// Copyright 2022 gRPC 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
//
//     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.

#ifndef GRPC_SRC_CORE_EXT_TRANSPORT_CHAOTIC_GOOD_FRAME_HEADER_H
#define GRPC_SRC_CORE_EXT_TRANSPORT_CHAOTIC_GOOD_FRAME_HEADER_H

#include <grpc/support/port_platform.h>
#include <stddef.h>

#include <cstdint>

#include "absl/status/statusor.h"
#include "src/core/util/bitset.h"

namespace grpc_core {
namespace chaotic_good {

// Remember to add new frame types to frame_fuzzer.cc
enum class FrameType : uint8_t {
  kSettings = 0x00,
  kClientInitialMetadata = 0x80,
  kClientEndOfStream = 0x81,
  kServerInitialMetadata = 0x91,
  kServerTrailingMetadata = 0x92,
  kMessage = 0xa0,
  kCancel = 0xff,
};

inline std::ostream& operator<<(std::ostream& out, FrameType type) {
  switch (type) {
    case FrameType::kSettings:
      return out << "Settings";
    case FrameType::kClientInitialMetadata:
      return out << "ClientInitialMetadata";
    case FrameType::kClientEndOfStream:
      return out << "ClientEndOfStream";
    case FrameType::kMessage:
      return out << "Message";
    case FrameType::kServerInitialMetadata:
      return out << "ServerInitialMetadata";
    case FrameType::kServerTrailingMetadata:
      return out << "ServerTrailingMetadata";
    case FrameType::kCancel:
      return out << "Cancel";
    default:
      return out << "Unknown[" << static_cast<int>(type) << "]";
  }
}

struct FrameHeader {
  FrameType type = FrameType::kCancel;
  uint16_t payload_connection_id = 0;
  uint32_t stream_id = 0;
  uint32_t payload_length = 0;

  // Parses a frame header from a buffer of 12 bytes. All 12 bytes are consumed.
  static absl::StatusOr<FrameHeader> Parse(const uint8_t* data);
  // Serializes a frame header into a buffer of 12 bytes.
  void Serialize(uint8_t* data) const;
  // Report contents as a string
  std::string ToString() const;
  // Required padding to maintain alignment.
  uint32_t Padding(uint32_t alignment) const {
    if (payload_connection_id == 0) {
      return 0;
    }
    if (payload_length % alignment == 0) {
      return 0;
    }
    return alignment - (payload_length % alignment);
  }

  bool operator==(const FrameHeader& h) const {
    return type == h.type && stream_id == h.stream_id &&
           payload_connection_id == h.payload_connection_id &&
           payload_length == h.payload_length;
  }
  // Frame header size is fixed to 12 bytes.
  enum { kFrameHeaderSize = 12 };
};

inline std::ostream& operator<<(std::ostream& out, const FrameHeader& h) {
  return out << h.ToString();
}

}  // namespace chaotic_good
}  // namespace grpc_core

#endif  // GRPC_SRC_CORE_EXT_TRANSPORT_CHAOTIC_GOOD_FRAME_HEADER_H