// SPDX-License-Identifier: Apache-2.0

// ----------------------------------------------------------------------------

// Copyright 2011-2026 Arm Limited

//

// Licensed under the Apache License, Version 2.0 (the "License"); you may not

// use this file except in compliance with the License. You may obtain a copy

// of the License at:

//

//     http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the

// License for the specific language governing permissions and limitations

// under the License.

// ----------------------------------------------------------------------------

/**

 * @brief Functions for converting between symbolic and physical encodings.

 */

#include "astcenc_internal.h"

#include <cassert>

/**

 * @brief Reverse bits in a byte.

 *

 * @param p   The value to reverse.

  *

 * @return The reversed result.

 */

static inline int bitrev8(int p)

{

  p = ((p & 0x0F) << 4) | ((p >> 4) & 0x0F);

  p = ((p & 0x33) << 2) | ((p >> 2) & 0x33);

  p = ((p & 0x55) << 1) | ((p >> 1) & 0x55);

  return p;

}

/**

 * @brief Read up to 8 bits at an arbitrary bit offset.

 *

 * The stored value is at most 8 bits, but can be stored at an offset of between 0 and 7 bits so may

 * span two separate bytes in memory.

 *

 * @param         bitcount    The number of bits to read.

 * @param         bitoffset   The bit offset to read from, between 0 and 7.

 * @param[in,out] ptr         The data pointer to read from.

 *

 * @return The read value.

 */

static inline int read_bits(

  int bitcount,

  int bitoffset,

  const uint8_t* ptr

) {

  int mask = (1 << bitcount) - 1;

  ptr += bitoffset >> 3;

  bitoffset &= 7;

  int value = ptr[0] | (ptr[1] << 8);

  value >>= bitoffset;

  value &= mask;

  return value;

}

#if !defined(ASTCENC_DECOMPRESS_ONLY)

/**

 * @brief Write up to 8 bits at an arbitrary bit offset.

 *

 * The stored value is at most 8 bits, but can be stored at an offset of between 0 and 7 bits so

 * may span two separate bytes in memory.

 *

 * @param         value       The value to write.

 * @param         bitcount    The number of bits to write, starting from LSB.

 * @param         bitoffset   The bit offset to store at, between 0 and 7.

 * @param[in,out] ptr         The data pointer to write to.

 */

static inline void write_bits(

  int value,

  int bitcount,

  int bitoffset,

  uint8_t* ptr

) {

  int mask = (1 << bitcount) - 1;

  value &= mask;

  ptr += bitoffset >> 3;

  bitoffset &= 7;

  value <<= bitoffset;

  mask <<= bitoffset;

  mask = ~mask;

  ptr[0] &= mask;

  ptr[0] |= value;

  ptr[1] &= mask >> 8;

  ptr[1] |= value >> 8;

}

/* See header for documentation. */

void symbolic_to_physical(

  const block_size_descriptor& bsd,

  const symbolic_compressed_block& scb,

  uint8_t pcb[16]

) {

  assert(scb.block_type != SYM_BTYPE_ERROR);

  // Constant color block using UNORM16 colors

  if (scb.block_type == SYM_BTYPE_CONST_U16)

  {

    // There is currently no attempt to coalesce larger void-extents

    static const uint8_t cbytes[8] { 0xFC, 0xFD, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

    for (unsigned int i = 0; i < 8; i++)

    {

      pcb[i] = cbytes[i];

    }

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

    {

      pcb[2 * i + 8] = scb.constant_color[i] & 0xFF;

      pcb[2 * i + 9] = (scb.constant_color[i] >> 8) & 0xFF;

    }

    return;

  }

  // Constant color block using FP16 colors

  if (scb.block_type == SYM_BTYPE_CONST_F16)

  {

    // There is currently no attempt to coalesce larger void-extents

    static const uint8_t cbytes[8]  { 0xFC, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

    for (unsigned int i = 0; i < 8; i++)

    {

      pcb[i] = cbytes[i];

    }

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

    {

      pcb[2 * i + 8] = scb.constant_color[i] & 0xFF;

      pcb[2 * i + 9] = (scb.constant_color[i] >> 8) & 0xFF;

    }

    return;

  }

  unsigned int partition_count = scb.partition_count;

  // Compress the weights.

