#ifndef OT_LAYOUT_GPOS_PAIRPOSFORMAT2_HH
#define OT_LAYOUT_GPOS_PAIRPOSFORMAT2_HH

#include "ValueFormat.hh"

namespace OT {
namespace Layout {
namespace GPOS_impl {

template <typename Types>
struct PairPosFormat2_4
{
  protected:
  HBUINT16      format;                 /* Format identifier--format = 2 */
  typename Types::template OffsetTo<Coverage>
                coverage;               /* Offset to Coverage table--from
                                         * beginning of subtable */
  ValueFormat   valueFormat1;           /* ValueRecord definition--for the
                                         * first glyph of the pair--may be zero
                                         * (0) */
  ValueFormat   valueFormat2;           /* ValueRecord definition--for the
                                         * second glyph of the pair--may be
                                         * zero (0) */
  typename Types::template OffsetTo<ClassDef>
                classDef1;              /* Offset to ClassDef table--from
                                         * beginning of PairPos subtable--for
                                         * the first glyph of the pair */
  typename Types::template OffsetTo<ClassDef>
                classDef2;              /* Offset to ClassDef table--from
                                         * beginning of PairPos subtable--for
                                         * the second glyph of the pair */
  HBUINT16      class1Count;            /* Number of classes in ClassDef1
                                         * table--includes Class0 */
  HBUINT16      class2Count;            /* Number of classes in ClassDef2
                                         * table--includes Class0 */
  ValueRecord   values;                 /* Matrix of value pairs:
                                         * class1-major, class2-minor,
                                         * Each entry has value1 and value2 */
  public:
  DEFINE_SIZE_ARRAY (10 + 3 * Types::size, values);

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    if (!(c->check_struct (this)
       && coverage.sanitize (c, this)
       && classDef1.sanitize (c, this)
       && classDef2.sanitize (c, this))) return_trace (false);

    unsigned int len1 = valueFormat1.get_len ();
    unsigned int len2 = valueFormat2.get_len ();
    unsigned int stride = len1 + len2;
    unsigned int record_size = valueFormat1.get_size () + valueFormat2.get_size ();
    unsigned int count = (unsigned int) class1Count * (unsigned int) class2Count;
    return_trace (c->check_range ((const void *) values,
                                  count,
                                  record_size) &&
                  valueFormat1.sanitize_values_stride_unsafe (c, this, &values[0], count, stride) &&
                  valueFormat2.sanitize_values_stride_unsafe (c, this, &values[len1], count, stride));
  }

  bool intersects (const hb_set_t *glyphs) const
  {
    return (this+coverage).intersects (glyphs) &&
           (this+classDef2).intersects (glyphs);
  }

  void closure_lookups (hb_closure_lookups_context_t *c) const {}
  void collect_variation_indices (hb_collect_variation_indices_context_t *c) const
  {
    if (!intersects (c->glyph_set)) return;
    if ((!valueFormat1.has_device ()) && (!valueFormat2.has_device ())) return;

    hb_set_t klass1_glyphs, klass2_glyphs;
    if (!(this+classDef1).collect_coverage (&klass1_glyphs)) return;
    if (!(this+classDef2).collect_coverage (&klass2_glyphs)) return;

    hb_set_t class1_set, class2_set;
    for (const unsigned cp : + c->glyph_set->iter () | hb_filter (this + coverage))
    {
      if (!klass1_glyphs.has (cp)) class1_set.add (0);
      else
      {
        unsigned klass1 = (this+classDef1).get (cp);
        class1_set.add (klass1);
      }
    }

    class2_set.add (0);
    for (const unsigned cp : + c->glyph_set->iter () | hb_filter (klass2_glyphs))
    {
      unsigned klass2 = (this+classDef2).get (cp);
      class2_set.add (klass2);
    }

    if (class1_set.is_empty ()
        || class2_set.is_empty ()
        || (class2_set.get_population() == 1 && class2_set.has(0)))
      return;

