/*

 * Copyright © 2011,2012  Google, Inc.

 *

 *  This is part of HarfBuzz, a text shaping library.

 *

 * Permission is hereby granted, without written agreement and without

 * license or royalty fees, to use, copy, modify, and distribute this

 * software and its documentation for any purpose, provided that the

 * above copyright notice and the following two paragraphs appear in

 * all copies of this software.

 *

 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR

 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES

 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN

 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH

 * DAMAGE.

 *

 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,

 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS

 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO

 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

 *

 * Google Author(s): Behdad Esfahbod

 */

#include "hb.hh"

#ifndef HB_NO_OT_SHAPE

#include "hb-ot-shape-normalize.hh"

#include "hb-ot-shaper.hh"

#include "hb-ot-shape.hh"

/*

 * HIGHLEVEL DESIGN:

 *

 * This file exports one main function: _hb_ot_shape_normalize().

 *

 * This function closely reflects the Unicode Normalization Algorithm,

 * yet it's different.

 *

 * Each shaper specifies whether it prefers decomposed (NFD) or composed (NFC).

 * The logic however tries to use whatever the font can support.

 *

 * In general what happens is that: each grapheme is decomposed in a chain

 * of 1:2 decompositions, marks reordered, and then recomposed if desired,

 * so far it's like Unicode Normalization.  However, the decomposition and

 * recomposition only happens if the font supports the resulting characters.

 *

 * The goals are:

 *

 *   - Try to render all canonically equivalent strings similarly.  To really

 *     achieve this we have to always do the full decomposition and then

 *     selectively recompose from there.  It's kinda too expensive though, so

 *     we skip some cases.  For example, if composed is desired, we simply

 *     don't touch 1-character clusters that are supported by the font, even

 *     though their NFC may be different.

 *

 *   - When a font has a precomposed character for a sequence but the 'ccmp'

 *     feature in the font is not adequate, use the precomposed character

 *     which typically has better mark positioning.

 *

 *   - When a font does not support a combining mark, but supports it precomposed

 *     with previous base, use that.  This needs the itemizer to have this

 *     knowledge too.  We need to provide assistance to the itemizer.

 *

 *   - When a font does not support a character but supports its canonical

 *     decomposition, well, use the decomposition.

 *

 *   - The shapers can customize the compose and decompose functions to

 *     offload some of their requirements to the normalizer.  For example, the

 *     Indic shaper may want to disallow recomposing of two matras.

 */

static inline void

set_glyph (hb_glyph_info_t &info, hb_font_t *font)

{

  (void) font->get_nominal_glyph (info.codepoint, &info.glyph_index());

}

static inline void

output_char (hb_buffer_t *buffer, hb_codepoint_t unichar, hb_codepoint_t glyph)

{

  /* This is very confusing indeed. */

  buffer->cur().glyph_index() = glyph;

  (void) buffer->output_glyph (unichar);

  _hb_glyph_info_set_unicode_props (&buffer->prev(), buffer);

}

static inline void

next_char (hb_buffer_t *buffer, hb_codepoint_t glyph)

{

  buffer->cur().glyph_index() = glyph;

  (void) buffer->next_glyph ();

}

static inline void

skip_char (hb_buffer_t *buffer)

{

  buffer->skip_glyph ();

}

/* Returns 0 if didn't decompose, number of resulting characters otherwise. */

static inline unsigned int

decompose (const hb_ot_shape_normalize_context_t *c, bool shortest, hb_codepoint_t ab)

{

  hb_codepoint_t a = 0, b = 0, a_glyph = 0, b_glyph = 0;

  hb_buffer_t * const buffer = c->buffer;

  hb_font_t * const font = c->font;

  if (!c->decompose (c, ab, &a, &b) ||

      (b && !font->get_nominal_glyph (b, &b_glyph)))

    return 0;

  bool has_a = (bool) font->get_nominal_glyph (a, &a_glyph);

  if (shortest && has_a) {

    /* Output a and b */

    output_char (buffer, a, a_glyph);

    if (likely (b)) {

      output_char (buffer, b, b_glyph);

      return 2;

