/**
    * 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.rendering.engine;
  
  import info.magnolia.cms.core.AggregationState;
  import info.magnolia.context.MgnlContext;
  import info.magnolia.registry.RegistrationException;
  import info.magnolia.rendering.context.RenderingContext;
  import info.magnolia.rendering.renderer.Renderer;
  import info.magnolia.rendering.renderer.registry.RendererRegistry;
  import info.magnolia.rendering.template.RenderableDefinition;
  import info.magnolia.rendering.template.assignment.TemplateDefinitionAssignment;
  import info.magnolia.rendering.template.variation.RenderableVariationResolver;
  
  import java.util.Collections;
  import java.util.Map;
  
  import javax.inject.Provider;
  import javax.jcr.Node;
  
  /**
   * Default implementation of {@link RenderingEngine}.
   *
   * @version $Id$
   */
  public class DefaultRenderingEngine implements RenderingEngine {
  
      protected static final Map<String, Object> EMPTY_CONTEXT = Collections.emptyMap();
  
      private RendererRegistry rendererRegistry;
      private TemplateDefinitionAssignment templateDefinitionAssignment;
      private Provider<RenderingContext> renderingContextProvider;
      private RenderableVariationResolver variationResolver;
  
      /**
       * Used to create an observed proxy object.
       */
      protected DefaultRenderingEngine() {
      }
  
      public DefaultRenderingEngine(RendererRegistry rendererRegistry, TemplateDefinitionAssignment templateDefinitionAssignment, RenderableVariationResolver variationResolver, Provider<RenderingContext> renderingContextProvider) {
          this.rendererRegistry = rendererRegistry;
          this.templateDefinitionAssignment = templateDefinitionAssignment;
          this.variationResolver = variationResolver;
          this.renderingContextProvider = renderingContextProvider;
      }
  
      @Override
      public void render(Node content, OutputProvider out) throws RenderException {
          render(content, EMPTY_CONTEXT, out);
      }
  
      @Override
      public void render(Node content, Map<String, Object> contextObjects, OutputProvider out) throws RenderException {
          render(content, getRenderableDefinitionFor(content), contextObjects, out);
      }
  
      @Override
      public void render(Node content, RenderableDefinition definition, Map<String, Object> contextObjects, OutputProvider out) throws RenderException {
  
          final Renderer renderer = getRendererFor(definition);
          final RenderingContext renderingContext = getRenderingContext();
  
          RenderableDefinition variation = variationResolver.resolveVariation(definition);
  
          AggregationState aggregationState = MgnlContext.getAggregationState();
  
          String previousTemplateVariation = aggregationState.getRenderableVariation();
         renderingContext.push(content, variation != null ? variation : definition, out);
         try {
             aggregationState.setRenderableVariation(variation != null ? variation.getName() : null);
             renderer.render(renderingContext, contextObjects);
         } finally {
             renderingContext.pop();
             aggregationState.setRenderableVariation(previousTemplateVariation);
         }
     }
 
     protected RenderableDefinition getRenderableDefinitionFor(Node content) throws RenderException {
         try {
             return templateDefinitionAssignment.getAssignedTemplateDefinition(content);
         } catch (RegistrationException e) {
             throw new RenderException("Can't resolve RenderableDefinition for node [" + content + "]", e);
         }
     }
 
     protected Renderer getRendererFor(RenderableDefinition definition) throws RenderException {
         final String renderType = definition.getRenderType();
         if (renderType == null) {
             throw new RenderException("No renderType defined for definition [" + definition + "]");
         }
         try {
             return rendererRegistry.get(renderType);
         } catch (RegistrationException e) {
             throw new RenderException("Can't find renderer [" + renderType + "]", e);
         }
     }
 
     @Override
     public RenderingContext getRenderingContext() {
         return renderingContextProvider.get();
     }
 
 }