/*
 * Copyright 2022 The Android Open Source Project
 *
 * 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.
 */

#include <cstring>

#include "ultrahdr/ultrahdrcommon.h"
#include "ultrahdr/icc.h"

namespace ultrahdr {

static void Matrix3x3_apply(const Matrix3x3* m, float* x) {
  float y0 = x[0] * m->vals[0][0] + x[1] * m->vals[0][1] + x[2] * m->vals[0][2];
  float y1 = x[0] * m->vals[1][0] + x[1] * m->vals[1][1] + x[2] * m->vals[1][2];
  float y2 = x[0] * m->vals[2][0] + x[1] * m->vals[2][1] + x[2] * m->vals[2][2];
  x[0] = y0;
  x[1] = y1;
  x[2] = y2;
}

bool Matrix3x3_invert(const Matrix3x3* src, Matrix3x3* dst) {
  double a00 = src->vals[0][0];
  double a01 = src->vals[1][0];
  double a02 = src->vals[2][0];
  double a10 = src->vals[0][1];
  double a11 = src->vals[1][1];
  double a12 = src->vals[2][1];
  double a20 = src->vals[0][2];
  double a21 = src->vals[1][2];
  double a22 = src->vals[2][2];

  double b0 = a00 * a11 - a01 * a10;
  double b1 = a00 * a12 - a02 * a10;
  double b2 = a01 * a12 - a02 * a11;
  double b3 = a20;
  double b4 = a21;
  double b5 = a22;

  double determinant = b0 * b5 - b1 * b4 + b2 * b3;

  if (determinant == 0) {
    return false;
  }

  double invdet = 1.0 / determinant;
  if (invdet > +FLT_MAX || invdet < -FLT_MAX || !isfinitef_((float)invdet)) {
    return false;
  }

  b0 *= invdet;
  b1 *= invdet;
  b2 *= invdet;
  b3 *= invdet;
  b4 *= invdet;
  b5 *= invdet;

  dst->vals[0][0] = (float)(a11 * b5 - a12 * b4);
  dst->vals[1][0] = (float)(a02 * b4 - a01 * b5);
  dst->vals[2][0] = (float)(+b2);
  dst->vals[0][1] = (float)(a12 * b3 - a10 * b5);
  dst->vals[1][1] = (float)(a00 * b5 - a02 * b3);
  dst->vals[2][1] = (float)(-b1);
  dst->vals[0][2] = (float)(a10 * b4 - a11 * b3);
  dst->vals[1][2] = (float)(a01 * b3 - a00 * b4);
  dst->vals[2][2] = (float)(+b0);

  for (int r = 0; r < 3; ++r)
    for (int c = 0; c < 3; ++c) {
      if (!isfinitef_(dst->vals[r][c])) {
        return false;
      }
    }
  return true;
}

static Matrix3x3 Matrix3x3_concat(const Matrix3x3* A, const Matrix3x3* B) {
  Matrix3x3 m = {{{0, 0, 0}, {0, 0, 0}, {0, 0, 0}}};
  for (int r = 0; r < 3; r++)
    for (int c = 0; c < 3; c++) {
      m.vals[r][c] = A->vals[r][0] * B->vals[0][c] + A->vals[r][1] * B->vals[1][c] +
                     A->vals[r][2] * B->vals[2][c];
    }
  return m;
}

