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Java Simplified. Extensions and Useful Constructs for the Java Platform. Codeprimate Elements (a.k.a. cp-elements) is a Java library and micro-framework used to simplify the development of software applications written in Java. Elements packages several APIs into one library in order to address various application concerns and aspects of software design and development collectively and conveniently. Elements is a highly simple, yet robust and proven library built on solid OO principles, software design patterns and best practices to effectively solve common and reoccurring problems in software development.

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/*
 * Copyright 2016 Author or Authors.
 *
 * 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 org.cp.elements.lang;

import org.cp.elements.util.ArrayUtils;
import org.cp.elements.util.CollectionUtils;

/**
 * {@link Composite} is an interface defining a contract for objects implementing the Composite Software Design Pattern.
 *
 * @author John Blum
 * @see java.lang.FunctionalInterface
 * @see Compsite Software Design Pattern
 * @since 1.0.0
 */
@FunctionalInterface
@SuppressWarnings("unused")
public interface Composite {

  /**
   * Composes the two objects of type {@code T} into a single Composite object of type {@code T}
   * composed of the two given objects but acting as a single instance of {@code T}.
   *
   * @param one object to compose.
   * @param two object to compose.
   * @return an object of type {@code T} composed of the two given objects, both of type {@code T}.
   */
  T compose(T one, T two);

  /**
   * Composes the array of objects of type {@code T} into a single Composite object of type {@code T}
   * composed of the array of objects but acting as a single instance of {@code T}.
   *
   * @param objects array of objects to compose.
   * @return an object of type {@code T} composed of the array of objects of type {@code T}. Returns {@literal null}
   * if the array is {@literal null} or empty.
   * @see #compose(Object, Object)
   */
  @NullSafe
  @SuppressWarnings({ "unchecked", "varargs" })
  default T compose(T... objects) {
    T composite = null;

    for (T object : ArrayUtils.nullSafeArray(objects)) {
      composite = compose(composite, object);
    }

    return composite;
  }

  /**
   * Composes the {@link Iterable} objects of type {@code T} into a single Composite object of type {@code T}
   * composed of the {@link Iterable} objects but acting as a single instance of {@code T}.
   *
   * @param iterable array of objects to compose.
   * @return an object of type {@code T} composed of the {@link Iterable} objects of type {@code T}.
   * Returns {@literal null} if the {@link Iterable} is {@literal null} or empty.
   * @see #compose(Object, Object)
   */
  default T compose(Iterable iterable) {
    T composite = null;

    for (T object : CollectionUtils.nullSafeIterable(iterable)) {
      composite = compose(composite, object);
    }

    return composite;
  }
}