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Annotations-based syntax for GraphQL schema definition
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/*
 * 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
 */

package graphql.annotations.processor.util;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

/**
 * Operates on classes without using reflection.
 *
 * 
 * This class handles invalid {@code null} inputs as best it can. Each method documents its behavior in more detail.
 * 
 *
 * 
 * The notion of a {@code canonical name} includes the human readable name for the type, for example {@code int[]}. The
 * non-canonical method variants work with the JVM names, such as {@code [I}.
 * 
 * 
 * 
 * This class and the functions contained within are from the Apache commons-lang project.
 * 
 *
 */
public class ClassUtils {

    /**
     * Gets a {@link List} of all interfaces implemented by the given class and its superclasses.
     *
     * 
     * The order is determined by looking through each interface in turn as declared in the source file and following its
     * hierarchy up. Then each superclass is considered in the same way. Later duplicates are ignored, so the order is
     * maintained.
     * 
     *
     * @param cls the class to look up, may be {@code null}
     * @return the {@link List} of interfaces in order, {@code null} if null input
     */
    public static List> getAllInterfaces(final Class cls) {
        if (cls == null) {
            return null;
        }

        final LinkedHashSet> interfacesFound = new LinkedHashSet<>();
        getAllInterfaces(cls, interfacesFound);

        return new ArrayList<>(interfacesFound);
    }

    /**
     * Gets the interfaces for the specified class.
     *
     * @param cls the class to look up, may be {@code null}
     * @param interfacesFound the {@link Set} of interfaces for the class
     */
    private static void getAllInterfaces(Class cls, final HashSet> interfacesFound) {
        while (cls != null) {
            final Class[] interfaces = cls.getInterfaces();

            for (final Class i : interfaces) {
                if (interfacesFound.add(i)) {
                    getAllInterfaces(i, interfacesFound);
                }
            }

            cls = cls.getSuperclass();
        }
    }

    /**
     * ClassUtils instances should NOT be constructed in standard programming. Instead, the class should be used as
     * {@code ClassUtils.getShortClassName(cls)}.
     *
     * 
     * This constructor is public to permit tools that require a JavaBean instance to operate.
     * 
     */
    public ClassUtils() {
    }

}