  // They are encoded as an ordinary integer-sequence, then bit-reversed

  uint8_t weightbuf[16] { 0 };

  const auto& bm = bsd.get_block_mode(scb.block_mode);

  const auto& di = bsd.get_decimation_info(bm.decimation_mode);

  int weight_count = di.weight_count;

  quant_method weight_quant_method = bm.get_weight_quant_mode();

  float weight_quant_levels = static_cast<float>(get_quant_level(weight_quant_method));

  int is_dual_plane = bm.is_dual_plane;

  const auto& qat = quant_and_xfer_tables[weight_quant_method];

  int real_weight_count = is_dual_plane ? 2 * weight_count : weight_count;

  int bits_for_weights = get_ise_sequence_bitcount(real_weight_count, weight_quant_method);

  uint8_t weights[64];

  if (is_dual_plane)

  {

    for (int i = 0; i < weight_count; i++)

    {

      float uqw = static_cast<float>(scb.weights[i]);

      float qw = (uqw / 64.0f) * (weight_quant_levels - 1.0f);

      int qwi = static_cast<int>(qw + 0.5f);

      weights[2 * i] = qat.scramble_map[qwi];

      uqw = static_cast<float>(scb.weights[i + WEIGHTS_PLANE2_OFFSET]);

      qw = (uqw / 64.0f) * (weight_quant_levels - 1.0f);

      qwi = static_cast<int>(qw + 0.5f);

      weights[2 * i + 1] = qat.scramble_map[qwi];

    }

  }

  else

  {

    for (int i = 0; i < weight_count; i++)

    {

      float uqw = static_cast<float>(scb.weights[i]);

      float qw = (uqw / 64.0f) * (weight_quant_levels - 1.0f);

      int qwi = static_cast<int>(qw + 0.5f);

      weights[i] = qat.scramble_map[qwi];

    }

  }

  encode_ise(weight_quant_method, real_weight_count, weights, weightbuf, 0);

  for (int i = 0; i < 16; i++)

  {

    pcb[i] = static_cast<uint8_t>(bitrev8(weightbuf[15 - i]));

  }

  write_bits(scb.block_mode, 11, 0, pcb);

  write_bits(partition_count - 1, 2, 11, pcb);

  int below_weights_pos = 128 - bits_for_weights;

  // Encode partition index and color endpoint types for blocks with 2+ partitions

  if (partition_count > 1)

  {

    write_bits(scb.partition_index, 6, 13, pcb);

    write_bits(scb.partition_index >> 6, PARTITION_INDEX_BITS - 6, 19, pcb);

    if (scb.color_formats_matched)

    {

      write_bits(scb.color_formats[0] << 2, 6, 13 + PARTITION_INDEX_BITS, pcb);

    }

    else

    {

      // Check endpoint types for each partition to determine the lowest class present

      int low_class = 4;

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

      {

        int class_of_format = scb.color_formats[i] >> 2;

        low_class = astc::min(class_of_format, low_class);

      }

      if (low_class == 3)

      {

        low_class = 2;

      }

      int encoded_type = low_class + 1;

      int bitpos = 2;

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

      {

        int classbit_of_format = (scb.color_formats[i] >> 2) - low_class;

        encoded_type |= classbit_of_format << bitpos;

        bitpos++;

      }

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

      {

        int lowbits_of_format = scb.color_formats[i] & 3;

        encoded_type |= lowbits_of_format << bitpos;

        bitpos += 2;

      }

      int encoded_type_lowpart = encoded_type & 0x3F;

      int encoded_type_highpart = encoded_type >> 6;

      int encoded_type_highpart_size = (3 * partition_count) - 4;

      int encoded_type_highpart_pos = 128 - bits_for_weights - encoded_type_highpart_size;

      write_bits(encoded_type_lowpart, 6, 13 + PARTITION_INDEX_BITS, pcb);

      write_bits(encoded_type_highpart, encoded_type_highpart_size, encoded_type_highpart_pos, pcb);

      below_weights_pos -= encoded_type_highpart_size;

    }

  }

  else

  {

    write_bits(scb.color_formats[0], 4, 13, pcb);

  }

  // In dual-plane mode, encode the color component of the second plane of weights

  if (is_dual_plane)

  {

    write_bits(scb.plane2_component, 2, below_weights_pos - 2, pcb);

  }

  // Encode the color components

  uint8_t values_to_encode[32];

  int valuecount_to_encode = 0;

  const uint8_t* pack_table = color_uquant_to_scrambled_pquant_tables[scb.quant_mode - QUANT_6];

  for (unsigned int i = 0; i < scb.partition_count; i++)

  {

    int vals = 2 * (scb.color_formats[i] >> 2) + 2;

    assert(vals <= 8);

    for (int j = 0; j < vals; j++)

    {

      values_to_encode[j + valuecount_to_encode] = pack_table[scb.color_values[i][j]];

    }

    valuecount_to_encode += vals;

  }

  encode_ise(scb.get_color_quant_mode(), valuecount_to_encode, values_to_encode, pcb,

             scb.partition_count == 1 ? 17 : 19 + PARTITION_INDEX_BITS);

