/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements. See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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.apache.logging.log4j.core.helpers;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.status.StatusLogger;
  
  import java.io.InputStream;
  import java.io.InterruptedIOException;
  import java.lang.reflect.InvocationTargetException;
  import java.net.URL;
  
  /**
   * Load resources (or images) from various sources.
   */
  
  public final class Loader {
  
      private static final String TSTR = "Caught Exception while in Loader.getResource. This may be innocuous.";
  
      private static boolean ignoreTCL = false;
  
      private static final Logger LOGGER = StatusLogger.getLogger();
  
      static {
          String ignoreTCLProp = OptionConverter.getSystemProperty("log4j.ignoreTCL", null);
          if (ignoreTCLProp != null) {
              ignoreTCL = OptionConverter.toBoolean(ignoreTCLProp, true);
          }
      }
  
      private Loader() {
      }
  
      /**
       * This method will search for <code>resource</code> in different
       * places. The search order is as follows:
       * <p/>
       * <ol>
       * <p/>
       * <p><li>Search for <code>resource</code> using the thread context
       * class loader under Java2. If that fails, search for
       * <code>resource</code> using the class loader that loaded this
       * class (<code>Loader</code>). Under JDK 1.1, only the the class
       * loader that loaded this class (<code>Loader</code>) is used.
       * <p/>
       * <p><li>Try one last time with
       * <code>ClassLoader.getSystemResource(resource)</code>, that is is
       * using the system class loader in JDK 1.2 and virtual machine's
       * built-in class loader in JDK 1.1.
       * <p/>
       * </ol>
       * @param resource The resource to load.
       * @param defaultLoader The default ClassLoader.
       * @return A URL to the resource.
       */
      public static URL getResource(String resource, ClassLoader defaultLoader) {
          ClassLoader classLoader;
          URL url;
  
          try {
              classLoader = getTCL();
              if (classLoader != null) {
                  LOGGER.trace("Trying to find [" + resource + "] using context classloader "
                          + classLoader + ".");
                  url = classLoader.getResource(resource);
                  if (url != null) {
                      return url;
                  }
              }
  
              // We could not find resource. Let us now try with the classloader that loaded this class.
              classLoader = Loader.class.getClassLoader();
              if (classLoader != null) {
                  LOGGER.trace("Trying to find [" + resource + "] using " + classLoader + " class loader.");
                  url = classLoader.getResource(resource);
                  if (url != null) {
                      return url;
                  }
              }
              // We could not find resource. Finally try with the default ClassLoader.
              if (defaultLoader != null) {
                  LOGGER.trace("Trying to find [" + resource + "] using " + defaultLoader + " class loader.");
                  url = defaultLoader.getResource(resource);
                  if (url != null) {
                     return url;
                 }
             }
         } catch (IllegalAccessException t) {
             LOGGER.warn(TSTR, t);
         } catch (InvocationTargetException t) {
             if (t.getTargetException() instanceof InterruptedException
                 || t.getTargetException() instanceof InterruptedIOException) {
                 Thread.currentThread().interrupt();
             }
             LOGGER.warn(TSTR, t);
         } catch (Throwable t) {
             //
             //  can't be InterruptedException or InterruptedIOException
             //    since not declared, must be error or RuntimeError.
             LOGGER.warn(TSTR, t);
         }
 
         // Last ditch attempt: get the resource from the class path. It
         // may be the case that clazz was loaded by the Extentsion class
         // loader which the parent of the system class loader. Hence the
         // code below.
         LOGGER.trace("Trying to find [" + resource + "] using ClassLoader.getSystemResource().");
         return ClassLoader.getSystemResource(resource);
     }
 
