/*
 * Copyright © 2021  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.
 *
 */

#ifndef HB_OT_VAR_COMMON_HH
#define HB_OT_VAR_COMMON_HH

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


namespace OT {

template <typename MapCountT>
struct DeltaSetIndexMapFormat01
{
  friend struct DeltaSetIndexMap;

  unsigned get_size () const
  { return min_size + mapCount * get_width (); }

  private:
  DeltaSetIndexMapFormat01* copy (hb_serialize_context_t *c) const
  {
    TRACE_SERIALIZE (this);
    return_trace (c->embed (this));
  }

  template <typename T>
  bool serialize (hb_serialize_context_t *c, const T &plan)
  {
    unsigned int width = plan.get_width ();
    unsigned int inner_bit_count = plan.get_inner_bit_count ();
    const hb_array_t<const uint32_t> output_map = plan.get_output_map ();

    TRACE_SERIALIZE (this);
    if (unlikely (output_map.length && ((((inner_bit_count-1)&~0xF)!=0) || (((width-1)&~0x3)!=0))))
      return_trace (false);
    if (unlikely (!c->extend_min (this))) return_trace (false);

    entryFormat = ((width-1)<<4)|(inner_bit_count-1);
    mapCount = output_map.length;
    HBUINT8 *p = c->allocate_size<HBUINT8> (width * output_map.length);
    if (unlikely (!p)) return_trace (false);
    for (unsigned int i = 0; i < output_map.length; i++)
    {
      unsigned int v = output_map.arrayZ[i];
      if (v)
      {
	unsigned int outer = v >> 16;
	unsigned int inner = v & 0xFFFF;
	unsigned int u = (outer << inner_bit_count) | inner;
	for (unsigned int w = width; w > 0;)
	{
	  p[--w] = u;
	  u >>= 8;
	}
      }
      p += width;
    }
    return_trace (true);
  }

  uint32_t map (unsigned int v) const /* Returns 16.16 outer.inner. */
  {
    /* If count is zero, pass value unchanged.  This takes
     * care of direct mapping for advance map. */
    if (!mapCount)
      return v;

    if (v >= mapCount)
      v = mapCount - 1;

    unsigned int u = 0;
    { /* Fetch it. */
      unsigned int w = get_width ();
      const HBUINT8 *p = mapDataZ.arrayZ + w * v;
      for (; w; w--)
        u = (u << 8) + *p++;
    }

    { /* Repack it. */
      unsigned int n = get_inner_bit_count ();
      unsigned int outer = u >> n;
      unsigned int inner = u & ((1 << n) - 1);
      u = (outer<<16) | inner;
    }

    return u;
  }

  unsigned get_map_count () const       { return mapCount; }
  unsigned get_width () const           { return ((entryFormat >> 4) & 3) + 1; }
  unsigned get_inner_bit_count () const { return (entryFormat & 0xF) + 1; }


  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
                  c->check_range (mapDataZ.arrayZ,
                                  mapCount,
                                  get_width ()));
  }

  protected:
  HBUINT8       format;         /* Format identifier--format = 0 */
  HBUINT8       entryFormat;    /* A packed field that describes the compressed
                                 * representation of delta-set indices. */
  MapCountT     mapCount;       /* The number of mapping entries. */
  UnsizedArrayOf<HBUINT8>
                mapDataZ;       /* The delta-set index mapping data. */

  public:
  DEFINE_SIZE_ARRAY (2+MapCountT::static_size, mapDataZ);
};

struct DeltaSetIndexMap
{
  template <typename T>
  bool serialize (hb_serialize_context_t *c, const T &plan)
  {
    TRACE_SERIALIZE (this);
    unsigned length = plan.get_output_map ().length;
    u.format = length <= 0xFFFF ? 0 : 1;
    switch (u.format) {
    case 0: return_trace (u.format0.serialize (c, plan));
    case 1: return_trace (u.format1.serialize (c, plan));
    default:return_trace (false);
    }
  }

  uint32_t map (unsigned v) const
  {
    switch (u.format) {
    case 0: return (u.format0.map (v));
    case 1: return (u.format1.map (v));
    default:return v;
    }
  }

  unsigned get_map_count () const
  {
    switch (u.format) {
    case 0: return u.format0.get_map_count ();
    case 1: return u.format1.get_map_count ();
    default:return 0;
    }
  }

  unsigned get_width () const
  {
    switch (u.format) {
    case 0: return u.format0.get_width ();
    case 1: return u.format1.get_width ();
    default:return 0;
    }
  }

  unsigned get_inner_bit_count () const
  {
    switch (u.format) {
    case 0: return u.format0.get_inner_bit_count ();
    case 1: return u.format1.get_inner_bit_count ();
    default:return 0;
    }
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    if (!u.format.sanitize (c)) return_trace (false);
    switch (u.format) {
    case 0: return_trace (u.format0.sanitize (c));
    case 1: return_trace (u.format1.sanitize (c));
    default:return_trace (true);
    }
  }

  DeltaSetIndexMap* copy (hb_serialize_context_t *c) const
  {
    TRACE_SERIALIZE (this);
    switch (u.format) {
    case 0: return_trace (reinterpret_cast<DeltaSetIndexMap *> (u.format0.copy (c)));
    case 1: return_trace (reinterpret_cast<DeltaSetIndexMap *> (u.format1.copy (c)));
    default:return_trace (nullptr);
    }
  }

  protected:
  union {
  HBUINT8                            format;         /* Format identifier */
  DeltaSetIndexMapFormat01<HBUINT16> format0;
  DeltaSetIndexMapFormat01<HBUINT32> format1;
  } u;
  public:
  DEFINE_SIZE_UNION (1, format);
};


struct VarStoreInstancer
{
  VarStoreInstancer (const VariationStore *varStore,
		     const DeltaSetIndexMap *varIdxMap,
		     hb_array_t<int> coords) :
    varStore (varStore), varIdxMap (varIdxMap), coords (coords) {}

  operator bool () const { return varStore && bool (coords); }

  /* according to the spec, if colr table has varStore but does not have
   * varIdxMap, then an implicit identity mapping is used */
  float operator() (uint32_t varIdx, unsigned short offset = 0) const
  { return coords ? varStore->get_delta (varIdxMap ? varIdxMap->map (VarIdx::add (varIdx, offset)) : varIdx + offset, coords) : 0; }

  const VariationStore *varStore;
  const DeltaSetIndexMap *varIdxMap;
  hb_array_t<int> coords;
};

