/*

 * Copyright © 2018  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): Garret Rieger, Rod Sheeter, Behdad Esfahbod

 */

#include "hb.hh"

#include "hb-open-type.hh"

#include "hb-open-file.hh"

#include "hb-subset.hh"

#include "hb-subset-table.hh"

#include "hb-subset-accelerator.hh"

#include "hb-ot-cmap-table.hh"

#include "hb-ot-var-cvar-table.hh"

#include "hb-ot-head-table.hh"

#include "hb-ot-stat-table.hh"

#include "hb-ot-post-table-v2subset.hh"

/**

 * SECTION:hb-subset

 * @title: hb-subset

 * @short_description: Subsets font files.

 * @include: hb-subset.h

 *

 * Subsetting reduces the codepoint coverage of font files and removes all data

 * that is no longer needed. A subset input describes the desired subset. The input is

 * provided along with a font to the subsetting operation. Output is a new font file

 * containing only the data specified in the input.

 *

 * Currently most outline and bitmap tables are supported: glyf, CFF, CFF2, sbix,

 * COLR, and CBDT/CBLC. This also includes fonts with variable outlines via OpenType

 * variations. Notably EBDT/EBLC and SVG are not supported. Layout subsetting is supported

 * only for OpenType Layout tables (GSUB, GPOS, GDEF). Notably subsetting of graphite or AAT tables

 * is not yet supported.

 *

 * Fonts with graphite or AAT tables may still be subsetted but will likely need to use the

 * retain glyph ids option and configure the subset to pass through the layout tables untouched.

 */

hb_user_data_key_t _hb_subset_accelerator_user_data_key = {};

/*

 * The list of tables in the open type spec. Used to check for tables that may need handling

 * if we are unable to list the tables in a face.

 */

static hb_tag_t known_tables[] {

  HB_TAG('a','v','a','r'),

  HB_TAG('B','A','S','E'),

  HB_TAG('C','B','D','T'),

  HB_TAG('C','B','L','C'),

  HB_TAG('C','F','F',' '),

  HB_TAG('C','F','F','2'),

  HB_TAG('c','m','a','p'),

  HB_TAG('C','O','L','R'),

  HB_TAG('C','P','A','L'),

  HB_TAG('c','v','a','r'),

  HB_TAG('c','v','t',' '),

  HB_TAG('D','S','I','G'),

  HB_TAG('E','B','D','T'),

  HB_TAG('E','B','L','C'),

  HB_TAG('E','B','S','C'),

  HB_TAG('f','p','g','m'),

  HB_TAG('f','v','a','r'),

  HB_TAG('g','a','s','p'),

  HB_TAG('G','D','E','F'),

  HB_TAG('g','l','y','f'),

  HB_TAG('G','P','O','S'),

  HB_TAG('G','S','U','B'),

  HB_TAG('g','v','a','r'),

  HB_TAG('h','d','m','x'),

  HB_TAG('h','e','a','d'),

  HB_TAG('h','h','e','a'),

  HB_TAG('h','m','t','x'),

  HB_TAG('H','V','A','R'),

  HB_TAG('J','S','T','F'),

  HB_TAG('k','e','r','n'),

  HB_TAG('l','o','c','a'),

  HB_TAG('L','T','S','H'),

  HB_TAG('M','A','T','H'),

  HB_TAG('m','a','x','p'),

  HB_TAG('M','E','R','G'),

  HB_TAG('m','e','t','a'),

  HB_TAG('M','V','A','R'),

  HB_TAG('P','C','L','T'),

  HB_TAG('p','o','s','t'),

  HB_TAG('p','r','e','p'),

  HB_TAG('s','b','i','x'),

  HB_TAG('S','T','A','T'),

  HB_TAG('S','V','G',' '),

  HB_TAG('V','D','M','X'),

  HB_TAG('v','h','e','a'),

  HB_TAG('v','m','t','x'),

  HB_TAG('V','O','R','G'),

  HB_TAG('V','V','A','R'),

  HB_TAG('n','a','m','e'),

  HB_TAG('O','S','/','2')

};

static bool _table_is_empty (const hb_face_t *face, hb_tag_t tag)

{

  hb_blob_t* blob = hb_face_reference_table (face, tag);

  bool result = (blob == hb_blob_get_empty ());

  hb_blob_destroy (blob);

  return result;

}

static unsigned int

_get_table_tags (const hb_subset_plan_t* plan,

                 unsigned int  start_offset,

                 unsigned int *table_count, /* IN/OUT */

                 hb_tag_t     *table_tags /* OUT */)

{

  unsigned num_tables = hb_face_get_table_tags (plan->source, 0, nullptr, nullptr);

  if (num_tables)

    return hb_face_get_table_tags (plan->source, start_offset, table_count, table_tags);

  // If face has 0 tables associated with it, assume that it was built from

  // hb_face_create_tables and thus is unable to list its tables. Fallback to

  // checking each table type we can handle for existence instead.

  auto it =

      hb_concat (

          + hb_array (known_tables)

          | hb_filter ([&] (hb_tag_t tag) {

            return !_table_is_empty (plan->source, tag) && !plan->no_subset_tables.has (tag);

