#include <errno.h>
#include <wchar.h>

#include "locale_impl.h"
#include "stdio_impl.h"

static wint_t __fgetwc_unlocked_internal(FILE* f) {
  mbstate_t st = {};
  wchar_t wc;
  int c;
  unsigned char b;
  size_t l;

  /* Convert character from buffer if possible */
  if (f->rpos < f->rend) {
    l = mbrtowc(&wc, (void*)f->rpos, f->rend - f->rpos, &st);
    if (l + 2 >= 2) {
      f->rpos += l + !l; /* l==0 means 1 byte, null */
      return wc;
    }
    if (l == -1) {
      f->rpos++;
      return WEOF;
    }
  } else
    l = -2;

  /* Convert character byte-by-byte */
  while (l == -2) {
    b = c = getc_unlocked(f);
    if (c < 0) {
      if (!mbsinit(&st))
        errno = EILSEQ;
      return WEOF;
    }
    l = mbrtowc(&wc, (void*)&b, 1, &st);
    if (l == -1)
      return WEOF;
  }

  return wc;
}

wint_t __fgetwc_unlocked(FILE* f) {
  locale_t *ploc = &CURRENT_LOCALE, loc = *ploc;
  if (f->mode <= 0)
    fwide(f, 1);
  *ploc = f->locale;
  wchar_t wc = __fgetwc_unlocked_internal(f);
  *ploc = loc;
  return wc;
}

wint_t fgetwc(FILE* f) {
  wint_t c;
  FLOCK(f);
  c = __fgetwc_unlocked(f);
  FUNLOCK(f);
  return c;
}

weak_alias(__fgetwc_unlocked, fgetwc_unlocked);
weak_alias(__fgetwc_unlocked, getwc_unlocked);