static void float_XYZD50_to_grid16_lab(const float* xyz_float, uint8_t* grid16_lab) {
  float v[3] = {
      xyz_float[0] / kD50_x,
      xyz_float[1] / kD50_y,
      xyz_float[2] / kD50_z,
  };
  for (size_t i = 0; i < 3; ++i) {
    v[i] = v[i] > 0.008856f ? cbrtf(v[i]) : v[i] * 7.787f + (16 / 116.0f);
  }
  const float L = v[1] * 116.0f - 16.0f;
  const float a = (v[0] - v[1]) * 500.0f;
  const float b = (v[1] - v[2]) * 200.0f;
  const float Lab_unorm[3] = {
      L * (1 / 100.f),
      (a + 128.0f) * (1 / 255.0f),
      (b + 128.0f) * (1 / 255.0f),
  };
  // This will encode L=1 as 0xFFFF. This matches how skcms will interpret the
  // table, but the spec appears to indicate that the value should be 0xFF00.
  // https://crbug.com/skia/13807
  for (size_t i = 0; i < 3; ++i) {
    reinterpret_cast<uint16_t*>(grid16_lab)[i] =
        Endian_SwapBE16(float_round_to_unorm16(Lab_unorm[i]));
  }
}

std::string IccHelper::get_desc_string(const ultrahdr_transfer_function tf,
                                       const ultrahdr_color_gamut gamut) {
  std::string result;
  switch (gamut) {
    case ULTRAHDR_COLORGAMUT_BT709:
      result += "sRGB";
      break;
    case ULTRAHDR_COLORGAMUT_P3:
      result += "Display P3";
      break;
    case ULTRAHDR_COLORGAMUT_BT2100:
      result += "Rec2020";
      break;
    default:
      result += "Unknown";
      break;
  }
  result += " Gamut with ";
  switch (tf) {
    case ULTRAHDR_TF_SRGB:
      result += "sRGB";
      break;
    case ULTRAHDR_TF_LINEAR:
      result += "Linear";
      break;
    case ULTRAHDR_TF_PQ:
      result += "PQ";
      break;
    case ULTRAHDR_TF_HLG:
      result += "HLG";
      break;
    default:
      result += "Unknown";
      break;
  }
  result += " Transfer";
  return result;
}

std::shared_ptr<DataStruct> IccHelper::write_text_tag(const char* text) {
  uint32_t text_length = strlen(text);
  uint32_t header[] = {
      Endian_SwapBE32(kTAG_TextType),                       // Type signature
      0,                                                    // Reserved
      Endian_SwapBE32(1),                                   // Number of records
      Endian_SwapBE32(12),                                  // Record size (must be 12)
      Endian_SwapBE32(SetFourByteTag('e', 'n', 'U', 'S')),  // English USA
      Endian_SwapBE32(2 * text_length),                     // Length of string in bytes
      Endian_SwapBE32(28),                                  // Offset of string
  };

  uint32_t total_length = text_length * 2 + sizeof(header);
  total_length = (((total_length + 2) >> 2) << 2);  // 4 aligned
  std::shared_ptr<DataStruct> dataStruct = std::make_shared<DataStruct>(total_length);

  if (!dataStruct->write(header, sizeof(header))) {
    ALOGE("write_text_tag(): error in writing data");
    return dataStruct;
  }

  for (size_t i = 0; i < text_length; i++) {
    // Convert ASCII to big-endian UTF-16.
    dataStruct->write8(0);
    dataStruct->write8(text[i]);
  }

  return dataStruct;
}

std::shared_ptr<DataStruct> IccHelper::write_xyz_tag(float x, float y, float z) {
  uint32_t data[] = {
      Endian_SwapBE32(kXYZ_PCSSpace),
      0,
      static_cast<uint32_t>(Endian_SwapBE32(float_round_to_fixed(x))),
      static_cast<uint32_t>(Endian_SwapBE32(float_round_to_fixed(y))),
      static_cast<uint32_t>(Endian_SwapBE32(float_round_to_fixed(z))),
  };
  std::shared_ptr<DataStruct> dataStruct = std::make_shared<DataStruct>(sizeof(data));
  dataStruct->write(&data, sizeof(data));
  return dataStruct;
}

