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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.reflect;

import static org.cp.elements.util.stream.StreamUtils.stream;

import java.util.Iterator;
import java.util.Optional;
import java.util.ServiceLoader;

import org.cp.elements.service.annotation.Service;
import org.cp.elements.service.support.ServiceSupport;

/**
 * The {@link ProxyService} class is a service component used to load {@link ProxyFactory}
 * service provider implementations at application runtime.
 *
 * @author John Blum
 * @param  {@link Class} type of the {@link Object} to proxy.
 * @see java.lang.Iterable
 * @see java.util.ServiceLoader
 * @see org.cp.elements.lang.reflect.ProxyFactory
 * @see org.cp.elements.service.annotation.Service
 * @see org.cp.elements.service.support.ServiceSupport
 * @since 1.0.0
 */
@Service
@SuppressWarnings("unused")
public final class ProxyService implements Iterable, ServiceSupport> {

  private static ProxyService proxyServiceInstance;

  /**
   * Constructs, configures and initializes a single (Singleton) instance of the {@link ProxyService} class.
   *
   * @param  {@link Class} type of the {@link Object} to proxy.
   * @return a single instance of the {@link ProxyService} class.
   * @see org.cp.elements.lang.reflect.ProxyService
   */
  @SuppressWarnings("unchecked")
  public static synchronized  ProxyService newProxyService() {
    proxyServiceInstance = Optional.ofNullable(proxyServiceInstance).orElseGet(ProxyService::new);
    return proxyServiceInstance;
  }

  private final ServiceLoader proxyFactoriesLoader;

  /**
   * Constructs an instance of {@link ProxyService} that initializes all {@link ProxyFactory}
   * service provider implementations.
   *
   * @see org.cp.elements.lang.reflect.ProxyFactory
   * @see java.util.ServiceLoader#load(Class)
   */
  private ProxyService() {
    proxyFactoriesLoader = ServiceLoader.load(ProxyFactory.class);
  }

  /**
   * Determines whether any of the {@link ProxyFactory} service provider implementations managed by this
   * {@link ProxyService} is able to proxy the given target {@link Object}, given the array of {@link Class interfaces}.
   *
   * @param target {@link Object} to proxy.
   * @param proxyInterfaces array of {@link Class interfaces} to be implemented by the Proxy.
   * @return a boolean value of {@literal true} if there exists at least one {@link ProxyFactory}
   * service provider implementation that is able to proxy the given target {@link Object} with the given
   * array of {@link Class interfaces}.
   * @see org.cp.elements.lang.reflect.ProxyFactory#canProxy(Object, Class[])
   * @see java.lang.Class
   * @see java.lang.Object
   */
  @SuppressWarnings("unchecked")
  public boolean canProxy(Object target, Class... proxyInterfaces) {
    return stream(this).anyMatch(proxyFactory -> proxyFactory.canProxy(target, proxyInterfaces));
  }

  /**
   * Iterates over the {@link ProxyFactory} service provider implementations.
   *
   * @return an {@link Iterator} over the {@link ProxyFactory} service provider implementations.
   * @see org.cp.elements.lang.reflect.ProxyFactory
   * @see java.util.ServiceLoader#iterator()
   * @see java.util.Iterator
   * @see java.lang.Iterable
   */
  @Override
  public Iterator iterator() {
    return proxyFactoriesLoader.iterator();
  }

  /**
   * Clears the {@link ServiceLoader ServiceLoader's} provider cache of all service provider implementations
   * causing all {@link ProxyFactory} service provider implementations to be reloaded.
   *
   * @see java.util.ServiceLoader#reload()
   */
  public void reload() {
    this.proxyFactoriesLoader.reload();
  }
}