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/* This file is part of the OWL API.
 * The contents of this file are subject to the LGPL License, Version 3.0.
 * Copyright 2014, The University of Manchester
 * 
 * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License along with this program.  If not, see http://www.gnu.org/licenses/.
 *
 * Alternatively, the contents of this file may be used under the terms of the Apache License, Version 2.0 in which case, the provisions of the Apache License Version 2.0 are applicable instead of those above.
 * 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 org.semanticweb.owlapi.util;

import static org.semanticweb.owlapi.util.OWLAPIPreconditions.checkNotNull;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import javax.annotation.Nullable;

import org.semanticweb.owlapi.model.OWLClass;
import org.semanticweb.owlapi.model.OWLClassExpression;
import org.semanticweb.owlapi.model.OWLClassExpressionVisitor;
import org.semanticweb.owlapi.model.OWLObjectIntersectionOf;

/**
 * A utility class which checks if a class expression has a named conjunct or a specific named
 * conjunct.
 *
 * @author Matthew Horridge, The University Of Manchester, Bio-Health Informatics Group
 * @since 2.0.0
 */
public class NamedConjunctChecker {

    final Set conjuncts = new HashSet<>();
    private final NamedConjunctCheckerVisitor visitor = new NamedConjunctCheckerVisitor();
    @Nullable
    protected OWLClass conjunct;
    boolean found;
    boolean collect;

    /**
     * @param conj The conjunct to check for
     * @param classExpression The expression to be checked
     * @return true if a named class is a conjunct in a given class expression. For class
     *         expressions which aren't named classes or object intersections this method will
     *         always return false.
     */
    public boolean isNamedConjunct(OWLClass conj, OWLClassExpression classExpression) {
        checkNotNull(conj, "conj cannot be null");
        checkNotNull(classExpression, "classExpression cannot be null");
        reset();
        conjunct = conj;
        classExpression.accept(visitor);
        return found;
    }

    /**
     * Checks whether the specified expression has a named conjunct. For For class expressions which
     * aren't named classes or object intersections this method will always return false.
     *
     * @param classExpression The expression to be checked.
     * @return {@code true} if the expression is in fact a named class ( {@code OWLClass}) or if the
     *         expression is an intersection that has a named operand (included nested
     *         intersections), otherwise {@code false}
     */
    public boolean hasNamedConjunct(OWLClassExpression classExpression) {
        checkNotNull(classExpression, "classExpression cannot be null");
        reset();
        conjunct = null;
        classExpression.accept(visitor);
        return found;
    }

    private void reset() {
        found = false;
        collect = false;
    }

    /**
     * Gets the named conjuncts for the specified expression.
     *
     * @param classExpression The expression whose conjuncts are to be retrieved.
     * @return A set containing the named conjuncts of the specified expression. If the expression
     *         is not a named class or an intersection then the set will definitely be empty.
     */
    public Set getNamedConjuncts(OWLClassExpression classExpression) {
        checkNotNull(classExpression, "classExpression cannot be null");
        conjuncts.clear();
        reset();
        collect = true;
        classExpression.accept(visitor);
        return conjuncts;
    }

    private class NamedConjunctCheckerVisitor implements OWLClassExpressionVisitor {

        NamedConjunctCheckerVisitor() {}

        @Override
        public void visit(OWLClass ce) {
            if (conjunct == null) {
                found = true;
                if (collect) {
                    conjuncts.add(ce);
                }
            } else if (ce.equals(conjunct)) {
                found = true;
                if (collect) {
                    conjuncts.add(ce);
                }
            }
        }

        @Override
        public void visit(OWLObjectIntersectionOf ce) {
            Iterator it = ce.operands().iterator();
            while (it.hasNext()) {
                it.next().accept(this);
                if (found && !collect) {
                    return;
                }
            }
        }
    }
}