/*______________________________________________________________________________
 * 
 * net.innig.util.GraphType
 * 
 *______________________________________________________________________________
 * 
 * Copyright 2002 Paul Cantrell
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * (1) Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 * (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 of the author may not be used to endorse or promote
 *     products derived from this software without specific prior
 *     written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 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 AUTHOR 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.
 *_______________________________________________________________________________
 */

package net.innig.util;

import net.innig.collect.*;
import java.util.*;

/**
    An enumerated type with directed edges between its members.
    Useful for modeling types with a natural "is-a" relationship.
    
    <p align="center">
    <table cellpadding=4 cellspacing=2 border=0 bgcolor="#338833" width="90%"><tr><td bgcolor="#EEEEEE">
        <b>Maturity:</b>
        Brand spankin' new.
    </td></tr><tr><td bgcolor="#EEEEEE">
        <b>Plans:</b>
        Perhaps add JDO support.
    </td></tr></table>
    
    @author Paul Cantrell
    @version [Development version]
*/
public abstract class GraphType
    extends EnumeratedType
    {
    private static final MultiMap
        childMap = new HashMultiMap(),
        descendentMap = new HashMultiMap();
    
    //-----------------------------------------------------------------------------
    
    public GraphType(String name)
        { this(name, Collections.EMPTY_SET); }
    
    public GraphType(String name, GraphType parent)
        { this(name, Collections.singleton(parent)); }
    
    public GraphType(String name, GraphType[] parents)
        { this(name, Arrays.asList(parents)); }
    
    public GraphType(String name, Collection/*<GraphType>*/ parents)
        {
        super(name);
        setParents(parents);
        }
    
    protected void setParents(Collection/*<GraphType>*/ parents)
        {
        if(parents == null)
            throw new IllegalArgumentException("parents == null");
        if(this.parents != null)
            throw new IllegalArgumentException("You can only set the parents once. Sorry.");
        
        this.parents = Collections.unmodifiableSet(new HashSet(parents));
        ancestors = Collections.unmodifiableSet(
            Graphs.reachableNodes(
                this,
                new GraphWalker()
                    {
                    public Collection getEdgesFrom(Object node)
                        { return ((GraphType) node).getParents(); }
                    }));
        // delay children & descendents until all instances are accounted for!
        synchronized(childMap)
            {
            for(Iterator i = parents.iterator(); i.hasNext(); )
                childMap.put(i.next(), this);
            for(Iterator i = ancestors.iterator(); i.hasNext(); )
                descendentMap.put(i.next(), this);
            }
        }
    
    public boolean is(GraphType that)
        { return getAncestors().contains(that); }
    
    public Set getParents()
        { return parents; }
    
    public Set getAncestors()
        { return ancestors; }
    
    public Set getChildren()
        {
        synchronized(childMap)
            { return emptyIfNull(childMap.get(this)); }
        }
    
    public Set getDescendents()
        {
        synchronized(childMap)
            { return emptyIfNull(descendentMap.get(this)); }
        }
    
    private Set emptyIfNull(Set s)
        { return (s == null) ? Collections.EMPTY_SET : s; }
    
    private transient Set parents, ancestors, children, descendents;
    }