/*
    * 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.maven.shared.model.fileset.mappers;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.Properties;
  
  import org.apache.maven.shared.model.fileset.Mapper;
  
  /**
   * Element to define a FileNameMapper.
   */
  public final class MapperUtil {
      private static final String MAPPER_PROPERTIES = "mappers.properties";
  
      private static Properties implementations;
  
      private MapperUtil() {
          // nop
      }
  
      /**
       * Initializes a properties object to store the built-in classnames.
       */
      private static void initializeBuiltIns() {
          if (implementations == null) {
              Properties props = new Properties();
  
              ClassLoader cloader = Thread.currentThread().getContextClassLoader();
  
              try (InputStream stream = cloader.getResourceAsStream(MAPPER_PROPERTIES)) {
                  if (stream == null) {
                      throw new IllegalStateException("Cannot find classpath resource: " + MAPPER_PROPERTIES);
                  }
  
                  props.load(stream);
                  implementations = props;
              } catch (IOException e) {
                  throw new IllegalStateException("Cannot find classpath resource: " + MAPPER_PROPERTIES);
              }
          }
      }
  
      /**
       * Returns a fully configured FileNameMapper implementation.
       *
       * @param mapper {@link Mapper}
       * @return {@link FileNameMapper}
       * @throws MapperException in case of an error
       */
      public static FileNameMapper getFileNameMapper(Mapper mapper) throws MapperException {
          if (mapper == null) {
              return null;
          }
  
          initializeBuiltIns();
  
          String type = mapper.getType();
          String classname = mapper.getClassname();
  
          if (type == null && classname == null) {
              throw new MapperException("nested mapper or " + "one of the attributes type or classname is required");
          }
  
          if (type != null && classname != null) {
              throw new MapperException("must not specify both type and classname attribute");
          }
          if (type != null) {
              classname = implementations.getProperty(type);
          }
  
          try {
              FileNameMapper m = (FileNameMapper) Thread.currentThread()
                      .getContextClassLoader()
                      .loadClass(classname)
                      .newInstance();
  
              m.setFrom(mapper.getFrom());
              m.setTo(mapper.getTo());
  
              return m;
          } catch (ClassNotFoundException e) {
             throw new MapperException("Cannot find mapper implementation: " + classname, e);
         } catch (InstantiationException | IllegalAccessException e) {
             throw new MapperException("Cannot load mapper implementation: " + classname, e);
         }
     }
 }