/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2007, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.classloader.spi.base;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.security.AccessController;
import java.security.CodeSource;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;

import org.jboss.classloader.plugins.ClassLoaderUtils;
import org.jboss.classloader.spi.Loader;
import org.jboss.logging.Logger;

/**
 * ClassLoadingTask.
 * 
 * @author Scott.Stark@jboss.org
 * @author <a href="adrian@jboss.com">Adrian Brock</a>
 * @version $Revision: 1.1 $
 */
class ClassLoadingTask
{
   /** The log */
   protected static Logger log = Logger.getLogger("org.jboss.detailed.classloader.ClassLoadingTask");

   /**
    * TaskState.
    */
   enum TaskState
   {
      /** Found the classloader */
      FOUND_CLASS_LOADER,
      
      /** Next event */
      NEXT_EVENT,
      
      /** Waiting on event */
      WAIT_EVENT,
      
      /** Finished */
      FINISHED,
   }

   /** The class name */
   private String className;
   
   /** The reques thread */ 
   private Thread requestingThread;
   
   /** The requesting classloader */
   private ClassLoader classLoader;
   
   /** The loaded class */
   private Class<?> loadedClass;
   
   /** The error during the load */
   private Throwable loadException;
   
   /** The number of ThreadTasks remaining */
   private int threadTaskCount;

   /** The state of the requestingThread */
   private TaskState state;
   
   /** The Logger trace level flag */
   private boolean trace = log.isTraceEnabled();

   /** The number of class circularity errors */
   private int numCCE;

   /**
    * Create a new ClassLoadingTask.
    * 
    * @param className the class name
    * @param classLoader the requesting the classloader
    * @param requestingThread the requesting thread
    */
   ClassLoadingTask(String className, ClassLoader classLoader, Thread requestingThread)
   {
      this.className = className;
      this.requestingThread = requestingThread;
      this.classLoader = classLoader;
   }

   /**
    * Get the className.
    * 
    * @return the className.
    */
   String getClassName()
   {
      return className;
   }

   /**
    * Get the loadedClass.
    * 
    * @return the loadedClass.
    */
   synchronized Class<?> getLoadedClass()
   {
      return loadedClass;
   }

   /**
    * Get the loadException.
    * 
    * @return the loadException.
    */
   synchronized Throwable getLoadException()
   {
      return loadException;
   }

   /**
    * Get the numCCE.
    * 
    * @return the numCCE.
    */
   synchronized int incrementNumCCE()
   {
      return numCCE;
   }

   /**
    * Get the requestingThread.
    * 
    * @return the requestingThread.
    */
   Thread getRequestingThread()
   {
      return requestingThread;
   }

   /**
    * Get the state.
    * 
    * @return the state.
    */
   synchronized TaskState getState()
   {
      return state;
   }

   /**
    * Set the task into the finished state
    * 
    * @param loadedClass the loaded class
    */
   synchronized void finish(Class<?> loadedClass)
   {
      this.loadedClass = loadedClass;
      state = TaskState.FINISHED;
   }

   /**
    * Set the task into the found classloader state
    */
   synchronized void foundClassLoader()
   {
      state = TaskState.FOUND_CLASS_LOADER;
   }

   /**
    * Set the task into the finished state
    */
   synchronized void finish()
   {
      state = TaskState.FINISHED;
   }

   /**
    * Set the task into the wait on event state
    */
   synchronized void waitOnEvent()
   {
      state = TaskState.WAIT_EVENT;
   }

   /**
    * Set the task into the next event state
    */
   synchronized void nextEvent()
   {
      state = TaskState.NEXT_EVENT;
   }
   
   /**
    * Get the threadTaskCount.
    * 
    * @return the threadTaskCount.
    */
   synchronized int getThreadTaskCount()
   {
      return threadTaskCount;
   }

   @Override
   public String toString()
   {
      StringBuilder builder = new StringBuilder();
      builder.append(getClass().getSimpleName());
      builder.append('@').append(Integer.toHexString(System.identityHashCode(this)));
      builder.append('{');
      builder.append("className=").append(className);
      builder.append(" requestingThread=").append(requestingThread);
      builder.append(" requestingClassLoader: ").append(classLoader);
      if (loadedClass != null)
      {
         builder.append(" loadedClass=");
         ClassLoaderUtils.classToString(loadedClass, builder);
      }
      if (loadException != null)
         builder.append(" loadException: ").append(loadException);
      builder.append(" threadTaskCount: ").append(threadTaskCount);
      builder.append(" state: ").append(state);
      if (numCCE > 0)
         builder.append(", #CCE: ").append(numCCE);
      builder.append('}');
      if( trace && loadException != null )
      {
         StringWriter sw = new StringWriter();
         PrintWriter pw = new PrintWriter(sw);
         loadException.printStackTrace(pw);
         builder.append("loadException details:\n");
         builder.append(sw.toString());
      }
      return builder.toString();
   }