    }

    return 1;

  }

  if (unsigned ret = decompose (c, shortest, a)) {

    if (b) {

      output_char (buffer, b, b_glyph);

      return ret + 1;

    }

    return ret;

  }

  if (has_a) {

    output_char (buffer, a, a_glyph);

    if (likely (b)) {

      output_char (buffer, b, b_glyph);

      return 2;

    }

    return 1;

  }

  return 0;

}

static inline void

decompose_current_character (const hb_ot_shape_normalize_context_t *c, bool shortest)

{

  hb_buffer_t * const buffer = c->buffer;

  hb_codepoint_t u = buffer->cur().codepoint;

  hb_codepoint_t glyph = 0;

  if (shortest && c->font->get_nominal_glyph (u, &glyph, buffer->not_found))

  {

    next_char (buffer, glyph);

    return;

  }

  if (decompose (c, shortest, u))

  {

    skip_char (buffer);

    return;

  }

  if (!shortest && c->font->get_nominal_glyph (u, &glyph, buffer->not_found))

  {

    next_char (buffer, glyph);

    return;

  }

  if (_hb_glyph_info_is_unicode_space (&buffer->cur()))

  {

    hb_codepoint_t space_glyph;

    hb_unicode_funcs_t::space_t space_type = buffer->unicode->space_fallback_type (u);

    if (space_type != hb_unicode_funcs_t::NOT_SPACE &&

  (c->font->get_nominal_glyph (0x0020, &space_glyph) || (space_glyph = buffer->invisible)))

    {

      _hb_glyph_info_set_unicode_space_fallback_type (&buffer->cur(), space_type);

      next_char (buffer, space_glyph);

      buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_SPACE_FALLBACK;

      return;

    }

  }

  if (u == 0x2011u)

  {

    /* U+2011 is the only sensible character that is a no-break version of another character

     * and not a space.  The space ones are handled already.  Handle this lone one. */

    hb_codepoint_t other_glyph;

    if (c->font->get_nominal_glyph (0x2010u, &other_glyph))

    {

      next_char (buffer, other_glyph);

      return;

    }

  }

  next_char (buffer, glyph); /* glyph is initialized in earlier branches. */

}

static inline void

handle_variation_selector_cluster (const hb_ot_shape_normalize_context_t *c,

           unsigned int end,

           bool short_circuit HB_UNUSED)

{

  /* Currently if there's a variation-selector we give-up on normalization, it's just too hard. */

  hb_buffer_t * const buffer = c->buffer;

  hb_font_t * const font = c->font;

  for (; buffer->idx < end - 1 && buffer->successful;) {

    if (unlikely (buffer->unicode->is_variation_selector (buffer->cur(+1).codepoint))) {

      if (font->get_variation_glyph (buffer->cur().codepoint, buffer->cur(+1).codepoint, &buffer->cur().glyph_index()))

      {

  hb_codepoint_t unicode = buffer->cur().codepoint;

  (void) buffer->replace_glyphs (2, 1, &unicode);

      }

      else

      {

  /* Just pass on the two characters separately, let GSUB do its magic. */

  set_glyph (buffer->cur(), font);

  (void) buffer->next_glyph ();

        buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_VARIATION_SELECTOR_FALLBACK;

  _hb_glyph_info_set_variation_selector (&buffer->cur(), true);

  if (buffer->not_found_variation_selector != HB_CODEPOINT_INVALID)

    _hb_glyph_info_clear_default_ignorable (&buffer->cur());

  set_glyph (buffer->cur(), font);

  (void) buffer->next_glyph ();

      }

      /* Skip any further variation selectors. */

      while (buffer->idx < end &&

       buffer->successful &&

       unlikely (buffer->unicode->is_variation_selector (buffer->cur().codepoint)))

