/* A constant source.

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 All rights reserved.
 Permission is hereby granted, without written agreement and without
 license or royalty fees, to use, copy, modify, and distribute this
 software and its documentation for any purpose, provided that the above
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 of this software.

 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
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 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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 PT_COPYRIGHT_VERSION_2
 COPYRIGHTENDKEY

 */
package ptolemy.actor.lib;

import ptolemy.data.expr.Parameter;
import ptolemy.kernel.CompositeEntity;
import ptolemy.kernel.util.IllegalActionException;
import ptolemy.kernel.util.NameDuplicationException;
import ptolemy.kernel.util.Workspace;

//////////////////////////////////////////////////////////////////////////
//// Const

/**
 Produce a constant output. The value of the
 output is that of the token contained by the <i>value</i> parameter,
 which by default is an IntToken with value 1. The type of the output
 is that of <i>value</i> parameter.
 <p>
 If the trigger port is connected, then this actor fires only if a token is
 provided on any channel of the trigger port. The value of that token
 does not matter. Specifically, if there is no such token, the prefire()
 method returns false.

 @author Yuhong Xiong, Edward A. Lee
 @version $Id$
 @since Ptolemy II 0.2
 @Pt.ProposedRating Green (eal)
 @Pt.AcceptedRating Green (bilung)
 */
public class Const extends LimitedFiringSource {
    /** Construct a constant source with the given container and name.
     *  Create the <i>value</i> parameter, initialize its value to
     *  the default value of an IntToken with value 1.
     *  @param container The container.
     *  @param name The name of this actor.
     *  @exception IllegalActionException If the entity cannot be contained
     *   by the proposed container.
     *  @exception NameDuplicationException If the container already has an
     *   actor with this name.
     */
    public Const(CompositeEntity container, String name)
            throws NameDuplicationException, IllegalActionException {
        super(container, name);
        value = new Parameter(this, "value");
        value.setExpression("1");

        // Set the type constraint.
        output.setTypeAtLeast(value);

        _attachText("_iconDescription", "<svg>\n" + "<rect x=\"0\" y=\"0\" "
                + "width=\"60\" height=\"20\" " + "style=\"fill:white\"/>\n"
                + "</svg>\n");
    }

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

    /** The value produced by this constant source.
     *  By default, it contains an IntToken with value 1.  If the
     *  type of this token is changed during the execution of a model,
     *  then the director will be asked to redo type resolution.
     */
    public Parameter value;

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

    /** Clone the actor into the specified workspace. This calls the
     *  base class and then sets the value public variable in the new
     *  object to equal the cloned parameter in that new object.
     *  @param workspace The workspace for the new object.
     *  @return A new actor.
     *  @exception CloneNotSupportedException If a derived class contains
     *   an attribute that cannot be cloned.
     */
    public Object clone(Workspace workspace) throws CloneNotSupportedException {
        Const newObject = (Const) super.clone(workspace);

        // Set the type constraint.
        newObject.output.setTypeAtLeast(newObject.value);
        return newObject;
    }

    /** Send the token in the <i>value</i> parameter to the output.
     *  @exception IllegalActionException If it is thrown by the
     *   send() method sending out the token.
     */
    public void fire() throws IllegalActionException {
        super.fire();
        output.send(0, value.getToken());
    }
}