request_id.hpp

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#pragma once
// Request ids shared by the JSON order-entry encoders: "<kind><cl_ord_id>" with kind n/c/r/a
// (1 + 14 chars), so a WebSocket API response maps back to the command with no lookup
// table. Binance allows a 36-char string id, Bybit a 36-char reqId.
#include "fastmm/core/fixed_string.hpp"
#include "fastmm/core/strong_id.hpp"
 
#include <optional>
#include <string_view>
#include <utility>
 
namespace fastmm::venues {
 
using RequestId = FixedString<16>;
// Amend: a replace the venue applies to the resting order (Binance Spot keepPriority); its
// response has a different shape from a cancel-replace, so it needs its own kind.
enum class RequestKind : char {
  New = 'n',
  Cancel = 'c',
  Replace = 'r',
  Amend = 'a',
  Other = 'x',
};
 
[[nodiscard]] inline RequestId make_request_id(RequestKind kind, ClientOrderId id) noexcept {
  RequestId out;
  out.push_back(static_cast<char>(kind));
  out.append(encode_cl_ord_id(id).view());
  return out;
}
// Returns the kind and id encoded by make_request_id, or nullopt for foreign ids.
[[nodiscard]] inline std::optional<std::pair<RequestKind, ClientOrderId>> parse_request_id(
    std::string_view id) noexcept {
  if (id.size() != 1 + kClOrdIdChars) return std::nullopt;
  const char k = id[0];
  if (k != 'n' && k != 'c' && k != 'r' && k != 'a') return std::nullopt;
  const auto cl = decode_cl_ord_id(id.substr(1));
  if (!cl) return std::nullopt;
  return std::make_pair(static_cast<RequestKind>(k), *cl);
}
 
}  // namespace fastmm::venues