/**@file jserver.java
 * @author Brittany Kondo 100379346
 * @brief  Represents a multi-threaded server which can have several clients
 *         connected to it, its main purpose is to manage all messages sent
 *         among clients.
 * */
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.TreeMap;
import java.util.Vector;


public class jserver {
    //Stores all messages for every client created on the server
    public static TreeMap<String,Vector<String>> inbox = new TreeMap<String,Vector<String>>();

    /** Checks if a given user already exists on the server's inbox
     * @param  map  The tree map (which represents the inbox) to search
     * @param  user The user to search for
     * @return      True, if the user already exists in the map
     *              False, otherwise
     * */
    public static boolean doesUserExist(TreeMap<String,Vector<String>> map,String user){
        for (String key:map.keySet()){
            if (key.equalsIgnoreCase(user))
                return true;
        }
        return false;
    }
    //Handles an individual jclient and is used later to create a thread
    //for each client
    public static class jClientHandler implements Runnable {
          private Socket client;
          /** Constructs a new jclienthandler object
           * @param  client  A socket representing the client's connection to
           *                 the server
           * */
          jClientHandler(Socket client) {
           this.client = client;
          }

          /** Processes data received from the jclient class, invoked when the
           * thread containing this handler is run in the main program.
           * */
          public void run(){
            String line;
            BufferedReader reader = null;
            PrintWriter writer = null;
            try{
              //Initialize the reader and writer so that this socket can communicate with
              //the jclient
              reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
              writer = new PrintWriter(client.getOutputStream(),true);
            } catch (IOException e) {
              e.printStackTrace();
            }

              try{
                line = reader.readLine();
                //A new user is being added if there is a '1' appended to the beginning
                //of the line
                if ((line.charAt(0)=='1')&&(!doesUserExist(inbox,line.substring(1)))){
                    //Add the user to the inbox map
                    Vector <String> messages = new Vector<String>();
                    inbox.put(line.substring(1), messages);
                    System.out.println("Adding: "+line.substring(1));

                }
                //A message is being sent to a user if there is a '2' appended to the
                //beginning of the line
                else if (line.charAt(0)=='2'){

                    //Search for the first index of the double colons in the line
                    int indexOfColons = line.indexOf("::");
                    //Extract the sender and recipient's name from the line
                    String sender = line.substring(1,indexOfColons);
                    String recipient = line.substring(indexOfColons+2);
                    //Find the second occurrence of the double colons
                    indexOfColons = recipient.indexOf("::");
                    //Extract the message
                    String message = recipient.substring(indexOfColons+2);
                    recipient = recipient.substring(0,indexOfColons);
                    message = sender + " : " + message;
                    //add the message to the user's inbox
                    if (doesUserExist(inbox,recipient)){
                        synchronized (inbox.get(recipient)){
                        inbox.get(recipient).add(message);
                        }
                        System.out.println("Adding message to "+recipient+
                                " from " + sender+" \""+message+"\"");
                    }
                    else {
                        System.out.println("User does not exist");
                        writer.println("User does not exist");
                    }
                }
              //User wishes to retrieve their messages
                else if (line.charAt(0)=='3'){
                    String userName = line.substring(1);
                    if (!doesUserExist(inbox,userName)){
                        writer.println("User does not exist");
                        System.out.println("User does not exist");
                    }
                    else if (inbox.get(userName).size()>0){
                        //Display the user's messages
                        System.out.println("Writing " + userName + "'s messages: ");
                        String messages = userName + "'s messages: \n";
                        synchronized (inbox.get(userName)){
                        for (String message:inbox.get(userName)){
                            messages+=message + "\n";
                        }
                        writer.println(messages);
                        //clear all messages retrieved
                        inbox.get(userName).clear();
                        }
                    }
                    else {
                        System.out.println("No messages to write");
                        writer.println("No messages to display");
                    }

                }

               writer.close();
               reader.close();
               } catch (IOException e) {
                 e.printStackTrace();
               }

          }
        }

    public static void main(String[] args) {
        ServerSocket main = null;

        try {
            main = new ServerSocket(1500);
        } catch (IOException e1) {
            e1.printStackTrace();
        }

            while(true) {
                jClientHandler cl;
                try {
                cl = new jClientHandler(main.accept());
                Thread t = new Thread(cl);
                t.start();

            } catch(IOException e) {
                System.out.println("Error: " + e.getMessage());
            }
            }

    }

   }