std::shared_ptr<DataStruct> IccHelper::write_trc_tag(const int table_entries,
                                                     const void* table_16) {
  int total_length = 4 + 4 + 4 + table_entries * 2;
  total_length = (((total_length + 2) >> 2) << 2);  // 4 aligned
  std::shared_ptr<DataStruct> dataStruct = std::make_shared<DataStruct>(total_length);
  dataStruct->write32(Endian_SwapBE32(kTAG_CurveType));  // Type
  dataStruct->write32(0);                                // Reserved
  dataStruct->write32(Endian_SwapBE32(table_entries));   // Value count
  for (int i = 0; i < table_entries; ++i) {
    uint16_t value = reinterpret_cast<const uint16_t*>(table_16)[i];
    dataStruct->write16(value);
  }
  return dataStruct;
}

std::shared_ptr<DataStruct> IccHelper::write_trc_tag(const TransferFunction& fn) {
  if (fn.a == 1.f && fn.b == 0.f && fn.c == 0.f && fn.d == 0.f && fn.e == 0.f && fn.f == 0.f) {
    int total_length = 16;
    std::shared_ptr<DataStruct> dataStruct = std::make_shared<DataStruct>(total_length);
    dataStruct->write32(Endian_SwapBE32(kTAG_ParaCurveType));  // Type
    dataStruct->write32(0);                                    // Reserved
    dataStruct->write32(Endian_SwapBE16(kExponential_ParaCurveType));
    dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.g)));
    return dataStruct;
  }

  int total_length = 40;
  std::shared_ptr<DataStruct> dataStruct = std::make_shared<DataStruct>(total_length);
  dataStruct->write32(Endian_SwapBE32(kTAG_ParaCurveType));  // Type
  dataStruct->write32(0);                                    // Reserved
  dataStruct->write32(Endian_SwapBE16(kGABCDEF_ParaCurveType));
  dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.g)));
  dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.a)));
  dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.b)));
  dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.c)));
  dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.d)));
  dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.e)));
  dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.f)));
  return dataStruct;
}

float IccHelper::compute_tone_map_gain(const ultrahdr_transfer_function tf, float L) {
  if (L <= 0.f) {
    return 1.f;
  }
  if (tf == ULTRAHDR_TF_PQ) {
    // The PQ transfer function will map to the range [0, 1]. Linearly scale
    // it up to the range [0, 10,000/203]. We will then tone map that back
    // down to [0, 1].
    constexpr float kInputMaxLuminance = 10000 / 203.f;
    constexpr float kOutputMaxLuminance = 1.0;
    L *= kInputMaxLuminance;

    // Compute the tone map gain which will tone map from 10,000/203 to 1.0.
    constexpr float kToneMapA = kOutputMaxLuminance / (kInputMaxLuminance * kInputMaxLuminance);
    constexpr float kToneMapB = 1.f / kOutputMaxLuminance;
    return kInputMaxLuminance * (1.f + kToneMapA * L) / (1.f + kToneMapB * L);
  }
  if (tf == ULTRAHDR_TF_HLG) {
    // Let Lw be the brightness of the display in nits.
    constexpr float Lw = 203.f;
    const float gamma = 1.2f + 0.42f * std::log(Lw / 1000.f) / std::log(10.f);
    return std::pow(L, gamma - 1.f);
  }
  return 1.f;
}

std::shared_ptr<DataStruct> IccHelper::write_cicp_tag(uint32_t color_primaries,
                                                      uint32_t transfer_characteristics) {
  int total_length = 12;  // 4 + 4 + 1 + 1 + 1 + 1
  std::shared_ptr<DataStruct> dataStruct = std::make_shared<DataStruct>(total_length);
  dataStruct->write32(Endian_SwapBE32(kTAG_cicp));  // Type signature
  dataStruct->write32(0);                           // Reserved
  dataStruct->write8(color_primaries);              // Color primaries
  dataStruct->write8(transfer_characteristics);     // Transfer characteristics
  dataStruct->write8(0);                            // RGB matrix
  dataStruct->write8(1);                            // Full range
  return dataStruct;
}

void IccHelper::compute_lut_entry(const Matrix3x3& src_to_XYZD50, float rgb[3]) {
  // Compute the matrices to convert from source to Rec2020, and from Rec2020 to XYZD50.
  Matrix3x3 src_to_rec2020;
  const Matrix3x3 rec2020_to_XYZD50 = kRec2020;
  {
    Matrix3x3 XYZD50_to_rec2020;
    Matrix3x3_invert(&rec2020_to_XYZD50, &XYZD50_to_rec2020);
    src_to_rec2020 = Matrix3x3_concat(&XYZD50_to_rec2020, &src_to_XYZD50);
  }

