/*
    * $Id: CachingTilesContainer.java 1045365 2010-12-13 20:46:46Z apetrelli $
    *
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.apache.tiles.impl.mgmt;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.tiles.Definition;
  import org.apache.tiles.TilesContainer;
  import org.apache.tiles.TilesContainerWrapper;
  import org.apache.tiles.definition.NoSuchDefinitionException;
  import org.apache.tiles.mgmt.MutableTilesContainer;
  import org.apache.tiles.request.Request;
  
  /**
   * Manages custom and configured definitions, so they can be used by the
   * container, instead of using a simple {@link org.apache.tiles.definition.DefinitionsFactory}.
   *
   * @version $Rev: 1045365 $ $Date: 2010-12-14 07:46:46 +1100 (Tue, 14 Dec 2010) $
   */
  public class CachingTilesContainer extends TilesContainerWrapper implements MutableTilesContainer {
  
      /**
       * The default name of the attribute in which storing custom definitions.
       */
      private static final String DEFAULT_DEFINITIONS_ATTRIBUTE_NAME =
          "org.apache.tiles.impl.mgmt.DefinitionManager.DEFINITIONS";
  
      /**
       * The name of the attribute in which storing custom definitions.
       */
      private String definitionsAttributeName;
  
      /**
       * Constructor.
       * @param originalContainer The original container to wrap.
       */
      public CachingTilesContainer(TilesContainer originalContainer) {
          super(originalContainer);
          definitionsAttributeName = DEFAULT_DEFINITIONS_ATTRIBUTE_NAME;
      }
  
      /**
       * Constructor.
       * @param originalContainer The original container to wrap.
       * @param definitionsAttributeName The name of the attribute in which
       * storing custom definitions.
       */
      public CachingTilesContainer(TilesContainer originalContainer, String definitionsAttributeName) {
          super(originalContainer);
          this.definitionsAttributeName = definitionsAttributeName;
          if (this.definitionsAttributeName == null) {
              this.definitionsAttributeName = DEFAULT_DEFINITIONS_ATTRIBUTE_NAME;
          }
      }
  
      /**
       * Returns a definition by name.
       *
       * @param definition The name of the definition.
       * @param request The current request.
       * @return The requested definition, either main or custom.
       * @throws org.apache.tiles.definition.DefinitionsFactoryException If
       * something goes wrong when obtaining a main definition.
       */
      public Definition getDefinition(String definition,
              Request request) {
          Definition retValue = null;
          retValue = getCustomDefinition(definition, request);
          if (retValue == null) {
              retValue = super.getDefinition(definition, request);
          }
          return retValue;
      }
  
      /** {@inheritDoc} */
      @Override
      public boolean isValidDefinition(String definition, Request request) {
          if (getCustomDefinition(definition, request) != null) {
              return true;
          }
         return super.isValidDefinition(definition, request);
     }
 
     /** {@inheritDoc} */
     @Override
     public void register(Definition definition, Request request) {
         Map<String, Definition> definitions = getOrCreateDefinitions(request);
         if (definition.getName() == null) {
             definition.setName(getNextUniqueDefinitionName(definitions));
         }
 
         if (definition.isExtending()) {
             this.resolveInheritance(definition, request);
         }
 
         definitions.put(definition.getName(), definition);
     }
 
     /** {@inheritDoc} */
     @Override
     public void render(String definition, Request request) {
         Definition toRender = getDefinition(definition, request);
         if (toRender == null) {
             throw new NoSuchDefinitionException(
                     "Cannot find definition named '" + definition + "'");
         }
         super.render(toRender, request);
     }
 
     /**
      * Resolve inheritance.
      * First, resolve parent's inheritance, then set template to the parent's
      * template.
      * Also copy attributes set in parent, and not set in child
      * If instance doesn't extend anything, do nothing.
      *
      * @param definition The definition that needs to have its inheritances
      * resolved.
      * @param request The current request.
      * @throws org.apache.tiles.definition.DefinitionsFactoryException If an
      * inheritance can not be solved.
      */
     private void resolveInheritance(Definition definition,
             Request request) {
         // Already done, or not needed ?
         if (!definition.isExtending()) {
             return;
         }
 
         String parentDefinitionName = definition.getExtends();
 
         boolean recurse = true;
         Definition parent = getCustomDefinition(parentDefinitionName, request);
         if (parent == null) {
             parent = container.getDefinition(parentDefinitionName, request);
             recurse = false;
         }
 
         if (parent == null) {
             throw new NoSuchDefinitionException(
                     "Error while resolving definition inheritance: child '"
                             + definition.getName()
                             + "' can't find its ancestor '"
                             + parentDefinitionName
                             + "'. Please check your description file.");
         }
 
         // Resolve parent before itself.
         if (recurse) {
             resolveInheritance(parent, request);
         }
         definition.inherit(parent);
     }
 
     /**
      * Returns the map with custom definitions for the current request.
      *
      * @param request The current request.
      * @return A map that connects a definition name to a definition.
      */
     @SuppressWarnings("unchecked")
     private Map<String, Definition> getDefinitions(
             Request request) {
         return (Map<String, Definition>) request.getContext("request")
                 .get(definitionsAttributeName);
     }
 
     /**
      * Returns a map of type "definition name -> definition" and, if it has not
      * been defined before, creates one.
      *
      * @param request The current request.
      * @return A map that connects a definition name to a definition.
      */
     @SuppressWarnings("unchecked")
     private Map<String, Definition> getOrCreateDefinitions(
             Request request) {
         Map<String, Definition> definitions =
             (Map<String, Definition>) request.getContext("request").get(definitionsAttributeName);
         if (definitions == null) {
             definitions = new HashMap<String, Definition>();
             request.getContext("request")
                     .put(definitionsAttributeName, definitions);
         }
 
         return definitions;
     }
 
     /**
      * Create a unique definition name usable to store anonymous definitions.
      *
      * @param definitions The already created definitions.
      * @return The unique definition name to be used to store the definition.
      * @since 2.1.0
      */
     private String getNextUniqueDefinitionName(
             Map<String, Definition> definitions) {
         String candidate;
         int anonymousDefinitionIndex = 1;
 
         do {
             candidate = "$anonymousMutableDefinition" + anonymousDefinitionIndex;
             anonymousDefinitionIndex++;
         } while (definitions.containsKey(candidate));
 
         return candidate;
     }
 
     /**
      * Returns a custom definition from the cache.
      *
      * @param definition The definition to search.
      * @param request The request.
      * @return The requested definition.
      */
     private Definition getCustomDefinition(String definition, Request request) {
         Map<String, Definition> definitions = getDefinitions(request);
         if (definitions != null) {
             return definitions.get(definition);
         }
         return null;
     }
 }