/*
 * Copyright 2010 Sun Microsystems, Inc.  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.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package javax.lang.model.util;

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

/**
 * Shared package private superclass to avoid code bloat.
 *
 * @param <R> the return type of this visitor's methods.  Use {@code 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.
 *
 * @since 1.7
 */
class SharedSimpleElementVisitor<R, P> extends AbstractElementVisitor6<R, P> {
    /**
     * Default value to be returned; {@link #defaultAction
     * defaultAction} returns this value unless the method is
     * overridden.
     */
    protected final R DEFAULT_VALUE;

    /**
     * Constructor for concrete subclasses; uses {@code null} for the
     * default value.
     */
    protected SharedSimpleElementVisitor(){
        DEFAULT_VALUE = null;
    }

    /**
     * Constructor for concrete subclasses; uses the argument for the
     * default value.
     *
     * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
     */
    protected SharedSimpleElementVisitor(R defaultValue){
        DEFAULT_VALUE = defaultValue;
    }
    /**
     * The default action for visit methods.  The implementation in
     * this class just returns {@link #DEFAULT_VALUE}; subclasses will
     * commonly override this method.
     *
     * @param e the element to process
     * @param p a visitor-specified parameter
     * @return {@code DEFAULT_VALUE} unless overridden
     */
    protected R defaultAction(Element e, P p) {
        return DEFAULT_VALUE;
    }

    /**
     * {@inheritDoc} This implementation calls {@code defaultAction}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  the result of {@code defaultAction}
     */
    public R visitPackage(PackageElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * {@inheritDoc} This implementation calls {@code defaultAction}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  the result of {@code defaultAction}
     */
    public R visitType(TypeElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * {@inheritDoc} This implementation calls {@code defaultAction}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  the result of {@code defaultAction}
     */
    public R visitVariable(VariableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * {@inheritDoc} This implementation calls {@code defaultAction}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  the result of {@code defaultAction}
     */
    public R visitExecutable(ExecutableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * {@inheritDoc} This implementation calls {@code defaultAction}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  the result of {@code defaultAction}
     */
    public R visitTypeParameter(TypeParameterElement e, P p) {
        return defaultAction(e, p);
    }
}