// Program: 4033
//  Author: Manuel J. A. Eugster ( e0126312@student.tuwien.ac.at )
//  FileId: $Id: Scanner.java,v 1.1 2002/01/14 17:28:09 heder Exp $



package Wider;



import java.lang.*;



// CLASS:
//    Lexical analysis of a string.
//    Maybe better to extend class java.io.StreamTokenizer.
//
public class Scanner implements Token
{
  public int valueTok;        // Token
  public int valueNum;        // If token is a number, it is saved here
  
  private int pos;            // Actual position 
  private int resistorCount;  // Actual count of resistors
  private StringBuffer expr;  // Input expression
  
  
  
  // METHOD:
  //    Constructor.
  //
  public Scanner( StringBuffer expr ) throws ScannerException
  {
    this.expr = expr;
    this.pos = -1;
    this.valueNum = 0;
    this.valueTok = 0;
    this.resistorCount = 0;
    
    
    nextToken();  // Provide first token
  }
  
  
   
  // METHOD:
  //    Provides next token from input string.
  //    Kind of token is saved and provided in valueTok,
  //    if it's a number, it's saved and provided in
  //    valueNum.
  // 
  public void nextToken() throws ScannerException
  {
    String num = new String();
    char c = 0;
    
    valueNum = 0;  // Delete last num value
    pos++;
    
    
    // Check position //
    if ( pos >= expr.length() )
    {
      valueTok = EOL;
      return;
    }
    
    
    // Check next token //
    switch ( ( c = expr.charAt( pos ) ) )
    {
      case T_BRO:
      {
        valueTok = T_BRO;
        return;
      }
      case T_BRC:
      {
        valueTok = T_BRC;
        return;        
      }
      case T_SER:
      {
        valueTok = T_SER;
        return;
      }
      case T_PAR:
      {
        valueTok = T_PAR;
        return;
      }
      default:  // All other things (resistor values)
      {
        // Get all chars until the next token // 
        while ( c != T_BRO && c != T_PAR && c != T_SER && c != T_BRC && pos < expr.length() )
        {
          num += c;
          pos++;
          
          if ( pos < expr.length() )
          {
            c = expr.charAt( pos );
          }
        }
        pos--;  // Because of the incremention above 
        

        // Semantic check //
        try
        {
          valueNum = Integer.parseInt( num );
        }
        catch ( NumberFormatException e )
        {
          throw new ScannerException( "Bad resistor value" );
        }
        
        
        // Count check //
        if ( ( resistorCount++ ) >= MAX_RES )
        {
          throw new ScannerException( "Too much resistors" );
        }

        
        valueTok = T_NUM;
        return;
      }
    }
  }
}