/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2004 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "Apache BSF", "Apache", and "Apache Software Foundation"
 *    must not be used to endorse or promote products derived from
 *    this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many individuals
 * on behalf of the Apache Software Foundation and was originally created by
 * Sanjiva Weerawarana and others at International Business Machines
 * Corporation. For more information on the Apache Software Foundation,
 * please see <http://www.apache.org/>.
 */

package org.apache.bsf.engines.java;

import java.util.*;
import java.io.*;
import java.lang.*;
import java.lang.reflect.Method;

import org.apache.bsf.*;
import org.apache.bsf.util.BSFEngineImpl;
import org.apache.bsf.util.EngineUtils;
import org.apache.bsf.util.*;
import org.apache.bsf.util.DebugLog;

/**
 * This is the interface to Java from the
 * Bean Scripting Framework.
 * <p>
 * The Java code must be written script-style -- that is, just the body of
 * the function, without class or method headers or footers.
 * The JavaEngine will generate those via a "boilerplate" wrapper:
 * <pre>
 * <code>
 * import java.lang.*;
 * import java.util.*;
 * public class $$CLASSNAME$$ {
 *   static public Object BSFJavaEngineEntry(org.apache.bsf.BSFManager bsf) {
 *     // Your code will be placed here
 *   }
 * }
 * </code>
 * </pre>
 * $$CLASSNAME$$ will be replaced by a generated classname of the form
 * BSFJava*, and the bsf parameter can be used to retrieve application
 * objects registered with the Bean Scripting Framework.
 * <p>
 * If you use the placeholder string $$CLASSNAME$$ elsewhere
 * in your script -- including within text strings -- BSFJavaEngine will
 * replace it with the generated name of the class before the Java code
 * is compiled.
 * <p>
 * <h2>Hazards:</h2>
 * <p>
 * NOTE that it is your responsibility to convert the code into an acceptable
 * Java string. If you're invoking the JavaEngine directly (as in the
 * JSPLikeInJava example) that means \"quoting\" characters that would
 * otherwise cause trouble.
 * <p>
 * ALSO NOTE that it is your responsibility to return an object, or null in
 * lieu thereof!
 * <p>
 * Since the code has to be compiled to a Java classfile, invoking it involves
 * a fair amount of computation to load and execute the compiler. We are
 * currently making an attempt to manage that by caching the class
 * after it has been loaded, but the indexing is fairly primitive. It has
 * been suggested that the Bean Scripting Framework may want to support
 * preload-and-name-script and execute-preloaded-script-by-name options to
 * provide better control over when and how much overhead occurs.
 * <p>
 * @author Joe Kesselman
 */
public class JavaEngine extends BSFEngineImpl
{
  Class javaclass=null;
  private boolean bsfHandleCreated = false;
  static Hashtable codeToClass=new Hashtable();
  static String serializeCompilation="";
  static String placeholder="$$CLASSNAME$$";
  String minorPrefix;

  /**
   * Create a scratchfile, open it for writing, return its name.
   * Relies on the filesystem to provide us with uniqueness testing.
   * NOTE THAT uniqueFileOffset continues to count; we don't want to
   * risk reusing a classname we have previously loaded in this session
   * even if the classfile has been deleted.
   */
  private int uniqueFileOffset=-1;
  private class GeneratedFile 
  {
	File file=null;
	FileOutputStream fos=null;
	String className=null;
	GeneratedFile(File file,FileOutputStream fos,String className) 
	{
	  this.file=file;
	  this.fos=fos;
	  this.className=className;
	}
  }
  /**
   * Constructor.
   */
  public JavaEngine ()
  {
	// Do compilation-possible check here??????????????
  }
  public Object call (Object object, String method, Object[] args) 
	   throws BSFException
  {
	throw new BSFException (BSFException.REASON_UNSUPPORTED_FEATURE,
			    "call() is not currently supported by JavaEngine");
  }
  public void compileScript (String source, int lineNo, int columnNo,
		  Object script, CodeBuffer cb) throws BSFException {
	ObjInfo oldRet = cb.getFinalServiceMethodStatement ();

