package com.gitblit.sysinfo;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.util.Locale;
import java.util.StringTokenizer;

/**
 * This code was extracted from JavaMelody and refactored.
 *
 * @author Emeric Vernat
 * @author James Moger
 */
public final class PID {

    private PID() {
        super();
    }

    /**
     * @return PID of Java process
     */
    static String getPID() {
        String pid = System.getProperty("pid");
        if (pid == null) {
            // first, reliable with sun jdk (http://golesny.de/wiki/code:javahowtogetpid)
            final RuntimeMXBean rtb = ManagementFactory.getRuntimeMXBean();
            final String processName = rtb.getName();
            if (processName.indexOf('@') != -1) {
                pid = processName.substring(0, processName.indexOf('@'));
            } else {
                pid = getPIDFromOS();
            }
            System.setProperty("pid", pid);
        }
        return pid;
    }

    static String getPIDFromOS() {
        String pid;
        // following is not always reliable as is (for example, see issue 3 on solaris 10
        // or http://blog.igorminar.com/2007/03/how-java-application-can-discover-its.html)
        // Author: Santhosh Kumar T, http://code.google.com/p/jlibs/, licence LGPL
        // Author getpids.exe: Daniel Scheibli, http://www.scheibli.com/projects/getpids/index.html, licence GPL
        final String[] cmd;
        File tempFile = null;
        Process process = null;
        try {
            try {
                if (!System.getProperty("os.name").toLowerCase(Locale.ENGLISH).contains("windows")) {
                    cmd = new String[]{"/bin/sh", "-c", "echo $$ $PPID"};
                } else {
                    // getpids.exe is taken from http://www.scheibli.com/projects/getpids/index.html (GPL)
                    tempFile = File.createTempFile("getpids", ".exe");

                    // extract the embedded getpids.exe file from the jar and save it to above file
                    pump(PID.class.getResourceAsStream("getpids.exe"), new FileOutputStream(tempFile), true, true);
                    cmd = new String[]{tempFile.getAbsolutePath()};
                }
                process = Runtime.getRuntime().exec(cmd);
                final ByteArrayOutputStream bout = new ByteArrayOutputStream();
                pump(process.getInputStream(), bout, false, true);

                final StringTokenizer stok = new StringTokenizer(bout.toString());
                stok.nextToken(); // this is pid of the process we spanned
                pid = stok.nextToken();

                process.waitFor();
            } finally {
                if (process != null) {
                    process.getInputStream().close();
                    process.getOutputStream().close();
                    process.getErrorStream().close();
                    process.destroy();
                }
                if (tempFile != null && !tempFile.delete()) {
                    tempFile.deleteOnExit();
                }
            }
        } catch (InterruptedException e) {
            pid = e.toString();
        } catch (IOException e) {
            pid = e.toString();
        }
        return pid;
    }

    private static void pump(InputStream is, OutputStream os, boolean closeIn, boolean closeOut) throws IOException {
        try {
            final byte[] bytes = new byte[4 * 1024];
            int length = is.read(bytes);
            while (length != -1) {
                os.write(bytes, 0, length);
                length = is.read(bytes);
            }
        } finally {
            try {
                if (closeIn) {
                    is.close();
                }
            } finally {
                if (closeOut) {
                    os.close();
                }
            }
        }
    }
}