/* https://docs.microsoft.com/en-us/typography/opentype/spec/otvarcommonformats#tuplevariationheader */
struct TupleVariationHeader
{
  friend struct tuple_delta_t;
  unsigned get_size (unsigned axis_count) const
  { return min_size + get_all_tuples (axis_count).get_size (); }

  unsigned get_data_size () const { return varDataSize; }

  const TupleVariationHeader &get_next (unsigned axis_count) const
  { return StructAtOffset<TupleVariationHeader> (this, get_size (axis_count)); }

  bool unpack_axis_tuples (unsigned axis_count,
                           const hb_array_t<const F2DOT14> shared_tuples,
                           const hb_map_t *axes_old_index_tag_map,
                           hb_hashmap_t<hb_tag_t, Triple>& axis_tuples /* OUT */) const
  {
    const F2DOT14 *peak_tuple = nullptr;
    if (has_peak ())
      peak_tuple = get_peak_tuple (axis_count).arrayZ;
    else
    {
      unsigned int index = get_index ();
      if (unlikely ((index + 1) * axis_count > shared_tuples.length))
        return false;
      peak_tuple = shared_tuples.sub_array (axis_count * index, axis_count).arrayZ;
    }

    const F2DOT14 *start_tuple = nullptr;
    const F2DOT14 *end_tuple = nullptr;
    bool has_interm = has_intermediate ();

    if (has_interm)
    {
      start_tuple = get_start_tuple (axis_count).arrayZ;
      end_tuple = get_end_tuple (axis_count).arrayZ;
    }

    for (unsigned i = 0; i < axis_count; i++)
    {
      float peak = peak_tuple[i].to_float ();
      if (peak == 0.f) continue;

      hb_tag_t *axis_tag;
      if (!axes_old_index_tag_map->has (i, &axis_tag))
        return false;

      float start, end;
      if (has_interm)
      {
        start = start_tuple[i].to_float ();
        end = end_tuple[i].to_float ();
      }
      else
      {
        start = hb_min (peak, 0.f);
        end = hb_max (peak, 0.f);
      }
      axis_tuples.set (*axis_tag, Triple (start, peak, end));
    }

    return true;
  }

  float calculate_scalar (hb_array_t<int> coords, unsigned int coord_count,
                          const hb_array_t<const F2DOT14> shared_tuples,
			  const hb_vector_t<hb_pair_t<int,int>> *shared_tuple_active_idx = nullptr) const
  {
    const F2DOT14 *peak_tuple;

    unsigned start_idx = 0;
    unsigned end_idx = coord_count;
    unsigned step = 1;

    if (has_peak ())
      peak_tuple = get_peak_tuple (coord_count).arrayZ;
    else
    {
      unsigned int index = get_index ();
      if (unlikely ((index + 1) * coord_count > shared_tuples.length))
        return 0.f;
      peak_tuple = shared_tuples.sub_array (coord_count * index, coord_count).arrayZ;

      if (shared_tuple_active_idx)
      {
	if (unlikely (index >= shared_tuple_active_idx->length))
	  return 0.f;
	auto _ = (*shared_tuple_active_idx).arrayZ[index];
	if (_.second != -1)
	{
	  start_idx = _.first;
	  end_idx = _.second + 1;
	  step = _.second - _.first;
	}
	else if (_.first != -1)
	{
	  start_idx = _.first;
	  end_idx = start_idx + 1;
	}
      }
    }

    const F2DOT14 *start_tuple = nullptr;
    const F2DOT14 *end_tuple = nullptr;
    bool has_interm = has_intermediate ();
    if (has_interm)
    {
      start_tuple = get_start_tuple (coord_count).arrayZ;
      end_tuple = get_end_tuple (coord_count).arrayZ;
    }

    float scalar = 1.f;
    for (unsigned int i = start_idx; i < end_idx; i += step)
    {
      int peak = peak_tuple[i].to_int ();
      if (!peak) continue;

      int v = coords[i];
      if (v == peak) continue;

      if (has_interm)
      {
        int start = start_tuple[i].to_int ();
        int end = end_tuple[i].to_int ();
        if (unlikely (start > peak || peak > end ||
                      (start < 0 && end > 0 && peak))) continue;
        if (v < start || v > end) return 0.f;
        if (v < peak)
        { if (peak != start) scalar *= (float) (v - start) / (peak - start); }
        else
        { if (peak != end) scalar *= (float) (end - v) / (end - peak); }
      }
      else if (!v || v < hb_min (0, peak) || v > hb_max (0, peak)) return 0.f;
      else
        scalar *= (float) v / peak;
    }
    return scalar;
  }

  bool           has_peak () const { return tupleIndex & TuppleIndex::EmbeddedPeakTuple; }
  bool   has_intermediate () const { return tupleIndex & TuppleIndex::IntermediateRegion; }
  bool has_private_points () const { return tupleIndex & TuppleIndex::PrivatePointNumbers; }
  unsigned      get_index () const { return tupleIndex & TuppleIndex::TupleIndexMask; }

  protected:
  struct TuppleIndex : HBUINT16
  {
    enum Flags {
      EmbeddedPeakTuple   = 0x8000u,
      IntermediateRegion  = 0x4000u,
      PrivatePointNumbers = 0x2000u,
      TupleIndexMask      = 0x0FFFu
    };

