// Copyright (c) the JPEG XL Project Authors. All rights reserved.

//

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

#include "lib/jxl/fields.h"

#include <algorithm>

#include <cinttypes>  // PRIu64

#include <cmath>

#include <cstddef>

#include <cstring>

#include <hwy/base.h>

#include "lib/jxl/base/bits.h"

#include "lib/jxl/base/common.h"

#include "lib/jxl/base/compiler_specific.h"

#include "lib/jxl/base/printf_macros.h"

#include "lib/jxl/base/status.h"

#include "lib/jxl/dec_bit_reader.h"

#include "lib/jxl/field_encodings.h"

namespace jxl {

namespace {

using ::jxl::fields_internal::VisitorBase;

struct InitVisitor : public VisitorBase {

  Status Bits(const size_t /*unused*/, const uint32_t default_value,

              uint32_t* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  Status U32(const U32Enc /*unused*/, const uint32_t default_value,

             uint32_t* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  Status U64(const uint64_t default_value,

             uint64_t* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  Status Bool(bool default_value, bool* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  Status F16(const float default_value, float* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  // Always visit conditional fields to ensure they are initialized.

  Status Conditional(bool /*condition*/) override { return true; }

  Status AllDefault(const Fields& /*fields*/,

                    bool* JXL_RESTRICT all_default) override {

    // Just initialize this field and don't skip initializing others.

    JXL_RETURN_IF_ERROR(Bool(true, all_default));

    return false;

  }

  Status VisitNested(Fields* /*fields*/) override {

    // Avoid re-initializing nested bundles (their ctors already called

    // Bundle::Init for their fields).

    return true;

  }

};

// Similar to InitVisitor, but also initializes nested fields.

struct SetDefaultVisitor : public VisitorBase {

  Status Bits(const size_t /*unused*/, const uint32_t default_value,

              uint32_t* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  Status U32(const U32Enc /*unused*/, const uint32_t default_value,

             uint32_t* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  Status U64(const uint64_t default_value,

             uint64_t* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  Status Bool(bool default_value, bool* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  Status F16(const float default_value, float* JXL_RESTRICT value) override {

    *value = default_value;

    return true;

  }

  // Always visit conditional fields to ensure they are initialized.

  Status Conditional(bool /*condition*/) override { return true; }

  Status AllDefault(const Fields& /*fields*/,

                    bool* JXL_RESTRICT all_default) override {

    // Just initialize this field and don't skip initializing others.

    JXL_RETURN_IF_ERROR(Bool(true, all_default));

    return false;

  }

};

class AllDefaultVisitor : public VisitorBase {

 public:

  explicit AllDefaultVisitor() = default;

  Status Bits(const size_t bits, const uint32_t default_value,

              uint32_t* JXL_RESTRICT value) override {

    all_default_ &= *value == default_value;

    return true;

  }

  Status U32(const U32Enc /*unused*/, const uint32_t default_value,

             uint32_t* JXL_RESTRICT value) override {

    all_default_ &= *value == default_value;

    return true;

  }

  Status U64(const uint64_t default_value,

             uint64_t* JXL_RESTRICT value) override {

    all_default_ &= *value == default_value;

    return true;

  }

  Status F16(const float default_value, float* JXL_RESTRICT value) override {

    all_default_ &= std::abs(*value - default_value) < 1E-6f;

    return true;

  }

  Status AllDefault(const Fields& /*fields*/,

                    bool* JXL_RESTRICT /*all_default*/) override {

    // Visit all fields so we can compute the actual all_default_ value.

    return false;

  }

  bool AllDefault() const { return all_default_; }

 private:

  bool all_default_ = true;

};

class ReadVisitor : public VisitorBase {

 public:

  explicit ReadVisitor(BitReader* reader) : reader_(reader) {}

  Status Bits(const size_t bits, const uint32_t /*default_value*/,

              uint32_t* JXL_RESTRICT value) override {

    *value = BitsCoder::Read(bits, reader_);

    if (!reader_->AllReadsWithinBounds()) {

      return JXL_NOT_ENOUGH_BYTES("Not enough bytes for header");

    }

    return true;

