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/**

Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016.  All rights reserved.

Contact:
     SYSTAP, LLC DBA Blazegraph
     2501 Calvert ST NW #106
     Washington, DC 20008
     [email protected]

This program 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; version 2 of the License.

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, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
/*
 * Created on Aug 19, 2010
 */

package com.bigdata.striterator;

import com.bigdata.bop.IElement;
import com.bigdata.bop.IPredicate;
import com.bigdata.bop.IVariableOrConstant;
import com.bigdata.btree.DefaultTupleSerializer;
import com.bigdata.btree.ITupleSerializer;
import com.bigdata.btree.keys.IKeyBuilder;
import com.bigdata.btree.keys.SuccessorUtil;

/**
 * Abstract base class provides default behavior for generating keys for a given
 * index order.
 * 
 * @author Bryan Thompson
 */
abstract public class AbstractKeyOrder implements IKeyOrder {

    /**
     * {@inheritDoc}
     * 
     *       FIXME This needs to be reconciled with
     *       {@link ITupleSerializer#serializeKey(Object)}. For example, this
     *       does not play well with the {@link DefaultTupleSerializer}.
     */
	@Override
    public byte[] getKey(final IKeyBuilder keyBuilder, final E element) {
        
        keyBuilder.reset();

        final int keyArity = getKeyArity(); // use the key's "arity".

        for (int i = 0; i < keyArity; i++) {

            /*
             * Note: If you need to override the default IKeyBuilder behavior do
             * it in the invoked method.
             */
            appendKeyComponent(keyBuilder, i, ((IElement) element)
                    .get(getKeyOrder(i)));

        }

        return keyBuilder.getKey();
        
    }

	@Override
    public byte[] getFromKey(final IKeyBuilder keyBuilder,
            final IPredicate predicate) {

        keyBuilder.reset();

        final int keyArity = getKeyArity(); // use the key's "arity".

        boolean noneBound = true;

        for (int i = 0; i < keyArity; i++) {

            final IVariableOrConstant term = predicate.get(getKeyOrder(i));

            // Note: term MAY be null for the context position.
            if (term == null || term.isVar())
                break;

            /*
             * Note: If you need to override the default IKeyBuilder behavior do
             * it in the invoked method.
             */
            appendKeyComponent(keyBuilder, i, term.get());

            noneBound = false;

        }

        final byte[] key = noneBound ? null : keyBuilder.getKey();

        return key;
        
    }

	@Override
    public byte[] getToKey(final IKeyBuilder keyBuilder,
            final IPredicate predicate) {

        keyBuilder.reset();

        final int keyArity = getKeyArity(); // use the key's "arity".

        boolean noneBound = true;

        for (int i = 0; i < keyArity; i++) {

            final IVariableOrConstant term = predicate.get(getKeyOrder(i));

            // Note: term MAY be null for the context position.
            if (term == null || term.isVar())
                break;

            /*
             * Note: If you need to override the default IKeyBuilder behavior do
             * it in the invoked method.
             */
            appendKeyComponent(keyBuilder, i, term.get());

            noneBound = false;

        }

        final byte[] key = noneBound ? null : keyBuilder.getKey();

        return key == null ? null : SuccessorUtil.successor(key);

    }

    /**
     * Encodes an value into the key. This implementation uses the default
     * behavior of {@link IKeyBuilder}. If you need to specialize how a value
     * gets encoded into the key then you can override this method.
     */
    protected void appendKeyComponent(final IKeyBuilder keyBuilder,
            final int index, final Object keyComponent) {

        keyBuilder.append(keyComponent);

    }

}