/* A polymorphic switch with boolean select.

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This is similar to Switch and could be design/code reviewed at the same time.
*/
package ptolemy.actor.lib;

import ptolemy.actor.TypedAtomicActor;
import ptolemy.actor.TypedIOPort;
import ptolemy.data.BooleanToken;
import ptolemy.data.Token;
import ptolemy.data.type.BaseType;
import ptolemy.kernel.CompositeEntity;
import ptolemy.kernel.util.IllegalActionException;
import ptolemy.kernel.util.NameDuplicationException;
import ptolemy.kernel.util.StringAttribute;


//////////////////////////////////////////////////////////////////////////
//// BooleanSwitch

/**
   A type polymorphic switch with boolean valued control.  In an
   iteration, if an input token is available at the <i>control</i> input,
   that token is read, and its value is noted.  Its value specifies the
   input port that should be read next. If the <i>control</i> input is
   true, then if an input token is available on the <i>input</i> port,
   then it is is read and sent to the <i>trueOutput</i>.  Likewise with a
   false input and the <i>falseOutput</i> port.  Because tokens are
   immutable, the same Token is sent to the output, rather than a copy.
   The <i>input</i> port may receive Tokens of any type.

   <p>If no token has ever been received on the <i>control</i> port, then
   <i>falseOutput</i> is assumed to be the one to receive data.

   @author Steve Neuendorffer
   @version $Id: BooleanSwitch.java,v 1.23 2005/04/25 21:22:23 cxh Exp $
   @since Ptolemy II 2.0
   @Pt.ProposedRating Green (neuendor)
   @Pt.AcceptedRating Red (neuendor)
*/
public class BooleanSwitch extends TypedAtomicActor {
    /** Construct an actor in the specified container with the specified
     *  name.
     *  @param container The container.
     *  @param name The name of this actor within the container.
     *  @exception IllegalActionException If the actor cannot be contained
     *   by the proposed container.
     *  @exception NameDuplicationException If the name coincides with
     *   an actor already in the container.
     */
    public BooleanSwitch(CompositeEntity container, String name)
            throws IllegalActionException, NameDuplicationException {
        super(container, name);

        input = new TypedIOPort(this, "input", true, false);
        control = new TypedIOPort(this, "control", true, false);
        control.setTypeEquals(BaseType.BOOLEAN);
        trueOutput = new TypedIOPort(this, "trueOutput", false, true);
        falseOutput = new TypedIOPort(this, "falseOutput", false, true);
        trueOutput.setTypeAtLeast(input);
        falseOutput.setTypeAtLeast(input);

        // Put the control input on the bottom of the actor.
        StringAttribute controlCardinal = new StringAttribute(control,
                "_cardinal");
        controlCardinal.setExpression("SOUTH");
    }

    ///////////////////////////////////////////////////////////////////
    ////                     ports and parameters                  ////

    /** Input that selects one of the other input ports.  The type is
     *  BooleanToken.
     */
    public TypedIOPort control;

    /** The input port.  The type can be anything.
     */
    public TypedIOPort input;

    /** Output for tokens on the true path.  The type is at least the
     *  type of the input.
     */
    public TypedIOPort trueOutput;

    /** Output for tokens on the false path.  The type is at least the
     *  type of the input.
     */
    public TypedIOPort falseOutput;

    ///////////////////////////////////////////////////////////////////
    ////                         public methods                    ////

    /** Read a token from each input port.  If the token from the
     *  <i>control</i> input is true, then output the token consumed from the
     *  <i>input</i> port on the <i>trueOutput</i> port,
     *  otherwise output the token on the <i>falseOutput</i> port.
     *
     *  @exception IllegalActionException If there is no director.
     */
    public void fire() throws IllegalActionException {
        if (control.hasToken(0)) {
            _control = ((BooleanToken) control.get(0)).booleanValue();
        }

        if (input.hasToken(0)) {
            Token token = input.get(0);

            if (_control) {
                trueOutput.send(0, token);
            } else {
                falseOutput.send(0, token);
            }
        }
    }

    /** Initialize this actor so that the <i>falseOutput</i> is written
     *  to until a token arrives on the <i>control</i> input.
     *  @exception IllegalActionException If the parent class throws it.
     */
    public void initialize() throws IllegalActionException {
        super.initialize();
        _control = false;
    }

    ///////////////////////////////////////////////////////////////////
    ////                         private variables                 ////
    // The most recently read control token.
    private boolean _control = false;
}