import java.util.Scanner;
import java.io.*;
import java.net.*;

/**
 *
 * @author Arlidio Dobra
 * UDP Project for Computer Networking
 */

public class ServerApplication {

    public static void main() {

        /**
         * Varaiables to be used to determain amount of messages recieved,
         * Length of the messages combined & the value of all messages combined -
         * including # as seperators
         */
        int messageCount = 0, textLength = 0, stringLength = 0;
        String combinedStrings = "";

        //Below code implemented to force virtual machine to display console
        System.out.print("Server Client");


        //Defining inbound location of packets being sent
        int port = 8000;


        //Add proper comment
        try {

            //Socket defined and instructed to seek port 8000 - where client will send messages
            DatagramSocket serverSocket = new DatagramSocket(port);

            InetAddress host = InetAddress.getByName("localhost");

            //Buffer created to reserve memory for incoming messages - anticipating large messages
            byte[] buffer = new byte[65507];



            while (messageCount <= 3) {

                //Datagram packet defined to be used as receiving point of packets - implements parameter buffer
                DatagramPacket serverPacket = new DatagramPacket(buffer, buffer.length);


                //Seeks and recieves any packets present in socket
                serverSocket.receive(serverPacket);

                //Converts byte information into String and stores it into variable
                String gotMail = new String(serverPacket.getData());

                //Cuts out excess information from allocated buffer memory - leaving only used information
                //within variable
                gotMail = gotMail.trim();

                //nLength repsonsible for storing length of each recieved message after excess buffer is trimmed
                textLength += gotMail.length();

                //For each iteration and message which is recieved - msgCount will increase by increment of 1
                //until while loop condition is met and all messages have been recieved
                messageCount += 1;

                //IF loop respondisble for observing amount of messages recieved and placing seperators within the
                //message. For the first 2 recieved messages '#' will be added as seperator
                if (messageCount <= 2) {
                    gotMail += '#';
                }

                //combinedStrings holds value of message recieved from packet after '#' seperator has been appended
                combinedStrings += gotMail;

                if(messageCount == 3){
                    break;
                }

            }

        } catch (Exception ex) {
            return;
        }



        //Debugging Process
        System.out.println("\n" + "Combined text:" + combinedStrings);
        System.out.println("\n" + "Length of text:" + textLength);


        serverResponse(combinedStrings, textLength);
    }



    //Respondsible for returning message to clientApplication
    public static void serverResponse(String returnMessage, int messageLength){


        int port = 7650;

        String messageLengthStr = String.valueOf(messageLength);



        //Add proper comment
        try {

            //severSocket defined once more into try / catch as - to be used as socket where messages are to be sent
            DatagramSocket responseSocket = new DatagramSocket();

            /**
             * Parameters used to define IP address where packets are to be sent to.
             * "localhost" can be substituted for IP address of client machine -
             * For troubleshooting purposes "localhost" is defined to use current machine
             * to send/recieve messages
             */



            InetAddress host = InetAddress.getByName("localhost");


            byte[] responseByte = returnMessage.getBytes();
            DatagramPacket responsePacket = new DatagramPacket(responseByte, responseByte.length,
                             host,
                             port
            );
            responseSocket.send(responsePacket);


            byte[] responseByteTwo = messageLengthStr.getBytes();
            DatagramPacket responsePacketTwo = new DatagramPacket(responseByteTwo, responseByteTwo.length,
                             host,
                             port
            );
            responseSocket.send(responsePacketTwo);




        }


        catch(Exception ex){return;}
    }
}