}

#endif

/* See header for documentation. */

void physical_to_symbolic(

  const block_size_descriptor& bsd,

  const uint8_t pcb[16],

  symbolic_compressed_block& scb

) {

  uint8_t bswapped[16];

  scb.block_type = SYM_BTYPE_NONCONST;

  // Extract header fields

  int block_mode = read_bits(11, 0, pcb);

  if ((block_mode & 0x1FF) == 0x1FC)

  {

    // Constant color block

    // Check what format the data has

    if (block_mode & 0x200)

    {

      scb.block_type = SYM_BTYPE_CONST_F16;

    }

    else

    {

      scb.block_type = SYM_BTYPE_CONST_U16;

    }

    scb.partition_count = 0;

    for (int i = 0; i < 4; i++)

    {

      scb.constant_color[i] = pcb[2 * i + 8] | (pcb[2 * i + 9] << 8);

    }

    // Additionally, check that the void-extent

    if (bsd.dim_z == 1)

    {

      // 2D void-extent

      int rsvbits = read_bits(2, 10, pcb);

      if (rsvbits != 3)

      {

        scb.block_type = SYM_BTYPE_ERROR;

        return;

      }

      // Low values span 3 bytes so need two read_bits calls

      int vx_low_s = read_bits(8, 12, pcb) | (read_bits(5, 12 + 8, pcb) << 8);

      int vx_high_s = read_bits(13, 25, pcb);

      int vx_low_t = read_bits(8, 38, pcb) | (read_bits(5, 38 + 8, pcb) << 8);

      int vx_high_t = read_bits(13, 51, pcb);

      int all_ones = vx_low_s == 0x1FFF && vx_high_s == 0x1FFF &&

                     vx_low_t == 0x1FFF && vx_high_t == 0x1FFF;

      if ((vx_low_s >= vx_high_s || vx_low_t >= vx_high_t) && !all_ones)

      {

        scb.block_type = SYM_BTYPE_ERROR;

        return;

      }

    }

    else

    {

      // 3D void-extent

      int vx_low_s = read_bits(9, 10, pcb);

      int vx_high_s = read_bits(9, 19, pcb);

      int vx_low_t = read_bits(9, 28, pcb);

      int vx_high_t = read_bits(9, 37, pcb);

      int vx_low_r = read_bits(9, 46, pcb);

      int vx_high_r = read_bits(9, 55, pcb);

      int all_ones = vx_low_s == 0x1FF && vx_high_s == 0x1FF &&

                     vx_low_t == 0x1FF && vx_high_t == 0x1FF &&

                     vx_low_r == 0x1FF && vx_high_r == 0x1FF;

      if ((vx_low_s >= vx_high_s || vx_low_t >= vx_high_t || vx_low_r >= vx_high_r) && !all_ones)

      {

        scb.block_type = SYM_BTYPE_ERROR;

        return;

      }

    }

    return;

  }

  unsigned int packed_index = bsd.block_mode_packed_index[block_mode];

  if (packed_index == BLOCK_BAD_BLOCK_MODE)

  {

    scb.block_type = SYM_BTYPE_ERROR;

    return;

  }

  const auto& bm = bsd.get_block_mode(block_mode);

  const auto& di = bsd.get_decimation_info(bm.decimation_mode);

  int weight_count = di.weight_count;

  promise(weight_count > 0);

  quant_method weight_quant_method = static_cast<quant_method>(bm.quant_mode);

  int is_dual_plane = bm.is_dual_plane;

  int real_weight_count = is_dual_plane ? 2 * weight_count : weight_count;

  int partition_count = read_bits(2, 11, pcb) + 1;

  promise(partition_count > 0);

  scb.block_mode = static_cast<uint16_t>(block_mode);

  scb.partition_count = static_cast<uint8_t>(partition_count);

  for (int i = 0; i < 16; i++)

  {

    bswapped[i] = static_cast<uint8_t>(bitrev8(pcb[15 - i]));

  }

  int bits_for_weights = get_ise_sequence_bitcount(real_weight_count, weight_quant_method);

  int below_weights_pos = 128 - bits_for_weights;

  uint8_t indices[64];

  const auto& qat = quant_and_xfer_tables[weight_quant_method];

  decode_ise(weight_quant_method, real_weight_count, bswapped, indices, 0);

  if (is_dual_plane)

  {

    for (int i = 0; i < weight_count; i++)

    {

      scb.weights[i] = qat.unscramble_and_unquant_map[indices[2 * i]];

      scb.weights[i + WEIGHTS_PLANE2_OFFSET] = qat.unscramble_and_unquant_map[indices[2 * i + 1]];

    }

  }

  else

  {

    for (int i = 0; i < weight_count; i++)