  }

  Status U32(const U32Enc dist, const uint32_t /*default_value*/,

             uint32_t* JXL_RESTRICT value) override {

    *value = U32Coder::Read(dist, reader_);

    if (!reader_->AllReadsWithinBounds()) {

      return JXL_NOT_ENOUGH_BYTES("Not enough bytes for header");

    }

    return true;

  }

  Status U64(const uint64_t /*default_value*/,

             uint64_t* JXL_RESTRICT value) override {

    *value = U64Coder::Read(reader_);

    if (!reader_->AllReadsWithinBounds()) {

      return JXL_NOT_ENOUGH_BYTES("Not enough bytes for header");

    }

    return true;

  }

  Status F16(const float /*default_value*/,

             float* JXL_RESTRICT value) override {

    ok_ &= F16Coder::Read(reader_, value);

    if (!reader_->AllReadsWithinBounds()) {

      return JXL_NOT_ENOUGH_BYTES("Not enough bytes for header");

    }

    return true;

  }

  void SetDefault(Fields* fields) override { Bundle::SetDefault(fields); }

  bool IsReading() const override { return true; }

  // This never fails because visitors are expected to keep reading until

  // EndExtensions, see comment there.

  Status BeginExtensions(uint64_t* JXL_RESTRICT extensions) override {

    JXL_QUIET_RETURN_IF_ERROR(VisitorBase::BeginExtensions(extensions));

    if (*extensions == 0) return true;

    // For each nonzero bit, i.e. extension that is present:

    for (uint64_t remaining_extensions = *extensions; remaining_extensions != 0;

         remaining_extensions &= remaining_extensions - 1) {

      const size_t idx_extension =

          Num0BitsBelowLS1Bit_Nonzero(remaining_extensions);

      // Read additional U64 (one per extension) indicating the number of bits

      // (allows skipping individual extensions).

      JXL_RETURN_IF_ERROR(U64(0, &extension_bits_[idx_extension]));

      if (!SafeAdd(total_extension_bits_, extension_bits_[idx_extension],

                   total_extension_bits_)) {

        return JXL_FAILURE("Extension bits overflowed, invalid codestream");

      }

    }

    // Used by EndExtensions to skip past any _remaining_ extensions.

    pos_after_ext_size_ = reader_->TotalBitsConsumed();

    JXL_ENSURE(pos_after_ext_size_ != 0);

    return true;

  }

  Status EndExtensions() override {

    JXL_QUIET_RETURN_IF_ERROR(VisitorBase::EndExtensions());

    // Happens if extensions == 0: don't read size, done.

    if (pos_after_ext_size_ == 0) return true;

    // Not enough bytes as set by BeginExtensions or earlier. Do not return

    // this as a JXL_FAILURE or false (which can also propagate to error

    // through e.g. JXL_RETURN_IF_ERROR), since this may be used while

    // silently checking whether there are enough bytes. If this case must be

    // treated as an error, reader_>Close() will do this, just like is already

    // done for non-extension fields.

    if (!enough_bytes_) return true;

    // Skip new fields this (old?) decoder didn't know about, if any.

    const size_t bits_read = reader_->TotalBitsConsumed();

    uint64_t end;

    if (!SafeAdd(pos_after_ext_size_, total_extension_bits_, end)) {

      return JXL_FAILURE("Invalid extension size, caused overflow");

    }

    if (bits_read > end) {

      return JXL_FAILURE("Read more extension bits than budgeted");

    }

    const size_t remaining_bits = end - bits_read;

    if (remaining_bits != 0) {

      JXL_WARNING("Skipping %" PRIuS "-bit extension(s)", remaining_bits);

      reader_->SkipBits(remaining_bits);

      if (!reader_->AllReadsWithinBounds()) {

        return JXL_NOT_ENOUGH_BYTES("Not enough bytes for header");

      }

    }

    return true;

  }

  Status OK() const { return ok_; }

 private:

  // Whether any error other than not enough bytes occurred.

  bool ok_ = true;

  // Whether there are enough input bytes to read from.

  bool enough_bytes_ = true;

  BitReader* const reader_;

  // May be 0 even if the corresponding extension is present.

