/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you 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://opensource.org/licenses/ecl2.txt
   *
   * 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.opencastproject.index.service.catalog.adapter;
  
  import static java.lang.String.format;
  import static org.apache.commons.lang3.StringUtils.isBlank;
  
  import org.opencastproject.util.ConfigurationException;
  import org.opencastproject.util.XmlNamespaceContext;
  
  import java.util.Dictionary;
  import java.util.Enumeration;
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * This class parses a catalog UI adapter configuration and provides convenience access methods.
   */
  public final class CatalogUIAdapterConfiguration {
  
    /* Configuration keys */
    public static final String KEY_XML_ROOT_ELEMENT_NAME = "xml.rootElement.name";
    public static final String KEY_XML_ROOT_ELEMENT_NS_URI = "xml.rootElement.namespace.URI";
    public static final String XML_BINDING_KEY_PREFIX = "xml.namespaceBinding.";
    public static final String XML_BINDING_URI_SUFFIX = ".URI";
    public static final String XML_BINDING_PREFIX_SUFFIX = ".prefix";
  
    /** The raw configuration properties */
    private final Dictionary<String, ?> configProperties;
  
    /** The xml namespace binding context */
    private XmlNamespaceContext xmlNSContext;
  
    /**
     * Load configuration from a dictionary.
     *
     * @param properties
     *          The configuration properties
     * @return The parsed configuration as {@link CatalogUIAdapterConfiguration} instance
     * @throws ConfigurationException
     *           If the configuration has any errors
     */
    public static CatalogUIAdapterConfiguration loadFromDictionary(Dictionary<String, ?> properties)
            throws ConfigurationException {
      return new CatalogUIAdapterConfiguration(properties);
    }
  
    private CatalogUIAdapterConfiguration(Dictionary<String, ?> properties) throws ConfigurationException {
      this.configProperties = properties;
      loadXmlNSContext();
      validate();
    }
  
    /**
     * Validates the configuration and throws a {@link ConfigurationException} if there is any error.
     *
     * @throws ConfigurationException
     *           if the configuration is not valid
     */
    private void validate() throws ConfigurationException {
      if (configProperties.get(KEY_XML_ROOT_ELEMENT_NAME) == null) {
        throw new ConfigurationException(format(
            "Value for configuration key '%s' is missing", KEY_XML_ROOT_ELEMENT_NAME));
      }
  
      if (configProperties.get(KEY_XML_ROOT_ELEMENT_NS_URI) == null) {
        throw new ConfigurationException(format(
            "Value for configuration key '%s' is missing", KEY_XML_ROOT_ELEMENT_NS_URI));
      }
  
      if (xmlNSContext.getPrefix(getCatalogXmlRootNamespace()) == null) {
        throw new ConfigurationException(format(
            "Binding for XML namespace URI '%s' is missing", getCatalogXmlRootNamespace()));
      }
    }
  
    /**
     * Load the XML namespace bindings from the configuration and build the XML namespace context.
     */
    private void loadXmlNSContext() {
     final Enumeration<String> keys = configProperties.keys();
     final Map<String, String> prefixToUri = new HashMap<String, String>();
     while (keys.hasMoreElements()) {
       final String key = keys.nextElement();
       if (key.startsWith(XML_BINDING_KEY_PREFIX)) {
         // First, we need to get the name of the binding
         final String nsBindingName = getXmlBindingNameFromConfigKey(key);
         // Once we have the name, we're able to retrieve the URI as well as the prefix
         final String nsUri = (String) configProperties
                 .get(XML_BINDING_KEY_PREFIX + nsBindingName + XML_BINDING_URI_SUFFIX);
         final String nsPrefix = (String) configProperties
                 .get(XML_BINDING_KEY_PREFIX + nsBindingName + XML_BINDING_PREFIX_SUFFIX);
         // Check if URI and the prefix have valid values
         if (isBlank(nsUri)) {
           throw new ConfigurationException(format("No URI for namespace binding '%s' found", nsBindingName));
         }
         if (nsPrefix == null) {
           throw new ConfigurationException(format("No prefix for namespace binding '%s' found", nsBindingName));
         }
         // Add prefix & URI to the intermediate map
         prefixToUri.put(nsPrefix, nsUri);
       }
     }
 
     xmlNSContext = new XmlNamespaceContext(prefixToUri);
   }
 
   /**
    * Get the name of an XML namespace binding by one of its configuration keys.
    *
    * @param key
    *          the key name
    * @return the XML namespace binding name
    */
   private static String getXmlBindingNameFromConfigKey(final String key) {
     if (isBlank(key) || !key.startsWith(XML_BINDING_KEY_PREFIX)) {
       throw new IllegalArgumentException(format("The given key '%s' is not part of a XML binding definition", key));
     }
     final String keyWithoutPrefix = key.substring(XML_BINDING_KEY_PREFIX.length());
     return keyWithoutPrefix.substring(0, keyWithoutPrefix.indexOf("."));
   }
 
   /**
    * Return the value of the configuration property {@link CatalogUIAdapterConfiguration#KEY_XML_ROOT_ELEMENT_NAME}
    */
   public String getCatalogXmlRootElementName() {
     return (String) configProperties.get(KEY_XML_ROOT_ELEMENT_NAME);
   }
 
   /**
    * Return the value of the configuration property {@link CatalogUIAdapterConfiguration#KEY_XML_ROOT_ELEMENT_NS_URI}
    */
   public String getCatalogXmlRootNamespace() {
     return (String) configProperties.get(KEY_XML_ROOT_ELEMENT_NS_URI);
   }
 
   /**
    * Returns the XML namespace context that could be built out of the configuration.
    */
   public XmlNamespaceContext getXmlNamespaceContext() {
     return xmlNSContext;
   }
 
 }