law(pingpongplus,language(java))

public class Pingpongplus extends Law {

    public void sent(String source, String message, String dest) {

        String pingToY = "pingTo(" + dest + ")";
        String pingFromY = "pingFrom(" + dest + ")";

        if (message.startsWith("ping(") && !CS.has(pingToY)) {
            doAdd(pingToY);
            doForward();
	    return;
        }
        if (message.startsWith("pong(") && CS.has(pingFromY)) {
            doRemove(pingFromY);
            doForward();
            return;
        }
        if (message.equals("getCS")) {
            doDiscloseAllCS();
            return;
        }
        if (message.startsWith("display(")) {
            int dt = Integer.parseInt(getContentFromMessage(message));
            doImposeObligation("display", dt, "sec");
            doAdd("obTime(" + dt + ")"); 
            doShowEvents("all", "all");
            return;
        }
        if (message.equals("stopDisplay")) {
            Term timeTerm = CS.findT("obTime(%A)");
            doRemove(timeTerm);
            doRepealObligation("display");
            return;
        }

        doDeliver(Self, "messageIgnored", Self);
    }

    public void arrived(String source, String message, String dest) {
        if (message.startsWith("ping(")) {
            doAdd("pingFrom(" + source + ")");
            doDeliver();
        }
        if (message.startsWith("pong(")) {
            doRemove("pingTo(" + source + ")");
            doDeliver();
        } 
    }

    public void disconnected() {
        doImposeObligation("toQuit", 10, "min");
    } 

    public void reconnected() {
        doRepealObligation("toQuit");
    }

    public void obligationDue(Term obligationTerm) {

        if (obligationTerm.toString().equals("toQuit")) doQuit();

        if (obligationTerm.toString().equals("display")) {
            int dt = CS.fetchInt("obTime");
            doImposeObligation("display", dt, "sec");
            doShowEvents("all", "all");
        }
    }

    public void exception(Message m, String diagnostic) {

        if ((m.type == Const.FWD) && m.source.equals(Self) && m.s_payload.startsWith("ping")) {
            doRemove("pingTo(" + m.dest + ")");
            doDeliver("law", "exc(" + m.s_payload + ")", Self);
            return;
        }

        doDeliver("law", "exception(type(" + m.type + "),source(" + m.source + "),payload(" + m.s_payload 
            + "),dest(" + m.dest + "),diagnostic(" + diagnostic + "))", Self);
    }

    /*This is a helper method to retrieve the only argument of a regular expression*/

    public String getContentFromMessage(String anyMessage) { 
        int index = anyMessage.indexOf("("); 
        if (index == -1) return ""; 
        else return anyMessage.substring(index+1, anyMessage.length()-1); 
    } 

}