#include <wchar.h>
#include <time.h>
#include <locale.h>
#include "locale_impl.h"
#include "libc.h"

const char* __strftime_fmt_1(char (*s)[100],
                             size_t* l,
                             int f,
                             const struct tm* tm,
                             locale_t loc);

size_t __wcsftime_l(wchar_t* restrict s,
                    size_t n,
                    const wchar_t* restrict f,
                    const struct tm* restrict tm,
                    locale_t loc) {
  size_t l, k;
  char buf[100];
  wchar_t wbuf[100];
  wchar_t* p;
  const char* t_mb;
  const wchar_t* t;
  int plus;
  unsigned long width;
  for (l = 0; l < n; f++) {
    if (!*f) {
      s[l] = 0;
      return l;
    }
    if (*f != '%') {
      s[l++] = *f;
      continue;
    }
    f++;
    if ((plus = (*f == '+')))
      f++;
    width = wcstoul(f, &p, 10);
    if (*p == 'C' || *p == 'F' || *p == 'G' || *p == 'Y') {
      if (!width && p != f)
        width = 1;
    } else {
      width = 0;
    }
    f = p;
    if (*f == 'E' || *f == 'O')
      f++;
    t_mb = __strftime_fmt_1(&buf, &k, *f, tm, loc);
    if (!t_mb)
      break;
    k = mbstowcs(wbuf, t_mb, sizeof wbuf / sizeof *wbuf);
    if (k == (size_t)-1)
      return 0;
    t = wbuf;
    if (width) {
      for (; *t == '+' || *t == '-' || (*t == '0' && t[1]); t++, k--)
        ;
      width--;
      if (plus && tm->tm_year >= 10000 - 1900)
        s[l++] = '+';
      else if (tm->tm_year < -1900)
        s[l++] = '-';
      else
        width++;
      for (; width > k && l < n; width--)
        s[l++] = '0';
    }
    if (k >= n - l)
      k = n - l;
    wmemcpy(s + l, t, k);
    l += k;
  }
  if (n) {
    if (l == n)
      l = n - 1;
    s[l] = 0;
  }
  return 0;
}

size_t wcsftime(wchar_t* restrict wcs,
                size_t n,
                const wchar_t* restrict f,
                const struct tm* restrict tm) {
  return __wcsftime_l(wcs, n, f, tm, CURRENT_LOCALE);
}

weak_alias(__wcsftime_l, wcsftime_l);