  // Convert the source signal to linear.
  for (size_t i = 0; i < kNumChannels; ++i) {
    rgb[i] = pqOetf(rgb[i]);
  }

  // Convert source gamut to Rec2020.
  Matrix3x3_apply(&src_to_rec2020, rgb);

  // Compute the luminance of the signal.
  float L = bt2100Luminance({{{rgb[0], rgb[1], rgb[2]}}});

  // Compute the tone map gain based on the luminance.
  float tone_map_gain = compute_tone_map_gain(ULTRAHDR_TF_PQ, L);

  // Apply the tone map gain.
  for (size_t i = 0; i < kNumChannels; ++i) {
    rgb[i] *= tone_map_gain;
  }

  // Convert from Rec2020-linear to XYZD50.
  Matrix3x3_apply(&rec2020_to_XYZD50, rgb);
}

std::shared_ptr<DataStruct> IccHelper::write_clut(const uint8_t* grid_points,
                                                  const uint8_t* grid_16) {
  uint32_t value_count = kNumChannels;
  for (uint32_t i = 0; i < kNumChannels; ++i) {
    value_count *= grid_points[i];
  }

  int total_length = 20 + 2 * value_count;
  total_length = (((total_length + 2) >> 2) << 2);  // 4 aligned
  std::shared_ptr<DataStruct> dataStruct = std::make_shared<DataStruct>(total_length);

  for (size_t i = 0; i < 16; ++i) {
    dataStruct->write8(i < kNumChannels ? grid_points[i] : 0);  // Grid size
  }
  dataStruct->write8(2);  // Grid byte width (always 16-bit)
  dataStruct->write8(0);  // Reserved
  dataStruct->write8(0);  // Reserved
  dataStruct->write8(0);  // Reserved

  for (uint32_t i = 0; i < value_count; ++i) {
    uint16_t value = reinterpret_cast<const uint16_t*>(grid_16)[i];
    dataStruct->write16(value);
  }

  return dataStruct;
}

std::shared_ptr<DataStruct> IccHelper::write_mAB_or_mBA_tag(uint32_t type, bool has_a_curves,
                                                            const uint8_t* grid_points,
                                                            const uint8_t* grid_16) {
  const size_t b_curves_offset = 32;
  std::shared_ptr<DataStruct> b_curves_data[kNumChannels];
  std::shared_ptr<DataStruct> a_curves_data[kNumChannels];
  size_t clut_offset = 0;
  std::shared_ptr<DataStruct> clut;
  size_t a_curves_offset = 0;

  // The "B" curve is required.
  for (size_t i = 0; i < kNumChannels; ++i) {
    b_curves_data[i] = write_trc_tag(kLinear_TransFun);
  }

  // The "A" curve and CLUT are optional.
  if (has_a_curves) {
    clut_offset = b_curves_offset;
    for (size_t i = 0; i < kNumChannels; ++i) {
      clut_offset += b_curves_data[i]->getLength();
    }
    clut = write_clut(grid_points, grid_16);

    a_curves_offset = clut_offset + clut->getLength();
    for (size_t i = 0; i < kNumChannels; ++i) {
      a_curves_data[i] = write_trc_tag(kLinear_TransFun);
    }
  }

