package Util;

import java.io.*;
 

public class Lexer {

    // member varibles :
    private byte[] cur;                   //current character
    private int curr_line;                //current line#
    private int curr_col;                 //current column#
    private int token_col;
    private int max_token_col;
    private InputStream input_data;       //input file stream
    boolean EOF_FOUND;                    //End of file reached
  
    // constructor   
    public Lexer(InputStream in){ 
	cur=new byte[1];
	input_data=in;
	curr_line=0;
	curr_col=0;
	Read_A_Char();
	EOF_FOUND=false;
    }
    
    // private method : Read a single character
    private void Read_A_Char()
    { 
	try { if(input_data.read(cur,0,1)!=1) { 
	    EOF_FOUND=true; 
	    return; 
	} 
                                           
	if(cur[0]=='\n'||cur[0]=='\r') { 
	    curr_line++; 
	    curr_col=0; 
	    token_col=0;
	} // a new line 
	else 
	    curr_col++;
        }catch (Exception e1) { 
	    System.err.println("EXCEPTION in Lexer");
	}
    }


    public String getNextString(){ 

	/* If current character reached is EOF: */
	if(EOF_FOUND) 
	    return null;
	
	/* skip the whitespace except EOF*/
	while( Character.isWhitespace( (char)cur[0] ) ) { 
	    Read_A_Char();
	    if(EOF_FOUND) 
		return null;
	} 
    
	/* Record the initial position*/
	int start_col=curr_col;
	int start_line=curr_line;
	
	/* record the initial state, prepare to find a string */	
	String curr_string_token="";
	curr_string_token+=(char)cur[0];  //used to store found string
	

	/* serach longest string token:*/                   
	for( ; ; ){ 
	    Read_A_Char();                                    //stop when finds 
	    if( Character.isWhitespace((char)cur[0])               //a whitespace
		||EOF_FOUND)                                  //end of file
		break;  
	    else 
		curr_string_token+=(char)cur[0];
	} 
	
	token_col++;
	if(max_token_col<token_col)
	    max_token_col = token_col;

	return curr_string_token;
     
   
    }

    public int getTokenCol(){
	return max_token_col;
    }
    public int getLine(){
	return curr_line;
    }


}