/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * particular file as subject to the "Classpath" exception as provided

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

package javax.imageio.spi;

import java.io.Serializable;

import java.util.HashSet;

import java.util.Iterator;

import java.util.Set;

/**

 * A node in a directed graph.  In addition to an arbitrary

 * <code>Object</code> containing user data associated with the node,

 * each node maintains a <code>Set</code>s of nodes which are pointed

 * to by the current node (available from <code>getOutNodes</code>).

 * The in-degree of the node (that is, number of nodes that point to

 * the current node) may be queried.

 *

 */

class DigraphNode implements Cloneable, Serializable {

    /** The data associated with this node. */

    protected Object data;

    /**

     * A <code>Set</code> of neighboring nodes pointed to by this

     * node.

     */

    protected Set outNodes = new HashSet();

    /** The in-degree of the node. */

    protected int inDegree = 0;

    /**

     * A <code>Set</code> of neighboring nodes that point to this

     * node.

     */

    private Set inNodes = new HashSet();

    public DigraphNode(Object data) {

        this.data = data;

    }

    /** Returns the <code>Object</code> referenced by this node. */

    public Object getData() {

        return data;

    }

    /**

     * Returns an <code>Iterator</code> containing the nodes pointed

     * to by this node.

     */

    public Iterator getOutNodes() {

        return outNodes.iterator();

    }

    /**

     * Adds a directed edge to the graph.  The outNodes list of this

     * node is updated and the in-degree of the other node is incremented.

     *

     * @param node a <code>DigraphNode</code>.

     *

     * @return <code>true</code> if the node was not previously the

     * target of an edge.

     */

    public boolean addEdge(DigraphNode node) {

        if (outNodes.contains(node)) {

            return false;

        }

        outNodes.add(node);

        node.inNodes.add(this);

        node.incrementInDegree();

        return true;

    }

    /**

     * Returns <code>true</code> if an edge exists between this node

     * and the given node.

     *

     * @param node a <code>DigraphNode</code>.

     *

     * @return <code>true</code> if the node is the target of an edge.

     */

    public boolean hasEdge(DigraphNode node) {

        return outNodes.contains(node);

    }

    /**

     * Removes a directed edge from the graph.  The outNodes list of this

     * node is updated and the in-degree of the other node is decremented.

     *

     * @return <code>true</code> if the node was previously the target

     * of an edge.

     */

    public boolean removeEdge(DigraphNode node) {

        if (!outNodes.contains(node)) {

            return false;

        }

        outNodes.remove(node);

        node.inNodes.remove(this);

        node.decrementInDegree();

        return true;

    }

    /**

     * Removes this node from the graph, updating neighboring nodes

     * appropriately.

     */

    public void dispose() {

        Object[] inNodesArray = inNodes.toArray();

        for(int i=0; i<inNodesArray.length; i++) {

            DigraphNode node = (DigraphNode) inNodesArray[i];

            node.removeEdge(this);

        }

        Object[] outNodesArray = outNodes.toArray();

        for(int i=0; i<outNodesArray.length; i++) {

            DigraphNode node = (DigraphNode) outNodesArray[i];

            removeEdge(node);

        }

    }

    /** Returns the in-degree of this node. */

    public int getInDegree() {

        return inDegree;

    }

    /** Increments the in-degree of this node. */

    private void incrementInDegree() {

        ++inDegree;

    }

    /** Decrements the in-degree of this node. */

    private void decrementInDegree() {

        --inDegree;

    }

}