  int total_length = b_curves_offset;
  for (size_t i = 0; i < kNumChannels; ++i) {
    total_length += b_curves_data[i]->getLength();
  }
  if (has_a_curves) {
    total_length += clut->getLength();
    for (size_t i = 0; i < kNumChannels; ++i) {
      total_length += a_curves_data[i]->getLength();
    }
  }
  std::shared_ptr<DataStruct> dataStruct = std::make_shared<DataStruct>(total_length);
  dataStruct->write32(Endian_SwapBE32(type));             // Type signature
  dataStruct->write32(0);                                 // Reserved
  dataStruct->write8(kNumChannels);                       // Input channels
  dataStruct->write8(kNumChannels);                       // Output channels
  dataStruct->write16(0);                                 // Reserved
  dataStruct->write32(Endian_SwapBE32(b_curves_offset));  // B curve offset
  dataStruct->write32(Endian_SwapBE32(0));                // Matrix offset (ignored)
  dataStruct->write32(Endian_SwapBE32(0));                // M curve offset (ignored)
  dataStruct->write32(Endian_SwapBE32(clut_offset));      // CLUT offset
  dataStruct->write32(Endian_SwapBE32(a_curves_offset));  // A curve offset
  for (size_t i = 0; i < kNumChannels; ++i) {
    if (dataStruct->write(b_curves_data[i]->getData(), b_curves_data[i]->getLength())) {
      return dataStruct;
    }
  }
  if (has_a_curves) {
    dataStruct->write(clut->getData(), clut->getLength());
    for (size_t i = 0; i < kNumChannels; ++i) {
      dataStruct->write(a_curves_data[i]->getData(), a_curves_data[i]->getLength());
    }
  }
  return dataStruct;
}

std::shared_ptr<DataStruct> IccHelper::writeIccProfile(ultrahdr_transfer_function tf,
                                                       ultrahdr_color_gamut gamut) {
  ICCHeader header;

  std::vector<std::pair<uint32_t, std::shared_ptr<DataStruct>>> tags;

  // Compute profile description tag
  std::string desc = get_desc_string(tf, gamut);

  tags.emplace_back(kTAG_desc, write_text_tag(desc.c_str()));

  Matrix3x3 toXYZD50;
  switch (gamut) {
    case ULTRAHDR_COLORGAMUT_BT709:
      toXYZD50 = kSRGB;
      break;
    case ULTRAHDR_COLORGAMUT_P3:
      toXYZD50 = kDisplayP3;
      break;
    case ULTRAHDR_COLORGAMUT_BT2100:
      toXYZD50 = kRec2020;
      break;
    default:
      // Should not fall here.
      return nullptr;
  }

  // Compute primaries.
  {
    tags.emplace_back(kTAG_rXYZ,
                      write_xyz_tag(toXYZD50.vals[0][0], toXYZD50.vals[1][0], toXYZD50.vals[2][0]));
    tags.emplace_back(kTAG_gXYZ,
                      write_xyz_tag(toXYZD50.vals[0][1], toXYZD50.vals[1][1], toXYZD50.vals[2][1]));
    tags.emplace_back(kTAG_bXYZ,
                      write_xyz_tag(toXYZD50.vals[0][2], toXYZD50.vals[1][2], toXYZD50.vals[2][2]));
  }

  // Compute white point tag (must be D50)
  tags.emplace_back(kTAG_wtpt, write_xyz_tag(kD50_x, kD50_y, kD50_z));

  // Compute transfer curves.
  if (tf != ULTRAHDR_TF_PQ) {
    if (tf == ULTRAHDR_TF_HLG) {
      std::vector<uint8_t> trc_table;
      trc_table.resize(kTrcTableSize * 2);
      for (uint32_t i = 0; i < kTrcTableSize; ++i) {
        float x = i / (kTrcTableSize - 1.f);
        float y = hlgOetf(x);
        y *= compute_tone_map_gain(tf, y);
        float_to_table16(y, &trc_table[2 * i]);
      }

