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 * 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
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package com.sun.xml.internal.bind.v2.runtime;

import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.Map;
import java.util.Set;

/**
 * Bi-directional map between elements, inner peers,
 * and outer peers.
 *
 * <p>
 * TODO: this should be rewritten for efficiency.
 *
 * @since 2.0
 *
 * @author
 *     Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)
 */
public final class AssociationMap<XmlNode> {
    final static class Entry<XmlNode> {
        /** XML element. */
        private XmlNode element;
        /** inner peer, or null. */
        private Object inner;
        /** outer peer, or null. */
        private Object outer;

        public XmlNode element() {
                return element;
        }
        public Object inner() {
                return inner;
        }
        public Object outer() {
                return outer;
        }
    }

    private final Map<XmlNode,Entry<XmlNode>> byElement = new IdentityHashMap<XmlNode,Entry<XmlNode>>();
    private final Map<Object,Entry<XmlNode>> byPeer = new IdentityHashMap<Object,Entry<XmlNode>>();
    private final Set<XmlNode> usedNodes = new HashSet<XmlNode>();

    /** Records the new {@code element <->inner} peer association. */
    public void addInner( XmlNode element, Object inner ) {
        Entry<XmlNode> e = byElement.get(element);
        if(e!=null) {
                if(e.inner!=null)
                byPeer.remove(e.inner);
            e.inner = inner;
        } else {
                e = new Entry<XmlNode>();
            e.element = element;
            e.inner = inner;
        }

        byElement.put(element,e);

        Entry<XmlNode> old = byPeer.put(inner,e);
        if(old!=null) {
            if(old.outer!=null)
                byPeer.remove(old.outer);
            if(old.element!=null)
                byElement.remove(old.element);
        }
    }

    /** Records the new {@code element <-> outer} peer association. */
    public void addOuter( XmlNode element, Object outer ) {
        Entry<XmlNode> e = byElement.get(element);
        if(e!=null) {
            if(e.outer!=null)
                byPeer.remove(e.outer);
            e.outer = outer;
        } else {
            e = new Entry<XmlNode>();
            e.element = element;
            e.outer = outer;
        }

        byElement.put(element,e);

        Entry<XmlNode> old = byPeer.put(outer,e);
        if(old!=null) {
            old.outer=null;

            if(old.inner==null)
                // remove this entry
                byElement.remove(old.element);
        }
    }

    public void addUsed( XmlNode n ) {
        usedNodes.add(n);
    }

    public Entry<XmlNode> byElement( Object e ) {
        return byElement.get(e);
    }

    public Entry<XmlNode> byPeer( Object o ) {
        return byPeer.get(o);
    }

    public Object getInnerPeer( XmlNode element ) {
        Entry e = byElement(element);
        if(e==null)     return null;
        else            return e.inner;
    }

    public Object getOuterPeer( XmlNode element ) {
        Entry e = byElement(element);
        if(e==null)     return null;
        else            return e.outer;
    }
}