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path: root/src/ch/epfl/xblast/server/Server.java
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package ch.epfl.xblast.server;

import ch.epfl.xblast.Lists;
import ch.epfl.xblast.PlayerAction;
import ch.epfl.xblast.PlayerID;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.StandardProtocolFamily;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
import java.util.*;

/**
 * The Server class.
 *
 * @author Pacien TRAN-GIRARD (261948)
 */
public class Server {

    public static final int DEFAULT_PORT = 2016;
    private static final int DEFAULT_EXPECTED_CLIENTS = PlayerID.values().length;

    private static InetSocketAddress listeningInterface(String host, int port) {
        if (Objects.isNull(host))
            return new InetSocketAddress(port);
        else
            return new InetSocketAddress(host, port);
    }

    private static DatagramChannel openChannel(InetSocketAddress iface) {
        try {
            DatagramChannel chan = DatagramChannel.open(StandardProtocolFamily.INET);
            chan.bind(iface);
            return chan;
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(1);
            return null;
        }
    }

    private static Optional<Map.Entry<SocketAddress, PlayerAction>> receiveAction(DatagramChannel chan, boolean block) {
        try {
            ByteBuffer buf = ByteBuffer.allocate(1);
            chan.configureBlocking(block);
            SocketAddress client = chan.receive(buf);
            PlayerAction action = PlayerAction.fromByte(buf.get(0));
            return Optional.of(new AbstractMap.SimpleImmutableEntry<>(client, action));
        } catch (IOException | IllegalArgumentException e) {
            return Optional.empty();
        }
    }

    private static Map.Entry<SocketAddress, PlayerAction> acceptAction(DatagramChannel chan) {
        Optional<Map.Entry<SocketAddress, PlayerAction>> action;

        do {
            action = receiveAction(chan, true);
        } while (!action.isPresent());

        return action.get();
    }

    private static SocketAddress acceptRegistration(DatagramChannel chan) {
        Map.Entry<SocketAddress, PlayerAction> clientAction;

        do {
            clientAction = acceptAction(chan);
        } while (clientAction.getValue() != PlayerAction.JOIN_GAME);

        return clientAction.getKey();
    }

    private static List<SocketAddress> acceptRegistrations(DatagramChannel chan, int registrations) {
        List<SocketAddress> clients = new ArrayList<>(registrations);

        while (clients.size() < registrations) {
            SocketAddress client = acceptRegistration(chan);
            if (!clients.contains(client))
                clients.add(client);
        }

        return Collections.unmodifiableList(clients);
    }

    private final InetSocketAddress iface;
    private final int expectedClients;
    private Map<SocketAddress, PlayerID> registeredClients;

    public Server(String iface, Integer port, Integer expectedClients) {
        this.iface = listeningInterface(iface, Optional.ofNullable(port).orElse(DEFAULT_PORT));
        this.expectedClients = Optional.ofNullable(expectedClients).orElse(DEFAULT_EXPECTED_CLIENTS);
    }

    public void run() {
        DatagramChannel chan = openChannel(this.iface);
        List<SocketAddress> clients = acceptRegistrations(chan, this.expectedClients);
        this.registeredClients = Lists.linearAdjustedMap(clients, Arrays.asList(PlayerID.values()));

        System.out.println(this.registeredClients);
    }

}