#include <cstdlib>
#include <stdio.h>
#include <errno.h>
#include <cstring>
#include <limits.h>
#include <stdint.h>

/**
 * @brief Convert a given string to an unsigned 64 bit integer
 *
 * @param str Input string to convert
 * @param n Integer output
 * @return EXIT_SUCCESS if succesful otherwise EXIT_FAILURE
 */
int32_t sstrtoull(const char* str, uint64_t& n) noexcept {
	errno = 0;
	char* endptr = nullptr;
	const uint64_t a = strtoull(str, &endptr, 10);

	switch(errno){
		case 0:
			n = a;
			return EXIT_SUCCESS;
		case ERANGE:
			fprintf(stderr, "Error while converting to integer : numerical result out of range (");
			if(a == 0)
				fprintf(stderr, "underflow occurred");
			else if(a == ULLONG_MAX)
				fprintf(stderr, "overflow occurred");
			else
				fprintf(stderr, "unspecified");
			fprintf(stderr, ")\n");
			return EXIT_FAILURE;
		default:
			fprintf(stderr, "Unspecified error occurred while converting to integer: %s\n", strerror(errno));
			return EXIT_FAILURE;
	}
}

/**
 * @brief Swap two given memory values
 *
 * @tparam T Type of memory placeholder
 * @param a Firat memory pointer
 * @param b Second memory pointer
 */
template<typename T>
inline void swap(T* const a, T* const b) noexcept {
	const T temp = *a;
	*a = *b;
	*b = temp;

}

/**
 * @brief Convert a given number to string
 *
 * @param num Number to convert
 * @param offset of the string location to append
 * @param str String to append the number to
 * @return number of written bytes
 */
size_t ullstr(uint64_t num, const size_t offset, char* const str) noexcept {
	size_t i = 0;

	for (; num > 0; num /= 10)
		str[offset + i++] = num % 10 + '0';

	str[offset + i] = '\0';

	for (size_t j = 0; j < i / 2; ++j)
		swap(str + offset + j, str + offset + i - j - 1);
	return i;
}

/**
 * @brief Convert a given number to string
 *
 * @param num Number to convert
 * @param str String to append the number to
 * @return number of written bytes
 */
size_t ullstr(uint64_t num, char* const str) noexcept {
	return ullstr(num, 0, str);
}