    TuppleIndex& operator = (uint16_t i) { HBUINT16::operator= (i); return *this; }
    DEFINE_SIZE_STATIC (2);
  };

  hb_array_t<const F2DOT14> get_all_tuples (unsigned axis_count) const
  { return StructAfter<UnsizedArrayOf<F2DOT14>> (tupleIndex).as_array ((has_peak () + has_intermediate () * 2) * axis_count); }
  hb_array_t<const F2DOT14> get_peak_tuple (unsigned axis_count) const
  { return get_all_tuples (axis_count).sub_array (0, axis_count); }
  hb_array_t<const F2DOT14> get_start_tuple (unsigned axis_count) const
  { return get_all_tuples (axis_count).sub_array (has_peak () * axis_count, axis_count); }
  hb_array_t<const F2DOT14> get_end_tuple (unsigned axis_count) const
  { return get_all_tuples (axis_count).sub_array (has_peak () * axis_count + axis_count, axis_count); }

  HBUINT16      varDataSize;    /* The size in bytes of the serialized
                                 * data for this tuple variation table. */
  TuppleIndex   tupleIndex;     /* A packed field. The high 4 bits are flags (see below).
                                   The low 12 bits are an index into a shared tuple
                                   records array. */
  /* UnsizedArrayOf<F2DOT14> peakTuple - optional */
                                /* Peak tuple record for this tuple variation table — optional,
                                 * determined by flags in the tupleIndex value.
                                 *
                                 * Note that this must always be included in the 'cvar' table. */
  /* UnsizedArrayOf<F2DOT14> intermediateStartTuple - optional */
                                /* Intermediate start tuple record for this tuple variation table — optional,
                                   determined by flags in the tupleIndex value. */
  /* UnsizedArrayOf<F2DOT14> intermediateEndTuple - optional */
                                /* Intermediate end tuple record for this tuple variation table — optional,
                                 * determined by flags in the tupleIndex value. */
  public:
  DEFINE_SIZE_MIN (4);
};

enum packed_delta_flag_t
{
  DELTAS_ARE_ZERO      = 0x80,
  DELTAS_ARE_WORDS     = 0x40,
  DELTA_RUN_COUNT_MASK = 0x3F
};

struct tuple_delta_t
{
  public:
  hb_hashmap_t<hb_tag_t, Triple> axis_tuples;

  /* indices_length = point_count, indice[i] = 1 means point i is referenced */
  hb_vector_t<bool> indices;
  
  hb_vector_t<float> deltas_x;
  /* empty for cvar tuples */
  hb_vector_t<float> deltas_y;

  /* compiled data: header and deltas
   * compiled point data is saved in a hashmap within tuple_variations_t cause
   * some point sets might be reused by different tuple variations */
  hb_vector_t<char> compiled_tuple_header;
  hb_vector_t<char> compiled_deltas;

  tuple_delta_t () = default;
  tuple_delta_t (const tuple_delta_t& o) = default;

  tuple_delta_t (tuple_delta_t&& o) : tuple_delta_t ()
  {
    axis_tuples = std::move (o.axis_tuples);
    indices = std::move (o.indices);
    deltas_x = std::move (o.deltas_x);
    deltas_y = std::move (o.deltas_y);
  }

  tuple_delta_t& operator = (tuple_delta_t&& o)
  {
    hb_swap (*this, o);
    return *this;
  }

  void remove_axis (hb_tag_t axis_tag)
  { axis_tuples.del (axis_tag); }

  bool set_tent (hb_tag_t axis_tag, Triple tent)
  { return axis_tuples.set (axis_tag, tent); }

  tuple_delta_t& operator += (const tuple_delta_t& o)
  {
    unsigned num = indices.length;
    for (unsigned i = 0; i < num; i++)
    {
      if (indices.arrayZ[i])
      {
        if (o.indices.arrayZ[i])
        {
          deltas_x[i] += o.deltas_x[i];
          if (deltas_y && o.deltas_y)
            deltas_y[i] += o.deltas_y[i];
        }
      }
      else
      {
        if (!o.indices.arrayZ[i]) continue;
        indices.arrayZ[i] = true;
        deltas_x[i] = o.deltas_x[i];
        if (deltas_y && o.deltas_y)
          deltas_y[i] = o.deltas_y[i];
      }
    }
    return *this;
  }

  tuple_delta_t& operator *= (float scalar)
  {
    if (scalar == 1.0f)
      return *this;

    unsigned num = indices.length;
    for (unsigned i = 0; i < num; i++)
    {
      if (!indices.arrayZ[i]) continue;

      deltas_x[i] *= scalar;
      if (deltas_y)
        deltas_y[i] *= scalar;
    }
    return *this;
  }

  hb_vector_t<tuple_delta_t> change_tuple_var_axis_limit (hb_tag_t axis_tag, Triple axis_limit,
                                                          TripleDistances axis_triple_distances) const
  {
    hb_vector_t<tuple_delta_t> out;
    Triple *tent;
    if (!axis_tuples.has (axis_tag, &tent))
    {
      out.push (*this);
      return out;
    }

    if ((tent->minimum < 0.f && tent->maximum > 0.f) ||
        !(tent->minimum <= tent->middle && tent->middle <= tent->maximum))
      return out;

    if (tent->middle == 0.f)
    {
      out.push (*this);
      return out;
    }

    result_t solutions = rebase_tent (*tent, axis_limit, axis_triple_distances);
    for (auto t : solutions)
    {
      tuple_delta_t new_var = *this;
      if (t.second == Triple ())
        new_var.remove_axis (axis_tag);
      else
        new_var.set_tent (axis_tag, t.second);

      new_var *= t.first;
      out.push (std::move (new_var));
    }

    return out;
  }

  /* deltas should be compiled already before we compile tuple
   * variation header cause we need to fill in the size of the
   * serialized data for this tuple variation */
  //TODO(qxliu):add option to use sharedTuples in gvar
  bool compile_tuple_var_header (const hb_map_t& axes_index_map,
                                 unsigned points_data_length,
                                 const hb_map_t& axes_old_index_tag_map)
  {
    if (!compiled_deltas) return false;

    unsigned cur_axis_count = axes_index_map.get_population ();
    /* allocate enough memory: 1 peak + 2 intermediate coords + fixed header size */
    unsigned alloc_len = 3 * cur_axis_count * (F2DOT14::static_size) + 4;
    if (unlikely (!compiled_tuple_header.resize (alloc_len))) return false;

    unsigned flag = 0;
    /* skip the first 4 header bytes: variationDataSize+tupleIndex */
    F2DOT14* p = reinterpret_cast<F2DOT14 *> (compiled_tuple_header.begin () + 4);
    F2DOT14* end = reinterpret_cast<F2DOT14 *> (compiled_tuple_header.end ());
    hb_array_t<F2DOT14> coords (p, end - p);