  uint64_t extension_bits_[Bundle::kMaxExtensions] = {0};

  uint64_t total_extension_bits_ = 0;

  size_t pos_after_ext_size_ = 0;  // 0 iff extensions == 0.

  friend Status jxl::CheckHasEnoughBits(Visitor* /* visitor */,

                                        size_t /* bits */);

};

class CanEncodeVisitor : public VisitorBase {

 public:

  explicit CanEncodeVisitor() = default;

  Status Bits(const size_t bits, const uint32_t /*default_value*/,

              uint32_t* JXL_RESTRICT value) override {

    size_t encoded_bits = 0;

    ok_ &= BitsCoder::CanEncode(bits, *value, &encoded_bits);

    encoded_bits_ += encoded_bits;

    return true;

  }

  Status U32(const U32Enc enc, const uint32_t /*default_value*/,

             uint32_t* JXL_RESTRICT value) override {

    size_t encoded_bits = 0;

    ok_ &= U32Coder::CanEncode(enc, *value, &encoded_bits);

    encoded_bits_ += encoded_bits;

    return true;

  }

  Status U64(const uint64_t /*default_value*/,

             uint64_t* JXL_RESTRICT value) override {

    size_t encoded_bits = 0;

    ok_ &= U64Coder::CanEncode(*value, &encoded_bits);

    encoded_bits_ += encoded_bits;

    return true;

  }

  Status F16(const float /*default_value*/,

             float* JXL_RESTRICT value) override {

    size_t encoded_bits = 0;

    ok_ &= F16Coder::CanEncode(*value, &encoded_bits);

    encoded_bits_ += encoded_bits;

    return true;

  }

  Status AllDefault(const Fields& fields,

                    bool* JXL_RESTRICT all_default) override {

    *all_default = Bundle::AllDefault(fields);

    JXL_RETURN_IF_ERROR(Bool(true, all_default));

    return *all_default;

  }

  Status BeginExtensions(uint64_t* JXL_RESTRICT extensions) override {

    JXL_QUIET_RETURN_IF_ERROR(VisitorBase::BeginExtensions(extensions));

    extensions_ = *extensions;

    if (*extensions != 0) {

      JXL_ENSURE(pos_after_ext_ == 0);

      pos_after_ext_ = encoded_bits_;

      JXL_ENSURE(pos_after_ext_ != 0);  // visited "extensions"

    }

    return true;

  }

  // EndExtensions = default.

  Status GetSizes(size_t* JXL_RESTRICT extension_bits,

                  size_t* JXL_RESTRICT total_bits) {

    JXL_RETURN_IF_ERROR(ok_);

    *extension_bits = 0;

    *total_bits = encoded_bits_;

    // Only if extension field was nonzero will we encode their sizes.

    if (pos_after_ext_ != 0) {

      JXL_ENSURE(encoded_bits_ >= pos_after_ext_);

      *extension_bits = encoded_bits_ - pos_after_ext_;

      // Also need to encode *extension_bits and bill it to *total_bits.

      size_t encoded_bits = 0;

      ok_ &= U64Coder::CanEncode(*extension_bits, &encoded_bits);

      *total_bits += encoded_bits;

      // TODO(janwas): support encoding individual extension sizes. We

      // currently ascribe all bits to the first and send zeros for the

      // others.

      for (size_t i = 1; i < hwy::PopCount(extensions_); ++i) {

        encoded_bits = 0;

        ok_ &= U64Coder::CanEncode(0, &encoded_bits);

        *total_bits += encoded_bits;

      }

    }

    return true;

  }

 private:

  bool ok_ = true;

  size_t encoded_bits_ = 0;

  uint64_t extensions_ = 0;

  // Snapshot of encoded_bits_ after visiting the extension field, but NOT

  // including the hidden extension sizes.

  uint64_t pos_after_ext_ = 0;

};

}  // namespace

void Bundle::Init(Fields* fields) {

  InitVisitor visitor;

  if (!visitor.Visit(fields)) {

    JXL_DEBUG_ABORT("Init should never fail");

  }

}

void Bundle::SetDefault(Fields* fields) {

  SetDefaultVisitor visitor;

  if (!visitor.Visit(fields)) {

    JXL_DEBUG_ABORT("SetDefault should never fail");

