/*
 * Copyright (c) 2005, 2011, 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.lang.model.element.*;
import static javax.lang.model.element.ElementKind.*;
import javax.annotation.processing.SupportedSourceVersion;
import static javax.lang.model.SourceVersion.*;
import javax.lang.model.SourceVersion;


/**
 * A visitor of program elements based on their {@linkplain
 * ElementKind kind} with default behavior appropriate for the {@link
 * SourceVersion#RELEASE_6 RELEASE_6} source version.  For {@linkplain
 * Element elements} <tt><i>XYZ</i></tt> that may have more than one
 * kind, the <tt>visit<i>XYZ</i></tt> methods in this class delegate
 * to the <tt>visit<i>XYZKind</i></tt> method corresponding to the
 * first argument's kind.  The <tt>visit<i>XYZKind</i></tt> methods
 * call {@link #defaultAction defaultAction}, passing their arguments
 * to {@code defaultAction}'s corresponding parameters.
 *
 * <p> Methods in this class may be overridden subject to their
 * general contract.  Note that annotating methods in concrete
 * subclasses with {@link java.lang.Override @Override} will help
 * ensure that methods are overridden as intended.
 *
 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
 * implemented by this class may have methods added to it or the
 * {@code ElementKind} {@code enum} used in this case may have
 * constants added to it in the future to accommodate new, currently
 * unknown, language structures added to future versions of the
 * Java&trade; programming language.  Therefore, methods whose names
 * begin with {@code "visit"} may be added to this class in the
 * future; to avoid incompatibilities, classes which extend this class
 * should not declare any instance methods with names beginning with
 * {@code "visit"}.
 *
 * <p>When such a new visit method is added, the default
 * implementation in this class will be to call the {@link
 * #visitUnknown visitUnknown} method.  A new abstract element kind
 * 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 the new visitor is
 * introduced, all or portions of this visitor may be deprecated.
 *
 * @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.
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ah&eacute;
 *
 * @see ElementKindVisitor7
 * @since 1.6
 */
@SupportedSourceVersion(RELEASE_6)
public class ElementKindVisitor6<R, P>
                  extends SimpleElementVisitor6<R, P> {
    /**
     * Constructor for concrete subclasses; uses {@code null} for the
     * default value.
     */
    protected ElementKindVisitor6() {
        super(null);
    }

    /**
     * Constructor for concrete subclasses; uses the argument for the
     * default value.
     *
     * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
     */
    protected ElementKindVisitor6(R defaultValue) {
        super(defaultValue);
    }

    /**
     * {@inheritDoc}
     *
     * The element argument has kind {@code PACKAGE}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  {@inheritDoc}
     */
    @Override
    public R visitPackage(PackageElement e, P p) {
        assert e.getKind() == PACKAGE: "Bad kind on PackageElement";
        return defaultAction(e, p);
    }

    /**
     * Visits a type element, dispatching to the visit method for the
     * specific {@linkplain ElementKind kind} of type, {@code
     * ANNOTATION_TYPE}, {@code CLASS}, {@code ENUM}, or {@code
     * INTERFACE}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  the result of the kind-specific visit method
     */
    @Override
    public R visitType(TypeElement e, P p) {
        ElementKind k = e.getKind();
        switch(k) {
        case ANNOTATION_TYPE:
            return visitTypeAsAnnotationType(e, p);

        case CLASS:
            return visitTypeAsClass(e, p);

        case ENUM:
            return visitTypeAsEnum(e, p);

        case INTERFACE:
            return visitTypeAsInterface(e, p);

        default:
            throw new AssertionError("Bad kind " + k + " for TypeElement" + e);
        }
    }

