/***
 * ASM: a very small and fast Java bytecode manipulation framework Copyright (c) 2000-2011 INRIA,
 * France Telecom All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met: 1. Redistributions of source code must retain the
 * above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions
 * in binary form must reproduce the above copyright notice, this list of conditions and the
 * following disclaimer in the documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its contributors may be used to
 * endorse or promote products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.objectweb.asm;

/**
 * A visitor to visit a Java field. The methods of this class must be called in the following order:
 * ( <tt>visitAnnotation</tt> | <tt>visitAttribute</tt> )* <tt>visitEnd</tt>.
 * 
 * @author Eric Bruneton
 */
public abstract class FieldVisitor {

    /**
     * The ASM API version implemented by this visitor. The value of this field must be one of
     * {@link Opcodes#ASM4}.
     */
    protected final int api;

    /**
     * The field visitor to which this visitor must delegate method calls. May be null.
     */
    protected FieldVisitor fv;

    /**
     * Constructs a new {@link FieldVisitor}.
     * 
     * @param api the ASM API version implemented by this visitor. Must be one of
     *        {@link Opcodes#ASM4}.
     */
    public FieldVisitor(final int api) {
        this(api, null);
    }

    /**
     * Constructs a new {@link FieldVisitor}.
     * 
     * @param api the ASM API version implemented by this visitor. Must be one of
     *        {@link Opcodes#ASM4}.
     * @param fv the field visitor to which this visitor must delegate method calls. May be null.
     */
    public FieldVisitor(final int api, final FieldVisitor fv) {
        if (api != Opcodes.ASM4) {
            throw new IllegalArgumentException();
        }
        this.api = api;
        this.fv = fv;
    }

    /**
     * Visits an annotation of the field.
     * 
     * @param desc the class descriptor of the annotation class.
     * @param visible <tt>true</tt> if the annotation is visible at runtime.
     * @return a visitor to visit the annotation values, or <tt>null</tt> if this visitor is not
     *         interested in visiting this annotation.
     */
    public AnnotationVisitor visitAnnotation(String desc, boolean visible) {
        if (fv != null) {
            return fv.visitAnnotation(desc, visible);
        }
        return null;
    }

    /**
     * Visits a non standard attribute of the field.
     * 
     * @param attr an attribute.
     */
    public void visitAttribute(Attribute attr) {
        if (fv != null) {
            fv.visitAttribute(attr);
        }
    }

    /**
     * Visits the end of the field. This method, which is the last one to be called, is used to
     * inform the visitor that all the annotations and attributes of the field have been visited.
     */
    public void visitEnd() {
        if (fv != null) {
            fv.visitEnd();
        }
    }
}
