Automaton.java

/*
 *   Automaton.java
 *
 * Copyright 2000-2001-2002  aliCE team at deis.unibo.it
 *
 * This software is the proprietary information of deis.unibo.it
 * Use is subject to license terms.
 *
 */
package alice.tuprolog.ui;

/**
 * this abstract class is the base class for
 * implementing automaton abstraction
 *
 * automaton state behavior is expressed
 * in public method and the become method
 * allows to move computation from state to state
 *
 * method representing state must be public
 * (to allow correct behavior of reflection)
 */
public abstract class Automaton implements Runnable {

    /** method name representing state behavior */
    protected String state = "boot";

    /** arguments value eventually associated to state transition */
    protected Object[] arguments = null;

    /** arguments class eventually associated to state transition */
    protected Class<?>[] argType;

    public Automaton() {
        try {
            argType = new Class[]{ Class.forName("[Ljava.lang.Object;") };
        } catch (Exception ex) {
        }
    }

    protected void become(String s) {
        if (!state.equals("end")) {
            state = s;
            arguments = null;
        }
    }

    protected void become(String s, Object[] args) {
        if (!state.equals("end")) {
            state = s;
            arguments = args;
        }
    }

    /** boot state of automaton */
    public abstract void boot();

    @Override
    public void run() {
        while (true) {
            try {
                if (!state.equals("end"))
                    if (arguments == null)
                        this.getClass().getDeclaredMethod(state, (Class<?>[]) null).invoke(this, (Object[]) null);
                    else
                        this.getClass().getDeclaredMethod(state, argType).invoke(this, arguments);
                else {
                    end();
                    break;
                }
            } catch (Exception ex) {
                ex.printStackTrace();
                error();
            }
        }
    }

    /** idle state */
    public void idle() {
        try {
            wait();
        } catch (Exception ex) {
        }
    }

    /** shutdown state */
    public void end() {
    }

    /** error state */
    public void error() {
        become("end");
    }
}