/*
    * Copyright 2007-2008 Volker Fritzsch
    *
    * 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 motej;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Properties;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * 
   * <p>
   * @author <a href="mailto:vfritzsch@users.sourceforge.net">Volker Fritzsch</a>
   */
  public class ExtensionProvider {
  	
  	private static Map<String, Class<? extends Extension>> lookup;
  	
  	private Logger log = LoggerFactory.getLogger(ExtensionProvider.class);
  	
  	@SuppressWarnings("unchecked")
  	public ExtensionProvider() {
  		synchronized(ExtensionProvider.class) {
  			if (lookup == null) {
  				log.debug("Initializing lookup.");
  				lookup = new HashMap<String, Class<? extends Extension>>();
  				InputStream in = ExtensionProvider.class.getResourceAsStream("/motejx/extensions/extensions.properties");
  				Properties props = new Properties();
  				
  				if (in == null) {
  					log.info("no extensions.properties found. as a result, no extensions will be available.");
  					return;
  				}
  				
  				try {
  					props.load(in);
  					for (Object o : props.keySet()) {
  						String key = (String) o;
  						String value = props.getProperty(key);
  						
  						if (log.isDebugEnabled()) {
  							log.debug("Adding extension (" + key + " / " + value + ").");
  						}
  						
  						Class<? extends Extension> clazz = (Class<? extends Extension>) Class.forName(value);
  						lookup.put(key, clazz);
  					}
  				} catch (IOException ex) {
  					log.warn(ex.getMessage(), ex);
  				} catch (ClassNotFoundException ex) {
  					log.warn(ex.getMessage(), ex);
  				}
  			}
  		}
  		log.debug("Lookup initialized.");
  	}
  	
  	public Extension getExtension(byte[] id) {
  		String id0 = Integer.toHexString(id[0] & 0xff);
  		if (id0.length() == 1) {
  			id0 = "0" + id0;
  		}
  		String id1 = Integer.toHexString(id[1] & 0xff);
  		if (id1.length() == 1) {
  			id1 = "0" + id1;
  		}
  		String key = id0 + id1;
  		Class<? extends Extension> clazz = lookup.get(key);
  		
  		if (clazz == null) {
  			log.warn("No matching extension found for key: " + key);
  			return null;
  		}
  		
  		Extension extension = null;
  		try {
  			extension = clazz.newInstance();
  		} catch (InstantiationException ex) {
  			log.error(ex.getMessage(), ex);
  		} catch (IllegalAccessException ex) {
  			log.error(ex.getMessage(), ex);
  		}
 		return extension;
 	}
 }