    /* encode peak coords */
    unsigned peak_count = encode_peak_coords(coords, flag, axes_index_map, axes_old_index_tag_map);
    if (!peak_count) return false;

    /* encode interim coords, it's optional so returned num could be 0 */
    unsigned interim_count = encode_interm_coords (coords.sub_array (peak_count), flag, axes_index_map, axes_old_index_tag_map);

    //TODO(qxliu): add option to use shared_points in gvar
    flag |= TupleVariationHeader::TuppleIndex::PrivatePointNumbers;

    unsigned serialized_data_size = points_data_length + compiled_deltas.length;
    TupleVariationHeader *o = reinterpret_cast<TupleVariationHeader *> (compiled_tuple_header.begin ());
    o->varDataSize = serialized_data_size;
    o->tupleIndex = flag;

    unsigned total_header_len = 4 + (peak_count + interim_count) * (F2DOT14::static_size);
    return compiled_tuple_header.resize (total_header_len);
  }

  unsigned encode_peak_coords (hb_array_t<F2DOT14> peak_coords,
                               unsigned& flag,
                               const hb_map_t& axes_index_map,
                               const hb_map_t& axes_old_index_tag_map) const
  {
    unsigned orig_axis_count = axes_old_index_tag_map.get_population ();
    auto it = peak_coords.iter ();
    unsigned count = 0;
    for (unsigned i = 0; i < orig_axis_count; i++)
    {
      if (!axes_index_map.has (i)) /* axis pinned */
        continue;
      hb_tag_t axis_tag = axes_old_index_tag_map.get (i);
      Triple *coords;
      if (!axis_tuples.has (axis_tag, &coords))
        (*it).set_int (0);
      else
        (*it).set_float (coords->middle);
      it++;
      count++;
    }
    flag |= TupleVariationHeader::TuppleIndex::EmbeddedPeakTuple;
    return count;
  }

  /* if no need to encode intermediate coords, then just return p */
  unsigned encode_interm_coords (hb_array_t<F2DOT14> coords,
                                 unsigned& flag,
                                 const hb_map_t& axes_index_map,
                                 const hb_map_t& axes_old_index_tag_map) const
  {
    unsigned orig_axis_count = axes_old_index_tag_map.get_population ();
    unsigned cur_axis_count = axes_index_map.get_population ();

    auto start_coords_iter = coords.sub_array (0, cur_axis_count).iter ();
    auto end_coords_iter = coords.sub_array (cur_axis_count).iter ();
    bool encode_needed = false;
    unsigned count = 0;
    for (unsigned i = 0; i < orig_axis_count; i++)
    {
      if (!axes_index_map.has (i)) /* axis pinned */
        continue;
      hb_tag_t axis_tag = axes_old_index_tag_map.get (i);
      Triple *coords;
      float min_val = 0.f, val = 0.f, max_val = 0.f;
      if (axis_tuples.has (axis_tag, &coords))
      {
        min_val = coords->minimum;
        val = coords->middle;
        max_val = coords->maximum;
      }

      (*start_coords_iter).set_float (min_val);
      (*end_coords_iter).set_float (max_val);

      start_coords_iter++;
      end_coords_iter++;
      count += 2;
      if (min_val != hb_min (val, 0.f) || max_val != hb_max (val, 0.f))
        encode_needed = true;
    }

    if (encode_needed)
    {
      flag |= TupleVariationHeader::TuppleIndex::IntermediateRegion;
      return count;
    }
    return 0;
  }

  bool compile_deltas ()
  {
    hb_vector_t<int> rounded_deltas;
    if (unlikely (!rounded_deltas.alloc (indices.length)))
      return false;

    for (unsigned i = 0; i < indices.length; i++)
    {
      if (!indices[i]) continue;
      int rounded_delta = (int) roundf (deltas_x[i]);
      rounded_deltas.push (rounded_delta);
    }

    if (!rounded_deltas) return false;
    /* allocate enough memories 3 * num_deltas */
    unsigned alloc_len = 3 * rounded_deltas.length;
    if (deltas_y)
      alloc_len *= 2;

    if (unlikely (!compiled_deltas.resize (alloc_len))) return false;

    unsigned i = 0;
    unsigned encoded_len = encode_delta_run (i, compiled_deltas.as_array (), rounded_deltas);

    if (deltas_y)
    {
      /* reuse the rounded_deltas vector, check that deltas_y have the same num of deltas as deltas_x */
      unsigned j = 0;
      for (unsigned idx = 0; idx < indices.length; idx++)
      {
        if (!indices[idx]) continue;
        int rounded_delta = (int) roundf (deltas_y[idx]);

        if (j >= rounded_deltas.length) return false;

        rounded_deltas[j++] = rounded_delta;
      }

      if (j != rounded_deltas.length) return false;
      /* reset i because we reuse rounded_deltas for deltas_y */
      i = 0;
      encoded_len += encode_delta_run (i, compiled_deltas.as_array ().sub_array (encoded_len), rounded_deltas);
    }
    return compiled_deltas.resize (encoded_len);
  }

  unsigned encode_delta_run (unsigned& i,
                             hb_array_t<char> encoded_bytes,
                             const hb_vector_t<int>& deltas) const
  {
    unsigned num_deltas = deltas.length;
    unsigned encoded_len = 0;
    while (i < num_deltas)
    {
      int val = deltas[i];
      if (val == 0)
        encoded_len += encode_delta_run_as_zeroes (i, encoded_bytes.sub_array (encoded_len), deltas);
      else if (val >= -128 && val <= 127)
        encoded_len += encode_delta_run_as_bytes (i, encoded_bytes.sub_array (encoded_len), deltas);
      else
        encoded_len += encode_delta_run_as_words (i, encoded_bytes.sub_array (encoded_len), deltas);
    }
    return encoded_len;
  }

