#include <stdint.h>
#include <stddef.h>
#include <string/char.h>
#include <uprintf.h>
#include <limits.h>

// https://android.googlesource.com/platform/bionic/+/ics-mr0/libc/stdlib/strtoul.c
unsigned long string_conv_strtoul(const char *nptr, char **endptr, int base)
{
	const char *s;
	unsigned long acc, cutoff;
	int c;
	int neg, any, cutlim;
	/*
	 * See strtol for comments as to the logic used.
	 */
	s = nptr;
	do {
		c = (unsigned char) *s++;
	} while (string_chr_isspace(c));
	if (c == '-') {
		neg = 1;
		c = *s++;
	} else {
		neg = 0;
		if (c == '+')
			c = *s++;
	}
	if ((base == 0 || base == 16) &&
	    c == '0' && (*s == 'x' || *s == 'X')) {
		c = s[1];
		s += 2;
		base = 16;
	}
	if (base == 0)
		base = c == '0' ? 8 : 10;
	cutoff = ULONG_MAX / (unsigned long)base;
	cutlim = ULONG_MAX % (unsigned long)base;
	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
		if (string_chr_isdigit(c))
			c -= '0';
		else if (string_chr_isalpha(c))
			c -= string_chr_isupper(c) ? 'A' - 10 : 'a' - 10;
		else
			break;
		if (c >= base)
			break;
		if (any < 0)
			continue;
		if (acc > cutoff || (acc == cutoff && c > cutlim)) {
			any = -1;
			acc = ULONG_MAX;
		} else {
			any = 1;
			acc *= (unsigned long)base;
			acc += c;
		}
	}
	if (neg && any > 0)
		acc = -acc;
	if (endptr != 0)
		*endptr = (char *) (any ? s - 1 : nptr);
	return (acc);
}

// https://android.googlesource.com/platform/bionic/+/ics-mr0/libc/stdlib/strtol.c
long string_conv_strtol(const char *nptr, char **endptr, int base)
{
	const char *s;
	long acc, cutoff;
	int c;
	int neg, any, cutlim;
	/*
	 * Skip white space and pick up leading +/- sign if any.
	 * If base is 0, allow 0x for hex and 0 for octal, else
	 * assume decimal; if base is already 16, allow 0x.
	 */
	s = nptr;
	do {
		c = (unsigned char) *s++;
	} while (string_chr_isspace(c));
	if (c == '-') {
		neg = 1;
		c = *s++;
	} else {
		neg = 0;
		if (c == '+')
			c = *s++;
	}
	if ((base == 0 || base == 16) &&
	    c == '0' && (*s == 'x' || *s == 'X')) {
		c = s[1];
		s += 2;
		base = 16;
	}
	if (base == 0)
		base = c == '0' ? 8 : 10;
	/*
	 * Compute the cutoff value between legal numbers and illegal
	 * numbers.  That is the largest legal value, divided by the
	 * base.  An input number that is greater than this value, if
	 * followed by a legal input character, is too big.  One that
	 * is equal to this value may be valid or not; the limit
	 * between valid and invalid numbers is then based on the last
	 * digit.  For instance, if the range for longs is
	 * [-2147483648..2147483647] and the input base is 10,
	 * cutoff will be set to 214748364 and cutlim to either
	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
	 * the number is too big, and we will return a range error.
	 *
	 * Set any if any `digits' consumed; make it negative to indicate
	 * overflow.
	 */
	cutoff = neg ? LONG_MIN : LONG_MAX;
	cutlim = cutoff % base;
	cutoff /= base;
	if (neg) {
		if (cutlim > 0) {
			cutlim -= base;
			cutoff += 1;
		}
		cutlim = -cutlim;
	}
	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
		if (string_chr_isdigit(c))
			c -= '0';
		else if (string_chr_isalpha(c))
			c -= string_chr_isupper(c) ? 'A' - 10 : 'a' - 10;
		else
			break;
		if (c >= base)
			break;
		if (any < 0)
			continue;
		if (neg) {
			if (acc < cutoff || (acc == cutoff && c > cutlim)) {
				any = -1;
				acc = LONG_MIN;
			} else {
				any = 1;
				acc *= base;
				acc -= c;
			}
		} else {
			if (acc > cutoff || (acc == cutoff && c > cutlim)) {
				any = -1;
				acc = LONG_MAX;
			} else {
				any = 1;
				acc *= base;
				acc += c;
			}
		}
	}
	if (endptr != 0)
		*endptr = (char *) (any ? s - 1 : nptr);
	return (acc);
}

const char *human_size(uint64_t bytes, char *buf, size_t bufsize) {
  static const char *units[] = { "B", "KiB", "MiB", "GiB", "TiB", "PiB" };
  int unit = 0;

  // Scale down until value fits nicely
  uint64_t rem = 0;
  while (bytes >= 1024 && unit < (int)(sizeof(units)/sizeof(units[0])) - 1) {
    rem = bytes % 1024;
    bytes /= 1024;
    unit++;
  }

  if (unit == 0) {
    // Just bytes
    usnprintf(buf, bufsize, "%llu %s", (unsigned long long)bytes, units[unit]);
  } else {
    // Show one decimal place without using floats
    // Multiply remainder by 10 to get first decimal digit
    uint64_t frac = (rem * 10 + 512) / 1024; // rounded
    if (frac == 10) { // handle carry, e.g. 1023.9 -> 1024.0
      bytes++;
      frac = 0;
    }

    if (frac > 0) usnprintf(buf, bufsize, "%llu.%llu %s", (unsigned long long)bytes, (unsigned long long)frac, units[unit]);
    else usnprintf(buf, bufsize, "%llu %s", (unsigned long long)bytes, units[unit]);
  }

  return buf;
}