          })

          | hb_map ([] (hb_tag_t tag) -> hb_tag_t { return tag; }),

          plan->no_subset_tables.iter ()

          | hb_filter([&] (hb_tag_t tag) {

            return !_table_is_empty (plan->source, tag);

          }));

  it += start_offset;

  unsigned num_written = 0;

  while (bool (it) && num_written < *table_count)

    table_tags[num_written++] = *it++;

  *table_count = num_written;

  return num_written;

}

static bool

_is_table_present (hb_face_t *source, hb_tag_t tag)

{

  if (!hb_face_get_table_tags (source, 0, nullptr, nullptr)) {

    // If face has 0 tables associated with it, assume that it was built from

    // hb_face_create_tables and thus is unable to list its tables. Fallback to

    // checking if the blob associated with tag is empty.

    return !_table_is_empty (source, tag);

  }

  hb_tag_t table_tags[32];

  unsigned offset = 0, num_tables = ARRAY_LENGTH (table_tags);

  while (((void) hb_face_get_table_tags (source, offset, &num_tables, table_tags), num_tables))

  {

    for (unsigned i = 0; i < num_tables; ++i)

      if (table_tags[i] == tag)

  return true;

    offset += num_tables;

  }

  return false;

}

static bool

_should_drop_table (hb_subset_plan_t *plan, hb_tag_t tag)

{

  if (plan->drop_tables.has (tag))

    return true;

  switch (tag)

  {

  case HB_TAG('c','v','a','r'): /* hint table, fallthrough */

    return plan->all_axes_pinned || (plan->flags & HB_SUBSET_FLAGS_NO_HINTING);

  case HB_TAG('c','v','t',' '): /* hint table, fallthrough */

  case HB_TAG('f','p','g','m'): /* hint table, fallthrough */

  case HB_TAG('p','r','e','p'): /* hint table, fallthrough */

  case HB_TAG('h','d','m','x'): /* hint table, fallthrough */

  case HB_TAG('V','D','M','X'): /* hint table, fallthrough */

    return plan->flags & HB_SUBSET_FLAGS_NO_HINTING;

#ifdef HB_NO_SUBSET_LAYOUT

    // Drop Layout Tables if requested.

  case HB_TAG('G','D','E','F'):

  case HB_TAG('G','P','O','S'):

  case HB_TAG('G','S','U','B'):

  case HB_TAG('m','o','r','x'):

  case HB_TAG('m','o','r','t'):

  case HB_TAG('k','e','r','x'):

  case HB_TAG('k','e','r','n'):

    return true;

#endif

  case HB_TAG('a','v','a','r'):

  case HB_TAG('f','v','a','r'):

  case HB_TAG('g','v','a','r'):

  case HB_TAG('H','V','A','R'):

  case HB_TAG('V','V','A','R'):

  case HB_TAG('M','V','A','R'):

    return plan->all_axes_pinned;

  default:

    return false;

  }

}

static bool

_dependencies_satisfied (hb_subset_plan_t *plan, hb_tag_t tag,

                         const hb_set_t &subsetted_tags,

                         const hb_set_t &pending_subset_tags)

{

  switch (tag)

  {

  case HB_TAG('h','m','t','x'):

  case HB_TAG('v','m','t','x'):

  case HB_TAG('m','a','x','p'):

  case HB_TAG('O','S','/','2'):

    return !plan->normalized_coords || !pending_subset_tags.has (HB_TAG('g','l','y','f'));

  case HB_TAG('G','P','O','S'):

    return plan->all_axes_pinned || !pending_subset_tags.has (HB_TAG('G','D','E','F'));

  default:

    return true;

  }

}

static bool

_subset_table (hb_subset_plan_t *plan,

         hb_vector_t<char> &buf,

         hb_tag_t tag)

{

  if (plan->no_subset_tables.has (tag)) {

    return _hb_subset_table_passthrough (plan, tag);

  }

  DEBUG_MSG (SUBSET, nullptr, "subset %c%c%c%c", HB_UNTAG (tag));

  bool success;

  if (_hb_subset_table_layout (plan, buf, tag, &success) ||

      _hb_subset_table_var (plan, buf, tag, &success) ||

      _hb_subset_table_cff (plan, buf, tag, &success) ||

      _hb_subset_table_color (plan, buf, tag, &success) ||

      _hb_subset_table_other (plan, buf, tag, &success))

    return success;

  switch (tag)

  {

  case HB_TAG('h','e','a','d'):

    if (_is_table_present (plan->source, HB_TAG('g','l','y','f')) && !_should_drop_table (plan, HB_TAG('g','l','y','f')))

      return true; /* skip head, handled by glyf */

    return _hb_subset_table<const OT::head> (plan, buf);

  case HB_TAG('S','T','A','T'):

    if (!plan->user_axes_location.is_empty ()) return _hb_subset_table<const OT::STAT> (plan, buf);

    else return _hb_subset_table_passthrough (plan, tag);

  case HB_TAG('c','v','t',' '):

