/*
 * Copyright (c) 2005, 2023, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package javax.lang.model.util;

import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.*;
import static javax.lang.model.SourceVersion.*;


/**
 * A skeletal visitor of program elements with default behavior
 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
 * source version.
 *
 * @apiNote
 * <p id=note_for_subclasses><strong>WARNING:</strong> The {@code
 * ElementVisitor} interface implemented by this class may have
 * methods added to it in the future to accommodate new, currently
 * unknown, language structures added to future versions of the
 * Java programming language.  Therefore, methods whose names
 * begin with {@code "visit"} may be added to this class in the
 * future; to avoid incompatibilities, classes and subclasses which
 * extend this class should not declare any instance methods with
 * names beginning with {@code "visit"}.</p>
 *
 * <p>When such a new visit method is added, the default
 * implementation in this class will be to directly or indirectly call
 * the {@link #visitUnknown visitUnknown} method.  A new abstract
 * element visitor class will also be introduced to correspond to the
 * new language level; this visitor will have different default
 * behavior for the visit method in question.  When a new visitor is
 * introduced, portions of this visitor class may be deprecated,
 * including its constructors.
 *
 * @param <R> the return type of this visitor's methods.  Use {@link
 *            Void} for visitors that do not need to return results.
 * @param <P> the type of the additional parameter to this visitor's
 *            methods.  Use {@code Void} for visitors that do not need an
 *            additional parameter.
 *
 * @see AbstractElementVisitor7
 * @see AbstractElementVisitor8
 * @see AbstractElementVisitor9
 * @see AbstractElementVisitor14
 * @since 1.6
 */
@SupportedSourceVersion(RELEASE_6)
public abstract class AbstractElementVisitor6<R, P> implements ElementVisitor<R, P> {
    /**
     * Constructor for concrete subclasses to call.
     * @deprecated Release 6 is obsolete; update to a visitor for a newer
     * release level.
     */
    @Deprecated(since="9")
    protected AbstractElementVisitor6(){}

    /**
     * Visits any program element as if by passing itself to that
     * element's {@link Element#accept accept} method.  The invocation
     * {@code v.visit(elem, p)} is equivalent to {@code elem.accept(v,
     * p)}.
     *
     * @param e  the element to visit
     * @param p  a visitor-specified parameter
     * @return a visitor-specified result
     */
    public final R visit(Element e, P p) {
        return e.accept(this, p);
    }

    /**
     * Visits any program element as if by passing itself to that
     * element's {@link Element#accept accept} method and passing
     * {@code null} for the additional parameter.  The invocation
     * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,
     * null)}.
     *
     * @param e  the element to visit
     * @return a visitor-specified result
     */
    public final R visit(Element e) {
        return e.accept(this, null);
    }

    /**
     * {@inheritDoc ElementVisitor}
     *
     * @implSpec The default implementation of this method in
     * {@code AbstractElementVisitor6} will always throw
     * {@code new UnknownElementException(e, p)}.
     * This behavior is not required of a subclass.
     *
     * @param e {@inheritDoc ElementVisitor}
     * @param p {@inheritDoc ElementVisitor}
     * @return  {@inheritDoc ElementVisitor}
     * @throws UnknownElementException {@inheritDoc ElementVisitor}
     */
    @Override
    public R visitUnknown(Element e, P p) {
        throw new UnknownElementException(e, p);
    }

    /**
     * {@inheritDoc ElementVisitor}
     *
     * @implSpec Visits a {@code ModuleElement} by calling {@code
     * visitUnknown}.
     *
     * @param e  {@inheritDoc ElementVisitor}
     * @param p  {@inheritDoc ElementVisitor}
     * @return   {@inheritDoc ElementVisitor}
     *
     * @since 9
     */
    @Override
    public R visitModule(ModuleElement e, P p) {
        // Use implementation from interface default method
        return ElementVisitor.super.visitModule(e, p);
    }

    /**
     * {@inheritDoc ElementVisitor}
     *
     * @implSpec Visits a {@code RecordComponentElement} by calling {@code
     * visitUnknown}.
     *
     * @param e  {@inheritDoc ElementVisitor}
     * @param p  {@inheritDoc ElementVisitor}
     * @return   {@inheritDoc ElementVisitor}
     *
     * @since 14
     */
    @Override
    public R visitRecordComponent(RecordComponentElement e, P p) {
        // Use implementation from interface default method
        return ElementVisitor.super.visitRecordComponent(e, p);
    }
}