/*

 * Copyright © 2017  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

 */

#ifndef HB_KERN_HH

#define HB_KERN_HH

#include "hb-open-type.hh"

#include "hb-aat-layout-common.hh"

#include "hb-ot-layout-gpos-table.hh"

namespace OT {

template <typename Driver>

struct hb_kern_machine_t

{

  hb_kern_machine_t (const Driver &driver_,

                     bool crossStream_ = false) :

                       driver (driver_),

                       crossStream (crossStream_) {}

  HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW

  void kern (hb_font_t   *font,

             hb_buffer_t *buffer,

             hb_mask_t    kern_mask,

             bool         scale = true) const

  {

    OT::hb_ot_apply_context_t c (1, font, buffer);

    c.set_lookup_mask (kern_mask);

    c.set_lookup_props (OT::LookupFlag::IgnoreMarks);

    OT::hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c.iter_input;

    skippy_iter.init (&c);

    bool horizontal = HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction);

    unsigned int count = buffer->len;

    hb_glyph_info_t *info = buffer->info;

    hb_glyph_position_t *pos = buffer->pos;

    for (unsigned int idx = 0; idx < count;)

    {

      if (!(info[idx].mask & kern_mask))

      {

        idx++;

        continue;

      }

      skippy_iter.reset (idx, 1);

      if (!skippy_iter.next ())

      {

        idx++;

        continue;

      }

      unsigned int i = idx;

      unsigned int j = skippy_iter.idx;

      hb_position_t kern = driver.get_kerning (info[i].codepoint,

                                               info[j].codepoint);

      if (likely (!kern))

        goto skip;

      if (horizontal)

      {

        if (scale)

          kern = font->em_scale_x (kern);

        if (crossStream)

        {

          pos[j].y_offset = kern;

          buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;

        }

        else

        {

          hb_position_t kern1 = kern >> 1;

          hb_position_t kern2 = kern - kern1;

          pos[i].x_advance += kern1;

          pos[j].x_advance += kern2;

          pos[j].x_offset += kern2;

        }

      }

      else

      {

        if (scale)

          kern = font->em_scale_y (kern);

        if (crossStream)

        {

          pos[j].x_offset = kern;

          buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;

        }

        else

        {

          hb_position_t kern1 = kern >> 1;

          hb_position_t kern2 = kern - kern1;

          pos[i].y_advance += kern1;

          pos[j].y_advance += kern2;

          pos[j].y_offset += kern2;

        }

      }

      buffer->unsafe_to_break (i, j + 1);

    skip:

      idx = skippy_iter.idx;

    }

  }

  const Driver &driver;

  bool crossStream;

};

} /* namespace OT */

#endif /* HB_KERN_HH */