/*

  * 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.any23.rdf;

 import org.slf4j.Logger;

 import org.slf4j.LoggerFactory;

 import java.io.IOException;

 import java.io.InputStream;

 import java.net.URI;

 import java.net.URISyntaxException;

 import java.util.Map;

 import java.util.Properties;

 /**

  * This class act as a container for various well-known and adopted <i>RDF</i> Vocabulary prefixes.

  */

 public class PopularPrefixes {

     private static final Logger logger = LoggerFactory.getLogger(PopularPrefixes.class);

     private static final String RESOURCE_NAME = "/org/apache/any23/prefixes/prefixes.properties";

     private static Prefixes popularPrefixes = getPrefixes();

     private static Prefixes getPrefixes() {

         Prefixes prefixes = new Prefixes();

         Properties properties = new Properties();

         try {

             logger.info(String.format("Loading prefixes from %s", RESOURCE_NAME));

             properties.load(getResourceAsStream());

         } catch (IOException e) {

             logger.error(String.format("Error while loading prefixes from %s", RESOURCE_NAME), e);

             throw new RuntimeException(String.format("Error while loading prefixes from %s", RESOURCE_NAME));

         }

         popularPrefixes = new Prefixes();

         for (Map.Entry entry : properties.entrySet()) {

             if (testURICompliance((String) entry.getValue())) {

                 prefixes.add(

                         (String) entry.getKey(),

                         (String) entry.getValue()

                 );

             } else {

                 logger.warn(String.format("Prefixes entry '%s' is not a well-formad URI. Skipped.", entry.getValue()));

             }

         }

         return prefixes;

     }

     /**

      * This method perform a prefix lookup. Given a set of prefixes it returns {@link Prefixes} bag

      * class containing them.

      *

      * @param prefixes the input prefixes where perform the lookup

      * @return a {@link Prefixes} containing all the prefixes mathing the input parameter

      */

     public static Prefixes createSubset(String... prefixes) {

         return popularPrefixes.createSubset(prefixes);

     }

     /**

      * @return a {@link Prefixes} with a set of well-known prefixes

      */

     public static Prefixes get() {

         return popularPrefixes;

     }

     /**

      * Checks the compliance of the <i>URI</i>.

      *

      * @param stringUri the string of the URI to be checked

      * @return <code>true</code> if <i> stringUri</i> is a valid URI,

      *         <code>false</code> otherwise.

      */

     private static boolean testURICompliance(String stringUri) {

         try {

             new URI(stringUri);

         } catch (URISyntaxException e) {

             return false;

         }

         return true;

     }

     /**

       * Loads the prefixes list configuration file.

       *

       * @return the input stream containing the configuration.

       */

      private static InputStream getResourceAsStream() {

          InputStream result;

          result = PopularPrefixes.class.getResourceAsStream(RESOURCE_NAME);

          if (result == null) {

              result = PopularPrefixes.class.getClassLoader().getResourceAsStream(RESOURCE_NAME);

              if (result == null) {

                  result = ClassLoader.getSystemResourceAsStream(RESOURCE_NAME);

              }

          }

          return result;

      }

 }