/* Copyright (c) 2009 Peter Troshin
 * Copyright (c) 2013 Alexander Sherstnev
 * 
 *  Java Bioinformatics Analysis Web Services (JABAWS)
 * @version: 2.5
 * 
 *  This library is free software; you can redistribute it and/or modify it under the terms of the
 *  Apache License version 2 as published by the Apache Software Foundation
 * 
 *  This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 *  even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the Apache 
 *  License for more details.
 * 
 *  A copy of the license is in apache_license.txt. It is also available here:
 * @see: http://www.apache.org/licenses/LICENSE-2.0.txt
 * 
 * Any republication or derived work distributed in source code form
 * must include this copyright and license notice.
 */

package compbio.engine.local;

import java.io.File;
import java.io.IOException;
import java.io.PrintStream;
import java.util.List;
import java.util.Map.Entry;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import org.apache.log4j.Logger;

import compbio.engine.client.ConfiguredExecutable;
import compbio.engine.client.PathValidator;
import compbio.engine.client.PipedExecutable;
import compbio.engine.client.EngineUtil;
import compbio.engine.client.Executable.ExecProvider;
import compbio.engine.local.StreamGobbler.OutputType;
import compbio.metadata.JobStatus;
import compbio.metadata.JobSubmissionException;
import compbio.util.FileUtil;
import compbio.util.SysPrefs;
import compbio.util.annotation.Immutable;

@Immutable
public final class ExecutableWrapper implements
	Callable<ConfiguredExecutable<?>> {

	public static final String PROC_IN_FILE = "procInput.txt";
	public static final String PROC_OUT_FILE = "procOutput.txt";
	public static final String PROC_ERR_FILE = "procError.txt";

	private static ExecutorService es;
	private final ConfiguredExecutable<?> confExec;
	private final ProcessBuilder pbuilder;

	private static final Logger log = Logger.getLogger(ExecutableWrapper.class);

	public ExecutableWrapper(ConfiguredExecutable<?> executable, String workDirectory) throws JobSubmissionException {
		this.confExec = executable;
		String cmd = null;
		try {
			cmd = executable.getCommand(ExecProvider.Local);
			PathValidator.validateExecutable(cmd);
		} catch (IllegalArgumentException e) {
			log.error(e.getMessage(), e.getCause());
			throw new JobSubmissionException(e);
		}
		List<String> params = executable.getParameters().getCommands();
		params.add(0, cmd);

		pbuilder = new ProcessBuilder(params);
		if (executable.getEnvironment() != null) {
			log.debug("Setting command environment variables: " + pbuilder.environment());
			EngineUtil.mergeEnvVariables(pbuilder.environment(), executable.getEnvironment());
			log.debug("Process environment:" + pbuilder.environment());
		}
		log.debug("Setting command: " + pbuilder.command());
		PathValidator.validateDirectory(workDirectory);
		pbuilder.directory(new File(workDirectory));
		log.debug("Current working directory is " + SysPrefs.getCurrentDirectory());
		log.debug("Setting working directory: " + workDirectory);
		// Initialize private executor to dump processes output if any to the file system
		synchronized (log) {
			if (es == null) {
				/* 
				 * Two threads are necessary for the process to write in two streams error and output
				 * simultaneously and hold the stream until exit. If only one thread is used, the
				 * second stream may never get access to the thread efficiently deadlocking the proccess!
				 */
			this.es = Executors.newCachedThreadPool();
				log.debug("Initializing executor for local processes output dump");
				// Make sure that the executors are going to be properly closed
				Runtime.getRuntime().addShutdownHook(new Thread() {
				@Override
				public void run() {
					shutdownService();
				}
				});
			}
		}
	}

	/**
	 * Stops internal executor service which captures streams of native
	 * executables. This method is intended for stopping service if deployed in
	 * the web application content. There is NO NEED of using this method
	 * otherwise as the executor service is taken care of internally.
	*/
	public static final void shutdownService() {
		if (es != null) {
			es.shutdownNow();
		}
	}

