// Copyright 2024 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.

//

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

// File: log/internal/structured_proto.h

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

#ifndef ABSL_LOG_INTERNAL_STRUCTURED_PROTO_H_

#define ABSL_LOG_INTERNAL_STRUCTURED_PROTO_H_

#include <cstddef>

#include <cstdint>

#include <variant>

#include "absl/base/config.h"

#include "absl/log/internal/proto.h"

#include "absl/types/span.h"

#include "absl/types/variant.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace log_internal {

// Sum type holding a single valid protobuf field suitable for encoding.

struct StructuredProtoField final {

  // Numeric type encoded with varint encoding:

  // https://protobuf.dev/programming-guides/encoding/#varints

  using Varint = std::variant<uint64_t, int64_t, uint32_t, int32_t, bool>;

  // Fixed-length 64-bit integer encoding:

  // https://protobuf.dev/programming-guides/encoding/#non-varints

  using I64 = std::variant<uint64_t, int64_t, double>;

  // Length-delimited record type (string, sub-message):

  // https://protobuf.dev/programming-guides/encoding/#length-types

  using LengthDelimited = absl::Span<const char>;

  // Fixed-length 32-bit integer encoding:

  // https://protobuf.dev/programming-guides/encoding/#non-varints

  using I32 = std::variant<uint32_t, int32_t, float>;

  // Valid record type:

  // https://protobuf.dev/programming-guides/encoding/#structure

  using Value = std::variant<Varint, I64, LengthDelimited, I32>;

  // Field number for the protobuf value.

  uint64_t field_number;

  // Value to encode.

  Value value;

};

// Estimates the number of bytes needed to encode `field` using

// protobuf encoding.

//

// The returned value might be larger than the actual number of bytes needed.

inline size_t BufferSizeForStructuredProtoField(StructuredProtoField field) {

  // Visitor to estimate the number of bytes of one of the types contained

  // inside `StructuredProtoField`.

  struct BufferSizeVisitor final {

    size_t operator()(StructuredProtoField::Varint /*unused*/) {

      return BufferSizeFor(field_number, WireType::kVarint);

    }

    size_t operator()(StructuredProtoField::I64 /*unused*/) {

      return BufferSizeFor(field_number, WireType::k64Bit);

    }

    size_t operator()(StructuredProtoField::LengthDelimited length_delimited) {

      return BufferSizeFor(field_number, WireType::kLengthDelimited) +

             length_delimited.size();

    }

    size_t operator()(StructuredProtoField::I32 /*unused*/) {

      return BufferSizeFor(field_number, WireType::k32Bit);

    }

    uint64_t field_number;

  };

  return std::visit(BufferSizeVisitor{field.field_number}, field.value);

}

// Encodes `field` into `buf` using protobuf encoding.

//

// On success, returns `true` and advances `buf` to the end of

// the bytes consumed.

//

// On failure (if `buf` was too small), returns `false`.

bool EncodeStructuredProtoField(StructuredProtoField field,

                                absl::Span<char>& buf);

}  // namespace log_internal

ABSL_NAMESPACE_END

}  // namespace absl

#endif  // ABSL_LOG_INTERNAL_STRUCTURED_PROTO_H_