has not terminated.
        //So check if it has completed 
        //if not just destroy it.
        if (p != null && !shell.completed.get()) {
          shell.setTimedOut();
          p.destroy();
        }
      }
    }
  }
  
  /**
   * This is an IOException with exit code added.
   */
  public static class ExitCodeException extends IOException {
    int exitCode;
    
    public ExitCodeException(int exitCode, String message) {
      super(message);
      this.exitCode = exitCode;
    }
    
    public int getExitCode() {
      return exitCode;
    }
  }
  
  /**
   * process manage container
   *
   */
  public static class ProcessContainer extends ConcurrentHashMap<Integer, Process>{
	  private static final ProcessContainer container = new ProcessContainer();
	  private ProcessContainer(){
		  super();
	  }
	  public static final ProcessContainer getInstance(){
		return container;
	  }
	  
	  public static void putProcess(Process process){
		  getInstance().put(process.hashCode(), process);
	  }
	  public static int processSize(){
		  return getInstance().size();
	  }
	  
	  public static void removeProcess(Process process){
		  getInstance().remove(process.hashCode());
	  }
	  
	  public static void destroyAllProcess(){
		  Set<Entry<Integer, Process>> set = getInstance().entrySet();
		  for (Entry<Integer, Process> entry : set) {
			try{  
			  entry.getValue().destroy();
		  	} catch (Exception e) {
		  		logger.error("Destroy All Processes error", e);
		  	}
		  }
		  
		  logger.info("close " + set.size() + " executing process tasks");
	  }
  }	  
}