/***************************************
 *                                     *
 *  JBoss: The OpenSource J2EE WebOS   *
 *                                     *
 *  Distributable under LGPL license.  *
 *  See terms of license at gnu.org.   *
 *                                     *
 ***************************************/

package org.jboss.iiop.rmi.marshal.strategy;

import java.lang.reflect.Method;

import java.rmi.RemoteException;

import org.omg.CORBA.UserException;
import org.omg.CORBA.portable.IDLEntity;
import org.omg.CORBA.portable.UnknownException;
import org.omg.CORBA_2_3.portable.InputStream;
import org.omg.CORBA_2_3.portable.OutputStream;

import org.jboss.iiop.rmi.ExceptionAnalysis;
import org.jboss.iiop.rmi.RMIIIOPViolationException;

import org.jboss.iiop.rmi.marshal.CDRStream;
import org.jboss.iiop.rmi.marshal.CDRStreamReader;
import org.jboss.iiop.rmi.marshal.CDRStreamWriter;

/**
 * A <code>SkeletonStrategy</code> for a given method knows how to 
 * unmarshalthe sequence of method parameters from a CDR input stream, how to 
 * marshal into a CDR output stream the return value of the method, and how to
 * marshal into a CDR output stream any exception thrown by the method.
 *
 * @author  <a href="mailto:reverbel@ime.usp.br">Francisco Reverbel</a>
 * @version $Revision: 1.1.2.2 $
 */
public class SkeletonStrategy 
{
   /**
    * Each <code>CDRStreamReader</code> in the array unmarshals a method 
    * parameter.
    */
   private CDRStreamReader[] paramReaders;

   /**
    * A <code>Method</code> instance.
    */
   private Method m;

   /**
    * Each <code>ExceptionWriter</code> in the array knows how to marshal 
    * an exception that may be thrown be the method. The array is sorted so
    * that no writer for a derived exception appears after the base 
    * exception writer.
    */
   private ExceptionWriter[] excepWriters;

   /**
    * A <code>CDRStreamWriter</code> that marshals the return value of the 
    * method.
    */
   private CDRStreamWriter retvalWriter;

   // Public  -----------------------------------------------------------------

   /*
    * Constructs a <code>SkeletonStrategy</code> for a given method.
    */
   public SkeletonStrategy(Method m) 
   {
      // Keep the method
      this.m = m;

      // Initialize paramReaders
      Class[] paramTypes = m.getParameterTypes();
      int len = paramTypes.length;
      paramReaders = new CDRStreamReader[len];
      for (int i = 0; i < len; i++) {
            paramReaders[i] = CDRStream.readerFor(paramTypes[i]);
      }

      // Initialize excepWriters
      Class[] excepTypes = m.getExceptionTypes();
      len = excepTypes.length; 
      int n = 0;
      for (int i = 0; i < len; i++) {
         if (!RemoteException.class.isAssignableFrom(excepTypes[i])) {
            n++;
         }
      }
      excepWriters = new ExceptionWriter[n];
      int j = 0;
      for (int i = 0; i < len; i++) {
         if (!RemoteException.class.isAssignableFrom(excepTypes[i])) {
            excepWriters[j++] = new ExceptionWriter(excepTypes[i]);
         }
      }
      ExceptionWriter.arraysort(excepWriters);

      // Initialize retvalWriter
      retvalWriter = CDRStream.writerFor(m.getReturnType());
   }

   /**
    * Unmarshals the sequence of method parameters from an input stream.
    *
    * @param in  a CDR input stream
    * @return    an object array with the parameters.
    */
   public Object[] readParams(InputStream in) 
   {
      int len = paramReaders.length;
      Object[] params = new Object[len];
      for (int i = 0; i < len; i++ ) {
         params[i] = paramReaders[i].read(in);
      }
      return params;
   }
   
   /**
    * Returns this <code>SkeletonStrategy</code>'s method.
    */
   public Method getMethod() 
   {
      return m;
   }

   /**
    * Returns true if this <code>SkeletonStrategy</code>'s method 
    * is non void.
    */
   public boolean isNonVoid() 
   {
      return (retvalWriter != null);
   }