      tags.emplace_back(kTAG_rTRC,
                        write_trc_tag(kTrcTableSize, reinterpret_cast<uint8_t*>(trc_table.data())));
      tags.emplace_back(kTAG_gTRC,
                        write_trc_tag(kTrcTableSize, reinterpret_cast<uint8_t*>(trc_table.data())));
      tags.emplace_back(kTAG_bTRC,
                        write_trc_tag(kTrcTableSize, reinterpret_cast<uint8_t*>(trc_table.data())));
    } else {
      tags.emplace_back(kTAG_rTRC, write_trc_tag(kSRGB_TransFun));
      tags.emplace_back(kTAG_gTRC, write_trc_tag(kSRGB_TransFun));
      tags.emplace_back(kTAG_bTRC, write_trc_tag(kSRGB_TransFun));
    }
  }

  // Compute CICP.
  if (tf == ULTRAHDR_TF_HLG || tf == ULTRAHDR_TF_PQ) {
    // The CICP tag is present in ICC 4.4, so update the header's version.
    header.version = Endian_SwapBE32(0x04400000);

    uint32_t color_primaries = 0;
    if (gamut == ULTRAHDR_COLORGAMUT_BT709) {
      color_primaries = kCICPPrimariesSRGB;
    } else if (gamut == ULTRAHDR_COLORGAMUT_P3) {
      color_primaries = kCICPPrimariesP3;
    }

    uint32_t transfer_characteristics = 0;
    if (tf == ULTRAHDR_TF_SRGB) {
      transfer_characteristics = kCICPTrfnSRGB;
    } else if (tf == ULTRAHDR_TF_LINEAR) {
      transfer_characteristics = kCICPTrfnLinear;
    } else if (tf == ULTRAHDR_TF_PQ) {
      transfer_characteristics = kCICPTrfnPQ;
    } else if (tf == ULTRAHDR_TF_HLG) {
      transfer_characteristics = kCICPTrfnHLG;
    }
    tags.emplace_back(kTAG_cicp, write_cicp_tag(color_primaries, transfer_characteristics));
  }

  // Compute A2B0.
  if (tf == ULTRAHDR_TF_PQ) {
    std::vector<uint8_t> a2b_grid;
    a2b_grid.resize(kGridSize * kGridSize * kGridSize * kNumChannels * 2);
    size_t a2b_grid_index = 0;
    for (uint32_t r_index = 0; r_index < kGridSize; ++r_index) {
      for (uint32_t g_index = 0; g_index < kGridSize; ++g_index) {
        for (uint32_t b_index = 0; b_index < kGridSize; ++b_index) {
          float rgb[3] = {
              r_index / (kGridSize - 1.f),
              g_index / (kGridSize - 1.f),
              b_index / (kGridSize - 1.f),
          };
          compute_lut_entry(toXYZD50, rgb);
          float_XYZD50_to_grid16_lab(rgb, &a2b_grid[a2b_grid_index]);
          a2b_grid_index += 6;
        }
      }
    }
    const uint8_t* grid_16 = reinterpret_cast<const uint8_t*>(a2b_grid.data());

    uint8_t grid_points[kNumChannels];
    for (size_t i = 0; i < kNumChannels; ++i) {
      grid_points[i] = kGridSize;
    }

    auto a2b_data = write_mAB_or_mBA_tag(kTAG_mABType,
                                         /* has_a_curves */ true, grid_points, grid_16);
    tags.emplace_back(kTAG_A2B0, std::move(a2b_data));
  }

  // Compute B2A0.
  if (tf == ULTRAHDR_TF_PQ) {
    auto b2a_data = write_mAB_or_mBA_tag(kTAG_mBAType,
                                         /* has_a_curves */ false,
                                         /* grid_points */ nullptr,
                                         /* grid_16 */ nullptr);
    tags.emplace_back(kTAG_B2A0, std::move(b2a_data));
  }

  // Compute copyright tag
  tags.emplace_back(kTAG_cprt, write_text_tag("Google Inc. 2022"));

