package jp.vmi;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.nio.charset.Charset;

public class Multicast {
    private static final Charset UTF8 = Charset.forName("UTF-8");

    private final InetAddress addr;
    private final int port;

    private Sender sender = null;
    private Receiver receiver = null;

    public Multicast(String host, int port) throws UnknownHostException {
        this.addr = InetAddress.getByName(host);
        this.port = port;
    }

    public class Sender {
        private final DatagramSocket socket;

        public Sender() throws SocketException {
            socket = new DatagramSocket();
        }

        public void send(String msg) throws IOException {
            byte[] data = msg.getBytes(UTF8);
            DatagramPacket packet = new DatagramPacket(data, data.length, addr, port);
            socket.send(packet);
        }
    }

    synchronized public Sender getSender() throws SocketException {
        if (sender == null)
            sender = new Sender();
        return sender;
    }

    public class Receiver {
        private final MulticastSocket socket;
        private final byte[] buffer = new byte[8 * 1024 + 1];
        private final DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

        public Receiver() throws IOException {
            socket = new MulticastSocket(port);
            socket.joinGroup(addr);
        }

        public String receive() throws IOException {
            socket.receive(packet);
            int off = packet.getOffset();
            int len = packet.getLength();
            return new String(buffer, off, len, UTF8);
        }

        public InetAddress getAddress() {
            return packet.getAddress();
        }
    }

    synchronized public Receiver getReceiver() throws IOException {
        if (receiver == null)
            receiver = new Receiver();
        return receiver;
    }
}