/*

 * 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.

 *

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package com.sun.tools.internal.xjc.reader.gbind;

import java.util.LinkedHashSet;

/**

 * Factory methods for {@link ElementSet}.

 *

 * @author Kohsuke Kawaguchi

 */

public final class ElementSets {

    /**

     * Returns an union of two {@link ElementSet}s.

     *

     * This method performs better if lhs is bigger than rhs

     */

    public static ElementSet union(ElementSet lhs, ElementSet rhs) {

        if(lhs.contains(rhs))

            return lhs;

        if(lhs==ElementSet.EMPTY_SET)

            return rhs;

        if(rhs==ElementSet.EMPTY_SET)

            return lhs;

        return new MultiValueSet(lhs,rhs);

    }

    /**

     * {@link ElementSet} that has multiple {@link Element}s in it.

     *

     * This isn't particularly efficient or anything, but it will do for now.

     */

    private static final class MultiValueSet extends LinkedHashSet<Element> implements ElementSet {

        public MultiValueSet(ElementSet lhs, ElementSet rhs) {

            addAll(lhs);

            addAll(rhs);

            // not that anything will break with size==1 MultiValueSet,

            // but it does suggest that we are missing an easy optimization

            assert size()>1;

        }

        private void addAll(ElementSet lhs) {

            if(lhs instanceof MultiValueSet) {

                super.addAll((MultiValueSet)lhs);

            } else {

                for (Element e : lhs)

                    add(e);

            }

        }

        public boolean contains(ElementSet rhs) {

            // this isn't complete but sound

            return super.contains(rhs) || rhs==ElementSet.EMPTY_SET;

        }

        public void addNext(Element element) {

            for (Element e : this)

                e.addNext(element);

        }

    }

}