// Stateful binary frame parser for the sensor telemetry protocol.

#pragma once

#include <cstdint>

#include <span>

#include <vector>

struct Frame {

  uint8_t              type; // frame type identifier

  std::vector<uint8_t> body; // decoded frame payload

};

// Stateful binary frame parser for the sensor telemetry protocol.

// Frame layout: [0xCA][0xFE][len_hi][len_lo][type][reserved][body...]

// kMaxBodyBytes: maximum accepted body length; larger frames are dropped.

class FrameParser {

public:

  static constexpr uint16_t kMaxBodyBytes = 4096; // maximum body size per frame

  // Parameters:

  //   data - raw bytes received from the socket in this call

  //   out  - vector to append any complete Frame objects found in data

  // Returns: number of bytes consumed from data; re-feed unconsumed bytes next call

  size_t feed(std::span<const uint8_t> data, std::vector<Frame>& out);

  // Parameters: none

  // Returns: void; discards any partially buffered frame bytes

  void reset();

private:

  std::vector<uint8_t> buf_; // cross-call reassembly buffer

};