%{
#include <stdio.h>
#include <stdlib.h>

void yyerror(const char *s);
int yylex(void);

extern FILE* yyin;
%}

%union { int num; char var; }

%token <num> NUMBER
%token <var> VARIABLE
%token LPAREN RPAREN PLUS MINUS MULTIPLY

%%

input:
    expr { printf("\033[92mParsing complete\033[0m\n"); }
;

expr:
    term
    | expr PLUS term { printf("Found operator: +\n"); }
    | expr MINUS term { printf("Found operator: -\n"); }
;

term:
    factor
    | term MULTIPLY factor { printf("Found operator: *\n"); }
;

factor:
    NUMBER { printf("Found number: %d\n", $1); }
    | VARIABLE { printf("Found variable: %c\n", $1); }
    | LPAREN expr RPAREN
;

%%

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

int main(int argc, char** argv) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <input_file>\n", argv[0]);
        return 1;
    }
    FILE* input_file = fopen(argv[1], "r");
    if (!input_file) {
        perror("Failed to open input file");
        return 1;
    }

    yyin = input_file;

    printf("Parsing expression from file: %s\n", argv[1]);
    yyparse();
    fclose(input_file);
    
    return 0;
}