import java.io.*;
import java.net.*;

public class POP3 {

    private final static String DEF_POP = "ziggo.nl";
    private final static String DEF_USER = "jorrit.de.boer";
    private final static String DEF_PASS = "netwerken12345";
    private final static int DEF_PORT = 110;
    private String[] actions = {"STAT", "LIST", "USER", "PASS", "DELE", "RETR", "QUIT"};
    private String pop;
    private Socket sock;
    private int port;
    private BufferedReader rdr;
    private BufferedReader socketRdr;
    private BufferedWriter socketWrtr;

    public POP3(){
        rdr = new BufferedReader(new InputStreamReader(System.in));
        sock = new Socket();
    }

    public boolean connect(){
        String servMes;

        try{
            sock.connect(new InetSocketAddress(pop, port));
            socketRdr = new BufferedReader(new InputStreamReader(sock.getInputStream()));
            socketWrtr = new BufferedWriter(new OutputStreamWriter(sock.getOutputStream()));

            servMes = readResponse();
            if(servMes.contains("-ERR")){
                System.out.println("An error has occurred.");
                return false;
            }
            socketWrtr.write("USER " + actions[2] +"\n");
            socketWrtr.flush();

            servMes = readResponse();
            if(servMes.contains("-ERR")){
                System.out.println("Invalid username.");
                return false;
            }
            socketWrtr.write("PASS " + actions[3] +"\n");
            socketWrtr.flush();

            servMes = readResponse();
            if(servMes.contains("-ERR")){
                System.out.println("Invalid password.");
                return false;
            }
            return true;
        } catch(IOException e) {
            System.out.println("Could not establish a connection with these settings: " + pop + ":" + port + "\n");
        }
        return false;
    }

    public boolean isConnected() {
        return sock != null && sock.isConnected();
    }

    public void setPop() throws IOException {
        System.out.println("Enter pop address.");
        System.out.println("If unspecified, [pop." + DEF_POP + "] will be used.");
        pop = input();
        if(pop.isEmpty()){
            pop = DEF_POP;
        }

        System.out.println("Enter port address.");
        System.out.println("If unspecified, [" + DEF_PORT + "] will be used.");
        String portStr = input();
        if(portStr.isEmpty()){
            port = DEF_PORT;
        } else {
            port = Integer.parseInt(portStr);
        }

        System.out.println("Enter username.");
        System.out.println("If unspecified, [" + DEF_USER + "] will be used.");
        actions[2] = input();
        if(actions[2].isEmpty()){
            actions[2] = DEF_USER;
        }

        System.out.println("Enter password.");
        System.out.println("If unspecified, [" + DEF_PASS + "] will be used.");
        actions[3] = input();
        if(actions[3].isEmpty()){
            actions[3] = "mail";
        }
    }

    public String input() throws IOException{
        String str = new String();
        str = rdr.readLine();
        return str;
    }

    public boolean execute(String inputStr) {
        String[] tmpStr = inputStr.split("@");
        int option = 6;

        if(!inputStr.isEmpty()){
            option = Integer.parseInt(tmpStr[0]);
        }

        switch (option) {
        case 1:
            return stat();
        case 2:
            return list();
        case 3:
            return inputStr.contains("@") ? retrieve(tmpStr[1]) : false;
        case 4:
            return inputStr.contains("@") ? delete(tmpStr[1]) : false;
        case 5:
            return quit();
        default:
            return false;
        }
    }

    private boolean stat() {
        try {
            socketWrtr.write("STAT"+"\n");
            socketWrtr.flush();
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    private boolean list() {
        try {
            socketWrtr.write("LIST"+"\n");
            socketWrtr.flush();
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    private boolean retrieve(String str) {
        str = str.trim();
        try {
            socketWrtr.write("RETR " + str + "\n");
            socketWrtr.flush();
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    private boolean delete(String str) {
        try {
            socketWrtr.write("DELE " + str + "\n");
            socketWrtr.flush();
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    public String readResponse() {
        String str = "";
        if(!sock.isClosed()){
            try {
                str = socketRdr.readLine() + "\n";
                while(socketRdr.ready()){
                    str += socketRdr.readLine() + "\n";
                }
                System.out.println("Server response: " + str);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return str;
    }

    public boolean quit() {
        try {
            socketWrtr.write("QUIT"+"\n");
            socketWrtr.flush();
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }
}