import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.charset.Charset;

public class ServerPingConnection extends TcpConnection<ServerData> {
    public static final int ERROR_INVALID_PACKET = 0;

    private static final byte[] HEADER = {(byte) 0xFE, 0x01, (byte) 0xFA,
            0x00, 0x0B};
    private static final Charset CHARSET = Charset.forName("UTF-16BE");
    private String mHostname;
    private long startTime;
    private ServerData mServer;

    public ServerPingConnection(ServerData server, String hostname) {
        super(server.getHost(), server.getPort());
        this.mHostname = hostname;
        mServer = server;
        timeout(3000);
        byteOrder(ByteOrder.BIG_ENDIAN);
    }

    @Override
    protected boolean close() {
        return true;
    }

    @Override
    public void OnConnect(Selector selector) throws IOException {
        startTime = System.nanoTime();
        super.OnConnect(selector);
    }

    @Override
    public void OnWrite(SelectionKey selectionKey, ByteBuffer buffer) throws IOException {
        // HEADER
        buffer.put(HEADER);
        byte[] options = "MC|PingHost".getBytes(CHARSET);
        buffer.put(options);
        buffer.putShort((short) (7 + 2 * mHostname.length()));
        buffer.put((byte) 73);
        buffer.putShort((short) mHostname.length());
        buffer.put(mHostname.getBytes(CHARSET));
        buffer.putInt(25565);
        buffer.flip();

        int written = channel.write(buffer);
        Log.i("APP", written + "");
        selectionKey.interestOps(SelectionKey.OP_READ);
    }

    @Override
    public void onRead(SelectionKey selectionKey, ByteBuffer buffer) throws IOException {
        int read = channel.read(buffer);
        Log.i("APP", read + "");
        buffer.flip();
        byte type = buffer.get();
        // Error, invalid packet
        if (type != (byte) 0xFF) {
            postError(ERROR_INVALID_PACKET, mServer);
            return;
        }
        int length = buffer.getShort();

        CharBuffer charBuffer = Charset.defaultCharset().decode(buffer);
        // decoder will place a null terminator after each string, now there are
        // three because of UTF-16

        charBuffer.position(7);
        mServer.setPing((System.nanoTime() - startTime) / 1000000L);
        mServer.setProtocol(Integer.parseInt(readString(charBuffer)));
        mServer.setVersion(readString(charBuffer));
        mServer.setMotd(readString(charBuffer));
        mServer.setPlayerCount(Integer.parseInt(readString(charBuffer)));
        mServer.setMaxPlayers(Integer.parseInt(readString(charBuffer)));

        postSuccess(0, mServer);
    }

    private static String readString(CharBuffer buffer) {
        // UTF-16 to UTF-8 creates an extra null-byte
        StringBuilder builder = new StringBuilder();
        char c;
        while (buffer.hasRemaining() && (c = buffer.get()) != 0) {
            builder.append(c);
            if (buffer.hasRemaining()) buffer.get(); // skip null byte
        }

        if (buffer.hasRemaining()) buffer.get(); // skip null byte

        return builder.toString();
    }

}