     /**
      * This method will search for <code>resource</code> in different
      * places. The search order is as follows:
      * <p/>
      * <ol>
      * <p/>
      * <p><li>Search for <code>resource</code> using the thread context
      * class loader under Java2. If that fails, search for
      * <code>resource</code> using the class loader that loaded this
      * class (<code>Loader</code>). Under JDK 1.1, only the the class
      * loader that loaded this class (<code>Loader</code>) is used.
      * <p/>
      * <p><li>Try one last time with
      * <code>ClassLoader.getSystemResource(resource)</code>, that is is
      * using the system class loader in JDK 1.2 and virtual machine's
      * built-in class loader in JDK 1.1.
      * <p/>
      * </ol>
      * @param resource The resource to load.
      * @param defaultLoader The default ClassLoader.
      * @return An InputStream to read the resouce.
      */
     public static InputStream getResourceAsStream(String resource, ClassLoader defaultLoader) {
         ClassLoader classLoader;
         InputStream is;
 
         try {
             classLoader = getTCL();
             if (classLoader != null) {
                 LOGGER.trace("Trying to find [" + resource + "] using context classloader " + classLoader + ".");
                 is = classLoader.getResourceAsStream(resource);
                 if (is != null) {
                     return is;
                 }
             }
 
             // We could not find resource. Let us now try with the classloader that loaded this class.
             classLoader = Loader.class.getClassLoader();
             if (classLoader != null) {
                 LOGGER.trace("Trying to find [" + resource + "] using " + classLoader + " class loader.");
                 is = classLoader.getResourceAsStream(resource);
                 if (is != null) {
                     return is;
                 }
             }
 
             // We could not find resource. Finally try with the default ClassLoader.
             if (defaultLoader != null) {
                 LOGGER.trace("Trying to find [" + resource + "] using " + defaultLoader + " class loader.");
                 is = defaultLoader.getResourceAsStream(resource);
                 if (is != null) {
                     return is;
                 }
             }
         } catch (IllegalAccessException t) {
             LOGGER.warn(TSTR, t);
         } catch (InvocationTargetException t) {
             if (t.getTargetException() instanceof InterruptedException
                 || t.getTargetException() instanceof InterruptedIOException) {
                 Thread.currentThread().interrupt();
             }
             LOGGER.warn(TSTR, t);
         } catch (Throwable t) {
             //
             //  can't be InterruptedException or InterruptedIOException
             //    since not declared, must be error or RuntimeError.
             LOGGER.warn(TSTR, t);
         }
 
         // Last ditch attempt: get the resource from the class path. It
         // may be the case that clazz was loaded by the Extentsion class
         // loader which the parent of the system class loader. Hence the
         // code below.
         LOGGER.trace("Trying to find [" + resource + "] using ClassLoader.getSystemResource().");
         return ClassLoader.getSystemResourceAsStream(resource);
     }
 
     /**
      * Load a Class by name.
      * @param clazz The class name.
      * @return The Class.
      * @throws ClassNotFoundException if the Class could not be found.
      */
     public static Class loadClass(String clazz) throws ClassNotFoundException {
         // Just call Class.forName(clazz) if we are instructed to ignore the TCL.
         if (ignoreTCL) {
             return Class.forName(clazz);
         } else {
             try {
                 return getTCL().loadClass(clazz);
             } catch (Throwable e) {
                 return Class.forName(clazz);
             }
         }
     }
 
     /**
      * Return the ClassLoader to use.
      * @return the ClassLoader.
      */
     public static ClassLoader getClassLoader() {
         ClassLoader cl = null;
 
         try {
             cl = getTCL();
         } catch (Exception ex) {
             // Ignore the exception. The ClassLoader will be located.
         }
         if (cl == null) {
             cl = Loader.getClassLoader();
         }
         return cl;
     }
 
     private static ClassLoader getTCL() throws IllegalAccessException, InvocationTargetException {
         ClassLoader cl;
         if (System.getSecurityManager() == null) {
             cl = Thread.currentThread().getContextClassLoader();
         } else {
             cl = (ClassLoader) java.security.AccessController.doPrivileged(
                 new java.security.PrivilegedAction() {
                     public Object run() {
                         return Thread.currentThread().getContextClassLoader();
                     }
                 }
             );
         }
 
         return cl;
     }
 }