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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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).
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package java.lang.classfile.attribute;

import java.lang.classfile.Attribute;
import java.lang.classfile.AttributeMapper;
import java.lang.classfile.Attributes;
import java.lang.classfile.ClassElement;
import java.lang.classfile.constantpool.Utf8Entry;
import java.lang.constant.ClassDesc;
import java.util.Arrays;
import java.util.List;

import jdk.internal.classfile.impl.BoundAttribute;
import jdk.internal.classfile.impl.UnboundAttribute;
import jdk.internal.classfile.impl.Util;
import jdk.internal.javac.PreviewFeature;

/**
 * Models the {@link Attributes#loadableDescriptors() LoadableDescriptors}
 * attribute (JVMS {@jvms value-objects-4.7.32}), which permits the JVM to
 * load mentioned classes and interfaces before the {@code class} file carrying
 * this attribute is loaded.
 * <p>
 * This attribute only appears on classes, and does not permit {@linkplain
 * AttributeMapper#allowMultiple multiple instances} in a class.  It has a
 * data dependency on the {@linkplain AttributeMapper.AttributeStability#CP_REFS
 * constant pool}.
 * <p>
 * The attribute is a preview VM feature in the current Java SE release.
 *
 * @see Attributes#loadableDescriptors()
 * @jvms value-objects-4.7.32 The {@code LoadableDescriptors} Attribute
 * @since 28
 */
@PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS, reflective = true)
public sealed interface LoadableDescriptorsAttribute
        extends Attribute<LoadableDescriptorsAttribute>, ClassElement
        permits BoundAttribute.BoundLoadableDescriptorsAttribute, UnboundAttribute.UnboundLoadableDescriptorsAttribute {

    /**
     * {@return the list of loadable descriptors}
     */
    List<Utf8Entry> loadableDescriptors();

    /**
     * {@return the list of loadable descriptors, as nominal descriptors}
     */
    default List<ClassDesc> loadableDescriptorSymbols() {
        return Util.mappedList(loadableDescriptors(), Util::fieldTypeSymbol);
    }

    /**
     * {@return a {@code LoadableDescriptors} attribute}
     * @param loadableDescriptors the loadable descriptors
     * @throws IllegalArgumentException if the number of loadable descriptors
     *         exceeds the limit of {@link java.lang.classfile##u2 u2}
     */
    static LoadableDescriptorsAttribute of(List<Utf8Entry> loadableDescriptors) {
        return new UnboundAttribute.UnboundLoadableDescriptorsAttribute(loadableDescriptors);
    }

    /**
     * {@return a {@code LoadableDescriptors} attribute}
     * @param loadableDescriptors the loadable descriptors
     * @throws IllegalArgumentException if the number of loadable descriptors
     *         exceeds the limit of {@link java.lang.classfile##u2 u2}
     */
    static LoadableDescriptorsAttribute of(Utf8Entry... loadableDescriptors) {
        return of(List.of(loadableDescriptors));
    }

    /**
     * {@return a {@code LoadableDescriptors} attribute}
     * @param loadableDescriptors the loadable descriptors
     * @throws IllegalArgumentException if the number of loadable descriptors
     *         exceeds the limit of {@link java.lang.classfile##u2 u2}
     */
    static LoadableDescriptorsAttribute ofSymbols(List<ClassDesc> loadableDescriptors) {
        return of(Util.fieldDescriptorList(loadableDescriptors));
    }

    /**
     * {@return a {@code LoadableDescriptors} attribute}
     * @param loadableDescriptors the loadable descriptors
     * @throws IllegalArgumentException if the number of loadable descriptors
     *         exceeds the limit of {@link java.lang.classfile##u2 u2}
     */
    static LoadableDescriptorsAttribute ofSymbols(ClassDesc... loadableDescriptors) {
        return ofSymbols(Arrays.asList(loadableDescriptors));
    }
}
