/**************************************************************************
/* A simple demo class for dynamic method-invocation using reflection
/*
/* Copyright (c) 2004 by Bernhard Bablok (mail@bablokb.de)
/*
/* This program is free software; you can redistribute it and/or modify
/* it under the terms of the GNU General Public License as published
/* by  the Free Software Foundation; either version 2 of the License or
/* (at your option) any later version.
/*
/* This program 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 General Public License for more details.
/*
/* You should have received a copy of the GNU General Public License
/* along with this program; see the file COPYING.  If not, write to
/* the Free Software Foundation Inc., 59 Temple Place - Suite 330,
/* Boston, MA  02111-1307 USA
/**************************************************************************/

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

/**
    A simple demo class for dynamic method-invocation using reflection

   @version $Revision: 1.1 $
   @author  $Author: bablokb $
*/

public class MathCalc {

  //////////////////////////////////////////////////////////////////////////////

  /**
     Parse a given call. The method name is the first element in the linked list.

     @param line The argument line.
  */

  private LinkedList parse(String line) {
    StringTokenizer tokenizer = new StringTokenizer(line," \t\n\r\f,()");
    LinkedList list = new LinkedList();
    while (tokenizer.hasMoreTokens())
      list.add(tokenizer.nextToken());
    return list;
  }

  //////////////////////////////////////////////////////////////////////////////

  /**
     Search for the correct method in {@link java.lang.Math}.

     @param list The linked list with method name and arguments.
  */
  
  private Method searchMethod(LinkedList list) throws NoSuchMethodException {
    if (list.size() < 1)
      throw new IllegalArgumentException("empty line!");
    String name = (String) list.removeFirst();

    Class[] args = new Class[list.size()];
    for (int i=0;i<args.length;++i)
      args[i] = Double.TYPE;
    return Math.class.getDeclaredMethod(name,args);
  }

  //////////////////////////////////////////////////////////////////////////////

  /**
     Execute a given method.

     @param method    The method of {@link java.lang.Math} to execute
     @param arguments The linked list with arguments.
  */
  
  public Object execute(Method method, LinkedList arguments) 
    throws IllegalAccessException, IllegalArgumentException, 
                              InvocationTargetException {
    Double[] args = new Double[arguments.size()];
    Iterator iter = arguments.iterator();
    int i = 0;
    while (iter.hasNext())
      args[i++] = new Double((String) iter.next());

    return method.invoke(null,args);
  }

  //////////////////////////////////////////////////////////////////////////////

  /**
     Main entry point.

     @param args Commandline arguments (ignored).
  */
  
  public static void main(String[] args) {
    try {
      MathCalc mc = new MathCalc();
      
      BufferedReader input =
        new BufferedReader(new InputStreamReader(System.in));
      while (true) {
        System.out.print("> ");
        String line = input.readLine();
        if (line == null)
          break;
        else if (line.length() == 0)
          continue;
        else {
          try {
            long t1 = System.currentTimeMillis();
            LinkedList list = mc.parse(line);
            long t2 = System.currentTimeMillis();
            Method m = mc.searchMethod(list);
            long t3 = System.currentTimeMillis();
            Object result = mc.execute(m,list);
            long t4 = System.currentTimeMillis();
            System.out.println(result.toString() +
                       "\n\tparse:   " + (t2-t1) + "msec" +
                       "\n\tsearch:  " + (t3-t2) + "msec" +
                       "\n\texecute: " + (t4-t3) + "msec\n");
          } catch (Exception e2) {
            System.out.println("error: " + e2.toString());
          }
        }
      }
      input.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}