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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.newapi;

import org.neo4j.internal.kernel.api.CloseListener;
import org.neo4j.internal.kernel.api.KernelReadTracer;
import org.neo4j.internal.kernel.api.NodeCursor;
import org.neo4j.internal.kernel.api.PropertyCursor;
import org.neo4j.internal.kernel.api.RelationshipTraversalCursor;
import org.neo4j.storageengine.api.PropertySelection;
import org.neo4j.storageengine.api.Reference;

import static org.neo4j.kernel.api.StatementConstants.NO_SUCH_NODE;
import static org.neo4j.kernel.api.StatementConstants.NO_SUCH_RELATIONSHIP;
import static org.neo4j.kernel.api.StatementConstants.NO_SUCH_RELATIONSHIP_TYPE;
import static org.neo4j.storageengine.api.LongReference.NULL_REFERENCE;

public final class Cursors
{
    private Cursors()
    {
        throw new UnsupportedOperationException( "Don't instantiate" );
    }

    /**
     * Returns an empty relationship traversal cursor.
     *
     * Note, the Read is required for situations where we for example try to
     * read properties from this cursor. If we did nothing in that case the
     * property cursor could end up in an undefined state that lead to errors
     * in some cases.
     */
    public static RelationshipTraversalCursor emptyTraversalCursor( org.neo4j.internal.kernel.api.Read read )
    {
        return new EmptyTraversalCursor( (Read) read );
    }

    public static class EmptyTraversalCursor implements RelationshipTraversalCursor
    {
        private final Read read;

        private EmptyTraversalCursor( Read read )
        {
            this.read = read;
        }

        @Override
        public void otherNode( NodeCursor cursor )
        {
            read.singleNode( NO_SUCH_NODE, cursor );
        }

        @Override
        public long otherNodeReference()
        {
            return NO_SUCH_NODE;
        }

        @Override
        public long originNodeReference()
        {
            return NO_SUCH_NODE;
        }

        @Override
        public boolean next()
        {
            return false;
        }

        @Override
        public void setTracer( KernelReadTracer tracer )
        {

        }

        @Override
        public void removeTracer()
        {

        }

        @Override
        public void close()
        {

        }

        @Override
        public void closeInternal()
        {

        }

        @Override
        public boolean isClosed()
        {
            return false;
        }

        @Override
        public void setCloseListener( CloseListener closeListener )
        {

        }

        @Override
        public void setToken( int token )
        {

        }

        @Override
        public int getToken()
        {
            return -1;
        }

        @Override
        public long relationshipReference()
        {
            return NO_SUCH_RELATIONSHIP;
        }

        @Override
        public int type()
        {
            return NO_SUCH_RELATIONSHIP_TYPE;
        }

        @Override
        public void source( NodeCursor cursor )
        {
            read.singleNode( NO_SUCH_NODE, cursor );
        }

        @Override
        public void target( NodeCursor cursor )
        {
            read.singleNode( NO_SUCH_NODE, cursor );
        }

        @Override
        public void properties( PropertyCursor cursor, PropertySelection selection )
        {
            ((DefaultPropertyCursor) cursor).initEmptyRelationship( read, read );
        }

        @Override
        public long sourceNodeReference()
        {
            return NO_SUCH_NODE;
        }

        @Override
        public long targetNodeReference()
        {
            return NO_SUCH_NODE;
        }

        @Override
        public Reference propertiesReference()
        {
            return NULL_REFERENCE;
        }
    }
}