/**
   Copyright (C) SYSTAP, LLC 2006-2012.  All rights reserved.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/
package com.bigdata.rdf.graph;

import java.util.List;

import org.openrdf.model.Value;
import org.openrdf.model.ValueFactory;

import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IVariable;

/**
 * An interface that may be used to extract variable bindings for the
 * vertices visited by the algorithm.
 * 
 * @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan
 *         Thompson</a>
 */
public interface IBinder<VS, ES, ST> {

    /**
     * The ordinal index of the variable that is bound by this
     * {@link IBinder}. By convention, index ZERO is the vertex. Indices
     * greater than ZERO are typically aspects of the state of the vertex.
     */
    int getIndex();

    /**
     * New multi-binding strategy allows binders to bind multiple values to
     * a given output variable (multiplying the number of solutions by the
     * number of bindings).
     * 
     * @param vf
     *            The {@link ValueFactory} used to create the return
     *            {@link Value}.
     *            
     * @param state
     * 			  The {@link IGASState}.
     * 	
     * @param u
     * 			  The vertex.
     * 
     * @param outVars
     * 			  The array of output variables.
     * 
     * @param bs
     *            The current binding set. Can be used to conditionally bind
     *            values based on the current solution.
     *            
     * @return The {@link Value} for that ordinal variable or
     *         <code>null</code> if there is no binding for that ordinal
     *         variable.
     */
    List<Value> bind(ValueFactory vf, IGASState<VS, ES, ST> state, 
    		Value u, IVariable<?>[] outVars, IBindingSet bs);

//    Value bind(ValueFactory vf, final IGASState<VS, ES, ST> state, Value u);
    
}