/*
    * $Id: ExecuteCommand.java 471754 2006-11-06 14:55:09Z husted $
    *
    * 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.struts.chain.commands;
  
  import org.apache.commons.chain.Catalog;
  import org.apache.commons.chain.CatalogFactory;
  import org.apache.commons.chain.Command;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.struts.chain.contexts.ActionContext;
  import org.apache.struts.config.ActionConfig;
  
  /**
   * <p>Invoke the appropriate <code>Command</code> for this request.  If the
   * context's <code>ActionConfig</code> has no <code>command</code> property
   * defined, no action will be taken.  If the specified command cannot be
   * found, a warning will be logged, but processing will continue.  Depending
   * on how the chain is configured, this can be used in place of an
   * <code>Action</code> or as a method of performing pre-processing. </p>
   *
   * <p>If used instead of an action, the command which is looked up should put
   * an ActionForward into the context, unless it has already dealt with the
   * response.</p>
   *
   * @version $Id: ExecuteCommand.java 471754 2006-11-06 14:55:09Z husted $
   */
  public class ExecuteCommand extends ActionCommandBase {
      // ------------------------------------------------------ Instance Variables
  
      /**
       * Provide Commons Logging instance for this class.
       */
      private static final Log LOG = LogFactory.getLog(ExecuteCommand.class);
  
      // ---------------------------------------------------------- Public Methods
  
      /**
       * <p>If the <code>context</code> is "valid", lookup a command and execute
       * it.</p>
       *
       * @param actionCtx The <code>Context</code> for the current request
       * @return the result of the lookup command's <code>execute</code> method,
       *         if executed, or <code>false</code> if it was not executed.
       * @throws Exception on any error
       */
      public boolean execute(ActionContext actionCtx)
          throws Exception {
          if (shouldProcess(actionCtx)) {
              Command command = getCommand(actionCtx);
  
              if (command != null) {
                  return (command.execute(actionCtx));
              }
          }
  
          return (false);
      }
  
      /**
       * <p>Evaluate the current context to see if a command should even be
       * executed.</p>
       *
       * @param context A valid ActionContext
       * @return TRUE if the pending Command should be executed
       */
      protected boolean shouldProcess(ActionContext context) {
          // Skip processing if the current request is not valid
          Boolean valid = context.getFormValid();
  
          return ((valid != null) && valid.booleanValue());
      }
  
      /**
       * <p>Find the <code>ActionConfig</code> in the current context and, if it
       * is properly configured, lookup the appropriate <code>commons-chain</code>
       * command.</p>
       *
       * @param context A valid ActionContext
       * @return a <code>Command</code> to execute, or null if none is specified
       *         or if the specified command cannot be found.
       */
     protected Command getCommand(ActionContext context) {
         ActionConfig actionConfig = context.getActionConfig();
 
         String commandName = actionConfig.getCommand();
 
         if (commandName == null) {
             return null;
         }
 
         String catalogName = actionConfig.getCatalog();
 
         return getCommand(commandName, catalogName);
     }
 
     /**
      * <p> Retrieve the specified Command from the specified Catalog. </p>
      *
      * @param commandName The Command to retrieve.
      * @param catalogName The Catalog to search.
      * @return Instantiated Command, or null
      */
     protected Command getCommand(String commandName, String catalogName) {
         if (commandName == null) {
             return null;
         }
 
         Catalog catalog;
 
         if (catalogName != null) {
             catalog = CatalogFactory.getInstance().getCatalog(catalogName);
 
             if (catalog == null) {
                 LOG.warn("When looking up " + commandName + ","
                     + " no catalog found under " + catalogName);
 
                 return null;
             }
         } else {
             catalogName = "the default catalog";
             catalog = CatalogFactory.getInstance().getCatalog();
 
             if (catalog == null) {
                 LOG.warn("When looking up " + commandName + ","
                     + " no default catalog found.");
 
                 return null;
             }
         }
 
         if (LOG.isDebugEnabled()) {
             LOG.debug("looking up command " + commandName + " in "
                 + catalogName);
         }
 
         return catalog.getCommand(commandName);
     }
 }