	if (oldRet != null && oldRet.isExecutable ()) {
	  cb.addServiceMethodStatement (oldRet.objName + ";");
	}

	cb.addServiceMethodStatement (script.toString ());
	cb.setFinalServiceMethodStatement (null);
  }
  /**
   * This is used by an application to evaluate a string containing
   * some expression. It should store the "bsf" handle where the
   * script can get to it, for callback purposes.
   * <p>
   * Note that Java compilation imposes serious overhead,
   * but in exchange you get full Java performance
   * once the classes have been created (minus the cache lookup cost).
   * <p>
   * Nobody knows whether javac is threadsafe.
   * I'm going to serialize access to protect it.
   * <p>
   * There is no published API for invoking javac as a class. There's a trick
   * that seems to work for Java 1.1.x, but it stopped working in Java 1.2.
   * We will attempt to use it, then if necessary fall back on invoking
   * javac via the command line.
   */
  public Object eval (String source, int lineNo, int columnNo, 
		      Object oscript) throws BSFException
  {
	if (debug)
	{
	  debugStream.println("JavaEngine: tempDir=" + tempDir);
	}

	Object retval=null;
	String classname=null;
	GeneratedFile gf=null;

	String basescript=oscript.toString();
	String script=basescript;	// May be altered by $$CLASSNAME$$ expansion

	try {
	  // Do we already have a class exactly matching this code?
	  javaclass=(Class)codeToClass.get(basescript);
	  
	  if(javaclass!=null)
	{
	  classname=javaclass.getName();
	}
	  else
	{
	  gf=openUniqueFile(tempDir, "BSFJava",".java");
	  if(gf==null)
	    throw new BSFException("couldn't create JavaEngine scratchfile");
	  
	  // Obtain classname
	  classname=gf.className;

	  // Write the kluge header to the file.
	  gf.fos.write(("import java.lang.*;"+
			"import java.util.*;"+
			"public class "+classname+" {\n" +
						"  static public Object BSFJavaEngineEntry(org.apache.bsf.BSFManager bsf) {\n")
		       .getBytes());

	  // Edit the script to replace placeholder with the generated
	  // classname. Note that this occurs _after_ the cache was checked!
	  int startpoint,endpoint;
	  if((startpoint=script.indexOf(placeholder))>=0)
	    {
	      StringBuffer changed=new StringBuffer();
	      for(;
		  startpoint>=0;
		  startpoint=script.indexOf(placeholder,startpoint))
		{
		  changed.setLength(0);	// Reset for 2nd pass or later
		  if(startpoint>0)
		    changed.append(script.substring(0,startpoint));
		  changed.append(classname);
		  endpoint=startpoint+placeholder.length();
		  if(endpoint<script.length())
		    changed.append(script.substring(endpoint));
		  script=changed.toString();
		}
	    }

	  // MJD - debug
//    BSFDeclaredBean tempBean;
//    String          className;
//
//    for (int i = 0; i < declaredBeans.size (); i++) {
//      tempBean  = (BSFDeclaredBean) declaredBeans.elementAt (i);
//      className = StringUtils.getClassName (tempBean.bean.getClass ());
//
//      gf.fos.write ((className + " " +
//                     tempBean.name + " = (" + className +
//                     ")bsf.lookupBean(\"" +
//                     tempBean.name + "\");").getBytes ());
//    }
	// MJD - debug

	// Copy the input to the file.
	  // Assumes all available -- probably mistake, but same as other engines.
	  gf.fos.write(script.getBytes());
	  // Close the method and class
	  gf.fos.write(("\n  }\n}\n").getBytes());
	  gf.fos.close();
	  
	  // Compile through Java to .class file
	  // May not be threadsafe. Serialize access on static object:
	  synchronized(serializeCompilation)
	    {
	      JavaUtils.JDKcompile(gf.file.getPath(), classPath);
	    }
	  
