/*
    * Copyright 2012-2013 smartics, Kronseder & Reiner GmbH
    *
    * Licensed 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 de.smartics.properties.impl.config.ds;
  
  import java.io.BufferedInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Serializable;
  import java.net.URL;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.List;
  import java.util.Properties;
  
  import org.apache.commons.io.IOUtils;
  
  import de.smartics.properties.api.config.ds.DataSourceConfiguration;
  import de.smartics.properties.api.core.domain.PropertiesContext;
  
  /**
   * Responsible to read configuration properties to connect to a data source
   * stored via JNDI.
   */
  public class DataSourceConfigurationPropertiesLoader implements Serializable
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    /**
     * The class version identifier.
     * <p>
     * The value of this constant is {@value}.
     * </p>
     */
    private static final long serialVersionUID = 1L;
  
    /**
     * The location within the classpath to find the configuration file to load.
     */
    public static final String CLASSPATH_LOCATION =
        PropertiesContext.BOOT_PROPERTIES_HOME + "/datasource.properties";
  
    // --- members --------------------------------------------------------------
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     */
    public DataSourceConfigurationPropertiesLoader()
    {
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
  
    // --- init -----------------------------------------------------------------
  
    // --- get&set --------------------------------------------------------------
  
    // --- business -------------------------------------------------------------
  
    /**
     * Loads the data source configuration.
     *
     * @return the data source configuration.
     * @throws IllegalStateException if the configuration cannot be loaded.
     */
    public DataSourceConfiguration load() throws IllegalStateException
    {
      try
      {
        final Properties properties = loadProperties();
  
        final DataSourceConfiguration config =
            new DataSourceConfiguration(properties);
        return config;
      }
      catch (final IOException e)
      {
        throw new IllegalStateException(
            String.format("Cannot configure the access to a data source: %s",
               e.getMessage(), e));
     }
   }
 
   private Properties loadProperties() throws IOException, IllegalStateException
   {
     final Enumeration<URL> urlsEnum =
         Thread.currentThread().getContextClassLoader()
             .getResources(CLASSPATH_LOCATION);
     final List<URL> urls = Collections.list(urlsEnum);
     final int count = urls.size();
     if (count == 1)
     {
       final URL url = urls.get(0);
       final Properties properties = new Properties();
       final InputStream in = new BufferedInputStream(url.openStream());
       try
       {
         properties.load(in);
       }
       finally
       {
         IOUtils.closeQuietly(in);
       }
       properties.setProperty(DataSourceConfiguration.CONFIG_SOURCE_ID,
           url.toExternalForm());
       return properties;
     }
     else if (count == 0)
     {
       throw new IllegalStateException(String.format(
           "Cannot find '%s' to configure the access to a data source.",
           CLASSPATH_LOCATION));
     }
     else
     {
       throw new IllegalStateException(
           String
               .format(
                   "Found more than one configuration for '%s' to access a data source: %s",
                   CLASSPATH_LOCATION, urls));
     }
   }
 
   // --- object basics --------------------------------------------------------
 
 }