/*
 * Copyright (c) 2003, 2018, 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
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 */

package java.lang;

import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.lang.constant.ClassDesc;
import java.lang.constant.Constable;
import java.lang.constant.ConstantDescs;
import java.lang.constant.DynamicConstantDesc;
import java.lang.invoke.MethodHandles;
import java.util.Optional;

import static java.util.Objects.requireNonNull;

/**
 * This is the common base class of all Java language enumeration types.
 *
 * More information about enums, including descriptions of the
 * implicitly declared methods synthesized by the compiler, can be
 * found in section 8.9 of
 * <cite>The Java&trade; Language Specification</cite>.
 *
 * <p> Note that when using an enumeration type as the type of a set
 * or as the type of the keys in a map, specialized and efficient
 * {@linkplain java.util.EnumSet set} and {@linkplain
 * java.util.EnumMap map} implementations are available.
 *
 * @param <E> The enum type subclass
 * @serial exclude
 * @author Josh Bloch
 * @author Neal Gafter
 * @see Class#getEnumConstants()
 * @see java.util.EnumSet
 * @see java.util.EnumMap
 * @since 1.5
 */
@SuppressWarnings("serial") // No serialVersionUID needed due to
 // special-casing of enum types.
public abstract class Enum<E extends Enum<E>>
 implements Constable, Comparable<E>, Serializable {
 /**
 * The name of this enum constant, as declared in the enum declaration.
 * Most programmers should use the {@link #toString} method rather than
 * accessing this field.
 */
 private final String name;

 /**
 * Returns the name of this enum constant, exactly as declared in its
 * enum declaration.
 *
 * <b>Most programmers should use the {@link #toString} method in
 * preference to this one, as the toString method may return
 * a more user-friendly name.</b> This method is designed primarily for
 * use in specialized situations where correctness depends on getting the
 * exact name, which will not vary from release to release.
 *
 * @return the name of this enum constant
 */
 public final String name() {
 return name;
 }

 /**
 * The ordinal of this enumeration constant (its position
 * in the enum declaration, where the initial constant is assigned
 * an ordinal of zero).
 *
 * Most programmers will have no use for this field. It is designed
 * for use by sophisticated enum-based data structures, such as
 * {@link java.util.EnumSet} and {@link java.util.EnumMap}.
 */
 private final int ordinal;

 /**
 * Returns the ordinal of this enumeration constant (its position
 * in its enum declaration, where the initial constant is assigned
 * an ordinal of zero).
 *
 * Most programmers will have no use for this method. It is
 * designed for use by sophisticated enum-based data structures, such
 * as {@link java.util.EnumSet} and {@link java.util.EnumMap}.
 *
 * @return the ordinal of this enumeration constant
 */
 public final int ordinal() {
 return ordinal;
 }

 /**
 * Sole constructor. Programmers cannot invoke this constructor.
 * It is for use by code emitted by the compiler in response to
 * enum type declarations.
 *
 * @param name - The name of this enum constant, which is the identifier
 * used to declare it.
 * @param ordinal - The ordinal of this enumeration constant (its position
 * in the enum declaration, where the initial constant is assigned
 * an ordinal of zero).
 */
 protected Enum(String name, int ordinal) {
 this.name = name;
 this.ordinal = ordinal;
 }

 /**
 * Returns the name of this enum constant, as contained in the
 * declaration. This method may be overridden, though it typically
 * isn't necessary or desirable. An enum type should override this
 * method when a more "programmer-friendly" string form exists.
 *
 * @return the name of this enum constant
 */
 public String toString() {
 return name;
 }

 /**
 * Returns true if the specified object is equal to this
 * enum constant.
 *
 * @param other the object to be compared for equality with this object.
 * @return true if the specified object is equal to this
 * enum constant.
 */
 public final boolean equals(Object other) {
 return this==other;
 }

 /**
 * Returns a hash code for this enum constant.
 *
 * @return a hash code for this enum constant.
 */
 public final int hashCode() {
 return super.hashCode();
 }

 /**
 * Throws CloneNotSupportedException. This guarantees that enums
 * are never cloned, which is necessary to preserve their "singleton"
 * status.
 *
 * @return (never returns)
 */
 protected final Object clone() throws CloneNotSupportedException {
 throw new CloneNotSupportedException();
 }

 /**
 * Compares this enum with the specified object for order. Returns a
 * negative integer, zero, or a positive integer as this object is less
 * than, equal to, or greater than the specified object.
 *
 * Enum constants are only comparable to other enum constants of the
 * same enum type. The natural order implemented by this
 * method is the order in which the constants are declared.
 */
 public final int compareTo(E o) {
 Enum<?> other = (Enum<?>)o;
 Enum<E> self = this;
 if (self.getClass() != other.getClass() && // optimization
 self.getDeclaringClass() != other.getDeclaringClass())
 throw new ClassCastException();
 return self.ordinal - other.ordinal;
 }