  // Compute the size of the profile.
  size_t tag_data_size = 0;
  for (const auto& tag : tags) {
    tag_data_size += tag.second->getLength();
  }
  size_t tag_table_size = kICCTagTableEntrySize * tags.size();
  size_t profile_size = kICCHeaderSize + tag_table_size + tag_data_size;

  std::shared_ptr<DataStruct> dataStruct =
      std::make_shared<DataStruct>(profile_size + kICCIdentifierSize);

  // Write identifier, chunk count, and chunk ID
  if (!dataStruct->write(kICCIdentifier, sizeof(kICCIdentifier)) || !dataStruct->write8(1) ||
      !dataStruct->write8(1)) {
    ALOGE("writeIccProfile(): error in identifier");
    return dataStruct;
  }

  // Write the header.
  header.data_color_space = Endian_SwapBE32(Signature_RGB);
  header.pcs = Endian_SwapBE32(tf == ULTRAHDR_TF_PQ ? Signature_Lab : Signature_XYZ);
  header.size = Endian_SwapBE32(profile_size);
  header.tag_count = Endian_SwapBE32(tags.size());

  if (!dataStruct->write(&header, sizeof(header))) {
    ALOGE("writeIccProfile(): error in header");
    return dataStruct;
  }

  // Write the tag table. Track the offset and size of the previous tag to
  // compute each tag's offset. An empty SkData indicates that the previous
  // tag is to be reused.
  uint32_t last_tag_offset = sizeof(header) + tag_table_size;
  uint32_t last_tag_size = 0;
  for (const auto& tag : tags) {
    last_tag_offset = last_tag_offset + last_tag_size;
    last_tag_size = tag.second->getLength();
    uint32_t tag_table_entry[3] = {
        Endian_SwapBE32(tag.first),
        Endian_SwapBE32(last_tag_offset),
        Endian_SwapBE32(last_tag_size),
    };
    if (!dataStruct->write(tag_table_entry, sizeof(tag_table_entry))) {
      ALOGE("writeIccProfile(): error in writing tag table");
      return dataStruct;
    }
  }

  // Write the tags.
  for (const auto& tag : tags) {
    if (!dataStruct->write(tag.second->getData(), tag.second->getLength())) {
      ALOGE("writeIccProfile(): error in writing tags");
      return dataStruct;
    }
  }

  return dataStruct;
}

bool IccHelper::tagsEqualToMatrix(const Matrix3x3& matrix, const uint8_t* red_tag,
                                  const uint8_t* green_tag, const uint8_t* blue_tag) {
  std::shared_ptr<DataStruct> red_tag_test =
      write_xyz_tag(matrix.vals[0][0], matrix.vals[1][0], matrix.vals[2][0]);
  std::shared_ptr<DataStruct> green_tag_test =
      write_xyz_tag(matrix.vals[0][1], matrix.vals[1][1], matrix.vals[2][1]);
  std::shared_ptr<DataStruct> blue_tag_test =
      write_xyz_tag(matrix.vals[0][2], matrix.vals[1][2], matrix.vals[2][2]);
  return memcmp(red_tag, red_tag_test->getData(), kColorantTagSize) == 0 &&
         memcmp(green_tag, green_tag_test->getData(), kColorantTagSize) == 0 &&
         memcmp(blue_tag, blue_tag_test->getData(), kColorantTagSize) == 0;
}

ultrahdr_color_gamut IccHelper::readIccColorGamut(void* icc_data, size_t icc_size) {
  // Each tag table entry consists of 3 fields of 4 bytes each.
  static const size_t kTagTableEntrySize = 12;

  if (icc_data == nullptr || icc_size < sizeof(ICCHeader) + kICCIdentifierSize) {
    return ULTRAHDR_COLORGAMUT_UNSPECIFIED;
  }

  if (memcmp(icc_data, kICCIdentifier, sizeof(kICCIdentifier)) != 0) {
    return ULTRAHDR_COLORGAMUT_UNSPECIFIED;
  }

  uint8_t* icc_bytes = reinterpret_cast<uint8_t*>(icc_data) + kICCIdentifierSize;

