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An unofficial backport of the JDK Classfile API to Java 17
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/*
 * Copyright (c) 2022, 2024, 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 io.github.dmlloyd.classfile;

import io.github.dmlloyd.classfile.attribute.RuntimeInvisibleAnnotationsAttribute;
import io.github.dmlloyd.classfile.attribute.RuntimeInvisibleParameterAnnotationsAttribute;
import io.github.dmlloyd.classfile.attribute.RuntimeVisibleAnnotationsAttribute;
import io.github.dmlloyd.classfile.attribute.RuntimeVisibleParameterAnnotationsAttribute;
import io.github.dmlloyd.classfile.constantpool.Utf8Entry;
import java.lang.constant.ClassDesc;
import java.util.List;

import io.github.dmlloyd.classfile.impl.AnnotationImpl;
import io.github.dmlloyd.classfile.impl.TemporaryConstantPool;
import io.github.dmlloyd.classfile.impl.Util;

/**
 * Models an {@code annotation} structure (JVMS {@jvms 4.7.16}) or part of a {@code
 * type_annotation} structure (JVMS {@jvms 4.7.20}). This model indicates the
 * interface of the annotation and a set of element-value pairs.
 * 
 * This model can reconstruct an annotation, given the location of the modeled structure
 * in the class file and the definition of the annotation interface.
 * 
 * Two {@code Annotation} objects should be compared using the {@link
 * Object#equals(Object) equals} method.
 *
 * @apiNote
 * For Java programs, the location of the modeled structure indicates the source code
 * element or type (JLS {@jls 9.7.4}) on which the reconstructed annotation appears,
 * and the annotation interface definition determines whether the reconstructed annotation has
 * elements with default values (JLS {@jls 9.6.2}), and whether the reconstructed annotation
 * is a container annotation for multiple annotations (JLS {@jls 9.7.5}).
 *
 * @see AnnotationElement
 * @see AnnotationValue
 * @see TypeAnnotation
 * @see RuntimeVisibleAnnotationsAttribute
 * @see RuntimeInvisibleAnnotationsAttribute
 * @see RuntimeVisibleParameterAnnotationsAttribute
 * @see RuntimeInvisibleParameterAnnotationsAttribute
 *
 * @since 24
 */
public sealed interface Annotation
        permits AnnotationImpl {

    /**
     * {@return the constant pool entry holding the {@linkplain Class#descriptorString
     * descriptor string} of the annotation interface}
     */
    Utf8Entry className();

    /**
     * {@return the annotation interface, as a symbolic descriptor}
     */
    default ClassDesc classSymbol() {
        return Util.fieldTypeSymbol(className());
    }

    /**
     * {@return the element-value pairs of the annotation}
     */
    List elements();

    /**
     * {@return an annotation}
     * @param annotationClass the constant pool entry holding the descriptor string
     *                        of the annotation interface
     * @param elements the element-value pairs of the annotation
     */
    static Annotation of(Utf8Entry annotationClass,
                         List elements) {
        return new AnnotationImpl(annotationClass, elements);
    }

    /**
     * {@return an annotation}
     * @param annotationClass the constant pool entry holding the descriptor string
     *                        of the annotation interface
     * @param elements the element-value pairs of the annotation
     */
    static Annotation of(Utf8Entry annotationClass,
                         AnnotationElement... elements) {
        return of(annotationClass, List.of(elements));
    }

    /**
     * {@return an annotation}
     * @param annotationClass the descriptor of the annotation interface
     * @param elements the element-value pairs of the annotation
     */
    static Annotation of(ClassDesc annotationClass,
                         List elements) {
        return of(TemporaryConstantPool.INSTANCE.utf8Entry(annotationClass), elements);
    }

    /**
     * {@return an annotation}
     * @param annotationClass the descriptor of the annotation interface
     * @param elements the element-value pairs of the annotation
     */
    static Annotation of(ClassDesc annotationClass,
                         AnnotationElement... elements) {
        return of(TemporaryConstantPool.INSTANCE.utf8Entry(annotationClass), elements);
    }
}