    /**
     * Visits an {@code ANNOTATION_TYPE} type element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitTypeAsAnnotationType(TypeElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits a {@code CLASS} type element by calling {@code
     * defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitTypeAsClass(TypeElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits an {@code ENUM} type element by calling {@code
     * defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitTypeAsEnum(TypeElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits an {@code INTERFACE} type element by calling {@code
     * defaultAction}.
     *.
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitTypeAsInterface(TypeElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits a variable element, dispatching to the visit method for
     * the specific {@linkplain ElementKind kind} of variable, {@code
     * ENUM_CONSTANT}, {@code EXCEPTION_PARAMETER}, {@code FIELD},
     * {@code LOCAL_VARIABLE}, {@code PARAMETER}, or {@code RESOURCE_VARIABLE}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  the result of the kind-specific visit method
     */
    @Override
    public R visitVariable(VariableElement e, P p) {
        ElementKind k = e.getKind();
        switch(k) {
        case ENUM_CONSTANT:
            return visitVariableAsEnumConstant(e, p);

        case EXCEPTION_PARAMETER:
            return visitVariableAsExceptionParameter(e, p);

        case FIELD:
            return visitVariableAsField(e, p);

        case LOCAL_VARIABLE:
            return visitVariableAsLocalVariable(e, p);

        case PARAMETER:
            return visitVariableAsParameter(e, p);

        case RESOURCE_VARIABLE:
            return visitVariableAsResourceVariable(e, p);

        default:
            throw new AssertionError("Bad kind " + k + " for VariableElement" + e);
        }
    }

    /**
     * Visits an {@code ENUM_CONSTANT} variable element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitVariableAsEnumConstant(VariableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits an {@code EXCEPTION_PARAMETER} variable element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitVariableAsExceptionParameter(VariableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits a {@code FIELD} variable element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitVariableAsField(VariableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits a {@code LOCAL_VARIABLE} variable element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitVariableAsLocalVariable(VariableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits a {@code PARAMETER} variable element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitVariableAsParameter(VariableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits a {@code RESOURCE_VARIABLE} variable element by calling
     * {@code visitUnknown}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code visitUnknown}
     *
     * @since 1.7
     */
    public R visitVariableAsResourceVariable(VariableElement e, P p) {
        return visitUnknown(e, p);
    }

    /**
     * Visits an executable element, dispatching to the visit method
     * for the specific {@linkplain ElementKind kind} of executable,
     * {@code CONSTRUCTOR}, {@code INSTANCE_INIT}, {@code METHOD}, or
     * {@code STATIC_INIT}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  the result of the kind-specific visit method
     */
    @Override
    public R visitExecutable(ExecutableElement e, P p) {
        ElementKind k = e.getKind();
        switch(k) {
        case CONSTRUCTOR:
            return visitExecutableAsConstructor(e, p);

        case INSTANCE_INIT:
            return visitExecutableAsInstanceInit(e, p);

        case METHOD:
            return visitExecutableAsMethod(e, p);

        case STATIC_INIT:
            return visitExecutableAsStaticInit(e, p);

        default:
            throw new AssertionError("Bad kind " + k + " for ExecutableElement" + e);
        }
    }

    /**
     * Visits a {@code CONSTRUCTOR} executable element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitExecutableAsConstructor(ExecutableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits an {@code INSTANCE_INIT} executable element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitExecutableAsInstanceInit(ExecutableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits a {@code METHOD} executable element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitExecutableAsMethod(ExecutableElement e, P p) {
        return defaultAction(e, p);
    }

    /**
     * Visits a {@code STATIC_INIT} executable element by calling
     * {@code defaultAction}.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     * @return  the result of {@code defaultAction}
     */
    public R visitExecutableAsStaticInit(ExecutableElement e, P p) {
        return defaultAction(e, p);
    }


    /**
     * {@inheritDoc}
     *
     * The element argument has kind {@code TYPE_PARAMETER}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     * @return  {@inheritDoc}
     */
    @Override
    public R visitTypeParameter(TypeParameterElement e, P p) {
        assert e.getKind() == TYPE_PARAMETER: "Bad kind on TypeParameterElement";
        return defaultAction(e, p);
    }
}