    {

      scb.weights[i] = qat.unscramble_and_unquant_map[indices[i]];

    }

  }

  if (is_dual_plane && partition_count == 4)

  {

    scb.block_type = SYM_BTYPE_ERROR;

    return;

  }

  scb.color_formats_matched = 0;

  // Determine the format of each endpoint pair

  int color_formats[BLOCK_MAX_PARTITIONS];

  int encoded_type_highpart_size = 0;

  if (partition_count == 1)

  {

    color_formats[0] = read_bits(4, 13, pcb);

    scb.partition_index = 0;

  }

  else

  {

    encoded_type_highpart_size = (3 * partition_count) - 4;

    below_weights_pos -= encoded_type_highpart_size;

    int encoded_type = read_bits(6, 13 + PARTITION_INDEX_BITS, pcb) |

                      (read_bits(encoded_type_highpart_size, below_weights_pos, pcb) << 6);

    int baseclass = encoded_type & 0x3;

    if (baseclass == 0)

    {

      for (int i = 0; i < partition_count; i++)

      {

        color_formats[i] = (encoded_type >> 2) & 0xF;

      }

      below_weights_pos += encoded_type_highpart_size;

      scb.color_formats_matched = 1;

      encoded_type_highpart_size = 0;

    }

    else

    {

      int bitpos = 2;

      baseclass--;

      for (int i = 0; i < partition_count; i++)

      {

        color_formats[i] = (((encoded_type >> bitpos) & 1) + baseclass) << 2;

        bitpos++;

      }

      for (int i = 0; i < partition_count; i++)

      {

        color_formats[i] |= (encoded_type >> bitpos) & 3;

        bitpos += 2;

      }

    }

    scb.partition_index = static_cast<uint16_t>(read_bits(10, 13, pcb));

    // Reject blocks selecting a partitioning that is not present in this

    // block size descriptor. A SELF_DECOMPRESS_ONLY context drops the

    // partitionings its compressor never emits, so a texture compressed

    // with a different context can reference an inactive entry. This is an

    // API contract break from the application, and should not happen in

    // valid usage.

    if (bsd.partitioning_packed_index[partition_count - 2][scb.partition_index] == BLOCK_BAD_PARTITIONING)

    {

      scb.block_type = SYM_BTYPE_ERROR;

      return;

    }

  }

  for (int i = 0; i < partition_count; i++)

  {

    scb.color_formats[i] = static_cast<uint8_t>(color_formats[i]);

  }

  // Determine number of color endpoint integers

  int color_integer_count = 0;

  for (int i = 0; i < partition_count; i++)

  {

    int endpoint_class = color_formats[i] >> 2;

    color_integer_count += (endpoint_class + 1) * 2;

  }

  if (color_integer_count > 18)

  {

    scb.block_type = SYM_BTYPE_ERROR;

    return;

  }

  // Determine the color endpoint format to use

  static const int color_bits_arr[5] { -1, 115 - 4, 113 - 4 - PARTITION_INDEX_BITS, 113 - 4 - PARTITION_INDEX_BITS, 113 - 4 - PARTITION_INDEX_BITS };

  int color_bits = color_bits_arr[partition_count] - bits_for_weights - encoded_type_highpart_size;

  if (is_dual_plane)

  {

    color_bits -= 2;

  }

  if (color_bits < 0)

  {

    color_bits = 0;

  }

  int color_quant_level = quant_mode_table[color_integer_count >> 1][color_bits];

  if (color_quant_level < QUANT_6)

  {

    scb.block_type = SYM_BTYPE_ERROR;

    return;

  }

  // Unpack the integer color values and assign to endpoints

  scb.quant_mode = static_cast<quant_method>(color_quant_level);

  uint8_t values_to_decode[32];

  decode_ise(static_cast<quant_method>(color_quant_level), color_integer_count, pcb,

             values_to_decode, (partition_count == 1 ? 17 : 19 + PARTITION_INDEX_BITS));

  int valuecount_to_decode = 0;

  const uint8_t* unpack_table = color_scrambled_pquant_to_uquant_tables[scb.quant_mode - QUANT_6];

  for (int i = 0; i < partition_count; i++)

  {

    int vals = 2 * (color_formats[i] >> 2) + 2;

    for (int j = 0; j < vals; j++)

    {

      scb.color_values[i][j] = unpack_table[values_to_decode[j + valuecount_to_decode]];

    }

    valuecount_to_decode += vals;

  }

  // Fetch component for second-plane in the case of dual plane of weights.

  scb.plane2_component = -1;

  if (is_dual_plane)

  {

    scb.plane2_component = static_cast<int8_t>(read_bits(2, below_weights_pos - 2, pcb));

  }

}