   /**
    * Marshals into an output stream the return value of the method.
    *
    * @param out    a CDR output stream
    * @param retVal the value to be written.
    */
   public void writeRetval(OutputStream out, Object retVal) 
   {
      retvalWriter.write(out, retVal);
   }

   /**
    * Marshals into an output stream an exception thrown by the method.
    *
    * @param out    a CDR output stream
    * @param e      the exception to be written.
    */
   public void writeException(OutputStream out, Exception e) 
   {
      int len = excepWriters.length;
      for (int i = 0; i < len; i++) {
         if (excepWriters[i].getExceptionClass().isInstance(e)) {
            excepWriters[i].write(out, e);
            return;
         }
      }
      throw new UnknownException(e);
   }

   // Static inner class (private) --------------------------------------------

   /**
    * An <code>ExceptionWriter</code> knows how to write exceptions of a given
    * class to a CDR output stream.
    */
   private static class ExceptionWriter 
         implements CDRStreamWriter 
   {
      /**
       * The exception class.
       */
      private Class clz;
  
      /*
       * If the exception class corresponds to an IDL-defined exception, this
       * field contains the write method of the associated helper class. 
       * A null value indicates that the exception class does not correspond
       * to an IDL-defined exception.
       */
      private java.lang.reflect.Method writeMethod = null;

      /**
       * The CORBA repository id of the exception class. (This field is used
       * if the exception class does not correspond to an IDL-defined 
       * exception. An IDL-generated helper class provides the repository id 
       * of an IDL-defined exception.)
       */
      private String reposId;
      
      /**
       * Constructs an <code>ExceptionWriter</code> for a given exception 
       * class.
       */
      ExceptionWriter(Class clz) 
      {
         this.clz = clz;
         if (IDLEntity.class.isAssignableFrom(clz) 
             && UserException.class.isAssignableFrom(clz)) {

            // This ExceptionWriter corresponds to an IDL-defined exception
            String helperClassName = clz.getName() + "Helper";
            try {
               Class helperClass =
                  clz.getClassLoader().loadClass(helperClassName);
               Class[] paramTypes =
                  { org.omg.CORBA.portable.OutputStream.class, clz };
               writeMethod = helperClass.getMethod("write", paramTypes);
            }
            catch (ClassNotFoundException e) {
               throw new RuntimeException("Error loading class " 
                                          + helperClassName + ": " + e);
            }
            catch (NoSuchMethodException e) {
                throw new RuntimeException("No write method in helper class "
                                           + helperClassName + ": " + e);
            }
             
         }
         else {
            // This ExceptionWriter does not correspond to an IDL-defined 
            // exception
            try {
               this.reposId = ExceptionAnalysis.getExceptionAnalysis(clz)
                  .getExceptionRepositoryId();
            }
            catch (RMIIIOPViolationException e) {
               throw new RuntimeException("Cannot obtain "
                                          + "exception repository id for " 
                                          + clz.getName() + ":\n" + e);
            }
         }
      }
      
      /**
       * Gets the exception <code>Class</code>.
       */
      Class getExceptionClass() 
      {
         return clz;
      }
      
      /**
       * Writes an exception to a CDR output stream.
       */
      public void write(OutputStream out, Object excep) 
      {
         if (writeMethod != null) {
            try {
               writeMethod.invoke(null, new Object[] { out, excep });
            }
            catch (IllegalAccessException e) {
               throw new RuntimeException("Internal error: " + e);
            }
            catch (java.lang.reflect.InvocationTargetException e) {
               throw new RuntimeException("Exception marshaling IDLEntity: "
                                          + e.getTargetException());
            }
         }
         else {
            out.write_string(reposId);
            out.write_value((Exception)excep, clz);
         }
      }
      
      /**
       * Sorts an <code>ExceptionWriter</code> array so that no derived 
       * exception strategy appears after a base exception strategy.
       */
      static void arraysort(ExceptionWriter[] a) 
      {
         int len = a.length;
         
         for (int i = 0; i < len - 1; i++) {
            for (int j = i + 1; j < len; j++) {
               if (a[i].clz.isAssignableFrom(a[j].clz)) {
                  ExceptionWriter tmp = a[i];
                  
                  a[i] = a[j];
                  a[j] = tmp;
               }
            }
         }
      }
      
   } // end of inner class ExceptionWriter
   
}
