/*
Research Project:   Graphical Database for Category Theory
                    J. Bradbury, Dr. R. Rosebrugh, I. Rutherford
                    Mount Allison University 2001
File:               GMLlexer.java
                    (author: Larry Barowski, Auburn University, 10/25/96)
Description:	      A GML lexer. No distinction is made between Integer and Real
                    (all numbers are real).
*/

  //Import statement
   import java.io.InputStream;
   import java.lang.String;
   import java.lang.Math;
   import java.lang.System;

   public class GMLlexer
   {
      public static int GMLstring = 256;
      public static int GMLinteger = 257;
      public static int GMLreal = 258;
      public static int GMLeof = 259;
      public static int GMLkey = 260;
   
      private InputStream stream_;
      private int linenumber_ = 0;
      private int nextChar_ = '\n';
   
      private String stringval_;
      private double doubleval_;
   
      private int tokenType_;
   
   
      public GMLlexer(InputStream streamin)
      {
         stream_ = streamin;
      }
   
   
      public int nextToken() throws java.io.IOException
      {
         skipWhitespace_();
      
         if((nextChar_ >= 'a' && nextChar_ <= 'z') ||
         (nextChar_ >= 'A' && nextChar_ <= 'Z'))
            // Key
         {
            stringval_ = "";
            int index = 0;
            while((nextChar_ >= 'a' && nextChar_ <= 'z') ||
            (nextChar_ >= 'A' && nextChar_ <= 'Z') ||
            (nextChar_ >= '0' && nextChar_ <= '9'))
            {
               stringval_ += String.valueOf((char)nextChar_);
               nextChar_ = stream_.read();
            }
            return (tokenType_ = GMLkey);
         }
         else if(nextChar_ == '-' || (nextChar_ >= '0' && nextChar_ <= '9'))
         {
            // Number
            double fracval = 0, expval = 0, intval = 0;
            boolean havefrac = false, haveexp = false, isneg = false, expisneg = false;
         
            if(nextChar_ == '-')
            {
               isneg = true;
               nextChar_ = stream_.read();
               if(nextChar_ < '0' || nextChar_ > '9')
                  ; // throw a parse warning
            }
         
            while(nextChar_ >= '0' && nextChar_ <= '9')
            {
               intval = intval * 10 + nextChar_ - '0';
               // Add check here later for overflow.
               nextChar_ = stream_.read();
            }
         
            if(nextChar_ == '.')
            {
               havefrac = true;
               nextChar_ = stream_.read();
               // Accepts no digits after decimal.
               while(nextChar_ >= '0' && nextChar_ <= '9')
               {
                  fracval = (fracval + (double)(nextChar_ - '0')) / 10.0;
                  nextChar_ = stream_.read();
               }
            }
         
            if(nextChar_ == 'e' || nextChar_ == 'E')
            {
               stream_.mark(3);
               nextChar_ = stream_.read();
               if(nextChar_ < '0' && nextChar_ > '9' && nextChar_ != '-' && nextChar_ != '+')
                  stream_.reset();
               else
               {
                  if(nextChar_ == '+' || nextChar_ == '-')
                  {
                     if(nextChar_ == '-')
                        expisneg = true;
                     nextChar_ = stream_.read();
                  }
               
                  if(nextChar_ < '0' && nextChar_ > '9')
                     stream_.reset();
                  else
                  {
                     haveexp = true;
                  
                     while(nextChar_ >= '0' && nextChar_ <= '9')
                     {
                        expval = expval * 10.0 + (double)(nextChar_ - '0');
                        nextChar_ = stream_.read();
                     }
                  }
               }
            }
            doubleval_ = intval;
            if(havefrac)
               doubleval_ += fracval;
            if(isneg)
               doubleval_ = -doubleval_;
            if(expisneg)
               expval = -expval;
            if(haveexp)
               doubleval_ *= Math.pow(10.0, expval);
         
            if(!havefrac && !haveexp)
               return (tokenType_ = GMLinteger);
            return GMLreal;
         }
         else if(nextChar_ == '\"')
            // String
         {
            stringval_ = "";
         
            nextChar_ = stream_.read();
            while(nextChar_ >= 0 && nextChar_ != '\"')
            {
               stringval_ += String.valueOf((char)nextChar_);
               nextChar_ = stream_.read();
            }
         
            if(nextChar_ != '\"')
               ; // throw a parse error - end of file in string constant
         
            nextChar_ = stream_.read();
            return (tokenType_ = GMLstring);
         }
         else if(nextChar_ != -1)
         {
            int retval = nextChar_;
            stringval_ = String.valueOf((char)nextChar_);
            nextChar_ = stream_.read();
            return (tokenType_ = retval);
         }
      
         return (tokenType_ = GMLeof);
      }
   
   
   
   
   
      public String getStringval()
      { 
         return stringval_;
      }
   
   
      public double getDoubleval()
      { 
         return doubleval_;
      }
   
   
   
      public int getTokenType()
      {
         return tokenType_;
      }
   
   
      public int getLineNumber()
      {
         return linenumber_;
      }
   
   
   
   
      private void skipWhitespace_() throws java.io.IOException
      {
         while(nextChar_ == ' ' || nextChar_ == '\t' || nextChar_ == '\n' || nextChar_ == '\r')
         {
            // Increment line number and skip comment lines.
            if(nextChar_ == '\n' || nextChar_ == '\r')
            {
               int chr = nextChar_;
               linenumber_++;
               nextChar_ = stream_.read();
               if(chr == '\r' && nextChar_ == '\n')
                  nextChar_ = stream_.read();
               if(nextChar_ == '#')
               {
                  while(nextChar_ != '\n' && nextChar_ != '\r'
                  && nextChar_ != -1)
                  {
                     chr = nextChar_;
                     nextChar_ = stream_.read();
                  }
                  if(chr == '\r' && nextChar_ == '\n')
                     nextChar_ = stream_.read();
               }
            }
            else
               nextChar_ = stream_.read();
         }
      }
   }