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Neo4j kernel is a lightweight, embedded Java database designed to store data structured as graphs rather than tables. For more information, see http://neo4j.org.

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/*
 * Copyright (c) 2002-2015 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.kernel.impl.util.diffsets;

import java.util.Collections;
import java.util.Iterator;
import java.util.Set;

import org.neo4j.collection.primitive.PrimitiveIntIterator;
import org.neo4j.collection.primitive.PrimitiveLongIterator;
import org.neo4j.function.Predicate;

public interface ReadableDiffSets extends SuperReadableDiffSets
{
    @Override
    ReadableDiffSets filterAdded( Predicate addedFilter );

    static final class Empty implements ReadableDiffSets
    {
        @SuppressWarnings( "unchecked" )
        public static  ReadableDiffSets instance()
        {
            return INSTANCE;
        }

        public static  ReadableDiffSets ifNull( ReadableDiffSets diffSets )
        {
            return diffSets == null ? Empty.instance() : diffSets;
        }

        private static final ReadableDiffSets INSTANCE = new Empty();

        private Empty()
        {
            // singleton
        }

        @Override
        public boolean isAdded( T elem )
        {
            return false;
        }

        @Override
        public boolean isRemoved( T elem )
        {
            return false;
        }

        @Override
        public Set getAdded()
        {
            return Collections.emptySet();
        }

        @Override
        public Set getRemoved()
        {
            return Collections.emptySet();
        }

        @Override
        public boolean isEmpty()
        {
            return true;
        }

        @Override
        public Iterator apply( Iterator source )
        {
            return source;
        }

        @Override
        public int delta()
        {
            return 0;
        }

        @Override
        public PrimitiveLongIterator augment( PrimitiveLongIterator source )
        {
            return source;
        }

        @Override
        public PrimitiveIntIterator augment( PrimitiveIntIterator source )
        {
            return source;
        }

        @Override
        public PrimitiveLongIterator augmentWithRemovals( PrimitiveLongIterator source )
        {
            return source;
        }

        @Override
        public ReadableDiffSets filterAdded( Predicate addedFilter )
        {
            return this;
        }

        @Override
        public void accept( DiffSetsVisitor visitor )
        {
        }
    }
}