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Rule base analysis for InteGraal. This is imported from Graal
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/*
 * Copyright (C) Inria Sophia Antipolis - Méditerranée / LIRMM
 * (Université de Montpellier & CNRS) (2014 - 2017)
 *
 * Contributors :
 *
 * Clément SIPIETER 
 * Mélanie KÖNIG
 * Swan ROCHER
 * Jean-François BAGET
 * Michel LECLÈRE
 * Marie-Laure MUGNIER 
 *
 *
 * This file is part of Graal .
 *
 * This software is governed by the CeCILL  license under French law and
 * abiding by the rules of distribution of free software.  You can  use,
 * modify and/ or redistribute the software under the terms of the CeCILL
 * license as circulated by CEA, CNRS and INRIA at the following URL
 * "http://www.cecill.info".
 *
 * As a counterpart to the access to the source code and  rights to copy,
 * modify and redistribute granted by the license, users are provided only
 * with a limited warranty  and the software's author,  the holder of the
 * economic rights,  and the successive licensors  have only  limited
 * liability.
 *
 * In this respect, the user's attention is drawn to the risks associated
 * with loading,  using,  modifying and/or developing or reproducing the
 * software by the user in light of its specific status of free software,
 * that may mean  that it is complicated to manipulate,  and  that  also
 * therefore means  that it is reserved for developers  and  experienced
 * professionals having in-depth computer knowledge. Users are therefore
 * encouraged to load and test the software's suitability as regards their
 * requirements in conditions enabling the security of their systems and/or
 * data to be ensured and,  more generally, to use and operate it in the
 * same conditions as regards security.
 *
 * The fact that you are presently reading this means that you have had
 * knowledge of the CeCILL license and that you accept its terms.
 */
package fr.lirmm.graphik.integraal.homomorphism;

import java.util.LinkedList;
import java.util.List;
import java.util.Set;

import org.apache.commons.collections4.SetUtils;
import org.apache.commons.lang3.tuple.Pair;

import fr.lirmm.graphik.integraal.api.core.Atom;
import fr.lirmm.graphik.integraal.api.core.AtomSet;
import fr.lirmm.graphik.integraal.api.core.AtomSetException;
import fr.lirmm.graphik.integraal.api.core.ConjunctiveQueryWithNegatedParts;
import fr.lirmm.graphik.integraal.api.core.InMemoryAtomSet;
import fr.lirmm.graphik.integraal.api.core.RulesCompilation;
import fr.lirmm.graphik.integraal.api.core.Substitution;
import fr.lirmm.graphik.integraal.api.core.Term;
import fr.lirmm.graphik.integraal.api.core.Variable;
import fr.lirmm.graphik.integraal.api.homomorphism.HomomorphismException;
import fr.lirmm.graphik.integraal.api.homomorphism.HomomorphismWithCompilation;
import fr.lirmm.graphik.util.stream.CloseableIterator;
import fr.lirmm.graphik.util.stream.CloseableIteratorAdapter;
import fr.lirmm.graphik.util.stream.CloseableIteratorAggregator;
import fr.lirmm.graphik.util.stream.converter.ConverterCloseableIterator;
import fr.lirmm.graphik.util.stream.filter.AndFilter;
import fr.lirmm.graphik.util.stream.filter.Filter;
import fr.lirmm.graphik.util.stream.filter.FilterIterator;

/**
 * Evaluation method for atomic queries with several negated parts.

 * Please refer to the definition of {@link ConjunctiveQueryWithNegatedParts}
 * for more details on the use of negation.

 * It is also assumed that the positive atoms are without constants AND multiple
 * occurrences of a single variable.
 * 
 * @author Clément Sipieter (INRIA) {@literal }
 */
public class AtomicQueryHomomorphismWithNegatedParts
		extends AbstractHomomorphismWithCompilation
		implements HomomorphismWithCompilation {

	private static final AtomicQueryHomomorphismWithNegatedParts INSTANCE = new AtomicQueryHomomorphismWithNegatedParts();

	// /////////////////////////////////////////////////////////////////////////
	// SINGLETON
	// /////////////////////////////////////////////////////////////////////////

	public static AtomicQueryHomomorphismWithNegatedParts instance() {
		return INSTANCE;
	}

	private AtomicQueryHomomorphismWithNegatedParts() {}
	
	// /////////////////////////////////////////////////////////////////////////
	// HOMOMORPHISM METHODS
	// /////////////////////////////////////////////////////////////////////////

	public CloseableIterator execute(ConjunctiveQueryWithNegatedParts query, AtomSet data,
			RulesCompilation compilation, Substitution s) throws HomomorphismException {
		try {

			// if the query contains more than one atom
			// only the first is considered

			Atom atom = query.getPositivePart().iterator().next();

			List ans = query.getAnswerVariables();

			List> iteratorsList = new LinkedList>();

			// rewrite it in all possible ways to account the compilation

			for (Pair im : compilation.getRewritingOf(atom)) {

				// then check if the atom can be mapped by homomorphimsm
				// by respecting the substitution
				iteratorsList.add(new ConverterCloseableIterator(data.match(im.getLeft(), s),
						new Atom2SubstitutionConverter(im.getLeft(), ans, im.getRight())));
			}

			@SuppressWarnings("resource")
			CloseableIterator subIt = new CloseableIteratorAggregator(
					(CloseableIterator>)
					new CloseableIteratorAdapter>(iteratorsList.iterator()));

			// manage negative parts
			Set variablesPositivePart = query.getPositivePart().getVariables();

			@SuppressWarnings("rawtypes")
			Filter[] filtersForNegatedParts = new Filter[query.getNegatedParts().size()];
			int i = 0;

			// iterate over all negated parts
			for (InMemoryAtomSet negPart : query.getNegatedParts()) {

				// compute frontier variables between positive and negative part
				Set frontier = SetUtils.intersection(variablesPositivePart, negPart.getVariables());

				// create a filter for each negative part
				// the filter pre-configures a backtrack execution
				// for a query made of the negated part and answer variables
				// corresponding to the frontier variables just computed
				filtersForNegatedParts[i++] = new NegFilter(negPart, frontier, data, compilation);

			}

			@SuppressWarnings("unchecked")
			Filter filter = new AndFilter(filtersForNegatedParts);

			return new FilterIterator(subIt, filter);

		} catch (AtomSetException e) {
			throw new HomomorphismException(e);
		}
	}

}