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/*
 * Copyright 2023-2024 wjybxx([email protected])
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cn.wjybxx.base;

import javax.annotation.Nonnull;
import java.util.Objects;

/**
 * @author wjybxx
 * date - 2023/5/19
 */
public abstract class AbstractConstant implements Constant {

    /** 常量在其所属常量池下的唯一id */
    private final int id;
    /** 常量的名字 */
    private final String name;
    /** 声明常量的池 */
    private final Object declaringPool;

    protected AbstractConstant(Builder builder) {
        this.id = builder.getIdOrThrow();
        this.name = Objects.requireNonNull(builder.getName());
        this.declaringPool = Objects.requireNonNull(builder.getDeclaringPool(), "declaringPool");
    }

    @Override
    public final int id() {
        return id;
    }

    @Override
    public final String name() {
        return name;
    }

    @Override
    public Object declaringPool() {
        return declaringPool;
    }

    @Override
    public String toString() {
        // 通常不应该覆盖该方法
        return name;
    }

    @Override
    public final int hashCode() {
        // 不对hashCode做任何假设
        return super.hashCode();
    }

    @Override
    public final boolean equals(Object obj) {
        // 只使用 == 比较相等性
        return this == obj;
    }

    @Override
    protected final Object clone() throws CloneNotSupportedException {
        throw new CloneNotSupportedException();
    }

    @Override
    public final int compareTo(final @Nonnull Constant other) {
        if (this == other) {
            return 0;
        }
        // 注意：
        // 1. 未比较名字也未比较其它信息 - 这可以保证同一个类中定义的常量，其结果与定义顺序相同，就像枚举。
        // 2. uniqueId与类初始化顺序有关，因此无法保证不同类中定义的常量的顺序。
        // 3. 有个例外，超类中定义的常量总是在子类前面，这是因为超类总是在子类之前初始化。
        if (declaringPool == other.declaringPool()) {
            if (id < other.id()) {
                return -1;
            }
            if (id > other.id()) {
                return 1;
            }
        }
        throw new Error("failed to compare two different constants, this: " + name + ", that: " + other.name());
    }
}