/**
    * This file Copyright (c) 2010-2011 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.objectfactory;
  
  /**
   * Static access utility for the currently set {@link ComponentProvider}. The current {@link ComponentProvider} is set
   * during start-up and there should be little reason to change it at runtime.
   *
   * Since Magnolia 4.5, you are encouraged to use IoC, only in rare cases should you need to directly use this class.
   *
   * @version $Id$
   * @see ComponentProvider
   */
  public class Components {
  
      private static volatile ComponentProvider componentProvider = new NullComponentProvider();
      private static ThreadLocal<ComponentProvider> threadLocalHierarchy = new ThreadLocal<ComponentProvider>();
  
      /**
       * Sets the current {@link ComponentProvider}.
       */
      public static void setComponentProvider(ComponentProvider provider) {
          componentProvider = provider;
      }
  
      /**
       * Returns the currently set {@link ComponentProvider}.
       */
      public static ComponentProvider getComponentProvider() {
          ComponentProvider scoped = threadLocalHierarchy.get();
          if (scoped != null) {
              return scoped;
          }
          return componentProvider;
      }
  
      public static void pushProvider(ComponentProvider provider) {
          if (threadLocalHierarchy.get() != null) {
              throw new IllegalStateException("Only one additional scope is supported");
          }
          threadLocalHierarchy.set(provider);
      }
  
      public static void popProvider() {
          threadLocalHierarchy.remove();
      }
  
      /**
       * Returns a component from the currently set {@link ComponentProvider}.
       *
       * @see ComponentProvider#getComponent(Class)
       * @deprecated since 4.5, use IoC to inject the component or use #getComponent(Class).
       */
      public static <T> T getSingleton(Class<T> type) {
          return getComponent(type);
      }
  
      public static <T> T newInstance(Class<T> type, Object... parameters) {
          return getComponentProvider().newInstance(type, parameters);
      }
  
      /**
       * Returns a component from the currently set {@link ComponentProvider}. Consider using IoC to inject the component instead.
       */
      public static <T> T getComponent(Class<T> type) {
          return getComponentProvider().getComponent(type);
      }
  
     private static class NullComponentProvider implements ComponentProvider {
 
         @Override
         public <C> Class<? extends C> getImplementation(Class<C> type) throws ClassNotFoundException {
             throw new IllegalStateException("No ComponentProvider has been set yet, something must have gone terribly wrong at startup.");
         }
 
         @Override
         public <T> T getComponent(Class<T> type) {
             throw new IllegalStateException("No ComponentProvider has been set yet, something must have gone terribly wrong at startup.");
         }
 
         @Override
         public <T> T getSingleton(Class<T> type) {
             throw new IllegalStateException("No ComponentProvider has been set yet, something must have gone terribly wrong at startup.");
         }
 
         public <T> T newInstance(Class<T> type) {
             throw new IllegalStateException("No ComponentProvider has been set yet, something must have gone terribly wrong at startup.");
         }
 
         @Override
         public <T> T newInstance(Class<T> type, Object... parameters) {
             throw new IllegalStateException("No ComponentProvider has been set yet, something must have gone terribly wrong at startup.");
         }
 
         @Override
         public <T> T newInstanceWithParameterResolvers(Class<T> type, ParameterResolver... parameters) {
             throw new IllegalStateException("No ComponentProvider has been set yet, something must have gone terribly wrong at startup.");
         }
 
         @Override
         public ComponentProvider getParent() {
             throw new IllegalStateException("No ComponentProvider has been set yet, something must have gone terribly wrong at startup.");
         }
 
     }
 }