/*
 * (c) Copyright 2010 Epimorphics Ltd.
 * All rights reserved.
 * [See end of file]
 */

package dev.joinengine;

import java.util.ArrayList ;
import java.util.List ;

import org.openjena.atlas.lib.Tuple ;

import com.hp.hpl.jena.graph.Node ;
import com.hp.hpl.jena.sparql.core.Var ;
import com.hp.hpl.jena.tdb.index.TupleIndex ;
import com.hp.hpl.jena.tdb.store.NodeId ;

public class JoinChooser
{
    // Temporary class for holding code being structured
    
    static List<TupleIndex> matchingIndexesStep1(Tuple<NodeId> pattern1, Tuple<NodeId> pattern2,TupleIndex[] indexes)
    {
        List<TupleIndex> indexes1 = matchingIndexesForPattern(pattern1, indexes) ;
        List<TupleIndex> indexes2 = matchingIndexesForPattern(pattern2, indexes) ;
        // Find common vars between pattern1 and pattern2
        // pattern1[i] -> pattern2[j]
        return null ;
    }
    
    private static List<Integer> patternMapping(Tuple<Node> pattern1, Tuple<Node> pattern2)
    {
        List<Integer> x = new ArrayList<Integer>() ;
        for ( Node n : pattern1.tuple() )
        {
            x.add(varLocation(pattern2, n)) ;
        }
        return x ;
    }
    
    /** Return the first index of Node n in Tuple<Node> pattern */
    // Function of Tuple? Tuple.find(T x) -> int or -1
    private static Integer location(Tuple<Node> pattern, Node n)
    {
        for ( int i = 0 ; i < pattern.size() ; i++ )
        {
            Node n2 = pattern.get(i) ;
            if ( n2 == null ) continue ;
            if ( n2.equals(n) )
                return i ;
        }
        return null ;
    }

    /** Return the first index of Node n in Tuple<Node> pattern */
    // Function of Tuple?
    private static Integer varLocation(Tuple<Node> pattern, Node n)
    {
        if ( Var.isVar(n)) return null ;
        return location(pattern, n) ;
    }

    /*
     * Find all indexes with maximal prefix for pattern.
     */
    static List<TupleIndex> matchingIndexesForPattern(Tuple<NodeId> pattern, TupleIndex[] indexes)
    {
        // Return all possibilities.
        List<TupleIndex> x = new ArrayList<TupleIndex>() ;
        
        // Step 1: fixedCols.
        // Assumes the weight function does this.
        int indexNumSlots = 0 ;
        for ( TupleIndex idx : indexes )
        {
            if ( idx == null ) continue ;
            int w = idx.weight(pattern) ;
            if ( w == indexNumSlots )
            {
                x.add(idx) ;
                continue ;
            }
            if ( w > indexNumSlots )
            {
                indexNumSlots = w ;
                x.add(idx) ;
                continue ;
            }
        }
        return x ;
    }
}

/*
 * (c) Copyright 2010 Epimorphics Ltd.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */