/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.jena.sparql.resultset;

import java.util.* ;

import org.apache.jena.atlas.iterator.Iter ;
import org.apache.jena.graph.Node ;
import org.apache.jena.query.* ;
import org.apache.jena.rdf.model.Model ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.engine.binding.BindingUtils ;
import org.apache.jena.sparql.util.NodeIsomorphismMap ;
import org.apache.jena.sparql.util.NodeUtils ;
import org.apache.jena.sparql.util.NodeUtils.EqualityTest ;

/** Comparison of ResultSets.
 *  Note that reading ResultSets is destructive so consider using {@link ResultSetRewindable}
 *  from {@link ResultSetFactory#makeRewindable} 
 */

public class ResultSetCompare
{
    // Need to extend then use Iso/IsoMatcher to do result sets.
    // That needs backtracking. 
    
    /* This is from the DAWG test suite.
     * Result set 1: 
     *   ---------------
     *   | x    | y    |
     *   ===============
     *   | _:b0 | _:b1 |
     *   | _:b2 | _:b3 |
     *   | _:b1 | _:b0 |
     *   ---------------
     * Result set 2: 
     *   ---------------
     *   | x    | y    |
     *   ===============
     *   | _:b1 | _:b0 |
     *   | _:b3 | _:b2 |
     *   | _:b2 | _:b3 |
     *   ---------------
     */

//    private static String[] rs1$ = {
//        "(resultset (?x ?y)",
//        "   (row (?x _:b0) (?y _:b1))",
//        "   (row (?x _:b2) (?y _:b3))",
//        "   (row (?x _:b1) (?y _:b0))",
//        ")"} ;
//    private static String[] rs2$ = {
//        "(resultset (?x ?y)",
//        "   (row (?x _:c1) (?y _:c0))",
//        "   (row (?x _:c3) (?y _:c2))",
//        "   (row (?x _:c2) (?y _:c3))",
//        ")"} ;
//   
    
    // Limitations:
    // This code does not do compare/isomorphism combined with value testing.
    // It drops to graph isomorphism, which is term based.
    
    /** Compare two result sets for equivalence.  Equivalence means:
     * A row rs1 has one matching row in rs2, and vice versa.
     * A row is only matched once.
     * Rows match if they have the same variables with the same values. 
     * bNodes must map to a consistent other bNodes.  Value comparisons of nodes.   
     * 
     * Destructive - rs1 and rs2 are both read, possibly to exhaustion. 
     * @param rs1 
     * @param rs2
     * @return true if they are equivalent
     */
    
    public static boolean equalsByValue(ResultSet rs1, ResultSet rs2) {
        if ( ! compareHeader(rs1, rs2) ) return false ;
        
        //return equivalent(convert(rs1), convert(rs2), new BNodeIso(NodeUtils.sameValue)) ;
        
        ResultSetRewindable rs1a = ResultSetFactory.makeRewindable(rs1) ;
        ResultSetRewindable rs2a = ResultSetFactory.makeRewindable(rs2) ;
        
        if ( equivalent(convert(rs1a), convert(rs2a), new BNodeIso(NodeUtils.sameValue)) )
            return true ;
        rs1a.reset() ;    
        rs2a.reset() ;
        return isomorphic(rs1a, rs2a) ;
    }
    
    public static boolean equalsByTest(Collection<Binding> b1, Collection<Binding> b2, EqualityTest match)
    {
        List<Binding> rows1 = new ArrayList<>(b1);
        List<Binding> rows2 = new ArrayList<>(b2);
        return equivalent(rows1, rows2, match);
    }


    /** compare two result sets for equivalence.  Equivalence means:
     * A row rs1 has one matching row in rs2, and vice versa.
     * A row is only matched once.
     * Rows match if they have the same variables with the same values, 
     * bNodes must map to a consistent other bNodes.  
     * Term comparisons of nodes.   
     * 
     * Destructive - rs1 and rs2 are both read, possibly to exhaustion. 
     * @param rs1 
     * @param rs2
     * @return true if they are equivalent
     */

    public static boolean equalsByTerm(ResultSet rs1, ResultSet rs2) {
        if ( ! compareHeader(rs1, rs2) ) return false ;

        //return equivalent(convert(rs1), convert(rs2), new BNodeIso(NodeUtils.sameTerm)) ;
        ResultSetRewindable rs1a = ResultSetFactory.makeRewindable(rs1) ;
        ResultSetRewindable rs2a = ResultSetFactory.makeRewindable(rs2) ;
        
        // Aligned rows
        if ( equivalent(convert(rs1a), convert(rs2a), new BNodeIso(NodeUtils.sameTerm)) )
            return true ;
        rs1a.reset() ;    
        rs2a.reset() ;
        return isomorphic(rs1a, rs2a) ;
    }

    
    /** Compare two result sets for equivalence.  Equivalence means:
     * Each row in rs1 matches the same index row in rs2.
     * Rows match if they have the same variables with the same values, 
     * bNodes must map to a consistent other bNodes.  
     * Value comparisons of nodes.   
     * 
     * Destructive - rs1 and rs2 are both read, possibly to exhaustion. 
     * @param rs1 
     * @param rs2
     * @return true if they are equivalent
     */

    public static boolean equalsByValueAndOrder(ResultSet rs1, ResultSet rs2) {
        if ( ! compareHeader(rs1, rs2) ) 
            return false ;
        return equivalentByOrder(convert(rs1) , convert(rs2), new BNodeIso(NodeUtils.sameValue)) ;
    }