 /**
 * Returns the Class object corresponding to this enum constant's
 * enum type. Two enum constants e1 and e2 are of the
 * same enum type if and only if
 * e1.getDeclaringClass() == e2.getDeclaringClass().
 * (The value returned by this method may differ from the one returned
 * by the {@link Object#getClass} method for enum constants with
 * constant-specific class bodies.)
 *
 * @return the Class object corresponding to this enum constant's
 * enum type
 */
 @SuppressWarnings("unchecked")
 public final Class<E> getDeclaringClass() {
 Class<?> clazz = getClass();
 Class<?> zuper = clazz.getSuperclass();
 return (zuper == Enum.class) ? (Class<E>)clazz : (Class<E>)zuper;
 }

 /**
 * Returns an enum descriptor {@code EnumDesc} for this instance, if one can be
 * constructed, or an empty {@link Optional} if one cannot be.
 *
 * @return An {@link Optional} containing the resulting nominal descriptor,
 * or an empty {@link Optional} if one cannot be constructed.
 * @since 12
 */
 @Override
 public final Optional<EnumDesc<E>> describeConstable() {
 return getDeclaringClass()
 .describeConstable()
 .map(c -> EnumDesc.of(c, name));
 }

 /**
 * Returns the enum constant of the specified enum type with the
 * specified name. The name must match exactly an identifier used
 * to declare an enum constant in this type. (Extraneous whitespace
 * characters are not permitted.)
 *
 * <p>Note that for a particular enum type {@code T}, the
 * implicitly declared {@code public static T valueOf(String)}
 * method on that enum may be used instead of this method to map
 * from a name to the corresponding enum constant. All the
 * constants of an enum type can be obtained by calling the
 * implicit {@code public static T[] values()} method of that
 * type.
 *
 * @param <T> The enum type whose constant is to be returned
 * @param enumType the {@code Class} object of the enum type from which
 * to return a constant
 * @param name the name of the constant to return
 * @return the enum constant of the specified enum type with the
 * specified name
 * @throws IllegalArgumentException if the specified enum type has
 * no constant with the specified name, or the specified
 * class object does not represent an enum type
 * @throws NullPointerException if {@code enumType} or {@code name}
 * is null
 * @since 1.5
 */
 public static <T extends Enum<T>> T valueOf(Class<T> enumType,
 String name) {
 T result = enumType.enumConstantDirectory().get(name);
 if (result != null)
 return result;
 if (name == null)
 throw new NullPointerException("Name is null");
 throw new IllegalArgumentException(
 "No enum constant " + enumType.getCanonicalName() + "." + name);
 }

 /**
 * enum classes cannot have finalize methods.
 */
 @SuppressWarnings("deprecation")
 protected final void finalize() { }

 /**
 * prevent default deserialization
 */
 private void readObject(ObjectInputStream in) throws IOException,
 ClassNotFoundException {
 throw new InvalidObjectException("can't deserialize enum");
 }

 private void readObjectNoData() throws ObjectStreamException {
 throw new InvalidObjectException("can't deserialize enum");
 }

 /**
 * A <a href="package-summary.html#nominal">nominal descriptor</a> for an
 * {@code enum} constant.
 *
 * @param <E> the type of the enum constant
 *
 * @since 12
 */
 public static final class EnumDesc<E extends Enum<E>>
 extends DynamicConstantDesc<E> {

 /**
 * Constructs a nominal descriptor for the specified {@code enum} class and name.
 *
 * @param constantType a {@link ClassDesc} describing the {@code enum} class
 * @param constantName the unqualified name of the enum constant
 * @throws NullPointerException if any argument is null
 * @jvms 4.2.2 Unqualified Names
 */
 private EnumDesc(ClassDesc constantType, String constantName) {
 super(ConstantDescs.BSM_ENUM_CONSTANT, requireNonNull(constantName), requireNonNull(constantType));
 }

 /**
 * Returns a nominal descriptor for the specified {@code enum} class and name
 *
 * @param <E> the type of the enum constant
 * @param enumClass a {@link ClassDesc} describing the {@code enum} class
 * @param constantName the unqualified name of the enum constant
 * @return the nominal descriptor
 * @throws NullPointerException if any argument is null
 * @jvms 4.2.2 Unqualified Names
 * @since 12
 */
 public static<E extends Enum<E>> EnumDesc<E> of(ClassDesc enumClass,
 String constantName) {
 return new EnumDesc<>(enumClass, constantName);
 }

 @Override
 @SuppressWarnings("unchecked")
 public E resolveConstantDesc(MethodHandles.Lookup lookup)
 throws ReflectiveOperationException {
 return Enum.valueOf((Class<E>) constantType().resolveConstantDesc(lookup), constantName());
 }

 @Override
 public String toString() {
 return String.format("EnumDesc[%s.%s]", constantType().displayName(), constantName());
 }
 }
}