/*

 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. 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.  Oracle designates this

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

 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.packager.services.singleton;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.io.OutputStream;

import java.io.PrintStream;

import java.net.Socket;

import java.nio.charset.Charset;

/**

 * The {@code SingleInstanceService} class provides public methods for using

 * Single Instance functionality for Java Packager. To use these methods,

 * the option named "-singleton" must be specified on javapackager command line.

 *

 * @since 10

 */

public class SingleInstanceService {

    static private boolean DEBUG = false;

    static private PrintStream DEBUG_STREAM = null;

    static private int currPort;

    static private String stringId = null;

    static private String randomNumberString = null;

    static private SingleInstanceImpl instance = null;

    static final int ENCODING_PLATFORM = 1;

    static final int ENCODING_UNICODE = 2;

    static final String ENCODING_PLATFORM_NAME = "UTF-8";

    static final String ENCODING_UNICODE_NAME = "UTF-16LE";

    static final String APP_ID_PREFIX = "javapackager.si.";

    private SingleInstanceService() {}

    static void enableDebug(boolean enable, PrintStream stream) {

        DEBUG = enable;

        DEBUG_STREAM = stream;

    }

    static void trace(String message) {

        if (DEBUG && DEBUG_STREAM != null) {

            DEBUG_STREAM.println(message);

        }

    }

    static void trace(Throwable t) {

        if (DEBUG && DEBUG_STREAM != null) {

            t.printStackTrace(DEBUG_STREAM);

        }

    }

    /**

     * Registers {@code SingleInstanceListener} for current process.

     * If the {@code SingleInstanceListener} object is already registered, or

     * {@code slistener} is {@code null}, then the registration is skipped.

     *

     * @param slistener the listener to handle the single instance behaviour.

     */

    public static void registerSingleInstance(SingleInstanceListener slistener) {

        registerSingleInstance(slistener, false);

    }

    /**

     * Registers {@code SingleInstanceListener} for current process.

     * If the {@code SingleInstanceListener} object is already registered, or

     * {@code slistener} is {@code null}, then the registration is skipped.

     *

     * @param slistener the listener to handle the single instance behaviour.

     * @param setFileHandler if {@code true}, the listener is notified when the

     *         application is asked to open a list of files. If OS is not MacOS,

     *         the parameter is ignored.

     */

    public static void registerSingleInstance(SingleInstanceListener slistener,

                                              boolean setFileHandler) {

        String appId = APP_ID_PREFIX + ProcessHandle.current().pid();

        registerSingleInstanceForId(slistener, appId, setFileHandler);

    }

    static void registerSingleInstanceForId(SingleInstanceListener slistener,

                                                   String stringId, boolean setFileHandler) {

        // register SingleInstanceListener for given Id

        instance = new SingleInstanceImpl();

        instance.addSingleInstanceListener(slistener, stringId);

        if (setFileHandler) {

            instance.setOpenFileHandler();

        }

    }

    /**

     * Unregisters {@code SingleInstanceListener} for current process.

     * If the {@code SingleInstanceListener} object is not registered, or

     * {@code slistener} is {@code null}, then the unregistration is skipped.

     *

     * @param slistener the listener for unregistering.

     */

    public static void unregisterSingleInstance(SingleInstanceListener slistener) {

        instance.removeSingleInstanceListener(slistener);

    }

    /**

     * Returns true if single instance server is running for the id

     */

    static boolean isServerRunning(String id) {

        trace("isServerRunning ? : "+ id);

        File siDir = new File(SingleInstanceImpl.SI_FILEDIR);

        String[] fList = siDir.list();

        if (fList != null) {

            String prefix = SingleInstanceImpl.getSingleInstanceFilePrefix(id);

            for (String file : fList) {

                trace("isServerRunning: " + file);

                trace("\t String id: " + id);

                trace("\t SingleInstanceFilePrefix: " + prefix);

                // if file with the same prefix already exist, server is running

                if (file.startsWith(prefix)) {

                    try {

                        currPort = Integer.parseInt(

                                    file.substring(file.lastIndexOf('_') + 1));

                        trace("isServerRunning: " + file + ": port: " + currPort);

                    } catch (NumberFormatException nfe) {

                        trace("isServerRunning: " + file + ": port parsing failed");

                        trace(nfe);

                        return false;

                    }

                    trace("Server running at port: " + currPort);

                    File siFile = new File(SingleInstanceImpl.SI_FILEDIR, file);

                    // get random number from single instance file

                    try (BufferedReader br = new BufferedReader(new FileReader(siFile))) {

                        randomNumberString = br.readLine();

                        trace("isServerRunning: " + file + ": magic: " + randomNumberString);

                    } catch (IOException ioe ) {

                        trace("isServerRunning: " + file + ": reading magic failed");

                        trace(ioe);

                    }

                    trace("isServerRunning: " + file + ": setting id - OK");

                    stringId = id;

                    return true;

                } else {

                    trace("isServerRunning: " + file + ": prefix NOK");

                }

            }

        } else {

            trace("isServerRunning: empty file list");

        }

        trace("isServerRunning: false");

        return false;

    }

    /**

     * Returns true if we connect successfully to the server for the stringId

     */

    static boolean connectToServer(String[] args) {

        trace("Connect to: " + stringId + " " + currPort);

        if (randomNumberString == null) {

            // should not happen

            trace("MAGIC number is null, bail out.");

            return false;

        }

        // Now we open the tcpSocket and the stream

        Socket socket = null;

        OutputStream os = null;

        PrintStream out = null;

        InputStreamReader isr = null;

        BufferedReader br = null;

        try {

            socket = new Socket("127.0.0.1", currPort);

            os = socket.getOutputStream();

            byte[] encoding = new byte[1];

            encoding[0] = ENCODING_PLATFORM;

            os.write(encoding);

            String encodingName = Charset.defaultCharset().name();

            out = new PrintStream(os, true, encodingName);

            isr = new InputStreamReader(socket.getInputStream(), encodingName);

            br = new BufferedReader(isr);

            // send random number

            out.println(randomNumberString);

            // send MAGICWORD

            out.println(SingleInstanceImpl.SI_MAGICWORD);

            for (String arg : args) {

                out.println(arg);

            }

            // indicate end of file transmission

            out.println(SingleInstanceImpl.SI_EOF);

            out.flush();

            // wait for ACK (OK) response

            trace("Waiting for ack");

            final int tries = 5;

            // try to listen for ACK

            for (int i=0; i < tries; i++) {

                String str = br.readLine();

                if (str != null && str.equals(SingleInstanceImpl.SI_ACK)) {

                    trace("Got ACK");

                    return true;

                }

            }

        } catch (java.net.SocketException se) {

            // no server is running - continue launch

            trace("No server is running - continue launch.");

            trace(se);

        } catch (Exception ioe) {

            trace(ioe);

        }

        finally {

            try {

                if (br != null) {

                    br.close();

                }

                if (isr != null) {

                    isr.close();

                }

                if (out != null) {

                    out.close();

                }

                if (os != null) {

                    os.close();

                }

                if (socket != null) {

                    socket.close();

                }

            } catch (IOException ioe) {

                trace(ioe);

            }

        }

        trace("No ACK from server, bail out.");

        return false;

    }

}