/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j.net;

import org.apache.log4j.plugins.Pauseable;
import org.apache.log4j.plugins.Receiver;
import org.apache.log4j.spi.Decoder;
import org.apache.log4j.spi.LoggingEvent;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.util.ArrayList;
import java.util.List;


/**
 * Receive LoggingEvents encoded with an XMLLayout, convert the XML data to a
 * LoggingEvent and post the LoggingEvent.
 *
 * @author Scott Deboy &lt;sdeboy@apache.org&gt;
 */
public class UDPReceiver extends Receiver implements PortBased, Pauseable {
    private static final int PACKET_LENGTH = 16384;
    private UDPReceiverThread receiverThread;
    private String encoding;

    //default to log4j xml decoder
    private String decoder = "org.apache.log4j.xml.XMLDecoder";
    private Decoder decoderImpl;
    protected boolean paused;
    private transient boolean closed = false;
    private int port;
    private DatagramSocket socket;
    UDPHandlerThread handlerThread;
    private boolean advertiseViaMulticastDNS;
    private ZeroConfSupport zeroConf;

    /**
     * The MulticastDNS zone advertised by a UDPReceiver
     */
    public static final String ZONE = "_log4j_xml_udp_receiver.local.";


    public int getPort() {
        return port;
    }

    public void setPort(int port) {
        this.port = port;
    }

    /**
     * The <b>Encoding</b> option specifies how the bytes are encoded.  If this
     * option is not specified, the system encoding will be used.
     */
    public void setEncoding(String encoding) {
        this.encoding = encoding;
    }

    /**
     * Returns value of the <b>Encoding</b> option.
     */
    public String getEncoding() {
        return encoding;
    }

    public String getDecoder() {
        return decoder;
    }

    public void setDecoder(String decoder) {
        this.decoder = decoder;
    }

    public boolean isPaused() {
        return paused;
    }

    public void setPaused(boolean b) {
        paused = b;
    }

    public void setAdvertiseViaMulticastDNS(boolean advertiseViaMulticastDNS) {
        this.advertiseViaMulticastDNS = advertiseViaMulticastDNS;
    }

    public boolean isAdvertiseViaMulticastDNS() {
        return advertiseViaMulticastDNS;
    }

    public synchronized void shutdown() {
        if (closed == true) {
            return;
        }
        closed = true;
        active = false;
        // Closing the datagram socket will unblock the UDPReceiverThread if it is
        // was waiting to receive data from the socket.
        if (socket != null) {
            socket.close();
        }

        if (advertiseViaMulticastDNS) {
            zeroConf.unadvertise();
        }

        try {
            if (handlerThread != null) {
                handlerThread.close();
                handlerThread.join();
            }
            if (receiverThread != null) {
                receiverThread.join();
            }
        } catch (InterruptedException ie) {
        }
    }

    /**
     * Returns true if this receiver is active.
     */
//  public synchronized boolean isActive() {
//    return isActive;
//}
    public void activateOptions() {
        try {
            Class c = Class.forName(decoder);
            Object o = c.newInstance();

            if (o instanceof Decoder) {
                this.decoderImpl = (Decoder) o;
            }
        } catch (ClassNotFoundException cnfe) {
            getLogger().warn("Unable to find decoder", cnfe);
        } catch (IllegalAccessException | InstantiationException iae) {
            getLogger().warn("Could not construct decoder", iae);
        }

        try {
            socket = new DatagramSocket(port);
            receiverThread = new UDPReceiverThread();
            receiverThread.start();
            handlerThread = new UDPHandlerThread();
            handlerThread.start();
            if (advertiseViaMulticastDNS) {
                zeroConf = new ZeroConfSupport(ZONE, port, getName());
                zeroConf.advertise();
            }
            active = true;
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }

    class UDPHandlerThread extends Thread {
        private final List<String> list = new ArrayList<>();

        public UDPHandlerThread() {
            setDaemon(true);
        }

        public void append(String data) {
            synchronized (list) {
                list.add(data);
                list.notify();
            }
        }

        /**
         * Allow the UDPHandlerThread to wakeup and exit gracefully.
         */
        void close() {
            synchronized (list) {
                list.notify();
            }
        }

        public void run() {
            ArrayList<String> list2 = new ArrayList<>();

            while (!UDPReceiver.this.closed) {
                synchronized (list) {
                    try {
                        while (!UDPReceiver.this.closed && list.size() == 0) {
                            list.wait(300);
                        }

                        if (list.size() > 0) {
                            list2.addAll(list);
                            list.clear();
                        }
                    } catch (InterruptedException ie) {
                    }
                }

                if (list2.size() > 0) {

                    for (Object aList2 : list2) {
                        String data = (String) aList2;
                        List<LoggingEvent> v = decoderImpl.decodeEvents(data);

                        if (v != null) {

                            for (Object aV : v) {
                                if (!isPaused()) {
                                    doPost((LoggingEvent) aV);
                                }
                            }
                        }
                    }

                    list2.clear();
                } else {
                    try {
                        synchronized (this) {
                            wait(1000);
                        }
                    } catch (InterruptedException ie) {
                    }
                }
            } // while
            getLogger().debug(UDPReceiver.this.getName() + "'s handler thread is exiting");
        } // run
    } // UDPHandlerThread

    class UDPReceiverThread extends Thread {
        public UDPReceiverThread() {
            setDaemon(true);
        }

        public void run() {
            byte[] b = new byte[PACKET_LENGTH];
            DatagramPacket p = new DatagramPacket(b, b.length);

            while (!UDPReceiver.this.closed) {
                try {
                    socket.receive(p);

                    //this string constructor which accepts a charset throws an exception if it is
                    //null
                    if (encoding == null) {
                        handlerThread.append(
                            new String(p.getData(), 0, p.getLength()));
                    } else {
                        handlerThread.append(
                            new String(p.getData(), 0, p.getLength(), encoding));
                    }
                } catch (SocketException se) {
                    //disconnected
                } catch (IOException ioe) {
                    ioe.printStackTrace();
                }
            }

            //LogLog.debug(UDPReceiver.this.getName() + "'s thread is ending.");
        }
    }
}