  ICCHeader* header = reinterpret_cast<ICCHeader*>(icc_bytes);

  // Use 0 to indicate not found, since offsets are always relative to start
  // of ICC data and therefore a tag offset of zero would never be valid.
  size_t red_primary_offset = 0, green_primary_offset = 0, blue_primary_offset = 0;
  size_t red_primary_size = 0, green_primary_size = 0, blue_primary_size = 0;
  for (size_t tag_idx = 0; tag_idx < Endian_SwapBE32(header->tag_count); ++tag_idx) {
    if (icc_size < kICCIdentifierSize + sizeof(ICCHeader) + ((tag_idx + 1) * kTagTableEntrySize)) {
      ALOGE(
          "Insufficient buffer size during icc parsing. tag index %zu, header %zu, tag size %zu, "
          "icc size %zu",
          tag_idx, kICCIdentifierSize + sizeof(ICCHeader), kTagTableEntrySize, icc_size);
      return ULTRAHDR_COLORGAMUT_UNSPECIFIED;
    }
    uint32_t* tag_entry_start =
        reinterpret_cast<uint32_t*>(icc_bytes + sizeof(ICCHeader) + tag_idx * kTagTableEntrySize);
    // first 4 bytes are the tag signature, next 4 bytes are the tag offset,
    // last 4 bytes are the tag length in bytes.
    if (red_primary_offset == 0 && *tag_entry_start == Endian_SwapBE32(kTAG_rXYZ)) {
      red_primary_offset = Endian_SwapBE32(*(tag_entry_start + 1));
      red_primary_size = Endian_SwapBE32(*(tag_entry_start + 2));
    } else if (green_primary_offset == 0 && *tag_entry_start == Endian_SwapBE32(kTAG_gXYZ)) {
      green_primary_offset = Endian_SwapBE32(*(tag_entry_start + 1));
      green_primary_size = Endian_SwapBE32(*(tag_entry_start + 2));
    } else if (blue_primary_offset == 0 && *tag_entry_start == Endian_SwapBE32(kTAG_bXYZ)) {
      blue_primary_offset = Endian_SwapBE32(*(tag_entry_start + 1));
      blue_primary_size = Endian_SwapBE32(*(tag_entry_start + 2));
    }
  }

  if (red_primary_offset == 0 || red_primary_size != kColorantTagSize ||
      kICCIdentifierSize + red_primary_offset + red_primary_size > icc_size ||
      green_primary_offset == 0 || green_primary_size != kColorantTagSize ||
      kICCIdentifierSize + green_primary_offset + green_primary_size > icc_size ||
      blue_primary_offset == 0 || blue_primary_size != kColorantTagSize ||
      kICCIdentifierSize + blue_primary_offset + blue_primary_size > icc_size) {
    return ULTRAHDR_COLORGAMUT_UNSPECIFIED;
  }

  uint8_t* red_tag = icc_bytes + red_primary_offset;
  uint8_t* green_tag = icc_bytes + green_primary_offset;
  uint8_t* blue_tag = icc_bytes + blue_primary_offset;

  // Serialize tags as we do on encode and compare what we find to that to
  // determine the gamut (since we don't have a need yet for full deserialize).
  if (tagsEqualToMatrix(kSRGB, red_tag, green_tag, blue_tag)) {
    return ULTRAHDR_COLORGAMUT_BT709;
  } else if (tagsEqualToMatrix(kDisplayP3, red_tag, green_tag, blue_tag)) {
    return ULTRAHDR_COLORGAMUT_P3;
  } else if (tagsEqualToMatrix(kRec2020, red_tag, green_tag, blue_tag)) {
    return ULTRAHDR_COLORGAMUT_BT2100;
  }

  // Didn't find a match to one of the profiles we write; indicate the gamut
  // is unspecified since we don't understand it.
  return ULTRAHDR_COLORGAMUT_UNSPECIFIED;
}

}  // namespace ultrahdr