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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 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.ConjunctiveQuery;
import fr.lirmm.graphik.integraal.api.core.RulesCompilation;
import fr.lirmm.graphik.integraal.api.core.Substitution;
import fr.lirmm.graphik.integraal.api.homomorphism.HomomorphismException;
import fr.lirmm.graphik.integraal.core.Substitutions;
import fr.lirmm.graphik.util.stream.CloseableIterator;
import fr.lirmm.graphik.util.stream.CloseableIteratorWithoutException;
import fr.lirmm.graphik.util.stream.Iterators;

/**
 * Query evaluation for a fully instanciated conjunctive query. A query is fully
 * instanciated when it contains only constants. So, either the input query is
 * fully instanciated OR the method execute has to be called by passing a
 * substitution which fully instanciates the query.
 * 
 * @author Clément Sipieter (INRIA) {@literal }
 *
 */
public class FullyInstantiatedQueryHomomorphism extends AbstractHomomorphismWithCompilation {

	// /////////////////////////////////////////////////////////////////////////
	// CONSTRUCTORS
	// /////////////////////////////////////////////////////////////////////////

	private static final FullyInstantiatedQueryHomomorphism INSTANCE = new FullyInstantiatedQueryHomomorphism();

	private FullyInstantiatedQueryHomomorphism() {

	}
	// /////////////////////////////////////////////////////////////////////////
	// CONSTRUCTORS
	// /////////////////////////////////////////////////////////////////////////

	public static FullyInstantiatedQueryHomomorphism instance() {
		return INSTANCE;
	}

	// /////////////////////////////////////////////////////////////////////////
	// HOMOMORPHISM METHODS
	// /////////////////////////////////////////////////////////////////////////

	@Override
	public CloseableIterator execute(ConjunctiveQuery q, AtomSet a, Substitution s)
			throws HomomorphismException {
		try {
			CloseableIteratorWithoutException queryAtomsIterator = q.getAtomSet().iterator();
			boolean contains = true;
			while (contains && queryAtomsIterator.hasNext()) {
				// verify if every fully instanciated atom is in the factbase
				contains = a.contains(s.createImageOf(queryAtomsIterator.next()));
			}
			if (contains) {
				return Iterators.singletonIterator(Substitutions.emptySubstitution());
			} else {
				return Iterators.emptyIterator();
			}
		} catch (AtomSetException e) {
			throw new HomomorphismException(e);
		}
	}

	@Override
	public CloseableIterator execute(ConjunctiveQuery q, AtomSet a, RulesCompilation rc, Substitution s)
			throws HomomorphismException {
		try {
			CloseableIteratorWithoutException it = q.getAtomSet().iterator();
			boolean contains = true;
			while (contains && it.hasNext()) {
				Atom atom = it.next();
				boolean containsAtom = false;
				for (Pair im : rc.getRewritingOf(s.createImageOf(atom))) {
					containsAtom = a.contains(im.getLeft());
					if (containsAtom) {
						break;
					}
				}
				contains = containsAtom;
			}
			if (contains) {
				return Iterators.singletonIterator(Substitutions.emptySubstitution());
			} else {
				return Iterators.emptyIterator();
			}
		} catch (AtomSetException e) {
			throw new HomomorphismException(e);
		}
	}

}