/*
    * Copyright 2007-2008 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.ken.util;
  
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.Map;
  
  import javax.xml.namespace.NamespaceContext;
  
  import org.apache.log4j.Logger;
  
  /**
   * XPath NamespaceContext that is configured with a predefined prefix->NS map.
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class ConfiguredNamespaceContext implements NamespaceContext {
      private static final Logger LOG = Logger.getLogger(ConfiguredNamespaceContext.class);
  
      private Map<String, String> prefixToNamespace = new HashMap<String, String>();
      private Map<String, HashSet<String>> namespaceToPrefix = new HashMap<String, HashSet<String>>();
  
      /**
       * Constructs a ConfiguredNamespaceContext.java.
       * @param prefixToNamespace
       */
      public ConfiguredNamespaceContext(Map<String, String> prefixToNamespace) {
          this.prefixToNamespace = prefixToNamespace;
          // create a reverse namespace to prefix(es) map
          for (Map.Entry<String, String> entry: prefixToNamespace.entrySet()) {
              String namespace = entry.getValue();
              String prefix = entry.getKey();
              HashSet<String> prefixes = namespaceToPrefix.get(namespace);
              if (prefixes == null) {
                  prefixes = new HashSet<String>(4);
                  namespaceToPrefix.put(namespace, prefixes);
              }
              prefixes.add(prefix);
          }
      }
  
      /**
       * @see javax.xml.namespace.NamespaceContext#getNamespaceURI(java.lang.String)
       */
      public String getNamespaceURI(String prefix) {
          //LOG.trace("getNamespaceURI(" + prefix + ")");
          if (prefix == null) {
              throw new IllegalArgumentException("The prefix cannot be null.");
          }
  
          return prefixToNamespace.get(prefix);
      }
  
      /**
       * @see javax.xml.namespace.NamespaceContext#getPrefix(java.lang.String)
       */
      public String getPrefix(String namespaceURI) {
          //LOG.trace("getPrefix(" + namespaceURI + ")");
          if (namespaceURI == null) {
              throw new IllegalArgumentException("The namespace uri cannot be null.");
          }
          Iterator<String> prefixes = getPrefixes(namespaceURI);
          if (prefixes != null) {
              return prefixes.next();
          } else {
              return null;
          }
      }
  
      /**
       * @see javax.xml.namespace.NamespaceContext#getPrefixes(java.lang.String)
       */
      public Iterator<String> getPrefixes(String namespaceURI) {
          //LOG.trace("getPrefixes(" + namespaceURI + ")");
          if (namespaceURI == null) {
              throw new IllegalArgumentException("The namespace uri cannot be null.");
          }
  
          HashSet<String> prefixes = namespaceToPrefix.get(namespaceURI);
          if (prefixes != null && prefixes.size() > 0) {
              return prefixes.iterator();
          } else {
              return null;
          }
      }
 }