    /** compare two result sets for equivalence.  Equivalence means:
     * Each row in rs1 matchs the same index row in rs2.
     * Rows match if they have the same variables with the same values, 
     * bNodes must map to a consistent other bNodes.  
     * RDF term comparisons of nodes.   
     * 
     * Destructive - rs1 and rs2 are both read, possibly to exhaustion. 
     * @param rs1 
     * @param rs2
     * @return true if they are equivalent
     */
    public static boolean equalsByTermAndOrder(ResultSet rs1, ResultSet rs2) {
        if ( ! compareHeader(rs1, rs2) ) return false ;
        return equivalentByOrder(convert(rs1) , convert(rs2), new BNodeIso(NodeUtils.sameTerm)) ;
    }

    /** compare two result sets for exact equality equivalence.
     * Exact equalitymeans:
     * Each row in rs1 matches the same index row in rs2.
     * Rows match if they have the same variables with the same values, 
     * bNodes must have same labels  
     * 
     * Destructive - rs1 and rs2 are both read, possibly to exhaustion. 
     * @param rs1 
     * @param rs2
     * @return true if they are equivalent
     */
    public static boolean equalsExact(ResultSet rs1, ResultSet rs2)
    {
        if ( ! compareHeader(rs1, rs2) ) return false ;

        return equivalentByOrder(convert(rs1) , convert(rs2), new EqualityTest(){}) ;
    }

    /** Compare two result sets for bNode isomorphism equivalence.
     * Only does RDF term comparison.
     */ 
    public static boolean isomorphic(ResultSet rs1, ResultSet rs2) {
        Model m1 = RDFOutput.encodeAsModel(rs1) ;
        Model m2 = RDFOutput.encodeAsModel(rs2) ;
        return m1.isIsomorphicWith(m2) ;
    }
    
    /** Compare two bindings, use the node equality test provided */
    static public boolean equal(Binding bind1, Binding bind2, NodeUtils.EqualityTest test) {
        if ( bind1 == bind2 ) 
            return true ;
        if ( bind1.size() != bind2.size() )
            return false ;
        // They are the same size so containment is enough.
        if ( ! containedIn(bind1, bind2, test) ) return false ;
        return true ;
    }
    
    static private boolean compareHeader(ResultSet rs1, ResultSet rs2) {
        if ( rs1 == null && rs2 == null ) 
            return true ;
        if ( rs1 == null ) 
            return false ;
        if ( rs2 == null ) 
            return false ;
        Set<String> names1 = new HashSet<>(rs1.getResultVars()) ;
        Set<String> names2 = new HashSet<>(rs2.getResultVars()) ;
        return names1.equals(names2) ;
    }

    static private List<Binding> convert(ResultSet rs) {
        return Iter.iter(rs).map(item -> BindingUtils.asBinding(item)).toList() ;
    }
    
    
//    static boolean equivalentByTerm(ResultSet rs1, ResultSet rs2)
//    {
//        return equivalent(convert(rs1), convert(rs2), sameTerm) ;
//    }
    
    static private boolean equivalent(Collection<Binding> rows1, Collection<Binding> rows2, EqualityTest match) {
        if ( rows1.size() != rows2.size() )
            return false ;
        for ( Binding row1 : rows1 ) {
            // find in rows2.
            Binding matched = null ;
            for ( Binding row2 : rows2 ) {
                // NEED BACKTRACKING

                if ( equal(row1, row2, match) ) {
                    matched = row2 ;
                    break ;
                }
            }

            if ( matched == null )
                return false ;
            // Remove matching.
            rows2.remove(matched) ;
        }
        return true ;
    }
    
    static private boolean equivalentByOrder(List<Binding> rows1, List<Binding> rows2, EqualityTest match) {
        if ( rows1.size() != rows2.size() )
             return false ;
        
        Iterator<Binding> iter1 = rows1.iterator() ;
        Iterator<Binding> iter2 = rows2.iterator() ;
        
        while ( iter1.hasNext() )
        {
            // Does not need backtracking because rows must
            // align and so must variables in a row.  
            Binding row1 = iter1.next() ;
            Binding row2 = iter2.next() ;
            if ( !equal(row1, row2, match) )
                return false ;
        }
        return true ;
    }
    
    // Is bind1 contained in bind2?  For every (var,value) in bind1, is it in bind2?
    // Maybe more in bind2.
    private static boolean containedIn(Binding bind1, Binding bind2, EqualityTest test) {
        // There are about 100 ways to do this! 
        Iterator<Var> iter1 =  bind1.vars() ;
        
        while(iter1.hasNext()) {
            Var v = iter1.next() ;
            Node n1 = bind1.get(v) ;
            Node n2 = bind2.get(v) ;
            if ( n2 == null )
                // v bound in bind1 and not in bind2.
                return false ;
            if ( ! test.equal(n1, n2) )
                return false ;
        }
        return true ;
    }
    
    public static class BNodeIso implements EqualityTest
    {
        private NodeIsomorphismMap mapping ;
        private EqualityTest literalTest ;
    
        public BNodeIso(EqualityTest literalTest) { 
            this.mapping = new NodeIsomorphismMap() ;
            this.literalTest = literalTest ;
        }
    
        @Override
        public boolean equal(Node n1, Node n2) {
            if ( n1 == null && n2 == null )
                return true ;
            if ( n1 == null )
                return false ;
            if ( n2 == null )
                return false ;

            if ( n1.isURI() && n2.isURI() )
                return n1.equals(n2) ;
            
            if ( n1.isLiteral() && n2.isLiteral() )
                return literalTest.equal(n1, n2) ;
            
            if ( n1.isBlank() && n2.isBlank() )
                return mapping.makeIsomorphic(n1, n2) ;
            
            return false ;
        }
    }
}