	/**
	 * It is vital that output and error streams are captured immediately for
	 * this call() to succeed. Thus each instance if ExecutableWrapper has 2 its
	 * own thread ready to capture the output. If executor could not execute
	 * capture immediately this could lead to the call method to stale, as
	 * execution could not proceed without output being captured. Every call to
	 * call() method will use 2 threads
	 * @throws JobSubmissionException 
	*/
	@Override
	public ConfiguredExecutable<?> call() throws IOException {
		Process proc = null;
		Future<?> errorf = null;
		Future<?> outputf = null;
		PrintStream errorStream = null;
		PrintStream outStream = null;
		PrintStream comStream = null;

		try {
			log.info("Calculation started at " + System.nanoTime());
			EngineUtil.writeStatFile(confExec.getWorkDirectory(), JobStatus.STARTED.toString());
			proc = pbuilder.start();

			// store input command and program environment
			comStream = new PrintStream(new File(pbuilder.directory() + File.separator + PROC_IN_FILE));
			comStream.append("# program command\n");
			for (String par : pbuilder.command()) {
			comStream.append(par + " ");
			}
			/*
			 * for testing purposes only...
			comStream.append("\n\n# program environment\n");
			for (Entry<String, String> var : pbuilder.environment().entrySet()) {
				comStream.append(var.getKey() + " =\t" + var.getValue() + "\n");
			}
			*/
			comStream.close();

			// any error message?
			errorStream = new PrintStream(new File(pbuilder.directory() + File.separator + getError()));
			StreamGobbler errorGobbler = new StreamGobbler(proc.getErrorStream(), errorStream, OutputType.ERROR);

			// any output?
			outStream = new PrintStream(new File(pbuilder.directory() + File.separator + getOutput()));
			StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), outStream, OutputType.OUTPUT);

			// kick it off
			errorf = es.submit(errorGobbler);
			outputf = es.submit(outputGobbler);

			// any error???
			int exitVal = proc.waitFor();
			//proc.getClass();
			log.info("Calculation completed at " + System.nanoTime());
			EngineUtil.writeStatFile(confExec.getWorkDirectory(), JobStatus.FINISHED.toString());

			// Let streams to write for a little more
			errorf.get(2, TimeUnit.SECONDS);
			outputf.get(2, TimeUnit.SECONDS);

			// Close streams
			errorStream.close();
			outStream.close();
			log.debug("Local process exit value: " + exitVal);
		} catch (ExecutionException e) {
			// Log and ignore this is not important
			log.trace("Native Process output threw exception: " + e.getMessage());
		} catch (TimeoutException e) {
			// Log and ignore this is not important
			log.trace("Native Process output took longer then 2s to write, aborting: " + e.getMessage());
		} catch (InterruptedException e) {
			log.error("Native Process was interrupted aborting: " + e.getMessage());
			System.err.println("Native Process was interrupted aborting: " + e.getMessage());
			proc.destroy();
			errorf.cancel(true);
			outputf.cancel(true);
			// restore interruption status
			Thread.currentThread().interrupt();
		} finally {
			// just to make sure that we do not left anything running
			if (proc != null) {
				proc.destroy();
			}
			if (errorf != null) {
				errorf.cancel(true);
			}
			if (outputf != null) {
				outputf.cancel(true);
			}
			FileUtil.closeSilently(log, errorStream);
			FileUtil.closeSilently(log, outStream);
		}
		return confExec;
	}

	private String getOutput() {
		if (confExec.getOutput() != null && confExec.getExecutable() instanceof PipedExecutable<?>) {
			return confExec.getOutput();
		}
		return PROC_OUT_FILE;
	}

	private String getError() {
		if (confExec.getError() != null && confExec.getExecutable() instanceof PipedExecutable<?>) {
			return confExec.getError();
		}
		return PROC_ERR_FILE;
	}

}