/*
 * Nancy Ide 
 * Character Stream Reader
 * Sample solution for CS331
 *
 */

#include "char_stream.h"
#include "error.h"
#include <cctype>


extern char Current_Line[];               // current input line
extern int  Line_Number;                  // line counter


CharStream::CharStream()
{
   fOpened = false;
}

CharStream::CharStream(const char filename[])
{
   this->open(filename);
   fOpened = this->good();
   Line_Number = 0;
   
   if (fOpened)
         SkipWhite();
}


void CharStream::Push_back(char Look_Ahead)
{
   CharStack.push(Look_Ahead);
}


void CharStream::SkipWhite(void)
{
   if ( Current_Line[Current_Char] == L_CURLY )
      SkipComment();

   while ( Current_Line[Current_Char] == BLANK 
             || Current_Line[Current_Char] == TAB)
   {
      Advance();

      if ( Current_Line[Current_Char] == L_CURLY )
	 SkipComment();
   }
}


void CharStream::SkipComment(void)
{
   
   while ( Current_Line[Current_Char] != R_CURLY )
   {
      Advance();

      if ( Current_Line[Current_Char] == L_CURLY )
         throw Error(1);
   }
   
   Advance();
}
   

CharStream::~CharStream()
{
   if ( fOpened )
      this->close();
}


char CharStream::CurrentChar(void)
{
   char C;

   if ( !CharStack.empty() )
   {
      C = ( CharStack.top() );
      CharStack.pop();
      return( C );
   }


   C = ( Current_Line[Current_Char] );


   if ( C == EOL_CHAR )
   {
       GetNewLine();
       while ( Current_Line[Current_Char] == EOL_CHAR )
       // handle multiple blank lines
	  GetNewLine();
       
       return(BLANK);
   }
      
   if ( C == L_CURLY )
   {
      SkipComment();

      return(BLANK);
   }

   if ( C == BLANK || C == TAB )                        
   // First blank is returned as a delimeter
   {
      SkipWhite();

      return(BLANK);
   }

   Advance();

   return (C);

}



void CharStream::GetNewLine(void)
{
   if (eof())
   {
      Current_Char = 0;
      Current_Line[Current_Char] = EOF_CHAR;
   }

   else
   {
      getline(Current_Line,LINE_SIZE-1);

      ++Line_Number;
      Current_Char = 0;
      SkipWhite();
   }
}


void CharStream::Advance(void)
{
   if ( Current_Line[Current_Char] == EOL_CHAR )
      GetNewLine();

   else ++Current_Char;
   
}

bool CharStream::Open(const char filename[])
{
   this->open(filename);
   fOpened = this->good();
   return fOpened;
}

void CharStream::Close(void)
{
   if ( fOpened )
      this->close();
}


bool CharStream::Valid (char c)
{
   return(  ( c == EOL_CHAR ) ||
            ( strchr( VALID_CHARS,c ) != NULL ) );
}