      {

  set_glyph (buffer->cur(), font);

  (void) buffer->next_glyph ();

      }

    }

    else

    {

      set_glyph (buffer->cur(), font);

      (void) buffer->next_glyph ();

    }

  }

  if (likely (buffer->idx < end))

  {

    set_glyph (buffer->cur(), font);

    (void) buffer->next_glyph ();

  }

}

static inline void

decompose_multi_char_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit)

{

  hb_buffer_t * const buffer = c->buffer;

  for (unsigned int i = buffer->idx; i < end && buffer->successful; i++)

    if (unlikely (buffer->unicode->is_variation_selector (buffer->info[i].codepoint))) {

      handle_variation_selector_cluster (c, end, short_circuit);

      return;

    }

  while (buffer->idx < end && buffer->successful)

    decompose_current_character (c, short_circuit);

}

static int

compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb)

{

  unsigned int a = _hb_glyph_info_get_modified_combining_class (pa);

  unsigned int b = _hb_glyph_info_get_modified_combining_class (pb);

  return a < b ? -1 : a == b ? 0 : +1;

}

void

_hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,

      hb_buffer_t *buffer,

      hb_font_t *font)

{

  if (unlikely (!buffer->len)) return;

  _hb_buffer_assert_unicode_vars (buffer);

  hb_ot_shape_normalization_mode_t mode = plan->shaper->normalization_preference;

  if (mode == HB_OT_SHAPE_NORMALIZATION_MODE_AUTO)

  {

    if (plan->has_gpos_mark)

      // https://github.com/harfbuzz/harfbuzz/issues/653#issuecomment-423905920

      //mode = HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED;

      mode = HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS;

    else

      mode = HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS;

  }

  hb_ot_shape_normalize_context_t c = {

    plan,

    buffer,

    font,

    buffer->unicode,

    plan->shaper->decompose ? plan->shaper->decompose : hb_ot_shape_normalize_context_t::decompose_unicode,

    plan->shaper->compose   ? plan->shaper->compose   : hb_ot_shape_normalize_context_t::compose_unicode

  };

  c.override_decompose_and_compose (plan->shaper->decompose, plan->shaper->compose);

  bool always_short_circuit = mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE;

  bool might_short_circuit = always_short_circuit ||

           (mode != HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED &&

            mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT);

  unsigned int count;

  /* We do a fairly straightforward yet custom normalization process in three

   * separate rounds: decompose, reorder, recompose (if desired).  Currently

   * this makes two buffer swaps.  We can make it faster by moving the last

   * two rounds into the inner loop for the first round, but it's more readable

   * this way. */

  /* First round, decompose */

  bool all_simple = true;

  {

    buffer->clear_output ();

    count = buffer->len;

    buffer->idx = 0;

    do

    {

      unsigned int end;

      for (end = buffer->idx + 1; end < count; end++)

  if (_hb_glyph_info_is_unicode_mark (&buffer->info[end]))

    break;

      if (end < count)

  end--; /* Leave one base for the marks to cluster with. */

      /* From idx to end are simple clusters. */

      if (might_short_circuit)

      {

  unsigned int done = font->get_nominal_glyphs (end - buffer->idx,

                  &buffer->cur().codepoint,

                  sizeof (buffer->info[0]),

                  &buffer->cur().glyph_index(),

                  sizeof (buffer->info[0]));

  if (unlikely (!buffer->next_glyphs (done))) break;

      }

      while (buffer->idx < end && buffer->successful)

  decompose_current_character (&c, might_short_circuit);

      if (buffer->idx == count || !buffer->successful)

  break;

      all_simple = false;

      /* Find all the marks now. */

      for (end = buffer->idx + 1; end < count; end++)

  if (!_hb_glyph_info_is_unicode_mark(&buffer->info[end]))

    break;

