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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
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 */
package io.github.dmlloyd.classfile.attribute;

import java.lang.constant.ClassDesc;
import java.lang.constant.MethodTypeDesc;
import java.util.Optional;

import io.github.dmlloyd.classfile.Attribute;
import io.github.dmlloyd.classfile.ClassElement;
import io.github.dmlloyd.classfile.constantpool.ClassEntry;
import io.github.dmlloyd.classfile.constantpool.NameAndTypeEntry;
import io.github.dmlloyd.classfile.constantpool.Utf8Entry;
import io.github.dmlloyd.classfile.impl.BoundAttribute;
import io.github.dmlloyd.classfile.impl.TemporaryConstantPool;
import io.github.dmlloyd.classfile.impl.UnboundAttribute;
import io.github.dmlloyd.classfile.impl.Util;
import io.github.dmlloyd.classfile.extras.PreviewFeature;

/**
 * Models the {@code EnclosingMethod} attribute (JVMS {@jvms 4.7.7}), which can appear
 * on classes, and indicates that the class is a local or anonymous class.
 * Delivered as a {@link ClassElement} when traversing the elements of a {@link
 * io.github.dmlloyd.classfile.ClassModel}.
 * 
 * The attribute does not permit multiple instances in a given location.
 * Subsequent occurrence of the attribute takes precedence during the attributed
 * element build or transformation.
 * 
 * This attribute was introduced in the Java SE Platform version 5.0.
 *
 * @since 22
 */
@PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
public sealed interface EnclosingMethodAttribute
        extends Attribute, ClassElement
        permits BoundAttribute.BoundEnclosingMethodAttribute,
                UnboundAttribute.UnboundEnclosingMethodAttribute {

    /**
     * {@return the innermost class that encloses the declaration of the current
     * class}
     */
    ClassEntry enclosingClass();

    /**
     * {@return the name and type of the enclosing method, if the class is
     * immediately enclosed by a method or constructor}
     */
    Optional enclosingMethod();

    /**
     * {@return the name of the enclosing method, if the class is
     * immediately enclosed by a method or constructor}
     */
    default Optional enclosingMethodName() {
        return enclosingMethod().map(NameAndTypeEntry::name);
    }

    /**
     * {@return the type of the enclosing method, if the class is
     * immediately enclosed by a method or constructor}
     */
    default Optional enclosingMethodType() {
        return enclosingMethod().map(NameAndTypeEntry::type);
    }

    /**
     * {@return the type of the enclosing method, if the class is
     * immediately enclosed by a method or constructor}
     */
    default Optional enclosingMethodTypeSymbol() {
        return enclosingMethod().map(Util::methodTypeSymbol);
    }

    /**
     * {@return an {@code EnclosingMethod} attribute}
     * @param className the class name
     * @param method the name and type of the enclosing method or {@code empty} if
     *               the class is not immediately enclosed by a method or constructor
     */
    static EnclosingMethodAttribute of(ClassEntry className,
                                       Optional method) {
        return new UnboundAttribute.UnboundEnclosingMethodAttribute(className, method.orElse(null));
    }

    /**
     * {@return an {@code EnclosingMethod} attribute}
     * @param className the class name
     * @param methodName the name of the enclosing method or {@code empty} if
     *                   the class is not immediately enclosed by a method or constructor
     * @param methodType the type of the enclosing method or {@code empty} if
     *                   the class is not immediately enclosed by a method or constructor
     * @throws IllegalArgumentException if {@code className} represents a primitive type
     */
    static EnclosingMethodAttribute of(ClassDesc className,
                                       Optional methodName,
                                       Optional methodType) {
        return new UnboundAttribute.UnboundEnclosingMethodAttribute(
                        TemporaryConstantPool.INSTANCE.classEntry(className),
                        methodName.isPresent() && methodType.isPresent()
                                ? TemporaryConstantPool.INSTANCE.nameAndTypeEntry(methodName.get(), methodType.get())
                                : null);
    }
}