#include <stdlib.h>
#include <stdio.h>
#define SIZE 1024

struct stack {
	long int data;
	struct stack *next;
};

void push(struct stack **s, long int i) {
	struct stack *nuevo = malloc(sizeof(struct stack));
	nuevo->data = i;
	nuevo->next = *s;
	*s = nuevo;
}

void pop(struct stack **s) {
	struct stack *temp = *s;
	*s = (*s)->next;
	free(temp);
}

int main(int argc, char **argv) {
	if (argc != 2) return 1;
	FILE *source = fopen(argv[1], "r");
	if (!source) return 1;
	struct stack *open_brackets = 0;
	char tape[SIZE] = {0};
	char *curr = tape;
	int lineNr = 1;
	int exit = 0;
	while (!feof(source) && !exit) {
		char c = fgetc(source);
		switch (c) {
		case '\n':
			lineNr++;
			break;
		case '+':
			*curr += 1;
			break;
		case '-':
			*curr -= 1;
			break;
		case '>':
			if (curr != &tape[SIZE - 1]) curr++;
			else curr = &tape[0];
			break;
		case '<':
			if (curr != &tape[0]) curr--;
			else curr = &tape[SIZE - 1];
			break;
		case '.':
			putchar(*curr);
			break;
		case ',':
			*curr = getchar();
			break;
		case '[':
			if (*curr) {
				push(&open_brackets, ftell(source));
			}
			else {
				int counter = 1;
				while (counter > 0 && !feof(source)) {
					c = fgetc(source);
					if (c == '[') counter++;
					else if (c == ']') counter--;
				}
				if (feof(source)) {
					printf("Error: Can't find matching ']' at line %d\n", lineNr);
					exit = 1;
				}
			}
			break;
		case ']':
			if (*curr && open_brackets) {
				fseek(source, open_brackets->data, SEEK_SET);
			}
			else if (open_brackets){
				pop(&open_brackets);
			}
			else {
				printf("Error: Can't find matching '[' at line %d\n", lineNr);
				exit = 1;
			}
		}
	}
	if (open_brackets) {
		lineNr = 1;
		rewind(source);
		while (ftell(source) != open_brackets->data) {
			if (fgetc(source) == '\n') lineNr++;
		}
		printf("Error: Can't find matching ']' at line %d\n", lineNr);
		while (open_brackets) pop(&open_brackets);
		exit = 1;
	}
	fclose(source);
	return exit;
}