/* gnu.classpath.tools.gjdoc.expr.Evaluator
   Copyright (C) 2004 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath 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, or (at your option)
any later version.

GNU Classpath 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 GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */

package gnu.classpath.tools.gjdoc.expr;

import java.io.StringReader;
import java.math.BigInteger;
import antlr.RecognitionException;
import antlr.TokenStreamException;
import java.util.Set;

public class Evaluator
{
   /**
    *  Try to evaluate the given Java expression in the context of the
    *  given environment.
    *
    *  @param expression the Java expression to evaluate. The
    *  expression string must not include a terminating semicolon.
    *
    *  @param source the FieldDoc (part of) whose constant field value
    *  expression is being evaluated.  Used to prevent circular
    *  references.
    *
    *  @param environment callback hook used by the Evaluator to query
    *  the value of static fields referenced in the expression.
    *
    *  @return a Java object representing the value of the expression,
    *  or <code>null</code> if the expression evaluates to
    *  <code>null</code>.
    *
    *  @throws IllegalExpressionException if the expression is
    *  invalid, uses unsupported syntax constructs (e.g. method calls,
    *  array access) or references unknown static fields.
    */
   public static Object evaluate(String expression,
                                 Set visitedFields,
                                 EvaluatorEnvironment environment)
      throws IllegalExpressionException
   {
      try {
         JavaLexer lexer = new JavaLexer(new StringReader(expression));
         JavaRecognizer recognizer = new JavaRecognizer(lexer);
         Expression e = recognizer.expression();
         ConstantExpression value = e.evaluate(new Context(environment, visitedFields));
         return value.asObject();
      }
      catch (RecognitionException e) {
         throw new IllegalExpressionException(e);
      }
      catch (TokenStreamException e) {
         throw new IllegalExpressionException(e);
      }
   }

   static int parseInt(String stringValue)
   {
      int base = 10;

      if (stringValue.startsWith("0x")) {
         base = 16;
         stringValue = stringValue.substring(2);
      }
      else if (stringValue.length() > 1 && stringValue.startsWith("0")) {
         base = 8;
         stringValue = stringValue.substring(1);
      }
      while (stringValue.length() > 1 && stringValue.startsWith("0")) {
         stringValue = stringValue.substring(1);
      }

      if (10 == base) {
         return Integer.parseInt(stringValue);
      }
      else {
         long result = Long.parseLong(stringValue, base);

         if (result > Integer.MAX_VALUE) {
            result -= 0x100000000L;
         }

         if (result > Integer.MAX_VALUE) {
            throw new NumberFormatException(result + " > " + Integer.MAX_VALUE);
         }
         else if (result < Integer.MIN_VALUE) {
            throw new NumberFormatException(result + " < " + Integer.MIN_VALUE);
         }
         else {
            return (int)result;
         }
      }
   }

   static long parseLong(String stringValue)
   {
      int base = 10;

      if (stringValue.startsWith("0x")) {
         base = 16;
         stringValue = stringValue.substring(2);
      }
      else if (stringValue.length() > 1 && stringValue.startsWith("0")) {
         base = 8;
         stringValue = stringValue.substring(1);
      }
      while (stringValue.length() > 1 && stringValue.startsWith("0")) {
         stringValue = stringValue.substring(1);
      }

      BigInteger bigInt = new BigInteger(stringValue, base);
      long result = bigInt.longValue();
      return result;
   }
}