/**
 * The details of how knock-knock jokes work. 
 *
 * @author Matt Boutell, taken directly from The Java Tutorial, java.sun.com.
 *         Created Oct 15, 2006.
 */

public class KnockKnockProtocol {
    private static final int WAITING = 0;
    private static final int SENTKNOCKKNOCK = 1;
    private static final int SENTCLUE = 2;
    private static final int ANOTHER = 3;

    private static final int NUMJOKES = 5;

    private int state = WAITING;
    private int currentJoke = 0;

    private String[] clues = { "Turnip", "Little Old Lady", "Atch", "Who", "Who" };
    private String[] answers = { "Turnip the heat, it's cold in here!",
                                 "I didn't know you could yodel!",
                                 "Bless you!",
                                 "Is there an owl in here?",
                                 "Is there an echo in here?" };

    /**
     * Generates knock-knock output, given a client's input.
     *
     * @param theInput Input from the user.
     * @return The next line of the knock-knock joke.
     */
    public String processInput(String theInput) {
        String theOutput = null;

        if (this.state == WAITING) {
            theOutput = "Knock! Knock!";
            this.state = SENTKNOCKKNOCK;
        } else if (this.state == SENTKNOCKKNOCK) {
            if (theInput.equalsIgnoreCase("Who's there?")) {
                theOutput = this.clues[this.currentJoke];
                this.state = SENTCLUE;
            } else {
                theOutput = "You're supposed to say \"Who's there?\"! " +
			    "Try again. Knock! Knock!";
            }
        } else if (this.state == SENTCLUE) {
            if (theInput.equalsIgnoreCase(this.clues[this.currentJoke] + " who?")) {
                theOutput = this.answers[this.currentJoke] + " Want another? (y/n)";
                this.state = ANOTHER;
            } else {
                theOutput = "You're supposed to say \"" + 
                this.clues[this.currentJoke] + 
			    " who?\"" + 
			    "! Try again. Knock! Knock!";
                this.state = SENTKNOCKKNOCK;
            }
        } else if (this.state == ANOTHER) {
            if (theInput.equalsIgnoreCase("y")) {
                theOutput = "Knock! Knock!";
                if (this.currentJoke == (NUMJOKES - 1))
                	this.currentJoke = 0;
                else
                	this.currentJoke++;
                this.state = SENTKNOCKKNOCK;
            } else {
                theOutput = "Bye.";
                this.state = WAITING;
            }
        }
        return theOutput;
    }
}