/* Casefolding mapping for Unicode substrings (locale dependent).
   Copyright (C) 2009-2018 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2009.

   This program is free software: you can redistribute it and/or
   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at your
       option) any later version.

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at your
       option) any later version.

   or both in parallel, as here.
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

UNIT *
FUNC (const UNIT *s, size_t n,
      casing_prefix_context_t prefix_context,
      casing_suffix_context_t suffix_context,
      const char *iso639_language,
      uninorm_t nf,
      UNIT *resultbuf, size_t *lengthp)
{
  /* Implement the three definitions of caseless matching, as described in
     Unicode 5.0, section "Default caseless matching":
       - If no normalization is requested, simply apply the casefolding.
           X -> toCasefold(X).
       - If canonical normalization is requested, apply it, and apply an NFD
         before.
           X -> NFD(toCasefold(NFD(X))).
       - If compatibility normalization is requested, apply it twice, apply
         the normalization after each, and apply an NFD before:
           X -> NFKD(toCasefold(NFKD(toCasefold(NFD(X))))).  */
  if (nf == NULL)
    /* X -> toCasefold(X) */
    return U_CASEMAP (s, n, prefix_context, suffix_context, iso639_language,
                      uc_tocasefold, offsetof (struct special_casing_rule, casefold[0]),
                      NULL,
                      resultbuf, lengthp);
  else
    {
      uninorm_t nfd = uninorm_decomposing_form (nf);
      /* X -> nf(toCasefold(NFD(X))) or
         X -> nf(toCasefold(nfd(toCasefold(NFD(X)))))  */
      int repeat = (uninorm_is_compat_decomposing (nf) ? 2 : 1);
      UNIT tmpbuf1[2048 / sizeof (UNIT)];
      UNIT tmpbuf2[2048 / sizeof (UNIT)];
      UNIT *tmp1;
      size_t tmp1_length;
      UNIT *tmp2;
      size_t tmp2_length;

      tmp1_length = sizeof (tmpbuf1) / sizeof (UNIT);
      tmp1 = U_NORMALIZE (UNINORM_NFD, s, n, tmpbuf1, &tmp1_length);
      if (tmp1 == NULL)
        /* errno is set here.  */
        return NULL;

      do
        {
          tmp2_length = sizeof (tmpbuf2) / sizeof (UNIT);
          tmp2 = U_CASEMAP (tmp1, tmp1_length,
                            prefix_context, suffix_context, iso639_language,
                            uc_tocasefold, offsetof (struct special_casing_rule, casefold[0]),
                            NULL,
                            tmpbuf2, &tmp2_length);
          if (tmp2 == NULL)
            {
              int saved_errno = errno;
              if (tmp1 != tmpbuf1)
                free (tmp1);
              errno = saved_errno;
              return NULL;
            }

          if (tmp1 != tmpbuf1)
            free (tmp1);

          if (repeat > 1)
            {
              tmp1_length = sizeof (tmpbuf1) / sizeof (UNIT);
              tmp1 = U_NORMALIZE (nfd, tmp2, tmp2_length,
                                  tmpbuf1, &tmp1_length);
            }
          else
            /* Last run through this loop.  */
            tmp1 = U_NORMALIZE (nf, tmp2, tmp2_length,
                                resultbuf, lengthp);
          if (tmp1 == NULL)
            {
              int saved_errno = errno;
              if (tmp2 != tmpbuf2)
                free (tmp2);
              errno = saved_errno;
              return NULL;
            }

          if (tmp2 != tmpbuf2)
            free (tmp2);
        }
      while (--repeat > 0);

      return tmp1;
    }
}