    unsigned len1 = valueFormat1.get_len ();
    unsigned len2 = valueFormat2.get_len ();
    const hb_array_t<const Value> values_array = values.as_array ((unsigned)class1Count * (unsigned) class2Count * (len1 + len2));
    for (const unsigned class1_idx : class1_set.iter ())
    {
      for (const unsigned class2_idx : class2_set.iter ())
      {
        unsigned start_offset = (class1_idx * (unsigned) class2Count + class2_idx) * (len1 + len2);
        if (valueFormat1.has_device ())
          valueFormat1.collect_variation_indices (c, this, values_array.sub_array (start_offset, len1));

        if (valueFormat2.has_device ())
          valueFormat2.collect_variation_indices (c, this, values_array.sub_array (start_offset+len1, len2));
      }
    }
  }

  void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    if (unlikely (!(this+coverage).collect_coverage (c->input))) return;
    if (unlikely (!(this+classDef2).collect_coverage (c->input))) return;
  }

  const Coverage &get_coverage () const { return this+coverage; }

  bool apply (hb_ot_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    hb_buffer_t *buffer = c->buffer;
    unsigned int index = (this+coverage).get_coverage  (buffer->cur().codepoint);
    if (likely (index == NOT_COVERED)) return_trace (false);

    hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_input;
    skippy_iter.reset (buffer->idx, 1);
    unsigned unsafe_to;
    if (!skippy_iter.next (&unsafe_to))
    {
      buffer->unsafe_to_concat (buffer->idx, unsafe_to);
      return_trace (false);
    }

    unsigned int len1 = valueFormat1.get_len ();
    unsigned int len2 = valueFormat2.get_len ();
    unsigned int record_len = len1 + len2;

    unsigned int klass1 = (this+classDef1).get_class (buffer->cur().codepoint);
    unsigned int klass2 = (this+classDef2).get_class (buffer->info[skippy_iter.idx].codepoint);
    if (unlikely (klass1 >= class1Count || klass2 >= class2Count))
    {
      buffer->unsafe_to_concat (buffer->idx, skippy_iter.idx + 1);
      return_trace (false);
    }

    const Value *v = &values[record_len * (klass1 * class2Count + klass2)];

    bool applied_first = false, applied_second = false;


    /* Isolate simple kerning and apply it half to each side.
     * Results in better cursor positinoing / underline drawing.
     *
     * Disabled, because causes issues... :-(
     * https://github.com/harfbuzz/harfbuzz/issues/3408
     * https://github.com/harfbuzz/harfbuzz/pull/3235#issuecomment-1029814978
     */
#ifndef HB_SPLIT_KERN
    if (0)
#endif
    {
      if (!len2)
      {
        const hb_direction_t dir = buffer->props.direction;
        const bool horizontal = HB_DIRECTION_IS_HORIZONTAL (dir);
        const bool backward = HB_DIRECTION_IS_BACKWARD (dir);
        unsigned mask = horizontal ? ValueFormat::xAdvance : ValueFormat::yAdvance;
        if (backward)
          mask |= mask >> 2; /* Add eg. xPlacement in RTL. */
        /* Add Devices. */
        mask |= mask << 4;

        if (valueFormat1 & ~mask)
          goto bail;

        /* Is simple kern. Apply value on an empty position slot,
         * then split it between sides. */

        hb_glyph_position_t pos{};
        if (valueFormat1.apply_value (c, this, v, pos))
        {
          hb_position_t *src  = &pos.x_advance;
          hb_position_t *dst1 = &buffer->cur_pos().x_advance;
          hb_position_t *dst2 = &buffer->pos[skippy_iter.idx].x_advance;
          unsigned i = horizontal ? 0 : 1;

          hb_position_t kern  = src[i];
          hb_position_t kern1 = kern >> 1;
          hb_position_t kern2 = kern - kern1;

          if (!backward)
          {
            dst1[i] += kern1;
            dst2[i] += kern2;
            dst2[i + 2] += kern2;
          }
          else
          {
            dst1[i] += kern1;
            dst1[i + 2] += src[i + 2] - kern2;
            dst2[i] += kern2;
          }

          applied_first = applied_second = kern != 0;
          goto success;
        }
        goto boring;
      }
    }
    bail:

