package ejava.util.jndi;
   
   import java.io.IOException;
   import java.io.InputStream;
   import java.util.Properties;
   
   import javax.naming.Context;
   import javax.naming.InitialContext;
   import javax.naming.NameClassPair;
  import javax.naming.NamingEnumeration;
  import javax.naming.NamingException;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * This class helps work with the JNDI tree.
   */
  public class JNDIUtil {
  	private static final Logger logger = LoggerFactory.getLogger(JNDIUtil.class);
  	public static final String PROPERTY_FILE="ejava-jndi.properties";
  	private static final String[] PATHS = new String[]{
  		"/" + PROPERTY_FILE, PROPERTY_FILE
  	};
  	
  	/**
  	 * This method will return a jndi.properties object that is based on the
  	 * properties found in ejava-jndi.properties that start with the provided
  	 * prefix. This method is useful when examples are using different JNDI
  	 * mechanisms and want to keep them separate by forming the jndi.properties
  	 * in memory.
  	 * @param prefix
  	 * @return Properties object that can be used during a new InitialContext(env)
  	 * @throws IOException
  	 */
      public static Properties getJNDIProperties(String prefix) throws IOException {
      	InputStream is = null;
      	for (int i=0; is==null && i<PATHS.length; i++) {
      		logger.debug("trying: " + PATHS[i]);
      		is = JNDIUtil.class.getResourceAsStream(PATHS[i]);
      	}
      	for (int i=0; is==null && i<PATHS.length; i++) {
      		logger.debug("trying loader for thread: " + PATHS[i]);
      		is = Thread.currentThread().getContextClassLoader().getResourceAsStream(PATHS[i]);
      	}
      	
      	Properties env = new Properties();
      	if (is!=null) {
          	Properties props = new Properties();
          	props.load(is);
          	is.close();
          	
          	for (String key : props.stringPropertyNames()) {
          		String value = props.getProperty(key);
          		if (key.startsWith(prefix) && value != null && !value.isEmpty()) {
          			String name=key.substring(prefix.length(),key.length());
          			env.put(name, value);
          		}
          	}
      	} else {
      		logger.warn("unable to locate ejava-jndi.properties from classpath");
      	}
      	return env;
      }
  	
      /**
       * Performs a JNDI lookup and will wait supplied number of seconds before 
       * giving up.
       * @param ctx
       * @param type
       * @param name
       * @param waitSecs
       * @return Object resolved from the lookup
       * @throws NamingException 
       */
      @SuppressWarnings("unchecked")
  	public static <T> T lookup(Context ctx, Class<T> type, String name, int waitSecs) 
  			throws NamingException {
      	logger.debug(String.format("looking up %s, wait=%d", name, waitSecs));
      	
      	T object=null;
      	//wait increments should be at least 1sec
      	long interval=Math.max(waitSecs*1000/10, 1000);
      	for (int elapsed=0; elapsed<(waitSecs*1000); elapsed += interval) {
      		if (elapsed + interval < waitSecs*1000) {
  	    		try {
  					object = (T) ctx.lookup(name);
  				} catch (Throwable ex) {
  					logger.debug(String.format("error in jndi.lookup(%s)=%s", name, ex));
  					try { Thread.sleep(interval); } catch (Exception ex2) {}
  				}
      		} else {
  				object = (T) ctx.lookup(name);
      		}
      	}
      	logger.debug("object=" + object);
      	return object;
      }
  		
 	/**
      * Produces a debug string listing the JNDI contents of the current, default 
      * Context.
      * @return String describing contents of context
 	 * @throws NamingException
 	 */
     public String dump() throws NamingException {
         return dump(new InitialContext(),"");
     }
 
     /**
      * Produces a debug string listing the JNDI contents of the specified 
      * Context.
      * @param context
      * @param name
      * @return String describing contents of context
      */
     public String dump(Context context, String name) {
         StringBuilder text = new StringBuilder();
         if (name==null) { name = ""; }
         try {
             text.append("listing ").append(name);
             doDump(0, text, context, name);
         }
         catch (NamingException ex) {}
         return text.toString();
     }
 
 	private void doDump(int level, StringBuilder text, Context context, String name) 
         throws NamingException {
         for (NamingEnumeration<NameClassPair> ne = context.list(name); ne.hasMore();) {
             NameClassPair ncp = (NameClassPair) ne.next();
             String objectName = ncp.getName();
             String className = ncp.getClassName();
             if (isContext(className)) {
             	text.append(getPad(level))
             	    .append("+")
             	    .append(objectName)
             	    .append(":")
             	    .append(className)
             	    .append('\n');
                 doDump(level + 1, text, context, name + "/" + objectName);
             } else {
             	text.append(getPad(level))
 	        	    .append("-")
 	        	    .append(objectName)
 	        	    .append(":")
 	        	    .append(className)
 	        	    .append('\n');
             }
         }
     }
     
 	protected boolean isContext(String className) {
         try {
 			Class<?> objectClass = Thread.currentThread().getContextClassLoader()
                     .loadClass(className);
             return Context.class.isAssignableFrom(objectClass);
         }
         catch (ClassNotFoundException ex) {
             //object is probably not a context, report as non-context
             return false;
         }
     }
 
     protected String getPad(int level) {
         StringBuilder pad = new StringBuilder();
         for (int i = 0; i < level; i++) {
             pad.append(" ");
         }
         return pad.toString();
     }
 }