#ifndef HB_NO_VAR

    if (_is_table_present (plan->source, HB_TAG('c','v','a','r')) &&

        plan->normalized_coords && !plan->pinned_at_default)

    {

      auto &cvar = *plan->source->table.cvar;

      return OT::cvar::add_cvt_and_apply_deltas (plan, cvar.get_tuple_var_data (), &cvar);

    }

#endif

    return _hb_subset_table_passthrough (plan, tag);

  }

  if (plan->flags & HB_SUBSET_FLAGS_PASSTHROUGH_UNRECOGNIZED)

    return _hb_subset_table_passthrough (plan, tag);

  // Drop table

  return true;

}

static void _attach_accelerator_data (hb_subset_plan_t* plan,

                                      hb_face_t* face /* IN/OUT */)

{

  if (!plan->inprogress_accelerator) return;

  // Transfer the accelerator from the plan to us.

  hb_subset_accelerator_t* accel = plan->inprogress_accelerator;

  plan->inprogress_accelerator = nullptr;

  if (accel->in_error ())

  {

    hb_subset_accelerator_t::destroy (accel);

    return;

  }

  // Populate caches that need access to the final tables.

  hb_blob_ptr_t<OT::cmap> cmap_ptr (hb_sanitize_context_t ().reference_table<OT::cmap> (face));

  accel->cmap_cache = OT::cmap::create_filled_cache (cmap_ptr);

  accel->destroy_cmap_cache = OT::SubtableUnicodesCache::destroy;

  if (!hb_face_set_user_data(face,

                             hb_subset_accelerator_t::user_data_key(),

                             accel,

                             hb_subset_accelerator_t::destroy,

                             true))

    hb_subset_accelerator_t::destroy (accel);

}

/**

 * hb_subset_or_fail:

 * @source: font face data to be subset.

 * @input: input to use for the subsetting.

 *

 * Subsets a font according to provided input. Returns nullptr

 * if the subset operation fails or the face has no glyphs.

 *

 * Since: 2.9.0

 **/

hb_face_t *

hb_subset_or_fail (hb_face_t *source, const hb_subset_input_t *input)

{

  if (unlikely (!input || !source)) return nullptr;

  if (unlikely (!source->get_num_glyphs ()))

  {

    DEBUG_MSG (SUBSET, nullptr, "No glyphs in source font.");

    return nullptr;

  }

  hb_subset_plan_t *plan = hb_subset_plan_create_or_fail (source, input);

  if (unlikely (!plan)) {

    return nullptr;

  }

  hb_face_t * result = hb_subset_plan_execute_or_fail (plan);

  hb_subset_plan_destroy (plan);

  return result;

}

/**

 * hb_subset_plan_execute_or_fail:

 * @plan: a subsetting plan.

 *

 * Executes the provided subsetting @plan.

 *

 * Return value:

 * on success returns a reference to generated font subset. If the subsetting operation fails

 * returns nullptr.

 *

 * Since: 4.0.0

 **/

hb_face_t *

hb_subset_plan_execute_or_fail (hb_subset_plan_t *plan)

{

  if (unlikely (!plan || plan->in_error ())) {

    return nullptr;

  }

  hb_tag_t table_tags[32];

  unsigned offset = 0, num_tables = ARRAY_LENGTH (table_tags);

  hb_set_t subsetted_tags, pending_subset_tags;

  while (((void) _get_table_tags (plan, offset, &num_tables, table_tags), num_tables))

  {

    for (unsigned i = 0; i < num_tables; ++i)

    {

      hb_tag_t tag = table_tags[i];

      if (_should_drop_table (plan, tag)) continue;

      pending_subset_tags.add (tag);

    }

    offset += num_tables;

  }

  bool success = true;

  {

    // Grouping to deallocate buf before calling hb_face_reference (plan->dest).

    hb_vector_t<char> buf;

    buf.alloc (8192 - 16);

    while (!pending_subset_tags.is_empty ())

    {

      if (subsetted_tags.in_error ()

    || pending_subset_tags.in_error ()) {

  success = false;

  goto end;

      }

      bool made_changes = false;

      for (hb_tag_t tag : pending_subset_tags)

      {

  if (!_dependencies_satisfied (plan, tag,

              subsetted_tags,

              pending_subset_tags))

  {

    // delayed subsetting for some tables since they might have dependency on other tables

    // in some cases: e.g: during instantiating glyf tables, hmetrics/vmetrics are updated

    // and saved in subset plan, hmtx/vmtx subsetting need to use these updated metrics values

    continue;

  }

  pending_subset_tags.del (tag);

  subsetted_tags.add (tag);

  made_changes = true;

  success = _subset_table (plan, buf, tag);

  if (unlikely (!success)) goto end;

      }

      if (!made_changes)

      {

  DEBUG_MSG (SUBSET, nullptr, "Table dependencies unable to be satisfied. Subset failed.");

  success = false;

  goto end;

      }

    }

  }

  if (success && plan->attach_accelerator_data) {

    _attach_accelerator_data (plan, plan->dest);

  }

end:

  return success ? hb_face_reference (plan->dest) : nullptr;

}