  unsigned encode_delta_run_as_zeroes (unsigned& i,
                                       hb_array_t<char> encoded_bytes,
                                       const hb_vector_t<int>& deltas) const
  {
    unsigned num_deltas = deltas.length;
    unsigned run_length = 0;
    auto it = encoded_bytes.iter ();
    unsigned encoded_len = 0;
    while (i < num_deltas && deltas[i] == 0)
    {
      i++;
      run_length++;
    }

    while (run_length >= 64)
    {
      *it++ = char (DELTAS_ARE_ZERO | 63);
      run_length -= 64;
      encoded_len++;
    }

    if (run_length)
    {
      *it++ = char (DELTAS_ARE_ZERO | (run_length - 1));
      encoded_len++;
    }
    return encoded_len;
  }

  unsigned encode_delta_run_as_bytes (unsigned &i,
                                      hb_array_t<char> encoded_bytes,
                                      const hb_vector_t<int>& deltas) const
  {
    unsigned start = i;
    unsigned num_deltas = deltas.length;
    while (i < num_deltas)
    {
      int val = deltas[i];
      if (val > 127 || val < -128)
        break;

      /* from fonttools: if there're 2 or more zeros in a sequence,
       * it is better to start a new run to save bytes. */
      if (val == 0 && i + 1 < num_deltas && deltas[i+1] == 0)
        break;

      i++;
    }
    unsigned run_length = i - start;

    unsigned encoded_len = 0;
    auto it = encoded_bytes.iter ();

    while (run_length >= 64)
    {
      *it++ = 63;
      encoded_len++;

      for (unsigned j = 0; j < 64; j++)
      {
        *it++ = static_cast<char> (deltas[start + j]);
        encoded_len++;
      }

      start += 64;
      run_length -= 64;
    }

    if (run_length)
    {
      *it++ = run_length - 1;
      encoded_len++;

      while (start < i)
      {
        *it++ = static_cast<char> (deltas[start++]);
        encoded_len++;
      }
    }

    return encoded_len;
  }

  unsigned encode_delta_run_as_words (unsigned &i,
                                      hb_array_t<char> encoded_bytes,
                                      const hb_vector_t<int>& deltas) const
  {
    unsigned start = i;
    unsigned num_deltas = deltas.length;
    while (i < num_deltas)
    {
      int val = deltas[i];
      
      /* start a new run for a single zero value*/
      if (val == 0) break;

      /* from fonttools: continue word-encoded run if there's only one
       * single value in the range [-128, 127] because it is more compact.
       * Only start a new run when there're 2 continuous such values. */
      if (val >= -128 && val <= 127 &&
          i + 1 < num_deltas &&
          deltas[i+1] >= -128 && deltas[i+1] <= 127)
        break;

      i++;
    }

    unsigned run_length = i - start;
    auto it = encoded_bytes.iter ();
    unsigned encoded_len = 0;
    while (run_length >= 64)
    {
      *it++ = (DELTAS_ARE_WORDS | 63);
      encoded_len++;

      for (unsigned j = 0; j < 64; j++)
      {
        int16_t delta_val = deltas[start + j];
        *it++ = static_cast<char> (delta_val >> 8);
        *it++ = static_cast<char> (delta_val & 0xFF);

        encoded_len += 2;
      }

      start += 64;
      run_length -= 64;
    }

    if (run_length)
    {
      *it++ = (DELTAS_ARE_WORDS | (run_length - 1));
      encoded_len++;
      while (start < i)
      {
        int16_t delta_val = deltas[start++];
        *it++ = static_cast<char> (delta_val >> 8);
        *it++ = static_cast<char> (delta_val & 0xFF);

        encoded_len += 2;
      }
    }
    return encoded_len;
  }
};

struct TupleVariationData
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    // here check on min_size only, TupleVariationHeader and var data will be
    // checked while accessing through iterator.
    return_trace (c->check_struct (this));
  }

  unsigned get_size (unsigned axis_count) const
  {
    unsigned total_size = min_size;
    unsigned count = tupleVarCount.get_count ();
    const TupleVariationHeader *tuple_var_header = &(get_tuple_var_header());
    for (unsigned i = 0; i < count; i++)
    {
      total_size += tuple_var_header->get_size (axis_count) + tuple_var_header->get_data_size ();
      tuple_var_header = &tuple_var_header->get_next (axis_count);
    }

    return total_size;
  }

  const TupleVariationHeader &get_tuple_var_header (void) const
  { return StructAfter<TupleVariationHeader> (data); }

  struct tuple_iterator_t;
  struct tuple_variations_t
  {
    hb_vector_t<tuple_delta_t> tuple_vars;

    private:
    /* referenced point set->compiled point data map */
    hb_hashmap_t<const hb_vector_t<bool>*, hb_bytes_t> point_data_map;
    /* referenced point set-> count map, used in finding shared points */
    hb_hashmap_t<const hb_vector_t<bool>*, unsigned> point_set_count_map;

    public:
    ~tuple_variations_t () { fini (); }
    void fini ()
    {
      for (auto _ : point_data_map.values ())
        _.fini ();

      point_set_count_map.fini ();
      tuple_vars.fini ();
    }

    unsigned get_var_count () const
    { return tuple_vars.length; }

    bool create_from_tuple_var_data (tuple_iterator_t iterator,
                                     unsigned tuple_var_count,
                                     unsigned point_count,
                                     bool is_gvar,
                                     const hb_map_t *axes_old_index_tag_map,
                                     const hb_vector_t<unsigned> &shared_indices,
                                     const hb_array_t<const F2DOT14> shared_tuples)
    {
      do
      {
        const HBUINT8 *p = iterator.get_serialized_data ();
        unsigned int length = iterator.current_tuple->get_data_size ();
        if (unlikely (!iterator.var_data_bytes.check_range (p, length)))
        { fini (); return false; }