    if (HB_BUFFER_MESSAGE_MORE && c->buffer->messaging ())
    {
      c->buffer->message (c->font,
			  "kerning glyphs at %d,%d",
			  c->buffer->idx, skippy_iter.idx);
    }

    applied_first = valueFormat1.apply_value (c, this, v, buffer->cur_pos());
    applied_second = valueFormat2.apply_value (c, this, v + len1, buffer->pos[skippy_iter.idx]);

    if (HB_BUFFER_MESSAGE_MORE && c->buffer->messaging ())
    {
      c->buffer->message (c->font,
			  "kerned glyphs at %d,%d",
			  c->buffer->idx, skippy_iter.idx);
    }

    success:
    if (applied_first || applied_second)
      buffer->unsafe_to_break (buffer->idx, skippy_iter.idx + 1);
    else
    boring:
      buffer->unsafe_to_concat (buffer->idx, skippy_iter.idx + 1);


    buffer->idx = skippy_iter.idx;
    if (len2)
      buffer->idx++;

    return_trace (true);
  }

  bool subset (hb_subset_context_t *c) const
  {
    TRACE_SUBSET (this);
    auto *out = c->serializer->start_embed (*this);
    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);
    out->format = format;

    hb_map_t klass1_map;
    out->classDef1.serialize_subset (c, classDef1, this, &klass1_map, true, true, &(this + coverage));
    out->class1Count = klass1_map.get_population ();

    hb_map_t klass2_map;
    out->classDef2.serialize_subset (c, classDef2, this, &klass2_map, true, false);
    out->class2Count = klass2_map.get_population ();

    unsigned len1 = valueFormat1.get_len ();
    unsigned len2 = valueFormat2.get_len ();

    hb_pair_t<unsigned, unsigned> newFormats = hb_pair (valueFormat1, valueFormat2);
    if (c->plan->flags & HB_SUBSET_FLAGS_NO_HINTING)
      newFormats = compute_effective_value_formats (klass1_map, klass2_map);

    out->valueFormat1 = newFormats.first;
    out->valueFormat2 = newFormats.second;

    for (unsigned class1_idx : + hb_range ((unsigned) class1Count) | hb_filter (klass1_map))
    {
      for (unsigned class2_idx : + hb_range ((unsigned) class2Count) | hb_filter (klass2_map))
      {
        unsigned idx = (class1_idx * (unsigned) class2Count + class2_idx) * (len1 + len2);
        valueFormat1.copy_values (c->serializer, newFormats.first, this, &values[idx], c->plan->layout_variation_idx_map);
        valueFormat2.copy_values (c->serializer, newFormats.second, this, &values[idx + len1], c->plan->layout_variation_idx_map);
      }
    }

    const hb_set_t &glyphset = *c->plan->glyphset_gsub ();
    const hb_map_t &glyph_map = *c->plan->glyph_map;

    auto it =
    + hb_iter (this+coverage)
    | hb_filter (glyphset)
    | hb_map_retains_sorting (glyph_map)
    ;

    out->coverage.serialize_serialize (c->serializer, it);
    return_trace (out->class1Count && out->class2Count && bool (it));
  }


  hb_pair_t<unsigned, unsigned> compute_effective_value_formats (const hb_map_t& klass1_map,
                                                                 const hb_map_t& klass2_map) const
  {
    unsigned len1 = valueFormat1.get_len ();
    unsigned len2 = valueFormat2.get_len ();

    unsigned format1 = 0;
    unsigned format2 = 0;

    for (unsigned class1_idx : + hb_range ((unsigned) class1Count) | hb_filter (klass1_map))
    {
      for (unsigned class2_idx : + hb_range ((unsigned) class2Count) | hb_filter (klass2_map))
      {
        unsigned idx = (class1_idx * (unsigned) class2Count + class2_idx) * (len1 + len2);
        format1 = format1 | valueFormat1.get_effective_format (&values[idx]);
        format2 = format2 | valueFormat2.get_effective_format (&values[idx + len1]);
      }
    }

    return hb_pair (format1, format2);
  }
};

}
}
}

#endif  // OT_LAYOUT_GPOS_PAIRPOSFORMAT2_HH