%{
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "symtab.h"

#define INT_TYPE 0

int yylex() ;

void yyerror(const char *s) {
   fprintf(stderr, "yyerror: %s\n", s) ;
   exit(1) ;
}

unsigned int global_var_no = 0 ;

FILE *of ;
%}

%union {
   char *strval ;
   int  ival ;
}

%token <strval> NAME 
%token <ival> NUMBER 
%token PRINT VAR
%left '+' '-'
%left '*' '/'
%nonassoc UMINUS

%type <ival> declaration
%type <ival> assignment
%type <ival> print_statement
%type <ival> expression

%%

program : program statement | statement ;

statement:
    declaration 
    | assignment
    | print_statement 
    ;

declaration: VAR NAME ';' {
        fprintf(stderr, "Variable %s delcared.\n", $2) ;

        st_entry s ;
        s.type = INT_TYPE ;
        s.var_no = global_var_no++ ;
        st_insert($2, s) ;
        fprintf(of, "VARIABLE %s\n", $2) ;
        free($2) ;
    }
    ;

assignment: NAME '=' expression ';' {
        fprintf(stderr, "Assignment for variable %s.\n", $1) ;

        st_entry *p ;
        p = st_find($1) ;
        fprintf(of, "%s !\n", $1) ;
        free($1) ;  
    }   
    ;

print_statement: PRINT NAME ';' {
        fprintf(stderr, "Printing variable %s.\n", $2) ;

        st_entry *p ;
        p = st_find($2) ;
        fprintf(of, "%s ? CR\n", $2) ;
        free($2) ;  
    }   
    ;

expression: 
    '(' expression ')' {
        /* do nothing */
        }   
    | expression '+' expression   { 
        fprintf (of, "+ ") ;  
        } 
    | expression '-' expression { 
        fprintf (of, "- ") ;  
        }
    | expression '*' expression { 
        fprintf (of, "* ") ;  
        } 
    | expression '/' expression { 
        fprintf (of, "/ ") ;  
        } 
    | '-' expression %prec UMINUS {
        fprintf (of, "negate ") ;
        }
    | NUMBER { 
        fprintf (of, "%d ", $1) ; 
        }
    ;
%%

int main () {

   st_init() ;   /* Currently does nothing */

   // fprintf (stderr, "Hello World\n") ;
   of = fopen ("out.fs", "w") ;
   assert(of != NULL) ;

   yyparse() ;

   fclose(of) ;
   return 0 ;
}  /* End of main() */