  }

}

bool Bundle::AllDefault(const Fields& fields) {

  AllDefaultVisitor visitor;

  if (!visitor.VisitConst(fields)) {

    JXL_DEBUG_ABORT("AllDefault should never fail");

  }

  return visitor.AllDefault();

}

Status Bundle::CanEncode(const Fields& fields, size_t* extension_bits,

                         size_t* total_bits) {

  CanEncodeVisitor visitor;

  JXL_QUIET_RETURN_IF_ERROR(visitor.VisitConst(fields));

  JXL_QUIET_RETURN_IF_ERROR(visitor.GetSizes(extension_bits, total_bits));

  return true;

}

Status Bundle::Read(BitReader* reader, Fields* fields) {

  ReadVisitor visitor(reader);

  JXL_RETURN_IF_ERROR(visitor.Visit(fields));

  return visitor.OK();

}

bool Bundle::CanRead(BitReader* reader, Fields* fields) {

  ReadVisitor visitor(reader);

  Status status = visitor.Visit(fields);

  // We are only checking here whether there are enough bytes. We still return

  // true for other errors because it means there are enough bytes to determine

  // there's an error. Use Read() to determine which error it is.

  return status.code() != StatusCode::kNotEnoughBytes;

}

size_t BitsCoder::MaxEncodedBits(const size_t bits) { return bits; }

Status BitsCoder::CanEncode(const size_t bits, const uint32_t value,

                            size_t* JXL_RESTRICT encoded_bits) {

  *encoded_bits = bits;

  if (value >= (1ULL << bits)) {

    return JXL_FAILURE("Value %u too large for %" PRIu64 " bits", value,

                       static_cast<uint64_t>(bits));

  }

  return true;

}

uint32_t BitsCoder::Read(const size_t bits, BitReader* JXL_RESTRICT reader) {

  return reader->ReadBits(bits);

}

size_t U32Coder::MaxEncodedBits(const U32Enc enc) {

  size_t extra_bits = 0;

  for (uint32_t selector = 0; selector < 4; ++selector) {

    const U32Distr d = enc.GetDistr(selector);

    if (d.IsDirect()) {

      continue;

    } else {

      extra_bits = std::max<size_t>(extra_bits, d.ExtraBits());

    }

  }

  return 2 + extra_bits;

}

Status U32Coder::CanEncode(const U32Enc enc, const uint32_t value,

                           size_t* JXL_RESTRICT encoded_bits) {

  uint32_t selector;

  size_t total_bits;

  const Status ok = ChooseSelector(enc, value, &selector, &total_bits);

  *encoded_bits = ok ? total_bits : 0;

  return ok;

}

uint32_t U32Coder::Read(const U32Enc enc, BitReader* JXL_RESTRICT reader) {

  const uint32_t selector = reader->ReadFixedBits<2>();

  const U32Distr d = enc.GetDistr(selector);

  if (d.IsDirect()) {

    return d.Direct();

  } else {

    return reader->ReadBits(d.ExtraBits()) + d.Offset();

  }

}

Status U32Coder::ChooseSelector(const U32Enc enc, const uint32_t value,

                                uint32_t* JXL_RESTRICT selector,

                                size_t* JXL_RESTRICT total_bits) {

  const size_t bits_required = 32 - Num0BitsAboveMS1Bit(value);

  JXL_ENSURE(bits_required <= 32);

  *selector = 0;

  *total_bits = 0;

  // It is difficult to verify whether Dist32Byte are sorted, so check all

  // selectors and keep the one with the fewest total_bits.

  *total_bits = 64;  // more than any valid encoding

  for (uint32_t s = 0; s < 4; ++s) {

    const U32Distr d = enc.GetDistr(s);

    if (d.IsDirect()) {

      if (d.Direct() == value) {

        *selector = s;

        *total_bits = 2;

        return true;  // Done, direct is always the best possible.

