/* Case mapping for UTF-8/UTF-16/UTF-32 strings (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,
      ucs4_t (*single_character_map) (ucs4_t),
      size_t offset_in_rule, /* offset in 'struct special_casing_rule' */
      uninorm_t nf,
      UNIT *resultbuf, size_t *lengthp)
{
  /* The result being accumulated.  */
  UNIT *result;
  size_t length;
  size_t allocated;

  /* Initialize the accumulator.  */
  if (nf != NULL || resultbuf == NULL)
    {
      result = NULL;
      allocated = 0;
    }
  else
    {
      result = resultbuf;
      allocated = *lengthp;
    }
  length = 0;

  {
    const UNIT *s_end = s + n;

    /* Helper for evaluating the FINAL_SIGMA condition:
       Last character that was not case-ignorable.  */
    ucs4_t last_char_except_ignorable =
      prefix_context.last_char_except_ignorable;

    /* Helper for evaluating the AFTER_SOFT_DOTTED and AFTER_I conditions:
       Last character that was of combining class 230 ("Above") or 0.  */
    ucs4_t last_char_normal_or_above =
      prefix_context.last_char_normal_or_above;

    while (s < s_end)
      {
        ucs4_t uc;
        int count = U_MBTOUC_UNSAFE (&uc, s, s_end - s);

        ucs4_t mapped_uc[3];
        unsigned int mapped_count;

        if (uc < 0x10000)
          {
            /* Look first in the special-casing table.  */
            char code[3];

            code[0] = (uc >> 8) & 0xff;
            code[1] = uc & 0xff;

            for (code[2] = 0; ; code[2]++)
              {
                const struct special_casing_rule *rule =
                  gl_unicase_special_lookup (code, 3);

                if (rule == NULL)
                  break;

                /* Test if the condition applies.  */
                /* Does the language apply?  */
                if (rule->language[0] == '\0'
                    || (iso639_language != NULL
                        && iso639_language[0] == rule->language[0]
                        && iso639_language[1] == rule->language[1]))
                  {
                    /* Does the context apply?  */
                    int context = rule->context;
                    bool applies;

                    if (context < 0)
                      context = - context;
                    switch (context)
                      {
                      case SCC_ALWAYS:
                        applies = true;
                        break;

                      case SCC_FINAL_SIGMA:
                        /* "Before" condition: preceded by a sequence
                           consisting of a cased letter and a case-ignorable
                           sequence.
                           "After" condition: not followed by a sequence
                           consisting of a case-ignorable sequence and then a
                           cased letter.  */
                        /* Test the "before" condition.  */
                        applies = uc_is_cased (last_char_except_ignorable);
                        /* Test the "after" condition.  */
                        if (applies)
                          {
                            const UNIT *s2 = s + count;
                            for (;;)
                              {
                                if (s2 < s_end)
                                  {
                                    ucs4_t uc2;
                                    int count2 = U_MBTOUC_UNSAFE (&uc2, s2, s_end - s2);
                                    /* Our uc_is_case_ignorable function is
                                       known to return false for all cased
                                       characters.  So we can call
                                       uc_is_case_ignorable first.  */
                                    if (!uc_is_case_ignorable (uc2))
                                      {
                                        applies = ! uc_is_cased (uc2);
                                        break;
                                      }
                                    s2 += count2;
                                  }
                                else
                                  {
                                    applies = ! uc_is_cased (suffix_context.first_char_except_ignorable);
                                    break;
                                  }
                              }
                          }
                        break;

                      case SCC_AFTER_SOFT_DOTTED:
                        /* "Before" condition: There is a Soft_Dotted character
                           before it, with no intervening character of
                           combining class 0 or 230 (Above).  */
                        /* Test the "before" condition.  */
                        applies = uc_is_property_soft_dotted (last_char_normal_or_above);
                        break;

                      case SCC_MORE_ABOVE:
                        /* "After" condition: followed by a character of
                           combining class 230 (Above) with no intervening
                           character of combining class 0 or 230 (Above).  */
                        /* Test the "after" condition.  */
                        {
                          const UNIT *s2 = s + count;
                          applies = false;
                          for (;;)
                            {
                              if (s2 < s_end)
                                {
                                  ucs4_t uc2;
                                  int count2 = U_MBTOUC_UNSAFE (&uc2, s2, s_end - s2);
                                  int ccc = uc_combining_class (uc2);
                                  if (ccc == UC_CCC_A)
                                    {
                                      applies = true;
                                      break;
                                    }
                                  if (ccc == UC_CCC_NR)
                                    break;
                                  s2 += count2;
                                }
                              else
                                {
                                  applies = ((suffix_context.bits & SCC_MORE_ABOVE_MASK) != 0);
                                  break;
                                }
                            }
                        }
                        break;

                      case SCC_BEFORE_DOT:
                        /* "After" condition: followed by COMBINING DOT ABOVE
                           (U+0307). Any sequence of characters with a
                           combining class that is neither 0 nor 230 may
                           intervene between the current character and the
                           combining dot above.  */
                        /* Test the "after" condition.  */
                        {
                          const UNIT *s2 = s + count;
                          applies = false;
                          for (;;)
                            {
                              if (s2 < s_end)
                                {
                                  ucs4_t uc2;
                                  int count2 = U_MBTOUC_UNSAFE (&uc2, s2, s_end - s2);
                                  if (uc2 == 0x0307) /* COMBINING DOT ABOVE */
                                    {
                                      applies = true;
                                      break;
                                    }
                                  {
                                    int ccc = uc_combining_class (uc2);
                                    if (ccc == UC_CCC_A || ccc == UC_CCC_NR)
                                      break;
                                  }
                                  s2 += count2;
                                }
                              else
                                {
                                  applies = ((suffix_context.bits & SCC_BEFORE_DOT_MASK) != 0);
                                  break;
                                }
                            }
                        }
                        break;