        hb_hashmap_t<hb_tag_t, Triple> axis_tuples;
        if (!iterator.current_tuple->unpack_axis_tuples (iterator.get_axis_count (), shared_tuples, axes_old_index_tag_map, axis_tuples)
            || axis_tuples.is_empty ())
        { fini (); return false; }

        hb_vector_t<unsigned> private_indices;
        bool has_private_points = iterator.current_tuple->has_private_points ();
        const HBUINT8 *end = p + length;
        if (has_private_points &&
            !TupleVariationData::unpack_points (p, private_indices, end))
        { fini (); return false; }

        const hb_vector_t<unsigned> &indices = has_private_points ? private_indices : shared_indices;
        bool apply_to_all = (indices.length == 0);
        unsigned num_deltas = apply_to_all ? point_count : indices.length;

        hb_vector_t<int> deltas_x;

        if (unlikely (!deltas_x.resize (num_deltas, false) ||
                      !TupleVariationData::unpack_deltas (p, deltas_x, end)))
        { fini (); return false; }

        hb_vector_t<int> deltas_y;
        if (is_gvar)
        {
          if (unlikely (!deltas_y.resize (num_deltas, false) ||
                        !TupleVariationData::unpack_deltas (p, deltas_y, end)))
          { fini (); return false; }
        }

        tuple_delta_t var;
        var.axis_tuples = std::move (axis_tuples);
        if (unlikely (!var.indices.resize (point_count) ||
                      !var.deltas_x.resize (point_count, false)))
        { fini (); return false; }

        if (is_gvar && unlikely (!var.deltas_y.resize (point_count, false)))
        { fini (); return false; }

        for (unsigned i = 0; i < num_deltas; i++)
        {
          unsigned idx = apply_to_all ? i : indices[i];
          if (idx >= point_count) continue;
          var.indices[idx] = true;
          var.deltas_x[idx] = static_cast<float> (deltas_x[i]);
          if (is_gvar)
            var.deltas_y[idx] = static_cast<float> (deltas_y[i]);
        }
        tuple_vars.push (std::move (var));
      } while (iterator.move_to_next ());
      return true;
    }

    void change_tuple_variations_axis_limits (const hb_hashmap_t<hb_tag_t, Triple>& normalized_axes_location,
                                              const hb_hashmap_t<hb_tag_t, TripleDistances>& axes_triple_distances)
    {
      for (auto _ : normalized_axes_location)
      {
        hb_tag_t axis_tag = _.first;
        Triple axis_limit = _.second;
        TripleDistances axis_triple_distances{1.f, 1.f};
        if (axes_triple_distances.has (axis_tag))
          axis_triple_distances = axes_triple_distances.get (axis_tag);

        hb_vector_t<tuple_delta_t> new_vars;
        for (const tuple_delta_t& var : tuple_vars)
        {
          hb_vector_t<tuple_delta_t> out = var.change_tuple_var_axis_limit (axis_tag, axis_limit, axis_triple_distances);
          if (!out) continue;
          unsigned new_len = new_vars.length + out.length;

          if (unlikely (!new_vars.alloc (new_len, false)))
          { fini (); return;}

          for (unsigned i = 0; i < out.length; i++)
            new_vars.push (std::move (out[i]));
        }
        tuple_vars.fini ();
        tuple_vars = std::move (new_vars);
      }
    }

    /* merge tuple variations with overlapping tents */
    void merge_tuple_variations ()
    {
      hb_vector_t<tuple_delta_t> new_vars;
      hb_hashmap_t<hb_hashmap_t<hb_tag_t, Triple>, unsigned> m;
      unsigned i = 0;
      for (const tuple_delta_t& var : tuple_vars)
      {
        /* if all axes are pinned, drop the tuple variation */
        if (var.axis_tuples.is_empty ()) continue;

        unsigned *idx;
        if (m.has (var.axis_tuples, &idx))
        {
          new_vars[*idx] += var;
        }
        else
        {
          new_vars.push (var);
          m.set (var.axis_tuples, i);
          i++;
        }
      }
      tuple_vars.fini ();
      tuple_vars = std::move (new_vars);
    }

    hb_bytes_t compile_point_set (const hb_vector_t<bool> &point_indices)
    {
      unsigned num_points = 0;
      for (bool i : point_indices)
        if (i) num_points++;

      unsigned indices_length = point_indices.length;
      /* If the points set consists of all points in the glyph, it's encoded with a
       * single zero byte */
      if (num_points == indices_length)
      {
        char *p = (char *) hb_calloc (1, sizeof (char));
        if (unlikely (!p)) return hb_bytes_t ();

        return hb_bytes_t (p, 1);
      }

      /* allocate enough memories: 2 bytes for count + 3 bytes for each point */
      unsigned num_bytes = 2 + 3 *num_points;
      char *p = (char *) hb_calloc (num_bytes, sizeof (char));
      if (unlikely (!p)) return hb_bytes_t ();

      unsigned pos = 0;
      /* binary data starts with the total number of reference points */
      if (num_points < 0x80)
        p[pos++] = num_points;
      else
      {
        p[pos++] = ((num_points >> 8) | 0x80);
        p[pos++] = num_points & 0xFF;
      }

      const unsigned max_run_length = 0x7F;
      unsigned i = 0;
      unsigned last_value = 0;
      unsigned num_encoded = 0;
      while (i < indices_length && num_encoded < num_points)
      {
        unsigned run_length = 0;
        unsigned header_pos = pos;
        p[pos++] = 0;

        bool use_byte_encoding = false;
        bool new_run = true;
        while (i < indices_length && num_encoded < num_points &&
               run_length <= max_run_length)
        {
          // find out next referenced point index
          while (i < indices_length && !point_indices[i])
            i++;

          if (i >= indices_length) break;

          unsigned cur_value = i;
          unsigned delta = cur_value - last_value;

          if (new_run)
          {
            use_byte_encoding = (delta <= 0xFF);
            new_run = false;
          }

          if (use_byte_encoding && delta > 0xFF)
            break;

          if (use_byte_encoding)
            p[pos++] = delta;
          else
          {
            p[pos++] = delta >> 8;
            p[pos++] = delta & 0xFF;
          }
          i++;
          last_value = cur_value;
          run_length++;
          num_encoded++;
        }

        if (use_byte_encoding)
          p[header_pos] = run_length - 1;
        else
          p[header_pos] = (run_length - 1) | 0x80;
      }
      return hb_bytes_t (p, pos);
    }

