/*
    * 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.myfaces.custom.requestParameterProvider;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  import java.io.IOException;
  import java.io.ObjectStreamException;
  import java.io.Serializable;
  
  import javax.faces.context.FacesContext;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /**
   * @author Thomas Obereder
   * @version 27.04.2006 22:42:32
   */
  public class RequestParameterProviderManager implements Serializable
  {
      private static final Log LOG = LogFactory.getLog(RequestParameterProviderManager.class);
  
      private static final String PAGE_PARAMETER_SEP = "?";
      private static final String PARAMETER_SEP = "&";
      private static final String PARAMETER_PROVIDER_MANAGER_KEY = "org.apache.myfaces.RequestParameterProviderManager";
  
      private List providers;
  
  
      private RequestParameterProviderManager()
      {
          providers = new ArrayList();
      }
  
      public static RequestParameterProviderManager getInstance()
      {
          FacesContext context = FacesContext.getCurrentInstance();
          if (context == null)
          {
              throw new IllegalStateException("no faces context available!");
          }
          return getInstance(context);
      }
  
      public static RequestParameterProviderManager getInstance(FacesContext context)
      {
          RequestParameterProviderManager manager =
                  (RequestParameterProviderManager) context.getExternalContext().getSessionMap().get(PARAMETER_PROVIDER_MANAGER_KEY);
  
          if (manager == null)
          {
              manager = new RequestParameterProviderManager();
              context.getExternalContext().getSessionMap().put(PARAMETER_PROVIDER_MANAGER_KEY, manager);
          }
  
          return manager;
      }
  
  
      /**
       * Register the given provider.
       * @param provider the provider to register.
       */
  
      public void register(RequestParameterProvider provider)
      {
          if(provider == null)
              LOG.warn("RequestParameterProvider is null -> no registration!");
          else
              this.providers.add(provider);
      }
  
  
      /**
       * Encode all fields of all providers, and attach the name-value pairs to url.
       * @param url the URL to which the fields should be attached.
       * @return the url after attaching all fields.
       */
  
      public String encodeAndAttachParameters(String url)
     {
             if (!isFilterCalled())
             {
                 throw new IllegalStateException("RequestParameterServletFilter not called. Please configure the filter " + RequestParameterServletFilter.class.getName() + " in your web.xml to cover your faces requests.");
             }
 
         StringBuffer sb = new StringBuffer();
         if(url == null)
         {
             LOG.warn("URL is null -> empty string is returned.");
             return sb.toString();
         }
 
         int nuofParams = -1;
         String firstSeparator = url.indexOf(PAGE_PARAMETER_SEP) == -1 ? PAGE_PARAMETER_SEP : PARAMETER_SEP;
         sb.append(url);
         for (Iterator it = providers.iterator(); it.hasNext();)
         {
             RequestParameterProvider provider = (RequestParameterProvider) it.next();
             String[] fields = provider.getFields();
             if (fields == null)
             {
                 continue;
             }
             for (int i = 0; i < fields.length; i++)
             {
                 nuofParams++;
 
                 sb.append(nuofParams == 0 ? firstSeparator : PARAMETER_SEP);
                 sb.append(fields[i]);
                 sb.append("=");
                 sb.append(provider.getFieldValue(fields[i]));
             }
         }
         return sb.toString();
     }
 
 
     /**
      * Check if there are any providers registered.
      * @return true, if the list is not null and not empty.
      */
     public boolean hasProviders()
     {
         return this.providers != null && !this.providers.isEmpty();
     }
 
     public boolean isFilterCalled()
     {
         FacesContext context = FacesContext.getCurrentInstance();
         if (context == null)
         {
             throw new IllegalStateException("no faces context available!");
         }
 
         return Boolean.TRUE.equals(context.getExternalContext().getRequestMap().get(RequestParameterServletFilter.REQUEST_PARAM_FILTER_CALLED));
     }
 
     private void writeObject(java.io.ObjectOutputStream out) throws IOException
     {
         // the conversation manager is not (yet) serializable, we just implement it
         // to make it work with distributed sessions
     }
 
     private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException
     {
         // nothing written, so nothing to read
     }
 
     private Object readResolve() throws ObjectStreamException
     {
         // do not return a real object, that way on first request a new manager will be created
         return null;
     }
 }