/*
    * Copyright 2007 Joachim Grueneis
    *
    * 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 org.exolab.castor.xml.util.resolvers;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  
  /**
   * Some helpers used by the resolver commands. This is a utility class which
   * is NOT meant to be instantiated.
   * 
   * @author <a href="mailto:jgrueneis AT gmail DOT com">Joachim Grueneis</a>
   * @version $Revision$ $Date$
   * @since 1.2
   */
  public final class ResolveHelpers {
  	private static final Log LOG = LogFactory.getLog(ResolveHelpers.class);
      
      /**
       * A private constructor as this is a utility class without an own state.
       */
  	private ResolveHelpers() {}
  
      /**
       * Qualifies the given <code>fileName</code> with the given
       * <code>packageName</code> and returns the resulting file path.<br>
       * If <code>packageName</code> is <code>null</code> or a zero-length
       * String, this method will return <code>fileName</code>.<br>
       *
       * @param fileName The file name to be qualified.
       * @param packageName The package name to be used for qualifying.
       * @return The qualified file path.
       */
      public static String getQualifiedFileName(String fileName, String packageName) {
          if (packageName == null || packageName.length() == 0) {
              return fileName;
          }
          
          StringBuffer result = new StringBuffer();
          result.append(packageName.replace('.', '/'));
          result.append('/');
          result.append(fileName);
          return result.toString();
      } //-- getQualifiedFileName
  
      /**
       * Gets the package name of the given class name.
       *
       * @param className
       *            The class name to retrieve the package name from.
       * @return The package name or the empty String if <code>className</code>
       *         is <code>null</code> or does not contain a package.
       */
      public static String getPackageName(String className) {
          if (className == null) {
              return "";
          }
  
          int idx = className.lastIndexOf('.');
          if (idx >= 0) {
              return className.substring(0, idx);
          }
          return "";
      } //-- getPackageName
  
      /**
       * Compares the two strings for equality. A Null and empty
       * strings are considered equal.
       *
       * @return true if the two strings are considered equal.
       */
      public static boolean namespaceEquals(String ns1, String ns2) {
          if (ns1 == null) {
              return ns2 == null || ns2.length() == 0;
          }
  
          if (ns2 == null) {
              return ns1.length() == 0;
          }
  
          return ns1.equals(ns2);
      } //-- namespaceEquals
  
      /**
       * Gets the <code>ClassLoader</code> that's actually to be used (e.g. for
      * loading resources).<br>
      * The actual <code>ClassLoader</code> is determined in the following way:
      * <lu>
      * <li> If the passed in "preferred" loader is not <code>null</code>, it
      * is used.
      * <li> If the loader of this XMLClassDescriptor is not <code>null</code>,
      * it is used.
      * <li> The context class loader of the current thread is used. </lu>
      *
      * @param loader The "preferred" <code>ClassLoader</code>.
      * @return The loader to be used.
      */
     public static ClassLoader getClassLoader(ClassLoader loader) {
         if (loader != null) {
             return loader;
         }
 
         return Thread.currentThread().getContextClassLoader();
     } //-- getClassLoader
     
     /**
      * Capsulates the ClassLoader.loadClass method to throw no exceptions but return null
      * instead. Any exception caught are logged with info severity.
      * @param classLoader the class loader to use
      * @param className the class to load
      * @return the loaded Class or null
      */
     public static Class loadClass(ClassLoader classLoader, String className) {
         if (classLoader == null) {
             String message = "Argument class loader must not be null";
             LOG.warn(message);
             throw new IllegalArgumentException(message);
         }
         
         if ((className == null) || (className.length() == 0)) {
             LOG.debug("Name of class to load is null or empty -> ignored!");
             return null;
         }
         
         try {
             return classLoader.loadClass(className);
         } catch (ClassNotFoundException e) {
             if (LOG.isDebugEnabled()) {
                 LOG.debug("Ignored problem at loading class: " + className
                         + " through class loader: " + classLoader + ", exception: " + e);
             }
             return null;
         }
     } //-- loadClass
 }