   /**
    * Creaqte a new thread task
    * 
    * @param loader the loader
    * @param thread the thread
    * @param reschedule whether this is a reschedule
    * @param releaseInNextTask whether to release in the next task
    * @return the thread task
    */
   synchronized ThreadTask newThreadTask(Loader loader, Thread thread, boolean reschedule, boolean releaseInNextTask)
   {
      // Only update the threadTaskCount if this is not a reschedule
      if (reschedule == false)
         ++threadTaskCount;
      return new ThreadTask(loader, thread, releaseInNextTask);
   }
   
   /**
    * Set the load exception
    * 
    * @param t the throwable
    */
   synchronized void setLoadError(Throwable t)
   {
       --threadTaskCount;
        if (trace)
            log.trace("setLoadedError, error="+t);
       loadException = t;
   }
   

   /** 
    * This is called from run on success or failure to mark the end
    * of the load attempt. This must decrement the threadTaskCount or
    * the ClassLoadingTask will never complete.
    * 
    * @param theClass the loaded class
    */
   private synchronized void setLoadedClass(Class<?> theClass)
   {
      --threadTaskCount;
      if (trace)
         log.trace("setLoadedClass, theClass=" + theClass);

      // Warn about duplicate classes
      if (this.loadedClass != null && theClass != null)
      {
         StringBuilder builder = new StringBuilder();
         builder.append("Duplicate class found: ").append(className).append('\n');
         ProtectionDomain pd = getProtectionDomain(loadedClass);
         CodeSource cs = pd != null ? pd.getCodeSource() : null;
         builder.append("Current CS: ").append(cs).append('\n');
         pd = getProtectionDomain(theClass);
         cs = pd != null ? pd.getCodeSource() : null;
         builder.append("Duplicate CS: ").append(cs);
         log.warn(builder.toString());
      }

      // Accept the first class
      if (theClass != null && loadedClass == null)
         this.loadedClass = theClass;
   }

   /** 
    * Thread Task
    */
   class ThreadTask
   {
      /** The loader */
      private Loader loader;
      
      /** The thread that owns the ucl monitor */
      private Thread thread;
      
      /** Whether to release in the next task */
      private boolean releaseInNextTask;

      /**
       * Create a new ThreadTask.
       * 
       * @param loader the loader
       * @param thread the thread
       * @param releaseInNextTask whether to release in the next task
       */
      ThreadTask(Loader loader, Thread thread, boolean releaseInNextTask)
      {
         this.loader = loader;
         this.thread = thread;
         this.releaseInNextTask = releaseInNextTask;
      }

      /**
       * Get the className.
       * 
       * @return the className.
       */
      String getClassName()
      {
         return className;
      }

      /**
       * Get the loadedClass.
       * 
       * @return the loadedClass.
       */
      Class<?> getLoadedClass()
      {
         return loadedClass;
      }

      @Override
      public String toString()
      {
         StringBuilder builder = new StringBuilder();
         builder.append("{thread=").append(thread);
         builder.append(" loader=").append(loader);
         builder.append(" requestingThread=").append(requestingThread);
         builder.append(" releaseInNextTask=").append(releaseInNextTask);
         builder.append("}");
         return builder.toString();
      }
      
      /**
       * Get the classloading task
       * 
       * @return the classloading task
       */
      ClassLoadingTask getLoadTask()
      {
         return ClassLoadingTask.this;
      }

      /**
       * Get the loader.
       * 
       * @return the loader.
       */
      Loader getLoader()
      {
         return loader;
      }

      /**
       * Get the classloader for this task
       * 
       * @return the classloader
       */
      BaseClassLoader getClassLoader()
      {
         if (loader instanceof BaseDelegateLoader)
         {
            BaseDelegateLoader delegateLoader = (BaseDelegateLoader) loader;
            BaseClassLoaderPolicy policy = delegateLoader.getPolicy();
            if (policy == null)
               throw new IllegalStateException("Null classloader policy for " + loader);
            return policy.getClassLoader();
         }
         return null;
      }
      
      /**
       * Get the thread.
       * 
       * @return the thread.
       */
      synchronized Thread getThread()
      {
         return thread;
      }

      /**
       * Set the thread.
       * 
       * @param thread the thread.
       */
      synchronized void setThread(Thread thread)
      {
         this.thread = thread;
      }

      /**
       * Get the releaseInNextTask.
       * 
       * @return the releaseInNextTask.
       */
      boolean isReleaseInNextTask()
      {
         return releaseInNextTask;
      }

      /**
       * Run the class load
       * 
       * @throws ClassNotFoundException
       */
      void run() throws ClassNotFoundException
      {
         if (loadedClass == null)
         {
            Class<?> theClass = loader.loadClass(className);
            setLoadedClass(theClass);
         }
         else if (trace)
         {
            log.trace("Already found class(" + loadedClass + "), skipping load class");
         }
      }
   }
   
   /**
    * Get the protection domain for a class
    * 
    * @param clazz the class
    * @return the protected domain or null if it doesn't have one
    */
   private static final ProtectionDomain getProtectionDomain(final Class<?> clazz)
   {
      SecurityManager sm = System.getSecurityManager();
      if (sm == null)
         return clazz.getProtectionDomain();
      
      return AccessController.doPrivileged(new PrivilegedAction<ProtectionDomain>()
      {
         public ProtectionDomain run()
         {
            return clazz.getProtectionDomain();
         }
      });
   }
}
