// Copyright 2020 The Abseil Authors.

//

// 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

//

//      https://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 "absl/log/internal/proto.h"

#include <algorithm>

#include <cassert>

#include <cstddef>

#include <cstdint>

#include <cstring>

#include "absl/base/attributes.h"

#include "absl/base/config.h"

#include "absl/types/span.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace log_internal {

namespace {

void EncodeRawVarint(uint64_t value, size_t size, absl::Span<char> *buf) {

  for (size_t s = 0; s < size; s++) {

    (*buf)[s] = static_cast<char>((value & 0x7f) | (s + 1 == size ? 0 : 0x80));

    value >>= 7;

  }

  buf->remove_prefix(size);

}

constexpr uint64_t MakeTagType(uint64_t tag, WireType type) {

  return tag << 3 | static_cast<uint64_t>(type);

}

}  // namespace

bool EncodeVarint(uint64_t tag, uint64_t value, absl::Span<char> *buf) {

  const uint64_t tag_type = MakeTagType(tag, WireType::kVarint);

  const size_t tag_type_size = VarintSize(tag_type);

  const size_t value_size = VarintSize(value);

  if (tag_type_size + value_size > buf->size()) {

    buf->remove_suffix(buf->size());

    return false;

  }

  EncodeRawVarint(tag_type, tag_type_size, buf);

  EncodeRawVarint(value, value_size, buf);

  return true;

}

bool Encode64Bit(uint64_t tag, uint64_t value, absl::Span<char> *buf) {

  const uint64_t tag_type = MakeTagType(tag, WireType::k64Bit);

  const size_t tag_type_size = VarintSize(tag_type);

  if (tag_type_size + sizeof(value) > buf->size()) {

    buf->remove_suffix(buf->size());

    return false;

  }

  EncodeRawVarint(tag_type, tag_type_size, buf);

  for (size_t s = 0; s < sizeof(value); s++) {

    (*buf)[s] = static_cast<char>(value & 0xff);

    value >>= 8;

  }

  buf->remove_prefix(sizeof(value));

  return true;

}

bool Encode32Bit(uint64_t tag, uint32_t value, absl::Span<char> *buf) {

  const uint64_t tag_type = MakeTagType(tag, WireType::k32Bit);

  const size_t tag_type_size = VarintSize(tag_type);

  if (tag_type_size + sizeof(value) > buf->size()) {

    buf->remove_suffix(buf->size());

    return false;

  }

  EncodeRawVarint(tag_type, tag_type_size, buf);

  for (size_t s = 0; s < sizeof(value); s++) {

    (*buf)[s] = static_cast<char>(value & 0xff);

    value >>= 8;

  }

  buf->remove_prefix(sizeof(value));

  return true;

}

bool EncodeBytes(uint64_t tag, absl::Span<const char> value,

                 absl::Span<char> *buf) {

  const uint64_t tag_type = MakeTagType(tag, WireType::kLengthDelimited);

  const size_t tag_type_size = VarintSize(tag_type);

  uint64_t length = value.size();

  const size_t length_size = VarintSize(length);

  if (tag_type_size + length_size + value.size() > buf->size()) {

    buf->remove_suffix(buf->size());

    return false;

  }

  EncodeRawVarint(tag_type, tag_type_size, buf);

  EncodeRawVarint(length, length_size, buf);

  memcpy(buf->data(), value.data(), value.size());

  buf->remove_prefix(value.size());

  return true;

}

bool EncodeBytesTruncate(uint64_t tag, absl::Span<const char> value,

                         absl::Span<char> *buf) {

  const uint64_t tag_type = MakeTagType(tag, WireType::kLengthDelimited);

  const size_t tag_type_size = VarintSize(tag_type);

  uint64_t length = value.size();

  const size_t length_size =

      VarintSize(std::min<uint64_t>(length, buf->size()));

  if (tag_type_size + length_size <= buf->size() &&

      tag_type_size + length_size + value.size() > buf->size()) {

    value.remove_suffix(tag_type_size + length_size + value.size() -

                        buf->size());

    length = value.size();

  }

  if (tag_type_size + length_size + value.size() > buf->size()) {

    buf->remove_suffix(buf->size());

    return false;

  }

  EncodeRawVarint(tag_type, tag_type_size, buf);

  EncodeRawVarint(length, length_size, buf);

  memcpy(buf->data(), value.data(), value.size());

  buf->remove_prefix(value.size());

  return true;

}

ABSL_MUST_USE_RESULT absl::Span<char> EncodeMessageStart(

    uint64_t tag, uint64_t max_size, absl::Span<char> *buf) {

  const uint64_t tag_type = MakeTagType(tag, WireType::kLengthDelimited);

  const size_t tag_type_size = VarintSize(tag_type);

  max_size = std::min<uint64_t>(max_size, buf->size());

  const size_t length_size = VarintSize(max_size);

  if (tag_type_size + length_size > buf->size()) {

    buf->remove_suffix(buf->size());

    return absl::Span<char>();

  }

  EncodeRawVarint(tag_type, tag_type_size, buf);

  const absl::Span<char> ret = buf->subspan(0, length_size);

  EncodeRawVarint(0, length_size, buf);

  return ret;

}

void EncodeMessageLength(absl::Span<char> msg, const absl::Span<char> *buf) {

  if (!msg.data()) return;

  assert(buf->data() >= msg.data());

  if (buf->data() < msg.data()) return;

  EncodeRawVarint(

      static_cast<uint64_t>(buf->data() - (msg.data() + msg.size())),

      msg.size(), &msg);

}

namespace {

uint64_t DecodeVarint(absl::Span<const char> *buf) {

  uint64_t value = 0;

  size_t s = 0;

  while (s < buf->size()) {

    value |= static_cast<uint64_t>(static_cast<unsigned char>((*buf)[s]) & 0x7f)

             << 7 * s;

    if (!((*buf)[s++] & 0x80)) break;

  }

  buf->remove_prefix(s);

  return value;

}

uint64_t Decode64Bit(absl::Span<const char> *buf) {

  uint64_t value = 0;

  size_t s = 0;

  while (s < buf->size()) {

    value |= static_cast<uint64_t>(static_cast<unsigned char>((*buf)[s]))

             << 8 * s;

    if (++s == sizeof(value)) break;

  }

  buf->remove_prefix(s);

  return value;

}

uint32_t Decode32Bit(absl::Span<const char> *buf) {

  uint32_t value = 0;

  size_t s = 0;

  while (s < buf->size()) {

    value |= static_cast<uint32_t>(static_cast<unsigned char>((*buf)[s]))

             << 8 * s;

    if (++s == sizeof(value)) break;

  }

  buf->remove_prefix(s);

  return value;

}

}  // namespace

bool ProtoField::DecodeFrom(absl::Span<const char> *data) {

  if (data->empty()) return false;

  const uint64_t tag_type = DecodeVarint(data);

  tag_ = tag_type >> 3;

  type_ = static_cast<WireType>(tag_type & 0x07);

  switch (type_) {

    case WireType::kVarint:

      value_ = DecodeVarint(data);

      break;

    case WireType::k64Bit:

      value_ = Decode64Bit(data);

      break;

    case WireType::kLengthDelimited: {

      value_ = DecodeVarint(data);

      data_ = data->subspan(

          0, static_cast<size_t>(std::min<uint64_t>(value_, data->size())));

      data->remove_prefix(data_.size());

      break;

    }

    case WireType::k32Bit:

      value_ = Decode32Bit(data);

      break;

  }

  return true;

}

}  // namespace log_internal

ABSL_NAMESPACE_END

}  // namespace absl