/**
    * Copyright 2005-2012 The Kuali Foundation
    *
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    *
   * 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.kuali.rice.krad.messages;
  
  import org.apache.commons.lang.StringUtils;
  import org.kuali.rice.coreservice.framework.CoreFrameworkServiceLocator;
  import org.kuali.rice.krad.util.KRADConstants;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  
  /**
   * Implementation of the {@link MessageService} that allows {@link MessageProvider} implementations
   * to be configured for exposing external message repositories
   *
   * <p>
   * This message service implementation essentially delegates all calls down to one or more message
   * providers. When more than one message provider is configured, providers higher up in the chain will
   * receive priority. That is, when finding a message the first provider that has the message will be used
   * and no others will be consulted. When finding a collection of messages, if the same message (key) exists
   * from more than one provider, the message from the first encountered provider (in the List) will
   * be used.
   * </p>
   *
   * <p>
   * The default namespace and component are constants of the service implementation and may not be changed.
   * </p>
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class MessageServiceImpl implements MessageService {
      private static org.apache.log4j.Logger LOG = org.apache.log4j.Logger.getLogger(MessageServiceImpl.class);
  
      private List<MessageProvider> messageProviders;
  
      /**
       * @see MessageService#getMessage(java.lang.String, java.lang.String, java.lang.String)
       */
      public Message getMessage(String namespace, String component, String key) {
          return getMessage(namespace, component, key, getDefaultLocaleCode());
      }
  
      /**
       * @see MessageService#getMessage(java.lang.String, java.lang.String, java.lang.String)
       */
      public Message getMessage(String namespace, String component, String key, String locale) {
          Message message = null;
  
          // use default namespace and component if not given
          if (StringUtils.isBlank(namespace)) {
              namespace = DEFAULT_NAMESPACE_CODE;
          }
  
          if (StringUtils.isBlank(component)) {
              component = DEFAULT_COMPONENT_CODE;
          }
  
          if (StringUtils.isBlank(locale)) {
              locale = getDefaultLocaleCode();
          }
  
          for (MessageProvider provider : messageProviders) {
              message = provider.getMessage(namespace, component, key, locale);
  
              if (message != null) {
                  // don't check with any additional providers
                  break;
              }
          }
  
          return message;
      }
  
      /**
       * @see MessageService#getMessageText(java.lang.String, java.lang.String, java.lang.String)
       */
      public String getMessageText(String namespace, String component, String key) {
          return getMessageText(namespace, component, key, getDefaultLocaleCode());
      }
  
      /**
       * @see MessageService#getMessageText(java.lang.String, java.lang.String, java.lang.String)
       */
      public String getMessageText(String namespace, String component, String key, String locale) {
          Message message = getMessage(namespace, component, key, locale);
         if (message != null) {
             return message.getText();
         }
 
         return null;
     }
 
     /**
      * @see MessageService#getMessageText(java.lang.String, java.lang.String, java.lang.String)
      */
     public String getMessageText(String key) {
         return getMessageText(key, getDefaultLocaleCode());
     }
 
     /**
      * @see MessageService#getMessageText(java.lang.String, java.lang.String, java.lang.String)
      */
     public String getMessageText(String key, String locale) {
         Message message = getMessage(null, null, key, locale);
         if (message != null) {
             return message.getText();
         }
 
         return null;
     }
 
     /**
      * @see MessageService#getAllMessagesForComponent(java.lang.String, java.lang.String)
      */
     public Collection<Message> getAllMessagesForComponent(String namespace, String component) {
         return getAllMessagesForComponent(namespace, component, getDefaultLocaleCode());
     }
 
     /**
      * @see MessageService#getAllMessagesForComponent(java.lang.String, java.lang.String)
      */
     public Collection<Message> getAllMessagesForComponent(String namespace, String component, String locale) {
         Collection<Message> messages = new ArrayList<Message>();
 
         if (StringUtils.isBlank(locale)) {
             locale = getDefaultLocaleCode();
         }
 
         for (MessageProvider provider : messageProviders) {
             Collection<Message> providerMessages = provider.getAllMessagesForComponent(namespace, component, locale);
             mergeMessages(messages, providerMessages);
         }
 
         return messages;
     }
 
     /**
      * Merges the second collection into the first collection
      *
      * <p>
      * If a message with the same key (namespace, component, and name) is found in both collections, the message
      * from first collection will remain. That is, the message in the second collection will NOT override
      * </p>
      *
      * @param messages collection to be merged into
      * @param messagesToMerge collection that will be merged with first
      */
     protected void mergeMessages(Collection<Message> messages, Collection<Message> messagesToMerge) {
         for (Message message : messagesToMerge) {
             if (!messages.contains(message)) {
                 messages.add(message);
             }
         }
     }
 
     /**
      * Retrieves the default locale code configured through a system parameter
      *
      * @return String configured default locale
      */
     protected String getDefaultLocaleCode() {
         return CoreFrameworkServiceLocator.getParameterService().getParameterValueAsString(KRADConstants.KNS_NAMESPACE,
                 KRADConstants.DetailTypes.ALL_DETAIL_TYPE, KRADConstants.ParameterNames.DEFAULT_LOCALE_CODE);
     }
 
     /**
      * Retrieves the collection of message providers configured with the message service
      *
      * @return List<MessageProvider> message provider implementations
      */
     protected List<MessageProvider> getMessageProviders() {
         return messageProviders;
     }
 
     /**
      * Setter for the collection of message providers that should be used by the message service
      * implementation
      *
      * @param messageProviders
      */
     public void setMessageProviders(List<MessageProvider> messageProviders) {
         this.messageProviders = messageProviders;
     }
 }