// Regex pattern to detect if path is relative by
// matching for valid '.' or '..' path components
static const regex_t dot_regex;
static const char *dot_pattern = "(^\\.{1,2}/|/\\.{1,2}/|/\\.{1,2}$)";

// Initializer function automatically invoked when shared library is loaded
__attribute__((constructor)) static void library_initialize(void)
{
	int err;
	if ((err = regcomp((regex_t *)&dot_regex, dot_pattern,
			   REG_EXTENDED | REG_NOSUB))) {
		fprintf(stderr, "error err=%d compiling regex=%s\n", err,
			dot_pattern);
		abort();
	}
}

static int make_abspath(const char *src, char *buff, size_t size)
{
	// Check if we even have relative path to resolve by
	// looking for '.' before the last directory component
	const char *rpos = strrchr(src, '/');
	if (!rpos || rpos == src || regexec(&dot_regex, src, 0, NULL, 0)) {
		GITCEPTOR_TRACE("not a relative path=%s\n", src);
		strncpy(buff, src, size);
		return 0;
	}

	char *last = NULL;
	char path[PATH_MAX];
	buff[0] = '\0';
	strncpy(path, src, sizeof(path));

	for (char *word = strtok_r(path, "/", &last); word;
	     word = strtok_r(NULL, "/", &last)) {
		// Skip referring to current directory or repeat slash
		if (!*word || !strcmp(word, ".")) {
			continue;
		}

		// Traverse up to parent directory by popping the current leaf
		if (!strcmp(word, "..")) {
			char *right_slash = strrchr(buff, '/');
			if (right_slash) {
				right_slash[0] = '\0';
			}
			continue;
		}

		// Append valid directory component to absolute path
		strncat(buff, "/", size);
		strncat(buff, word, size);
	}

	return '\0' == *buff ? -1 : 0;
}