rete.java

rule engine drools-2.0-beta-18

package org.drools.reteoo;

/*
 * $Id: Rete.java,v 1.22 2004/11/21 13:18:04 simon 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.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * The Rete-OO network.
 *
 * This node accepts an <code>Object</code>, and simply propagates it to all
 * <code>ObjectTypeNode</code> s for type testings.
 *
 * @see ObjectTypeNode
 *
 * @author <a href="mailto:[e-mail]">bob mcwhirter </a>
 */
class Rete
    implements
    Serializable
{
    // ------------------------------------------------------------
    // Instance members
    // ------------------------------------------------------------

    /** The set of <code>ObjectTypeNodes</code>. */
    private final Map objectTypeNodes = new HashMap( );

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

    /**
     * Construct.
     */
    public Rete()
    {
    }

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

    /**
     * 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
    {
        Iterator nodeIter = getObjectTypeNodeIterator( );

        while ( nodeIter.hasNext( ) )
        {
            ( (ObjectTypeNode) 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 retraction.
     */
    void retractObject(FactHandle handle,
                       WorkingMemoryImpl workingMemory) throws FactException
    {
        Iterator nodeIter = getObjectTypeNodeIterator( );

        while ( nodeIter.hasNext( ) )
        {
            ( (ObjectTypeNode) 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 modification.
     */
    void modifyObject(FactHandle handle,
                      Object object,
                      WorkingMemoryImpl workingMemory) throws FactException
    {
        Iterator nodeIter = getObjectTypeNodeIterator( );

        while ( nodeIter.hasNext( ) )
        {
            ( (ObjectTypeNode) nodeIter.next( ) ).modifyObject( handle,
                                                                object,
                                                                workingMemory );
        }
    }

    /**
     * Add an <code>ObjectTypeNode</code> child to this <code>Rete</code>.
     *
     * @param node
     *            The node to add.
     */
    void addObjectTypeNode(ObjectTypeNode node)
    {
        this.objectTypeNodes.put( node.getObjectType( ),
                                  node );
    }

    /**
     * Retrieve all <code>ObjectTypeNode</code> children of this node.
     *
     * @return The <code>Set</code> of <code>ObjectTypeNodes</code>.
     */
    Collection getObjectTypeNodes()
    {
        return this.objectTypeNodes.values( );
    }

    /**
     * Retrieve an <code>Iterator</code> over the <code>ObjectTypeNode</code>
     * children of this node.
     *
     * @return An <code>Iterator</code> over <code>ObjectTypeNodes</code>.
     */
    Iterator getObjectTypeNodeIterator()
    {
        return this.objectTypeNodes.values( ).iterator( );
    }

    /**
     * Retrieve an <code>ObjectTypeNode</code> keyed by
     * <code>ObjectType</code>.
     *
     * @param objectType
     *            The <code>ObjectType</code> key.
     *
     * @return The matching <code>ObjectTypeNode</code> if one has already
     *         been created, else <code>null</code>.
     */
    ObjectTypeNode getObjectTypeNode(ObjectType objectType)
    {
        return (ObjectTypeNode) this.objectTypeNodes.get( objectType );
    }

    /**
     * Retrieve an <code>ObjectTypeNode</code> keyed by
     * <code>ObjectType</code>, creating one, if necessary.
     *
     * @param objectType
     *            The <code>ObjectType</code> key.
     *
     * @return The matching <code>ObjectTypeNode</codeb>.
     */
    ObjectTypeNode getOrCreateObjectTypeNode(ObjectType objectType)
    {
        ObjectTypeNode node = getObjectTypeNode( objectType );

        if ( node == null )
        {
            node = new ObjectTypeNode( objectType );

            addObjectTypeNode( node );
        }

        return node;
    }
}