Gossip/Client/src/main/java/dev/wiing/gossip/client/Connection.java

package dev.wiing.gossip.client;

import dev.wiing.gossip.lib.PacketHandler;
import dev.wiing.gossip.lib.PacketManager;
import dev.wiing.gossip.lib.models.SecretUser;
import dev.wiing.gossip.lib.models.User;
import dev.wiing.gossip.lib.packets.*;

import java.io.IOException;
import java.net.Socket;
import java.net.SocketException;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

public class Connection {

    private static final Connection instance = new Connection();

    private final PacketManager packetManager = new PacketManager();

    private final PacketHandler packetHandler = new PacketHandler();

    private Thread handlerThread;

    private Socket socket;

    private SecretUser self;

    private final List<Packet> queuedPackets = Collections.synchronizedList(new LinkedList<>());

    private Connection() {
        packetManager.registerPackets();
    }

    public static Connection getInstance() {
        return instance;
    }

    public PacketManager getPacketManager() {
        return packetManager;
    }

    public PacketHandler getPacketHandler() {
        return packetHandler;
    }

    public static class PacketHandlerRunnable implements Runnable {
        private final Connection connection;

        public PacketHandlerRunnable(Connection connection) {
            this.connection = connection;
        }

        @Override
        public void run() {
            while (true) {
                try {
                    Packet packet;
                    if (connection.getSocket().getInputStream().available() > 0 || connection.queuedPackets.isEmpty()) {
                        packet = connection.nextPacket(false);
                    } else {
                        packet = connection.findPacketOfTypes(connection.packetHandler.getListeningTypes());
                    }

                    if (packet == null) continue;

                    if (!connection.getPacketHandler().runPacket(packet)) {
                        connection.queuedPackets.add(packet);
                    }
                } catch (SocketException e) {
                    break;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public void beginHandlingPackets() {
        handlerThread = new Thread(new PacketHandlerRunnable(this));
        handlerThread.start();
    }

    public Socket getSocket() {
        return socket;
    }

    public void setSocket(Socket socket) {
        this.socket = socket;
    }

    public void sendPacket(Packet packet) {
        try {
            getPacketManager().writePacket(getSocket().getOutputStream(), packet);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void sendPacketAuthenticated(AuthRequiredPacket packet) {
        packet.setAuth(getSelf().getUserSecret());
        sendPacket(packet);
    }

    public Packet nextPacket(boolean useQueue) throws SocketException {
        if (useQueue && !queuedPackets.isEmpty()) {
            return queuedPackets.remove(0);
        }

        try {
            return getPacketManager().readPacket(getSocket().getInputStream());
        } catch (SocketException e) {
            throw e;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    public Packet nextPacket() throws SocketException {
        return nextPacket(true);
    }

    public Packet nextPacket(short packetType) throws SocketException {
        while (true) {
            Packet packet = nextPacket(false);

            if (packet.getType() != packetType) {
                queuedPackets.add(packet);
                continue;
            }

            return packet;
        }
    }

    public Packet findPacketOfTypes(List<Short> types) {
        Packet packet = null;

        int i;
        for (i = 0; i < queuedPackets.size(); i++) {
            Packet queuedPacket = queuedPackets.get(i);

            if (types.contains(queuedPacket.getType())) {
                packet = queuedPacket;
                break;
            }
        }

        if (packet != null) {
            queuedPackets.remove(i);
            return packet;
        }

        return null;
    }

    public boolean findAck(short acknowledgement) throws IOException {

        while (true) {
            while (socket.getInputStream().available() > 0);

            AckPacket ack = null;

            int i;
            for (i = 0; i < queuedPackets.size(); i++) {
                Packet queuedPacket = queuedPackets.get(i);

                if (queuedPacket.getType() == AckPacket.TYPE) {
                    ack = (AckPacket) queuedPacket;

                    if (ack.getAcknowledgement() == acknowledgement) {
                        break;
                    }

                    ack = null;
                }
            }

            if (ack != null) {
                queuedPackets.remove(i);
                return true;
            }
        }
    }

    public SecretUser getSelf() {
        return self;
    }

    public void setSelf(SecretUser self) {
        this.self = self;

        userCache.put(self.getUserID(), new User(
                self.getUsername(),
                self.getAvatarID(),
                self.getUserID()
        ));
    }

    private final Map<Long, User> userCache = new ConcurrentHashMap<>();

    public User getUser(long userID) {
        User result;

        if ((result = userCache.getOrDefault(userID, null)) != null) {
            return result;
        }

        UserFetchPacket fetch = new UserFetchPacket();
        fetch.setUserID(userID);
        Connection.getInstance().sendPacket(fetch);

        Packet resp;
        try {
            resp = Connection.getInstance().nextPacket(UserDataPacket.TYPE);
        } catch (SocketException e) {
            throw new RuntimeException(e);
        }
        if (resp.getType() == UserDataPacket.TYPE) {
            UserDataPacket userData = (UserDataPacket)resp;
            result = new User(
                    userData.getUsername(),
                    userData.getAvatarID(),
                    userData.getUserID()
            );
            userCache.put(result.getUserID(), result);
        }

        return result;
    }
}