      /* idx to end is one non-simple cluster. */

      decompose_multi_char_cluster (&c, end, always_short_circuit);

    }

    while (buffer->idx < count && buffer->successful);

    buffer->sync ();

  }

  /* Second round, reorder (inplace) */

  if (!all_simple && buffer->message(font, "start reorder"))

  {

    count = buffer->len;

    hb_glyph_info_t *info = buffer->info;

    for (unsigned int i = 0; i < count; i++)

    {

      if (_hb_glyph_info_get_modified_combining_class (&info[i]) == 0)

  continue;

      unsigned int end;

      for (end = i + 1; end < count; end++)

  if (_hb_glyph_info_get_modified_combining_class (&info[end]) == 0)

    break;

      /* We are going to do a O(n^2).  Only do this if the sequence is short. */

      if (end - i > HB_OT_SHAPE_MAX_COMBINING_MARKS) {

  i = end;

  continue;

      }

      buffer->sort (i, end, compare_combining_class);

      if (plan->shaper->reorder_marks)

  plan->shaper->reorder_marks (plan, buffer, i, end);

      i = end;

    }

    (void) buffer->message(font, "end reorder");

  }

  if (buffer->scratch_flags & HB_BUFFER_SCRATCH_FLAG_HAS_CGJ)

  {

    /* For all CGJ, check if it prevented any reordering at all.

     * If it did NOT, then make it skippable.

     * https://github.com/harfbuzz/harfbuzz/issues/554

     */

    unsigned count = buffer->len;

    hb_glyph_info_t *info = buffer->info;

    for (unsigned int i = 1; i + 1 < count; i++)

      if (info[i].codepoint == 0x034Fu/*CGJ*/ &&

    (info_cc(info[i+1]) == 0 || info_cc(info[i-1]) <= info_cc(info[i+1])))

      {

  _hb_glyph_info_unhide (&info[i]);

      }

  }

  /* Third round, recompose */

  if (!all_simple &&

      buffer->successful &&

      (mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS ||

       mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT))

  {

    /* As noted in the comment earlier, we don't try to combine

     * ccc=0 chars with their previous Starter. */

    buffer->clear_output ();

    count = buffer->len;

    unsigned int starter = 0;

    (void) buffer->next_glyph ();

    while (buffer->idx < count /* No need for: && buffer->successful */)

    {

      hb_codepoint_t composed, glyph;

      if (/* We don't try to compose a non-mark character with it's preceding starter.

     * This is both an optimization to avoid trying to compose every two neighboring

     * glyphs in most scripts AND a desired feature for Hangul.  Apparently Hangul

     * fonts are not designed to mix-and-match pre-composed syllables and Jamo. */

    _hb_glyph_info_is_unicode_mark(&buffer->cur()))

      {

  if (/* If there's anything between the starter and this char, they should have CCC

       * smaller than this character's. */

      (starter == buffer->out_len - 1 ||

       info_cc (buffer->prev()) < info_cc (buffer->cur())) &&

      /* And compose. */

      c.compose (&c,

           buffer->out_info[starter].codepoint,

           buffer->cur().codepoint,

           &composed) &&

      /* And the font has glyph for the composite. */

      font->get_nominal_glyph (composed, &glyph))

  {

    /* Composes. */

    if (unlikely (!buffer->next_glyph ())) break; /* Copy to out-buffer. */

    buffer->merge_out_clusters (starter, buffer->out_len);

    buffer->out_len--; /* Remove the second composable. */

    /* Modify starter and carry on. */

    buffer->out_info[starter].codepoint = composed;

    buffer->out_info[starter].glyph_index() = glyph;

    _hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer);

    continue;

  }

      }

      /* Blocked, or doesn't compose. */

      if (unlikely (!buffer->next_glyph ())) break;

      if (info_cc (buffer->prev()) == 0)

  starter = buffer->out_len - 1;

    }

    buffer->sync ();

  }

}

#endif