/* SimpleElementVisitor6.java -- A simple visitor implementation for 1.6.
   Copyright (C) 2013  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath 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 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
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this exception to your version of the library, but you are not
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package javax.lang.model.util;

import javax.annotation.processing.SupportedSourceVersion;

import javax.lang.model.SourceVersion;

import javax.lang.model.element.Element;
import javax.lang.model.element.ElementVisitor;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.PackageElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.element.TypeParameterElement;
import javax.lang.model.element.VariableElement;

/**
 * <p>A simple implementation of {@link ElementVisitor} for the
 * 1.6 version of the Java programming language
 * ({@link SourceVersion#RELEASE_6}).  Each {@code visitXYZ} method
 * redirects to {@code defaultAction(element, parameter)}.
 * Implementors may extend this class and provide alternative
 * implementations of {@link #defaultAction(Element, P)} and
 * the {@code visitXYZ} methods as appropriate.</p>
 * <p>As the interface this class implements may be extended in future,
 * in order to support later language versions, methods beginning with
 * the phrase {@code "visit"} should be avoided in subclasses.  This
 * class itself will be extended to direct these new methods to the
 * {@link #visitUnknown(Element,P)} method and a new class will be
 * added to provide implementations for the new language version.
 * At this time, all or some of this class may be deprecated.</p>
 * 
 * @param <R> the return type of the visitor's methods.  {@code Void}
 *            can be used where there is no return value.
 * @param <P> the type of the additional parameter supplied to the visitor's
 *            methods.
 *
 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
 * @since 1.6
 */
@SupportedSourceVersion(SourceVersion.RELEASE_6)
public class SimpleElementVisitor6<R,P> extends AbstractElementVisitor6<R,P>
{

  /**
   * The default value returned by calls to {@link #defaultAction(Element, P)}.
   */
  protected final R DEFAULT_VALUE;

  /**
   * Constructs a new {@link SimpleElementVisitor6} with a {@code null}
   * default value.
   */
  protected SimpleElementVisitor6()
  {
    this(null);
  }

  /**
   * Constructs a new {@link SimpleElementVisitor6} with the specified
   * default value.
   *
   * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}.
   */
  protected SimpleElementVisitor6(R defaultValue)
  {
    DEFAULT_VALUE = defaultValue;
  }

  /**
   * The default action for all visitor methods.  The default implementation
   * simply returns {@link #DEFAULT_VALUE}.
   *
   * @param element the element to act upon.
   * @param parameter the optional parameter supplied to the visitor.
   * @return {@link #DEFAULT_VALUE}.
   */
  protected R defaultAction(Element element, P parameter)
  {
    return DEFAULT_VALUE;
  }

  /**
   * Visits an executable element.  This implementation simply
   * calls {@code defaultAction(element, parameter)}.
   *
   * @param element the executable element to visit.
   * @param parameter the additional parameter, specific to the visitor.
   *        May be {@code null}.
   * @return the result of {@code defaultAction(element, parameter)}.
   */
  @Override
  public R visitExecutable(ExecutableElement element, P parameter)
  {
    return defaultAction(element, parameter);
  }


  /**
   * Visits a package element.  This implementation simply
   * calls {@code defaultAction(element, parameter)}.
   *
   * @param element the package element to visit.
   * @param parameter the additional parameter, specific to the visitor.
   *        May be {@code null}.
   * @return the result of {@code defaultAction(element, parameter)}.
   */
  @Override
  public R visitPackage(PackageElement element, P parameter)
  {
    return defaultAction(element, parameter);
  }

  /**
   * Visits a type element.  This implementation simply
   * calls {@code defaultAction(element, parameter)}.
   *
   * @param element the type element to visit.
   * @param parameter the additional parameter, specific to the visitor.
   *        May be {@code null}.
   * @return the result of {@code defaultAction(element, parameter)}.
   */
  @Override
  public R visitType(TypeElement element, P parameter)
  {
    return defaultAction(element, parameter);
  }

  /**
   * Visits a type parameter element.  This implementation simply
   * calls {@code defaultAction(element, parameter)}.
   *
   * @param element the type parameter element to visit.
   * @param parameter the additional parameter, specific to the visitor.
   *        May be {@code null}.
   * @return the result of {@code defaultAction(element, parameter)}.
   */
  @Override
  public R visitTypeParameter(TypeParameterElement element, P parameter)
  {
    return defaultAction(element, parameter);
  }

  /**
   * Visits a variable element.  This implementation simply
   * calls {@code defaultAction(element, parameter)}.
   *
   * @param element the variable element to visit.
   * @param parameter the additional parameter, specific to the visitor.
   *        May be {@code null}.
   * @return the result of {@code defaultAction(element, parameter)}.
   */
  @Override
  public R visitVariable(VariableElement element, P parameter)
  {
    return defaultAction(element, parameter);
  }

}