                      case SCC_AFTER_I:
                        /* "Before" condition: There is an uppercase I before
                           it, and there is no intervening character of
                           combining class 0 or 230 (Above).  */
                        /* Test the "before" condition.  */
                        applies = (last_char_normal_or_above == 'I');
                        break;

                      default:
                        abort ();
                      }
                    if (rule->context < 0)
                      applies = !applies;

                    if (applies)
                      {
                        /* The rule applies.
                           Look up the mapping (0 to 3 characters).  */
                        const unsigned short *mapped_in_rule =
                          (const unsigned short *)((const char *)rule + offset_in_rule);

                        if (mapped_in_rule[0] == 0)
                          mapped_count = 0;
                        else
                          {
                            mapped_uc[0] = mapped_in_rule[0];
                            if (mapped_in_rule[1] == 0)
                              mapped_count = 1;
                            else
                              {
                                mapped_uc[1] = mapped_in_rule[1];
                                if (mapped_in_rule[2] == 0)
                                  mapped_count = 2;
                                else
                                  {
                                    mapped_uc[2] = mapped_in_rule[2];
                                    mapped_count = 3;
                                  }
                              }
                          }
                        goto found_mapping;
                      }
                  }

                /* Optimization: Save a hash table lookup in the next round.  */
                if (!rule->has_next)
                  break;
              }
          }

        /* No special-cased mapping.  So use the locale and context independent
           mapping.  */
        mapped_uc[0] = single_character_map (uc);
        mapped_count = 1;

       found_mapping:
        /* Found the mapping: uc maps to mapped_uc[0..mapped_count-1].  */
        {
          unsigned int i;

          for (i = 0; i < mapped_count; i++)
            {
              ucs4_t muc = mapped_uc[i];

              /* Append muc to the result accumulator.  */
              if (length < allocated)
                {
                  int ret = U_UCTOMB (result + length, muc, allocated - length);
                  if (ret == -1)
                    {
                      errno = EINVAL;
                      goto fail;
                    }
                  if (ret >= 0)
                    {
                      length += ret;
                      goto done_appending;
                    }
                }
              {
                size_t old_allocated = allocated;
                size_t new_allocated = 2 * old_allocated;
                if (new_allocated < 64)
                  new_allocated = 64;
                if (new_allocated < old_allocated) /* integer overflow? */
                  abort ();
                {
                  UNIT *larger_result;
                  if (result == NULL)
                    {
                      larger_result = (UNIT *) malloc (new_allocated * sizeof (UNIT));
                      if (larger_result == NULL)
                        {
                          errno = ENOMEM;
                          goto fail;
                        }
                    }
                  else if (result == resultbuf)
                    {
                      larger_result = (UNIT *) malloc (new_allocated * sizeof (UNIT));
                      if (larger_result == NULL)
                        {
                          errno = ENOMEM;
                          goto fail;
                        }
                      U_CPY (larger_result, resultbuf, length);
                    }
                  else
                    {
                      larger_result =
                        (UNIT *) realloc (result, new_allocated * sizeof (UNIT));
                      if (larger_result == NULL)
                        {
                          errno = ENOMEM;
                          goto fail;
                        }
                    }
                  result = larger_result;
                  allocated = new_allocated;
                  {
                    int ret = U_UCTOMB (result + length, muc, allocated - length);
                    if (ret == -1)
                      {
                        errno = EINVAL;
                        goto fail;
                      }
                    if (ret < 0)
                      abort ();
                    length += ret;
                    goto done_appending;
                  }
                }
              }
             done_appending: ;
            }
        }

        if (!uc_is_case_ignorable (uc))
          last_char_except_ignorable = uc;

        {
          int ccc = uc_combining_class (uc);
          if (ccc == UC_CCC_A || ccc == UC_CCC_NR)
            last_char_normal_or_above = uc;
        }

        s += count;
      }
  }

  if (nf != NULL)
    {
      /* Finally, normalize the result.  */
      UNIT *normalized_result;

      normalized_result = U_NORMALIZE (nf, result, length, resultbuf, lengthp);
      if (normalized_result == NULL)
        goto fail;

      free (result);
      return normalized_result;
    }

  if (length == 0)
    {
      if (result == NULL)
        {
          /* Return a non-NULL value.  NULL means error.  */
          result = (UNIT *) malloc (1);
          if (result == NULL)
            {
              errno = ENOMEM;
              goto fail;
            }
        }
    }
  else if (result != resultbuf && length < allocated)
    {
      /* Shrink the allocated memory if possible.  */
      UNIT *memory;

      memory = (UNIT *) realloc (result, length * sizeof (UNIT));
      if (memory != NULL)
        result = memory;
    }

  *lengthp = length;
  return result;

 fail:
  if (result != resultbuf)
    {
      int saved_errno = errno;
      free (result);
      errno = saved_errno;
    }
  return NULL;
}
