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

public class P4A {

	public static HashMap<String, String> map = new HashMap<String, String>();
    public static void main(String[] args) {
    	Socket connectionSocket = null;
    	BufferedReader in = null;
    	PrintStream printStream = null;
    	System.out.println("Server started.");
    	while(true) {
    		try (ServerSocket serverSocket = new ServerSocket(7777)) {
    			System.out.println("Socket opened.");
        		connectionSocket = serverSocket.accept();
        		System.out.println("Client connected.");
        		in = new BufferedReader( new InputStreamReader(connectionSocket.getInputStream()));
            	printStream = new PrintStream(connectionSocket.getOutputStream(), true);
            	String request = "";
            	while (!request.equals("EXIT")) {
                	System.out.println("Reading...");
                	request = in.readLine();
                	System.out.println("Request: " + request);
                	if(request.length()<3) {
                		System.out.println("ERR: Unknown Command!");
            			printStream.println("ERR: Unknown Command!");
            			continue;
                	}

                	switch(request.substring(0,3)) {
                		case "GET":
                			if(request.length() < 5 || (args = request.substring(4).split("\\s")).length != 1) {
                				printStream.println("ERR: Invalid number of arguments (1)!");
                				System.out.println("ERR: Invalid number of arguments (1)!");
                				break;
                			}
                			if(!map.containsKey(args[0])) {
                				printStream.println("ERR: Unknown Key!");
                				System.out.println("ERR: Unknown Key!");
                				break;
                			}
                			printStream.println("RES: " + map.get(args[0]));
                			System.out.println("RES: " + map.get(args[0]));
                			break;
                		case "PUT":
                			if(request.length() < 5 || (args = request.substring(4).split("\\s")).length != 2) {
                				printStream.println("ERR: Invalid number of arguments (2)!");
                				System.out.println("ERR: Invalid number of arguments (2)!");
                				break;
                			}
                			map.put(args[0], args[1]);
                			printStream.println("RES: OK");
                			System.out.println("RES: OK");
                			break;
                		default:
                			if(request.equals("EXIT")) {
                				continue;
                			}
                			System.out.println("ERR: Unknown Command!");
                			printStream.println("ERR: Unknown Command!");
                			break;
                	}

            	}
            	printStream.println("RES: BYE!");
            	printStream.close();
            	in.close();
            	connectionSocket.close();
            	serverSocket.close();
        	} catch (Exception e) {
        		System.err.println(e.getMessage());
        		printStream.println("ERR: Unknown Error!");
        	}
    	}
    }

}