/*

 * Copyright 2008-2009 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code 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 GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.jkernel;

import java.io.*;

/**

 * Invoked by DownloadManager to begin (in a new JRE) the process of downloading

 * all remaining JRE components in the background.  A mutex is used to ensure

 * that only one BackgroundDownloader can be active at a time.

 *

 */

public class BackgroundDownloader {

    public static final String BACKGROUND_DOWNLOAD_PROPERTY = "kernel.background.download";

    // relative to the bundle directory

    public static final String PID_PATH = "tmp" + File.separator + "background.pid";

    // Time to wait before beginning to download components.  Gives the JRE

    // which spawned this one a chance to get its downloads going.

    private static final int WAIT_TIME = 10000;

    private static Mutex backgroundMutex;

    static synchronized Mutex getBackgroundMutex() {

        if (backgroundMutex == null)

            backgroundMutex = Mutex.create(DownloadManager.MUTEX_PREFIX + "background");

        return backgroundMutex;

    }

    private static void doBackgroundDownloads() {

        if (DownloadManager.isJREComplete())

            return;

        if (getBackgroundMutex().acquire(0)) { // give up and exit immediately if we can't acquire mutex

            try {

                writePid();

                Thread.sleep(WAIT_TIME);

                DownloadManager.doBackgroundDownloads(false);

                DownloadManager.performCompletionIfNeeded();

            }

            catch (InterruptedException e) {

            }

            finally {

                getBackgroundMutex().release();

            }

        }

        else {

            System.err.println("Unable to acquire background download mutex.");

            System.exit(1);

        }

    }

    /**

     * Writes the current process ID to a file, so that the uninstaller can

     * find and kill this process if needed.

     */

    private static void writePid() {

        try {

            File pid = new File(DownloadManager.getBundlePath(), PID_PATH);

            pid.getParentFile().mkdirs();

            PrintStream out = new PrintStream(new FileOutputStream(pid));

            pid.deleteOnExit();

            out.println(DownloadManager.getCurrentProcessId());

            out.close();

        }

        catch (IOException e) {

            e.printStackTrace();

            System.exit(1);

        }

    }

    /**

     * Reads from an InputStream until exhausted, writing all data to the

     * specified OutputStream.

     */

    private static void send(InputStream in, OutputStream out)

                                throws IOException {

        int c;

        byte[] buffer = new byte[2048];

        while ((c = in.read(buffer)) > 0)

            out.write(buffer, 0, c);

    }

     /*

      * Returns the value of the BACKGROUND_DOWNLOAD_PROPERTY.

      * Checks if system property has been set first

      * then checks if registry key to disable background download

      * has been set.

      */

     public static boolean  getBackgroundDownloadProperty(){

         /*

          * Check registry key value

          */

         boolean bgDownloadEnabled = getBackgroundDownloadKey();

         /*

          * Check system property - it should override the registry

          * key value.

          */

         if (System.getProperty(BACKGROUND_DOWNLOAD_PROPERTY) != null){

             bgDownloadEnabled = Boolean.valueOf(

                      System.getProperty(BACKGROUND_DOWNLOAD_PROPERTY));

         }

         return bgDownloadEnabled;

    }

    // This method is to retrieve the value of registry key

    // that disables background download.

    static native boolean getBackgroundDownloadKey();

    static void startBackgroundDownloads() {

        if (!getBackgroundDownloadProperty()){

            // If getBackgroundDownloadProperty() returns false

            // we're doing the downloads from this VM; we don't want to

            // spawn another one

            return;

        }

        // if System.err isn't initialized yet, it means the charsets aren't

        // available yet and we're going to run into trouble down below.  Wait

        // until it's ready.

        while (System.err == null) {

            try {

                Thread.sleep(1000);

            }

            catch (InterruptedException e) {

                return;

            }

        }

        try {

            String args = "-D" + BACKGROUND_DOWNLOAD_PROPERTY + "=false -Xmx256m";

            String backgroundDownloadURL = DownloadManager.getBaseDownloadURL();

            // only set KERNEL_DOWNLOAD_URL_PROPERTY if we override

            // the default download url

            if (backgroundDownloadURL != null &&

                    backgroundDownloadURL.equals(

                    DownloadManager.DEFAULT_DOWNLOAD_URL) == false) {

                args += " -D" + DownloadManager.KERNEL_DOWNLOAD_URL_PROPERTY +

                        "=" + backgroundDownloadURL;

            };

            args += " sun.jkernel.BackgroundDownloader";

            final Process jvm = Runtime.getRuntime().exec("\"" + new File(System.getProperty("java.home"), "bin" +

                   File.separator + "java.exe") + "\" " + args);

            Thread outputReader = new Thread("kernelOutputReader") {

                public void run() {

                    try {

                        InputStream in = jvm.getInputStream();

                        send(in, new PrintStream(new ByteArrayOutputStream()));

                    }

                    catch (IOException e) {

                        e.printStackTrace();

                    }

                }

            };

            outputReader.setDaemon(true);

            outputReader.start();

            Thread errorReader = new Thread("kernelErrorReader") {

                public void run() {

                    try {

                        InputStream in = jvm.getErrorStream();

                        send(in, new PrintStream(new ByteArrayOutputStream()));

                    }

                    catch (IOException e) {

                        e.printStackTrace();

                    }

                }

            };

            errorReader.setDaemon(true);

            errorReader.start();

        }

        catch (Exception e) {

            e.printStackTrace();

            // TODO: error handling

        }

    }

    public static void main(String[] arg) {

        doBackgroundDownloads();

    }

}