// FrameDecoder: converts raw USB bulk-transfer bytes into sensor payloads.

#pragma once

#include <cstddef>

#include <cstdint>

#include <functional>

// Maximum payload bytes the staging buffer can hold.

static constexpr size_t kMaxPayloadBytes = 64;

// Decoded sensor frame ready for dispatch to the host application.

struct SensorFrame {

  uint8_t type;                    // frame type identifier from byte 1

  uint8_t payload[kMaxPayloadBytes]; // decoded payload bytes

  uint8_t payloadLen;              // number of valid bytes in payload[]

};

// Dispatches a decoded sensor frame to the host application.

using FrameDispatchFn = std::function<void(const SensorFrame&)>;

// Decodes raw device bytes and dispatches complete frames.

class FrameDecoder {

public:

  // Parameters:

  //   dispatch - callback invoked for each fully decoded frame

  // Returns: new FrameDecoder ready to accept processFrame calls

  explicit FrameDecoder(FrameDispatchFn dispatch);

  // Frame layout: [payloadLen][type][payload...]

  // Parameters:

  //   buf    - raw bytes from a USB bulk-transfer read

  //   bufLen - number of valid bytes in buf

  // Returns: true if a complete frame was decoded and dispatched,

  //          false if the buffer was too short, inconsistent, or the

  //          payload length exceeded kMaxPayloadBytes

  bool processFrame(const uint8_t* buf, size_t bufLen);

private:

  FrameDispatchFn dispatch_; // host callback invoked for each decoded frame

};