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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;

/**
 * The {@link Condition} interface defines a contract for implementing objects used to evaluate a required condition
 * of the application or system.
 *
 * @author John Blum
 * @see java.lang.FunctionalInterface
 * @since 1.0.0
 */
@FunctionalInterface
@SuppressWarnings("unused")
public interface Condition {

  Condition FALSE_CONDITION = () -> false;
  Condition TRUE_CONDITION = () -> true;

  /**
   * Evaluates the required criteria of this condition to determine whether the condition holds.
   *
   * @return a boolean value indicating whether the condition holds.
   */
  boolean evaluate();

  /**
   * Composes this {@link Condition} with the given {@link Condition} using the logical AND operator.
   *
   * @param condition {@link Condition} to compose with this {@link Condition} using logical AND.
   * @return a new {@link Condition} composed of this {@link Condition} with the given {@link Condition}
   * using the logical AND operator.
   */
  default Condition andThen(Condition condition) {
    return () -> this.evaluate() && condition.evaluate();
  }

  /**
   * Composes this {@link Condition} with the given {@link Condition} using the logical OR operator.
   *
   * @param condition {@link Condition} to compose with this {@link Condition} using logical OR.
   * @return a new {@link Condition} composed of this {@link Condition} with the given {@link Condition}
   * using the logical OR operator.
   */
  default Condition orElse(Condition condition) {
    return () -> this.evaluate() || condition.evaluate();
  }

  /**
   * Composes this {@link Condition} with the given {@link Condition} using the XOR operator.
   *
   * @param condition {@link Condition} to compose with this {@link Condition} using the XOR operator.
   * @return a new {@link Condition} composed of this {@link Condition} with the given {@link Condition}
   * using the XOR operator.
   */
  default Condition xor(Condition condition) {
    return () -> this.evaluate() ^ condition.evaluate();
  }
}