YapPrologSystem.java

package bots.prologbot.prologsystem;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringWriter;

import org.apache.commons.io.FileUtils;

import bots.prologbot.PrologBot;

public class YapPrologSystem implements PrologSystem {

	private final static String n = System.getProperty("line.separator");

	private static String file_dir_str = "./data/prologbot/";

	static {
		File file = new File("/dev/shm/");
		if (file.exists()) {
			file_dir_str = "/dev/shm/";
			try {
				FileUtils.copyFileToDirectory(new File("./data/prologbot/bk-yap.pl"), file);
			} catch (IOException e) {
				e.printStackTrace();
				file_dir_str = "./data/prologbot/";
			}
		}
	}

	private final static File directory = new File(file_dir_str);

	private final PrologBot bot;

	public YapPrologSystem(PrologBot bot) {
		this.bot = bot;
	}

	/* (non-Javadoc)
	 * @see bots.prologbot.prologsystem.PrologSystem#updateBotProlog(java.lang.String)
	 */
	@Override
	public synchronized void updateBotProlog(String prolog) {
		File file = new File(directory, bot.getName() + ".pl");
		StringWriter out = new StringWriter();
		out.write("% Generated by server" + n);
		out.write(":- include(bk-yap)." + n);
		out.write(":- include(state)." + n);
		out.write("" + n);
		out.write("% Generated by client" + n);
		out.write(prolog);
		writeToFile(file, out.toString());
	}

	private void writeToFile(File file, String prolog) {
		try {
			FileWriter out2 = new FileWriter(file);
			BufferedWriter out = new BufferedWriter(out2);
			out.write(prolog);
			out.close();
			out2.close();
		} catch (IOException e) {
			e.printStackTrace();
			System.err.println("Could not write prolog code.");
			System.exit(-1);
		}
	}

	/* (non-Javadoc)
	 * @see bots.prologbot.prologsystem.PrologSystem#updateState(java.lang.String)
	 */
	@Override
	public synchronized void updateState(String state) {
		writeToFile(new File(directory, "state.pl"), state);
	}

	/* (non-Javadoc)
	 * @see bots.prologbot.prologsystem.PrologSystem#executeQuery()
	 */
	@Override
	public synchronized String executeQuery() {
		try {
			ProcessBuilder pb = new ProcessBuilder("yap", "-l", bot.getName() + ".pl", "-g", "evaluate", "-q");
			pb.directory(directory);
			Process p = pb.start();
			int exitValue = p.waitFor();
			if (exitValue != 0) {
				throw new IllegalStateException();
			}
			InputStreamReader in = new InputStreamReader(p.getInputStream());
			BufferedReader result = new BufferedReader(in);
			String output = result.readLine();
			result.close();
			in.close();
			return output;
		} catch (IOException e) {
			e.printStackTrace();
			System.err.println("Could not query Prolog.");
			System.exit(-1);
		} catch (InterruptedException e) {
			e.printStackTrace();
			System.err.println("Could not query Prolog.");
			System.exit(-1);
		}
		return null;
	}

}