      }

      continue;

    }

    const size_t extra_bits = d.ExtraBits();

    const uint32_t offset = d.Offset();

    if (value < offset || value >= offset + (1ULL << extra_bits)) continue;

    // Better than prior encoding, remember it:

    if (2 + extra_bits < *total_bits) {

      *selector = s;

      *total_bits = 2 + extra_bits;

    }

  }

  if (*total_bits == 64) {

    return JXL_FAILURE("No feasible selector for %u", value);

  }

  return true;

}

uint64_t U64Coder::Read(BitReader* JXL_RESTRICT reader) {

  uint64_t selector = reader->ReadFixedBits<2>();

  if (selector == 0) {

    return 0;

  }

  if (selector == 1) {

    return 1 + reader->ReadFixedBits<4>();

  }

  if (selector == 2) {

    return 17 + reader->ReadFixedBits<8>();

  }

  // selector 3, varint, groups have first 12, then 8, and last 4 bits.

  uint64_t result = reader->ReadFixedBits<12>();

  uint64_t shift = 12;

  while (reader->ReadFixedBits<1>()) {

    if (shift == 60) {

      result |= static_cast<uint64_t>(reader->ReadFixedBits<4>()) << shift;

      break;

    }

    result |= static_cast<uint64_t>(reader->ReadFixedBits<8>()) << shift;

    shift += 8;

  }

  return result;

}

// Can always encode, but useful because it also returns bit size.

Status U64Coder::CanEncode(uint64_t value, size_t* JXL_RESTRICT encoded_bits) {

  if (value == 0) {

    *encoded_bits = 2;  // 2 selector bits

  } else if (value <= 16) {

    *encoded_bits = 2 + 4;  // 2 selector bits + 4 payload bits

  } else if (value <= 272) {

    *encoded_bits = 2 + 8;  // 2 selector bits + 8 payload bits

  } else {

    *encoded_bits = 2 + 12;  // 2 selector bits + 12 payload bits

    value >>= 12;

    int shift = 12;

    while (value > 0 && shift < 60) {

      *encoded_bits += 1 + 8;  // 1 continuation bit + 8 payload bits

      value >>= 8;

      shift += 8;

    }

    if (value > 0) {

      // This only could happen if shift == N - 4.

      *encoded_bits += 1 + 4;  // 1 continuation bit + 4 payload bits

    } else {

      *encoded_bits += 1;  // 1 stop bit

    }

  }

  return true;

}

Status F16Coder::Read(BitReader* JXL_RESTRICT reader,

                      float* JXL_RESTRICT value) {

  const uint32_t bits16 = reader->ReadFixedBits<16>();

  const uint32_t sign = bits16 >> 15;

  const uint32_t biased_exp = (bits16 >> 10) & 0x1F;

  const uint32_t mantissa = bits16 & 0x3FF;

  if (JXL_UNLIKELY(biased_exp == 31)) {

    return JXL_FAILURE("F16 infinity or NaN are not supported");

  }

  // Subnormal or zero

  if (JXL_UNLIKELY(biased_exp == 0)) {

    *value = (1.0f / 16384) * (mantissa * (1.0f / 1024));

    if (sign) *value = -*value;

    return true;

  }

  // Normalized: convert the representation directly (faster than ldexp/tables).

  const uint32_t biased_exp32 = biased_exp + (127 - 15);

  const uint32_t mantissa32 = mantissa << (23 - 10);

  const uint32_t bits32 = (sign << 31) | (biased_exp32 << 23) | mantissa32;

  memcpy(value, &bits32, sizeof(bits32));

  return true;

}

Status F16Coder::CanEncode(float value, size_t* JXL_RESTRICT encoded_bits) {

  *encoded_bits = MaxEncodedBits();

  if (std::isnan(value) || std::isinf(value)) {

    return JXL_FAILURE("Should not attempt to store NaN and infinity");

  }

  return std::abs(value) <= 65504.0f;

}

Status CheckHasEnoughBits(Visitor* visitor, size_t bits) {

  if (!visitor->IsReading()) return false;

  ReadVisitor* rv = static_cast<ReadVisitor*>(visitor);

  size_t have_bits = rv->reader_->TotalBytes() * kBitsPerByte;

  size_t want_bits = bits + rv->reader_->TotalBitsConsumed();

  if (have_bits < want_bits) {

    return JXL_NOT_ENOUGH_BYTES("Not enough bytes for header");

  }

  return true;

}

}  // namespace jxl