objecttypenode.java

rule engine drools-2.0-beta-18

package org.drools.reteoo;

/*
 * $Id: ObjectTypeNode.java,v 1.23 2004/11/19 02:13:46 mproctor Exp $
 *
 * Copyright 2001-2003 (C) The Werken Company. All Rights Reserved.
 *
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided that the
 * following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright statements and
 * notices. Redistributions must also contain a copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. The name "drools" must not be used to endorse or promote products derived
 * from this Software without prior written permission of The Werken Company.
 * For written permission, please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "drools" nor may
 * "drools" appear in their names without prior written permission of The Werken
 * Company. "drools" is a trademark of The Werken Company.
 *
 * 5. Due credit should be given to The Werken Company. (http://werken.com/)
 *
 * THIS SOFTWARE IS PROVIDED BY THE WERKEN COMPANY AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE WERKEN COMPANY OR ITS CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */

import org.drools.FactException;
import org.drools.FactHandle;
import org.drools.spi.ObjectType;

import java.io.Serializable;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * Filters <code>Objects</code> coming from the <code>Rete</code> using a
 * <code>ObjectType</code> semantic module.
 * 
 * <p>
 * It receives <code>Objects</code> from the <code>Rete</code>, uses a
 * <code>ObjectType</code> instance to determine membership, and propagates
 * matching <code>Objects</code> further to all matching
 * <code>ParameterNode</code>s.
 * </p>
 * 
 * @see ObjectType
 * @see ParameterNode
 * @see Rete
 * 
 * @author <a href="mailto:[e-mail]">[e-mail] </a>
 */
class ObjectTypeNode
    implements
    Serializable
{
    // ------------------------------------------------------------
    // Instance members
    // ------------------------------------------------------------

    /** The <code>ObjectType</code> semantic module. */
    private ObjectType objectType;

    /** The <code>ParameterNode</code> children. */
    private Set parameterNodes;

    // ------------------------------------------------------------
    // Constructors
    // ------------------------------------------------------------

    /**
     * Construct given a semantic <code>ObjectType</code>.
     * 
     * @param objectType
     *            The semantic object-type differentiator.
     */
    public ObjectTypeNode(ObjectType objectType)
    {
        this.objectType = objectType;
        this.parameterNodes = Collections.EMPTY_SET;
    }

    // ------------------------------------------------------------
    // Instance methods
    // ------------------------------------------------------------

    /**
     * Retrieve the semantic <code>ObjectType</code> differentiator.
     * 
     * @return The semantic <code>ObjectType</code> differentiator.
     */
    public ObjectType getObjectType()
    {
        return this.objectType;
    }

    /**
     * Add a <code>ParameterNode</code> child to this node.
     * 
     * @param node
     *            The <code>ParameterNode</code> child to add.
     */
    void addParameterNode(ParameterNode node)
    {
        if ( this.parameterNodes == Collections.EMPTY_SET )
        {
            this.parameterNodes = new HashSet( );
        }

        this.parameterNodes.add( node );
    }

    /**
     * Retrieve the <code>Set</code> of <code>ParameterNodes/code>
     *  children of this node.
     *
     *  @return The <code>Set</code> of <code>ParameterNode</code>
     *          children.
     */
    Set getParameterNodes()
    {
        return this.parameterNodes;
    }

    /**
     * Retreive an <code>Iterator</code> over <code>ParameterNode</code>
     * children of this node.
     * 
     * @return An <code>Iterator</code> over <code>ParameterNode</code>
     *         children of this node.
     */
    Iterator getParameterNodeIterator()
    {
        return this.parameterNodes.iterator( );
    }

    /**
     * Assert a new fact object into this <code>RuleBase</code> and the
     * specified <code>WorkingMemory</code>.
     * 
     * @param handle
     *            The fact handle.
     * @param object
     *            The object to assert.
     * @param workingMemory
     *            The working memory session.
     * 
     * @throws FactException
     *             if an error occurs during assertion.
     */
    void assertObject(FactHandle handle,
                      Object object,
                      WorkingMemoryImpl workingMemory) throws FactException
    {
        if ( !this.objectType.matches( object ) )
        {
            return;
        }

        Iterator nodeIter = getParameterNodeIterator( );

        while ( nodeIter.hasNext( ) )
        {
            ((ParameterNode) nodeIter.next( )).assertObject( handle,
                                                             object,
                                                             workingMemory );
        }
    }

    /**
     * Retract a fact object from this <code>RuleBase</code> and the specified
     * <code>WorkingMemory</code>.
     * 
     * @param handle
     *            The handle of the fact to retract.
     * @param workingMemory
     *            The working memory session.
     * 
     * @throws FactException
     *             if an error occurs during assertion.
     */
    void retractObject(FactHandle handle,
                       WorkingMemoryImpl workingMemory) throws FactException
    {
        Object object = workingMemory.getObject( handle );

        if ( !this.objectType.matches( object ) )
        {
            return;
        }

        Iterator nodeIter = getParameterNodeIterator( );

        while ( nodeIter.hasNext( ) )
        {
            ((ParameterNode) nodeIter.next( )).retractObject( handle,
                                                              workingMemory );
        }
    }

    /**
     * Modify a fact object in this <code>RuleBase</code> and the specified
     * <code>WorkingMemory</code>.
     * 
     * With the exception of time-based nodes, modification of a fact object is
     * semantically equivelent to retracting and re-asserting it.
     * 
     * @param handle
     *            The fact handle.
     * @param object
     *            The modified value object.
     * @param workingMemory
     *            The working memory session.
     * 
     * @throws FactException
     *             if an error occurs during assertion.
     */
    void modifyObject(FactHandle handle,
                      Object object,
                      WorkingMemoryImpl workingMemory) throws FactException
    {
        ObjectType objectType = getObjectType( );

        Iterator nodeIter = getParameterNodeIterator( );
        ParameterNode eachNode;

        if ( !objectType.matches( object ) )
        {
            while ( nodeIter.hasNext( ) )
            {
                eachNode = (ParameterNode) nodeIter.next( );

                eachNode.retractObject( handle,
                                        workingMemory );
            }
        }
        else
        {
            while ( nodeIter.hasNext( ) )
            {
                eachNode = (ParameterNode) nodeIter.next( );

                eachNode.modifyObject( handle,
                                       object,
                                       workingMemory );
            }
        }
    }
}