/*
    * 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.utils;
  
  import java.io.BufferedInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  import java.util.jar.JarEntry;
  import java.util.jar.JarFile;
  
  import org.apache.commons.io.IOUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Base implementation of class loaders that serve classes from the given
   * directories.
   *
   * @author <a href="mailto:robert.reiner@smartics.de">Robert Reiner</a>
   * @version $Revision:591 $
   */
  public abstract class AbstractProjectClassLoader extends ClassLoader
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    // --- members --------------------------------------------------------------
  
    /**
     * Reference to the logger for this class.
     */
    private final Logger log = LoggerFactory
        .getLogger(AbstractProjectClassLoader.class);
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     *
     * @param parent the parent class loader.
     */
    protected AbstractProjectClassLoader(final ClassLoader parent)
    {
      super(parent);
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
  
    // --- init -----------------------------------------------------------------
  
    // --- get&set --------------------------------------------------------------
  
    // --- business -------------------------------------------------------------
  
    /**
     * Ensures that the package of a class specified by the given name is already
     * defined. If it is not defined the loaded class instance will not have a
     * package reference.
     *
     * @param className the name of the class whose package is to check to be
     *          already defined.
     */
    protected final void ensurePackageProvided(final String className)
    {
      final int lastDotIndex = className.lastIndexOf('.');
      if (lastDotIndex != -1)
      {
        final String packageName = className.substring(0, lastDotIndex);
        final Package paccage = getPackage(packageName);
        if (paccage == null)
        {
          definePackage(packageName, null, null, null, null, null, null, null);
        }
      }
    }
  
    /**
     * Loads the class. Ensures that the package of the class is defined.
    *
    * @param className the name of the class.
    * @param classFile the file with the binary data.
    * @return the loaded class definition.
    * @throws ClassNotFoundException if the class cannot be loaded.
    */
   protected final Class<?> loadClassFile(final String className,
       final File classFile) throws ClassNotFoundException
   {
     ensurePackageProvided(className);
     InputStream in = null;
     try
     {
       in = new BufferedInputStream(new FileInputStream(classFile));
       final byte[] data = IOUtils.toByteArray(in);
       final Class<?> clazz = defineClass(className, data, 0, data.length);
       return clazz;
     }
     catch (final IOException e)
     {
       throw createClassNotFoundException(className, classFile, e);
     }
     finally
     {
       IOUtils.closeQuietly(in);
     }
   }
 
   /**
    * Opens a reader to the class file within the archive.
    *
    * @param className the name of the class to load.
    * @param fileName the name of the class file to load.
    * @param dirName the name of the directory the archive file is located.
    * @return the reader to the source file for the given class in the archive.
    * @throws ClassNotFoundException if the class cannot be found.
    */
   protected final Class<?> loadClassFromLibrary(final String className,
       final String fileName, final File dirName) throws ClassNotFoundException
   {
     ensurePackageProvided(className);
     try
     {
       final JarFile jarFile = new JarFile(dirName); // NOPMD
       final JarEntry entry = jarFile.getJarEntry(fileName);
       if (entry != null)
       {
         InputStream in = null;
         try
         {
           in = new BufferedInputStream(jarFile.getInputStream(entry));
           final byte[] data = IOUtils.toByteArray(in);
           final Class<?> clazz = defineClass(className, data, 0, data.length);
           return clazz;
         }
         finally
         {
           IOUtils.closeQuietly(in);
         }
       }
     }
     catch (final IOException e)
     {
       throw createClassNotFoundException(className, dirName, e);
     }
 
     throw createClassNotFoundException(className, dirName, null);
   }
 
   private ClassNotFoundException createClassNotFoundException(
       final String className, final File dirName, final IOException rootCause)
     throws ClassNotFoundException
   {
     final String message =
         String.format("Cannot load class '%s' from file '%s'.", className,
             dirName);
     if (log.isDebugEnabled())
     {
       log.debug(message);
     }
 
     return new ClassNotFoundException(message, rootCause);
   }
 
   /**
    * Opens a reader to the resource file within the archive.
    *
    * @param resourceName the name of the resource to load.
    * @param fileName the name of the resource file to load.
    * @param dirName the name of the directory the archive file is located.
    * @return the reader to the source file for the given class in the archive.
    * @throws IOException if the class cannot be found.
    */
   protected final URL loadResourceFromLibrary(final String resourceName,
       final String fileName, final File dirName) throws IOException
   {
     ensurePackageProvided(resourceName);
     try
     {
       return new URL("jar:file:" + dirName.getName() + "!/" + fileName);
     }
     catch (final IOException e)
     {
       final String message =
           "Cannot load class '" + resourceName + "' from file '" + dirName
               + "'.";
       if (log.isDebugEnabled())
       {
         log.debug(message);
       }
       final IOException ioe = new IOException(message);
       ioe.initCause(e);
       throw ioe; // NOPMD
     }
   }
 
   // --- object basics --------------------------------------------------------
 
 }