/* An actor that outputs the minimum value that it has received since the start
of execution.

 Copyright (c) 2008-2014 The Regents of the University of California.
 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
 copyright notice and the following two paragraphs appear in all copies
 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
 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
 SUCH DAMAGE.

 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
 CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
 ENHANCEMENTS, OR MODIFICATIONS.

 PT_COPYRIGHT_VERSION_2
 COPYRIGHTENDKEY

 */
package ptolemy.actor.lib;

import java.util.HashSet;
import java.util.Set;

import ptolemy.data.ScalarToken;
import ptolemy.data.type.BaseType;
import ptolemy.data.type.TypeConstant;
import ptolemy.graph.Inequality;
import ptolemy.kernel.CompositeEntity;
import ptolemy.kernel.util.IllegalActionException;
import ptolemy.kernel.util.NameDuplicationException;
import ptolemy.kernel.util.Workspace;

/**
 Output the minimum value seen since the start of execution of the model.
 On each firing, this actor consumes exactly one scalar token at its input port.
 The value of the token is compared to the minimum value maintained since the
 start of the execution. The lesser of the two is output to the output port in
 the same firing, and the minimum value is set with that greater value in
 postfire().

 @author Thomas Huining Feng
 @version $Id: RunningMinimum.java 70398 2014-10-22 23:44:32Z cxh $
 @since Ptolemy II 10.0
 @Pt.ProposedRating Yellow (tfeng)
 @Pt.AcceptedRating Red (tfeng)
 */
public class RunningMinimum extends Transformer {

    /** Construct an actor with the specified container and name.
     *
     *  @param container The composite actor to contain this one.
     *  @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 RunningMinimum(CompositeEntity container, String name)
            throws NameDuplicationException, IllegalActionException {
        super(container, name);
    }

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

    /** Clone this actor into the specified workspace. The new actor is
     *  <i>not</i> added to the directory of that workspace (you must do this
     *  yourself if you want it there).
     *  The result is a new actor with the same ports as the original, but
     *  no connections and no container.  A container must be set before
     *  much can be done with this actor.
     *
     *  @param workspace The workspace for the cloned object.
     *  @exception CloneNotSupportedException If cloned ports cannot have
     *   as their container the cloned entity (this should not occur), or
     *   if one of the attributes cannot be cloned.
     *  @return A new ComponentEntity.
     */
    @Override
    public Object clone(Workspace workspace) throws CloneNotSupportedException {
        RunningMinimum newObject = (RunningMinimum) super.clone(workspace);
        return newObject;
    }

    /** Consume a token at the input port, and produce the greater of that value
     *  and the maintained minimum value to the output port.
     *
     *  @exception IllegalActionException If getting token from input or
     *  sending token to output throws it.
     */
    @Override
    public void fire() throws IllegalActionException {
        super.fire();

        _value = (ScalarToken) input.get(0);
        if (_minimum == null || _value.isLessThan(_minimum).booleanValue()) {
            output.broadcast(_value);
        } else {
            output.broadcast(_minimum);
        }
    }

    /** Initialize the maintained minimum value to be null so it will be set
     *  with the first input at the input port.
     *
     *  @exception IllegalActionException If the initialize() method of the
     *  superclass throws it.
     */
    @Override
    public void initialize() throws IllegalActionException {
        super.initialize();

        _minimum = null;
    }

    /** Commit the minimum value observed since the start of execution to the
     *  minimum field to be compared with later inputs.
     *
     *  @exception IllegalActionException If the postfire() method of the
     *  superclass throws it.
     */
    @Override
    public boolean postfire() throws IllegalActionException {
        boolean result = super.postfire();

        if (_minimum == null || _value.isLessThan(_minimum).booleanValue()) {
            _minimum = _value;
        }

        return result;
    }

    /** Return true if the prefire() method of the superclass returns true, and
     *  there is at least one token at the input port.
     *
     *  @exception IllegalActionException If the prefire() method of the
     *  superclass throws it.
     */
    @Override
    public boolean prefire() throws IllegalActionException {
        return super.prefire() && input.hasToken(0);
    }

    ///////////////////////////////////////////////////////////////////
    ////                         protected methods                 ////

    /** Eliminate default constraints.
     *  @return null
     */
    @Override
    protected Set<Inequality> _defaultTypeConstraints() {
        return null;
    }

    /** Set input <= output, input <= Scalar. If backward type inference is
     *  enabled and input has no declared type, also set input >= output.
     *  @return A set of inequality constraints.
     */
    @Override
    protected Set<Inequality> _customTypeConstraints() {
        Set<Inequality> result = new HashSet<Inequality>();
        /* input <= output */
        result.add(new Inequality(input.getTypeTerm(), output.getTypeTerm()));
        /* input <= Scalar. */
        result.add(new Inequality(input.getTypeTerm(), new TypeConstant(
                BaseType.SCALAR)));
        /* input >= output if backward type inference is enabled */
        if (isBackwardTypeInferenceEnabled()
                && input.getTypeTerm().isSettable()) {
            result.add(new Inequality(output.getTypeTerm(), input.getTypeTerm()));
        }
        return result;
    }

    ///////////////////////////////////////////////////////////////////
    ////                         private variables                 ////

    // The minimum value observed so far.
    private ScalarToken _minimum;

    // The value observed in the current firing.
    private ScalarToken _value;
}