/*
 * WorldEdit, a Minecraft world manipulation toolkit
 * Copyright (C) sk89q <http://www.sk89q.com>
 * Copyright (C) WorldEdit team and contributors
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

package com.sk89q.worldedit.util.eventbus;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;

import java.util.Collections;
import java.util.List;
import java.util.Set;

/**
 * Holds a cache of class hierarchy.
 */
class HierarchyCache {

    private final LoadingCache<Class<?>, Set<Class<?>>> cache = CacheBuilder.newBuilder()
            .weakKeys()
            .build(CacheLoader.from(this::build));

    public Set<Class<?>> get(Class<?> concreteClass) {
        return cache.getUnchecked(concreteClass);
    }

    protected Set<Class<?>> build(Class<?> concreteClass) {
        List<Class<?>> parents = Lists.newLinkedList();
        Set<Class<?>> classes = Sets.newHashSet();

        parents.add(concreteClass);

        while (!parents.isEmpty()) {
            Class<?> clazz = parents.remove(0);
            classes.add(clazz);

            Class<?> parent = clazz.getSuperclass();
            if (parent != null) {
                parents.add(parent);
            }

            Collections.addAll(parents, clazz.getInterfaces());
        }

        return classes;
    }

}
