001/* -*- mode: Java; c-basic-offset: 2; indent-tabs-mode: nil; coding: utf-8-unix -*-
002 *
003 * Copyright © 2025 microBean™.
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
006 * the License. You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
011 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
012 * specific language governing permissions and limitations under the License.
013 */
014package org.microbean.attributes;
015
016import java.lang.constant.ClassDesc;
017import java.lang.constant.DynamicConstantDesc;
018import java.lang.constant.MethodHandleDesc;
019import java.lang.constant.MethodTypeDesc;
020
021import java.util.Objects;
022import java.util.Optional;
023
024import static java.lang.constant.ConstantDescs.BSM_INVOKE;
025import static java.lang.constant.ConstantDescs.CD_Class;
026import static java.lang.constant.DirectMethodHandleDesc.Kind.STATIC;
027
028/**
029 * A {@link Value} whose value is a {@code Class}.
030 *
031 * @param value the value
032 *
033 * @author <a href="https://about.me/lairdnelson" target="_top">Laird Nelson</a>
034 */
035public final record ClassValue(Class<?> value) implements Value<ClassValue> {
036
037  public static final ClassValue CLASS_JAVA_LANG_OBJECT = new ClassValue(Object.class);
038
039  public static final ClassValue CLASS_JAVA_LANG_STRING = new ClassValue(String.class);
040
041  /**
042   * Creates a new {@link ClassValue}.
043   *
044   * @param value the value; must not be {@code null}
045   *
046   * @exception NullPointerException if {@code value} is {@code null}
047   */
048  public ClassValue {
049    Objects.requireNonNull(value, "value");
050  }
051
052  @Override // Comparable<ClassValue>
053  public final int compareTo(final ClassValue other) {
054    if (other == null) {
055      return -1;
056    } else if (this.equals(other)) {
057      return 0;
058    }
059    return this.value().getName().compareTo(other.value().getName());
060  }
061
062  @Override // Constable
063  public final Optional<DynamicConstantDesc<ClassValue>> describeConstable() {
064    final ClassDesc cd = ClassDesc.of(this.getClass().getName());
065    return
066      Optional.of(DynamicConstantDesc.of(BSM_INVOKE,
067                                         MethodHandleDesc.ofMethod(STATIC,
068                                                                   cd,
069                                                                   "of",
070                                                                   MethodTypeDesc.of(cd,
071                                                                                     CD_Class)),
072                                         this.value().describeConstable().orElseThrow()));
073  }
074
075  @Override // Record
076  public final boolean equals(final Object other) {
077    return
078      other == this ||
079      // Follow java.lang.annotation.Annotation requirements.
080      other != null && other.getClass() == this.getClass() && this.value().equals(((ClassValue)other).value());
081  }
082
083  @Override // Record
084  public final int hashCode() {
085    // Follow java.lang.annotation.Annotation requirements.
086    return this.value().hashCode();
087  }
088
089  @Override // Record
090  public final String toString() {
091    return this.value().getName(); // binary name
092  }
093
094  /**
095   * Returns a {@link ClassValue} suitable for the supplied arguments.
096   *
097   * @param c a {@code Class}; must not be {@code null}
098   *
099   * @return a non-{@code null} {@link ClassValue}
100   *
101   * @exception NullPointerException if {@code c} is {@code null}
102   */
103  public static final ClassValue of(final Class<?> c) {
104    return
105      c == Object.class ? CLASS_JAVA_LANG_OBJECT :
106      c == String.class ? CLASS_JAVA_LANG_STRING :
107      new ClassValue(c);
108  }
109
110}