/*

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

 Contact:
 SYSTAP, LLC DBA Blazegraph
 2501 Calvert ST NW #106
 Washington, DC 20008
 licenses@blazegraph.com

 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 Nov 4, 2008
 */

package com.bigdata.relation.rule.eval;

import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IPredicate;
import com.bigdata.bop.IVariable;
import com.bigdata.bop.joinGraph.IEvaluationPlan;
import com.bigdata.relation.rule.IRule;
import com.bigdata.relation.rule.Rule;
import com.bigdata.striterator.IKeyOrder;

/**
 * @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
 * @version $Id$
 */
public interface IRuleState {

    /**
     * The {@link IRule} being evaluated.
     */
    public IRule getRule();

    /**
     * The evaluation plan.
     */
    public IEvaluationPlan getPlan();

    /**
     * The #of unbound variables for the predicates in the tail of the
     * {@link Rule} for the {@link #getPlan() evaluation plan}. The array is
     * correlated with the predicates index in the tail of the rule NOT with its
     * evaluation order.
     */
    public int[] getNVars();

    /**
     * An array of the {@link IKeyOrder} that will be used for each predicate in
     * the tail of the rule. The array is correlated with the predicates index
     * in the tail of the rule NOT with its evaluation order.
     * <p>
     * Note: The fully qualified index name for a given predicate is the name of
     * the relation for that predicate plus {@link IKeyOrder#getIndexName()}.
     */
    public IKeyOrder[] getKeyOrder();
    
    /**
     * A list of variables required for each tail, by tailIndex. Used to filter 
     * downstream variable binding sets.  
     */
    public IVariable[][] getRequiredVars();
    
    /**
     * Externalizes the rule and the evaluation order.
     */
    public String toString();

    /**
     * Shows the bindings (if given), the computed evaluation order, and the
     * computed {@link IKeyOrder} for each {@link IPredicate} in the rule.
     * 
     * @param bindingSet
     *            When non-<code>null</code>, the current variable bindings
     *            will be displayed. Otherwise, the names of variables will be
     *            displayed rather than their bindings.
     */
    public String toString(IBindingSet bindingSet);

}