	  // Load class.
	  javaclass=EngineUtils.loadClass (mgr, classname);

	  // Stash class for reuse
	  codeToClass.put(basescript,javaclass);
	}
	  
	  Object[] callArgs={mgr};      
	  retval=internal_call(this,"BSFJavaEngineEntry",callArgs);
	}
	
	
	catch(Exception e)
	  {
	e.printStackTrace ();
	throw new BSFException (BSFException.REASON_IO_ERROR, e.getMessage ());
	  }
	finally
	  {
	// Cleanup: delete the .java and .class files

//  if(gf!=null && gf.file!=null && gf.file.exists())
//    gf.file.delete();  // .java file


  if(classname!=null)
	{
	  // Generated class
	  File file=new File(tempDir+File.separatorChar+classname+".class");
//      if(file.exists())
//        file.delete();

	  // Search for and clean up minor classes, classname$xxx.class
	  file=new File(tempDir);  // ***** Is this required?
	  minorPrefix=classname+"$"; // Indirect arg to filter
	  String[] minor_classfiles=
		file.list(new FilenameFilter()
	  {
		// Starts with classname$ and ends with .class
		public boolean accept(File dir,String name)
		  {
			return
		(0==name.indexOf(minorPrefix))
		&&
		(name.lastIndexOf(".class")==name.length()-6)
		;
		  }
	  });
	  for(int i=0;i<minor_classfiles.length;++i)
		{
	file=new File(minor_classfiles[i]);
//    file.delete();
		}
	}
	  }

	return retval;
  }
  public void initialize (BSFManager mgr, String lang,
						  Vector declaredBeans) throws BSFException {
	super.initialize (mgr, lang, declaredBeans);
  }
  /**
   * Return an object from an extension.
   * @param object Object on which to make the internal_call (ignored).
   * @param method The name of the method to internal_call.
   * @param args an array of arguments to be
   * passed to the extension, which may be either
   * Vectors of Nodes, or Strings.
   */
  Object internal_call (Object object, String method, Object[] args) 
														  throws BSFException
  {
	//***** ISSUE: Only static methods are currently supported
	Object retval=null;
	try
	  {
	if(javaclass!=null)
	  {
	    //***** This should call the lookup used in BML, for typesafety
	    Class[] argtypes=new Class[args.length];
	    for(int i=0;i<args.length;++i)
	      argtypes[i]=args[i].getClass();
	    
	    Method m=MethodUtils.getMethod(javaclass,method,argtypes);
	    retval=m.invoke(null,args);
	  }
	  }
	catch(Exception e)
	  {
	throw new BSFException (BSFException.REASON_IO_ERROR, e.getMessage ());
	  }
	return retval;
  }
  private GeneratedFile openUniqueFile(String directory,String prefix,String suffix)
  {
	File file=null;
	FileOutputStream fos=null;
	int max=1000;		// Don't try forever
	GeneratedFile gf=null;
	int i;
	String className = null;
	for(i=max,++uniqueFileOffset;
	fos==null && i>0;
	--i,++uniqueFileOffset)	
	  {
	// Probably a timing hazard here... ***************
	try
	  {
	    className = prefix+uniqueFileOffset;
	    file=new File(directory+File.separatorChar+className+suffix);
	    if(file!=null && !file.exists())
	      fos=new FileOutputStream(file);
	  }
	catch(Exception e)
	  {
	    // File could not be opened for write, or Security Exception
	    // was thrown. If someone else created the file before we could
	    // open it, that's probably a threading conflict and we don't
	    // bother reporting it.
	    if(!file.exists())
	      {
		DebugLog.stderrPrintln("openUniqueFile: unexpected "+e, DebugLog.BSF_LOG_L0);
		e.printStackTrace();
	      }
	  }
	  }
	if(fos==null)
	  DebugLog.stderrPrintln("openUniqueFile: Failed "+max+"attempts.", DebugLog.BSF_LOG_L0);
	else
	  gf=new GeneratedFile(file,fos,className);
	return gf;
  }
}