    /* compile all point set and store byte data in a point_set->hb_bytes_t hashmap,
     * also update point_set->count map, which will be used in finding shared
     * point set*/
    bool compile_all_point_sets ()
    {
      for (const auto& tuple: tuple_vars)
      {
        const hb_vector_t<bool>* points_set = &(tuple.indices);
        if (point_data_map.has (points_set))
        {
          unsigned *count;
          if (unlikely (!point_set_count_map.has (points_set, &count) ||
                        !point_set_count_map.set (points_set, (*count) + 1)))
            return false;
          continue;
        }
        
        hb_bytes_t compiled_data = compile_point_set (*points_set);
        if (unlikely (compiled_data == hb_bytes_t ()))
          return false;
        
        if (!point_data_map.set (points_set, compiled_data) ||
            !point_set_count_map.set (points_set, 1))
          return false;
      }
      return true;
    }

    /* find shared points set which saves most bytes */
    hb_bytes_t find_shared_points ()
    {
      unsigned max_saved_bytes = 0;
      hb_bytes_t res{};

      for (const auto& _ : point_data_map.iter ())
      {
        const hb_vector_t<bool>* points_set = _.first;
        unsigned data_length = _.second.length;
        unsigned *count;
        if (unlikely (!point_set_count_map.has (points_set, &count) ||
                      *count <= 1))
          return hb_bytes_t ();

        unsigned saved_bytes = data_length * ((*count) -1);
        if (saved_bytes > max_saved_bytes)
        {
          max_saved_bytes = saved_bytes;
          res = _.second;
        }
      }
      return res;
    }

    void instantiate (const hb_hashmap_t<hb_tag_t, Triple>& normalized_axes_location,
                      const hb_hashmap_t<hb_tag_t, TripleDistances>& axes_triple_distances)
    {
      change_tuple_variations_axis_limits (normalized_axes_location, axes_triple_distances);
      merge_tuple_variations ();
    }

    bool compile_bytes (const hb_map_t& axes_index_map,
                        const hb_map_t& axes_old_index_tag_map)
    {
      // compile points set and store data in hashmap
      if (!compile_all_point_sets ())
        return false;
      // compile delta and tuple var header for each tuple variation
      for (auto& tuple: tuple_vars)
      {
        const hb_vector_t<bool>* points_set = &(tuple.indices);
        hb_bytes_t *points_data;
        if (unlikely (!point_data_map.has (points_set, &points_data)))
          return false;

        if (!tuple.compile_deltas ())
          return false;

        if (!tuple.compile_tuple_var_header (axes_index_map, points_data->length, axes_old_index_tag_map))
          return false;
      }
      return true;
    }

    bool serialize_var_headers (hb_serialize_context_t *c, unsigned& total_header_len) const
    {
      TRACE_SERIALIZE (this);
      for (const auto& tuple: tuple_vars)
      {
        tuple.compiled_tuple_header.as_array ().copy (c);
        if (c->in_error ()) return_trace (false);
        total_header_len += tuple.compiled_tuple_header.length;
      }
      return_trace (true);
    }

    bool serialize_var_data (hb_serialize_context_t *c) const
    {
      TRACE_SERIALIZE (this);
      for (const auto& tuple: tuple_vars)
      {
        const hb_vector_t<bool>* points_set = &(tuple.indices);
        hb_bytes_t *point_data;
        if (!point_data_map.has (points_set, &point_data))
          return_trace (false);

        point_data->copy (c);
        tuple.compiled_deltas.as_array ().copy (c);
        if (c->in_error ()) return_trace (false);
      }
      return_trace (true);
    }
  };

  struct tuple_iterator_t
  {
    unsigned get_axis_count () const { return axis_count; }

    void init (hb_bytes_t var_data_bytes_, unsigned int axis_count_, const void *table_base_)
    {
      var_data_bytes = var_data_bytes_;
      var_data = var_data_bytes_.as<TupleVariationData> ();
      index = 0;
      axis_count = axis_count_;
      current_tuple = &var_data->get_tuple_var_header ();
      data_offset = 0;
      table_base = table_base_;
    }

    bool get_shared_indices (hb_vector_t<unsigned int> &shared_indices /* OUT */)
    {
      if (var_data->has_shared_point_numbers ())
      {
        const HBUINT8 *base = &(table_base+var_data->data);
        const HBUINT8 *p = base;
        if (!unpack_points (p, shared_indices, (const HBUINT8 *) (var_data_bytes.arrayZ + var_data_bytes.length))) return false;
        data_offset = p - base;
      }
      return true;
    }

    bool is_valid () const
    {
      return (index < var_data->tupleVarCount.get_count ()) &&
             var_data_bytes.check_range (current_tuple, TupleVariationHeader::min_size) &&
             var_data_bytes.check_range (current_tuple, hb_max (current_tuple->get_data_size (),
                                                                current_tuple->get_size (axis_count)));
    }

    bool move_to_next ()
    {
      data_offset += current_tuple->get_data_size ();
      current_tuple = &current_tuple->get_next (axis_count);
      index++;
      return is_valid ();
    }

    const HBUINT8 *get_serialized_data () const
    { return &(table_base+var_data->data) + data_offset; }

    private:
    const TupleVariationData *var_data;
    unsigned int index;
    unsigned int axis_count;
    unsigned int data_offset;
    const void *table_base;

    public:
    hb_bytes_t var_data_bytes;
    const TupleVariationHeader *current_tuple;
  };

