#include "Protocol.h"
#include <stddef.h>

uint16_t packetCrc(const ProtocolPacket &p) {
  const uint8_t *data = reinterpret_cast<const uint8_t *>(&p);
  uint16_t crc = 0xFFFF;
  for (size_t i = 0; i < offsetof(ProtocolPacket, crc); ++i) {
    crc ^= static_cast<uint16_t>(data[i]) << 8;
    for (uint8_t b = 0; b < 8; ++b) crc = (crc & 0x8000) ? (crc << 1) ^ 0x1021 : crc << 1;
  }
  return crc;
}

void finalizePacket(ProtocolPacket &p) {
  p.magic = PROTOCOL_MAGIC; p.version = PROTOCOL_VERSION; p.crc = packetCrc(p);
}

bool validPacket(const ProtocolPacket &p) {
  return p.magic == PROTOCOL_MAGIC && p.version == PROTOCOL_VERSION &&
    p.type <= static_cast<uint8_t>(MessageType::ABORT) && p.crc == packetCrc(p);
}