#include <string>
#include <array>
#include <stdint.h>
#include "toolbox.hpp"

static constexpr const size_t STRING_BUFFER_SIZE = 64;
static constexpr const std::array<const char[3], 7> format_prefix = { "B", "KB", "MB", "GB", "TB", "PB", "EB" };

/**
 * @brief Convert a given numbers of bytes to a human readable format
 *
 * @param n Number of bytes
 * @return Human readable format of the numbers of bytes
 */
std::string format_bytes(uint64_t n) noexcept {
	char s[STRING_BUFFER_SIZE] = { 0 };

	if(n == 0){
		sprintf(s, "0%s", format_prefix[0]);
		return s;
	}

	size_t j = 0;
	for(int8_t i = static_cast<int8_t>(format_prefix.size() - 1) * 10; i >= 0; i -= 10){
		const uint64_t nsi = n >> i;
		if(nsi > 0){
			const int8_t idx = i / 10;
			j += ullstr(nsi, j, s);
			for(int k = 0; format_prefix[idx][k] > 0; ++k)
				s[j++] = format_prefix[idx][k];
			s[j++] = ' ';
			n &= u64(-1) >> (64 - i);
		}
	}

	/* Remove trailing character */
	s[j - 1] = '\0';

	return std::string(s);
}

#ifndef TEST
int32_t main(const int32_t argc, const char* const* argv) noexcept {

	uint64_t n = 0;
	if (argc > 2) return fprintf(stderr, "Invalid usage : (%s $NUMBER) or (echo $NUMBER | %s)\n", argv[0], argv[0]);
	else if (argc == 2){
		if(sstrtoull(argv[1], n) == EXIT_FAILURE)
			return EXIT_FAILURE;
	} else {
		size_t i = 0;
		char BUFFER[STRING_BUFFER_SIZE];
		for(int c; i < STRING_BUFFER_SIZE && (c = fgetc(stdin)) != EOF; ++i)
			BUFFER[i] = c;
		if(i == STRING_BUFFER_SIZE){
			fprintf(stderr, "Error while converting to integer : invalid stdin input (too large)\n");
			return EXIT_FAILURE;
		}
		if(sstrtoull(BUFFER, n) == EXIT_FAILURE)
			return EXIT_FAILURE;
	}

	printf("%s\n", format_bytes(n).c_str());
	return EXIT_SUCCESS;
}
#endif