  static bool get_tuple_iterator (hb_bytes_t var_data_bytes, unsigned axis_count,
                                  const void *table_base,
                                  hb_vector_t<unsigned int> &shared_indices /* OUT */,
                                  tuple_iterator_t *iterator /* OUT */)
  {
    iterator->init (var_data_bytes, axis_count, table_base);
    if (!iterator->get_shared_indices (shared_indices))
      return false;
    return iterator->is_valid ();
  }

  bool has_shared_point_numbers () const { return tupleVarCount.has_shared_point_numbers (); }

  static bool unpack_points (const HBUINT8 *&p /* IN/OUT */,
                             hb_vector_t<unsigned int> &points /* OUT */,
                             const HBUINT8 *end)
  {
    enum packed_point_flag_t
    {
      POINTS_ARE_WORDS     = 0x80,
      POINT_RUN_COUNT_MASK = 0x7F
    };

    if (unlikely (p + 1 > end)) return false;

    unsigned count = *p++;
    if (count & POINTS_ARE_WORDS)
    {
      if (unlikely (p + 1 > end)) return false;
      count = ((count & POINT_RUN_COUNT_MASK) << 8) | *p++;
    }
    if (unlikely (!points.resize (count, false))) return false;

    unsigned n = 0;
    unsigned i = 0;
    while (i < count)
    {
      if (unlikely (p + 1 > end)) return false;
      unsigned control = *p++;
      unsigned run_count = (control & POINT_RUN_COUNT_MASK) + 1;
      unsigned stop = i + run_count;
      if (unlikely (stop > count)) return false;
      if (control & POINTS_ARE_WORDS)
      {
        if (unlikely (p + run_count * HBUINT16::static_size > end)) return false;
        for (; i < stop; i++)
        {
          n += *(const HBUINT16 *)p;
          points.arrayZ[i] = n;
          p += HBUINT16::static_size;
        }
      }
      else
      {
        if (unlikely (p + run_count > end)) return false;
        for (; i < stop; i++)
        {
          n += *p++;
          points.arrayZ[i] = n;
        }
      }
    }
    return true;
  }

  static bool unpack_deltas (const HBUINT8 *&p /* IN/OUT */,
                             hb_vector_t<int> &deltas /* IN/OUT */,
                             const HBUINT8 *end)
  {
    unsigned i = 0;
    unsigned count = deltas.length;
    while (i < count)
    {
      if (unlikely (p + 1 > end)) return false;
      unsigned control = *p++;
      unsigned run_count = (control & DELTA_RUN_COUNT_MASK) + 1;
      unsigned stop = i + run_count;
      if (unlikely (stop > count)) return false;
      if (control & DELTAS_ARE_ZERO)
      {
        for (; i < stop; i++)
          deltas.arrayZ[i] = 0;
      }
      else if (control & DELTAS_ARE_WORDS)
      {
        if (unlikely (p + run_count * HBUINT16::static_size > end)) return false;
        for (; i < stop; i++)
        {
          deltas.arrayZ[i] = * (const HBINT16 *) p;
          p += HBUINT16::static_size;
        }
      }
      else
      {
        if (unlikely (p + run_count > end)) return false;
        for (; i < stop; i++)
        {
          deltas.arrayZ[i] = * (const HBINT8 *) p++;
        }
      }
    }
    return true;
  }

  bool has_data () const { return tupleVarCount; }

  bool decompile_tuple_variations (unsigned point_count,
                                   bool is_gvar,
                                   tuple_iterator_t iterator,
                                   const hb_map_t *axes_old_index_tag_map,
                                   const hb_vector_t<unsigned> &shared_indices,
                                   const hb_array_t<const F2DOT14> shared_tuples,
                                   tuple_variations_t& tuple_variations /* OUT */) const
  {
    return tuple_variations.create_from_tuple_var_data (iterator, tupleVarCount,
                                                        point_count, is_gvar,
                                                        axes_old_index_tag_map,
                                                        shared_indices,
                                                        shared_tuples);
  }

  bool serialize (hb_serialize_context_t *c,
                  bool is_gvar,
                  tuple_variations_t& tuple_variations) const
  {
    TRACE_SERIALIZE (this);
    auto *out = c->start_embed (this);
    if (unlikely (!c->extend_min (out))) return_trace (false);

    if (!c->check_assign (out->tupleVarCount, tuple_variations.get_var_count (),
                          HB_SERIALIZE_ERROR_INT_OVERFLOW)) return_trace (false);

    unsigned total_header_len = 0;

    if (!tuple_variations.serialize_var_headers (c, total_header_len))
      return_trace (false);
    
    unsigned data_offset = min_size + total_header_len;
    if (!is_gvar) data_offset += 4;
    if (!c->check_assign (out->data, data_offset, HB_SERIALIZE_ERROR_INT_OVERFLOW)) return_trace (false);

    return tuple_variations.serialize_var_data (c);
  }

  protected:
  struct TupleVarCount : HBUINT16
  {
    bool has_shared_point_numbers () const { return ((*this) & SharedPointNumbers); }
    unsigned int get_count () const { return (*this) & CountMask; }
    TupleVarCount& operator = (uint16_t i) { HBUINT16::operator= (i); return *this; }

    protected:
    enum Flags
    {
      SharedPointNumbers= 0x8000u,
      CountMask         = 0x0FFFu
    };
    public:
    DEFINE_SIZE_STATIC (2);
  };

  TupleVarCount tupleVarCount;  /* A packed field. The high 4 bits are flags, and the
                                 * low 12 bits are the number of tuple variation tables
                                 * for this glyph. The number of tuple variation tables
                                 * can be any number between 1 and 4095. */
  Offset16To<HBUINT8>
                data;           /* Offset from the start of the base table
                                 * to the serialized data. */
  /* TupleVariationHeader tupleVariationHeaders[] *//* Array of tuple variation headers. */
  public:
  DEFINE_SIZE_MIN (4);
};

} /* namespace OT */


#endif /* HB_OT_VAR_COMMON_HH */