/*
    * 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.spi.config.cache;
  
  import static de.smartics.properties.api.config.cache.CacheConfiguration.CACHE_ID;
  import static de.smartics.properties.api.config.cache.CacheConfiguration.CACHE_NAME;
  import static de.smartics.properties.api.config.cache.CacheConfiguration.JNDI_NAME;
  
  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 org.apache.commons.lang.StringUtils;
  
  import de.smartics.properties.api.config.cache.CacheConfiguration;
  import de.smartics.properties.api.core.domain.PropertiesContext;
  
  /**
   * Responsible to read configuration properties to connect to a cache stored via
   * JNDI.
   */
  public class CacheConfigurationPropertiesLoader 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 + "/cache.properties";
  
    // --- members --------------------------------------------------------------
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     */
    public CacheConfigurationPropertiesLoader()
    {
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
  
    // --- init -----------------------------------------------------------------
  
    // --- get&set --------------------------------------------------------------
  
    // --- business -------------------------------------------------------------
  
    /**
     * Loads the cache configuration from the classpath.
     *
     * @return the cache configuration.
     * @throws CacheException on any problem loading the cache.
     * @throws IllegalStateException if the configuration files cannot be found on
     *           the classpath.
     */
    public CacheConfiguration load() throws CacheException, IllegalStateException
    {
      try
      {
        final Properties properties = loadProperties();
        check(properties);
        final CacheConfiguration config = new CacheConfiguration(properties);
       return config;
     }
     catch (final IOException e)
     {
       throw new CacheException(CacheMessageBean.configFailure(e,
           CLASSPATH_LOCATION));
     }
   }
 
   private void check(final Properties properties) throws CacheException
   {
     checkProperty(properties, JNDI_NAME);
     checkProperty(properties, CACHE_NAME);
   }
 
   private void checkProperty(final Properties properties, final String key)
   {
     final String cacheName = properties.getProperty(key);
     if (StringUtils.isBlank(cacheName))
     {
       throw new CacheException(CacheMessageBean.missingProperty(
           CLASSPATH_LOCATION, key));
     }
   }
 
   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(CACHE_ID, url.toString());
 
       return properties;
     }
     else if (count == 0)
     {
       throw new IllegalStateException(String.format(
           "Cannot find '%s' to configure the access to a cache.",
           CLASSPATH_LOCATION));
     }
     else
     {
       throw new IllegalStateException(String.format(
           "Found more than one configuration for '%s' to access a cache: %s",
           CLASSPATH_LOCATION, urls));
     }
   }
 
   // --- object basics --------------------------------------------------------
 
 }