import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class OmokServlet extends HttpServlet {
    private static int idCount = 0;
    private static Hashtable dataMap = new Hashtable();

    public synchronized void doGet(HttpServletRequest request,
        HttpServletResponse response) throws IOException {
        String command =getParameterValue(request, "command");
        String result = "";

        if (command.equals("connect")) {
            dataMap.remove(String.valueOf(idCount));
            result = String.valueOf(idCount);
            idCount = (idCount > 999) ? 0 : idCount+1;
        }
        else if (command.equals("disconnect")) {
            String id = getParameterValue(request, "id");
            dataMap.put(id, "E");
        }
        else if (command.equals("sendData")) {
            String id   = getParameterValue(request, "id");
            String data = getParameterValue(request, "data");
            dataMap.put(id, data);
        }
        else if (command.equals("receiveData")) {
            String id =getParameterValue(request, "id");
            if (dataMap.containsKey(id)) {
                result = (String)dataMap.remove(id);
            }
        }

        PrintWriter pw = response.getWriter();
        pw.print(result);
        pw.flush();
        pw.close();
    }

    private String getParameterValue(HttpServletRequest request, String key) {
        String[] param = request.getParameterValues(key);
        if (param != null && param.length >= 0) return param[0];
        return "";
    }
}