/**
    * This file Copyright (c) 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.guice;
  
  import info.magnolia.context.MgnlContext;
  import info.magnolia.context.WebContext;
  
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpSession;
  
  import com.google.inject.Key;
  import com.google.inject.OutOfScopeException;
  import com.google.inject.Provider;
  import com.google.inject.Scope;
  import com.google.inject.Scopes;
  
  /**
   * Servlet scopes that use WebContext to get request and session.
   *
   * @version $Id$
   */
  public class MagnoliaScopes {
  
      private MagnoliaScopes() {
      }
  
      public static final Scope LAZY_SINGLETON = new LazySingletonScope();
  
      /**
       * HTTP servlet request scope.
       */
      public static final Scope LOCAL = new LocalScope();
  
      /**
       * HTTP session scope.
       */
      public static final Scope SESSION = new SessionScope();
  
      /**
       * Scope for lazy singletons.
       *
       * @version $Id$
       * @see info.magnolia.objectfactory.annotation.LazySingleton
       */
      public static class LazySingletonScope implements Scope {
  
          @Override
          public <T> Provider<T> scope(Key<T> key, Provider<T> creator) {
              return Scopes.SINGLETON.scope(key, creator);
          }
  
          @Override
          public String toString() {
              return "MagnoliaScopes.LAZY_SINGLETON";
          }
      }
  
      /**
       * A sentinel attribute value representing null.
       */
      enum NullObject {
          INSTANCE
      }
  
      /**
       * Scope for object local to the current request.
       *
       * @version $Id$
      * @see info.magnolia.objectfactory.annotation.LocalScoped
      */
     public static class LocalScope implements Scope {
 
         @Override
         public <T> Provider<T> scope(Key<T> key, final Provider<T> creator) {
             final String name = key.toString();
             return new Provider<T>() {
                 @Override
                 public T get() {
 
                     HttpServletRequest request = getRequest();
 
                     if (request == null) {
                         return null;
                     }
 
                     synchronized (request) {
                         Object obj = request.getAttribute(name);
                         if (NullObject.INSTANCE == obj) {
                             return null;
                         }
                         @SuppressWarnings("unchecked")
                         T t = (T) obj;
                         if (t == null) {
                             t = creator.get();
                             request.setAttribute(name, (t != null) ? t : NullObject.INSTANCE);
                         }
                         return t;
                     }
                 }
 
                 @Override
                 public String toString() {
                     return String.format("%s[%s]", creator, LOCAL);
                 }
             };
         }
 
         @Override
         public String toString() {
             return "MagnoliaScopes.LOCAL";
         }
     }
 
     /**
      * Scope for object local to the current session.
      *
      * @version $Id$
      * @see info.magnolia.objectfactory.annotation.SessionScoped
      */
     public static class SessionScope implements Scope {
 
         @Override
         public <T> Provider<T> scope(Key<T> key, final Provider<T> creator) {
             final String name = key.toString();
             return new Provider<T>() {
                 @Override
                 public T get() {
 
                     HttpSession session = getSession();
 
                     synchronized (session) {
                         Object obj = session.getAttribute(name);
                         if (NullObject.INSTANCE == obj) {
                             return null;
                         }
                         @SuppressWarnings("unchecked")
                         T t = (T) obj;
                         if (t == null) {
                             t = creator.get();
                             session.setAttribute(name, (t != null) ? t : NullObject.INSTANCE);
                         }
                         return t;
                     }
                 }
 
                 @Override
                 public String toString() {
                     return String.format("%s[%s]", creator, SESSION);
                 }
             };
         }
 
         @Override
         public String toString() {
             return "MagnoliaScopes.SESSION";
         }
     }
 
     private static HttpServletRequest getRequest() {
         WebContext webContext;
         try {
             webContext = MgnlContext.getWebContextOrNull();
             // when injecting request to objects outside of the request scope (e.g. on destroy)
             if (webContext == null) {
                 return null;
             }
         } catch (IllegalStateException e) {
             throw new OutOfScopeException("Cannot access scoped object." +
                     " MgnlContext does not have a WebContext set, this is most likely" +
                     " because we are not currently processing a HTTP request.", e);
         }
         HttpServletRequest request = webContext.getRequest();
         if (request == null) {
             throw new OutOfScopeException("Cannot access scoped object." +
                     " MgnlContext does not have a HttpServletRequest set, this is most likely" +
             " because we are not currently processing a HTTP request.");
         }
         return request;
     }
 
     private static HttpSession getSession() {
         try {
             return getRequest().getSession();
         } catch (IllegalStateException e) {
             throw new OutOfScopeException("Cannot access scoped object." +
                     " A session is not available and a new one could not be created," +
                     " likely because the response has already been committed.", e);
         }
     }
 }