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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) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.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 org.eclipse.collections.api.set.primitive.LongSet;
import org.eclipse.collections.api.set.primitive.MutableLongSet;
import org.eclipse.collections.impl.factory.primitive.LongSets;

import org.neo4j.kernel.impl.util.collection.CollectionsFactory;
import org.neo4j.memory.HeapEstimator;
import org.neo4j.memory.MemoryTracker;
import org.neo4j.util.VisibleForTesting;

/**
 * Primitive long version of collection that with given a sequence of add and removal operations, tracks
 * which elements need to actually be added and removed at minimum from some
 * target collection such that the result is equivalent to just
 * executing the sequence of additions and removals in order.
 */
public class MutableLongDiffSetsImpl implements MutableLongDiffSets
{
    private static final long SHALLOW_SIZE = HeapEstimator.shallowSizeOfInstance( MutableLongDiffSetsImpl.class );
    private static final MutableLongSet NOT_INITIALIZED = LongSets.mutable.empty().asUnmodifiable();

    private final CollectionsFactory collectionsFactory;
    private final MemoryTracker memoryTracker;
    private MutableLongSet added;
    private MutableLongSet removed;

    static MutableLongDiffSetsImpl createMutableLongDiffSetsImpl( CollectionsFactory collectionsFactory, MemoryTracker memoryTracker )
    {
        memoryTracker.allocateHeap( SHALLOW_SIZE );
        return new MutableLongDiffSetsImpl( collectionsFactory, memoryTracker );
    }

    @VisibleForTesting
    public MutableLongDiffSetsImpl( MutableLongSet added, MutableLongSet removed, CollectionsFactory collectionsFactory, MemoryTracker memoryTracker )
    {
        this.added = added;
        this.removed = removed;
        this.collectionsFactory = collectionsFactory;
        this.memoryTracker = memoryTracker;
    }

    protected MutableLongDiffSetsImpl( CollectionsFactory collectionsFactory, MemoryTracker memoryTracker )
    {
        this( NOT_INITIALIZED, NOT_INITIALIZED, collectionsFactory, memoryTracker );
    }

    @Override
    public boolean isAdded( long element )
    {
        return added.contains( element );
    }

    @Override
    public boolean isRemoved( long element )
    {
        return removed.contains( element );
    }

    @Override
    public void add( long element )
    {
        checkAddedElements();
        addElement( element );
    }

    @Override
    public boolean remove( long element )
    {
        checkRemovedElements();
        return removeElement( element );
    }

    @Override
    public int delta()
    {
        return added.size() - removed.size();
    }

    @Override
    public LongSet getAdded()
    {
        return added;
    }

    @Override
    public LongSet getRemoved()
    {
        return removed;
    }

    @Override
    public boolean isEmpty()
    {
        return added.isEmpty() && removed.isEmpty();
    }

    private void addElement( long element )
    {
        if ( removed.isEmpty() || !removed.remove( element ) )
        {
            added.add( element );
        }
    }

    private boolean removeElement( long element )
    {
        if ( !added.isEmpty() && added.remove( element ) )
        {
            return true;
        }
        return removed.add( element );
    }

    private void checkAddedElements()
    {
        if ( added == NOT_INITIALIZED )
        {
            added = collectionsFactory.newLongSet( memoryTracker );
        }
    }

    private void checkRemovedElements()
    {
        if ( removed == NOT_INITIALIZED )
        {
            removed = collectionsFactory.newLongSet( memoryTracker );
        }
    }
}