hub_pairing.h

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#pragma once
 
/// @file hub_pairing.h
/// @brief Internal pairing-state model for hub‑owned discovery and key‑exchange flows.
/// @ingroup hioc_hub
///
/// This header defines the state machine enum and context structures for the
/// three‑phase pairing procedure (the flow itself is implemented by PairingEngine),
/// which temporarily tracks a newly paired device in the controller's runtime
/// registry and installs the system key on the device:
///
/// Phase 1 — Discovery (broadcast 0x28 → device responds 0x29 → confirm 0x2C → ack 0x2D):
///   Controller broadcasts a discovery packet on the primary channel. A device in
///   pairing mode (PROG button pressed) responds with its node ID and type/subtype.
///   The controller validates the response and extracts device metadata, then sends a
///   discover-confirm (0x2C) directly to that device and — unless the `pairing_discover_confirm`
///   tuning mode is `skip` — waits up to a few seconds for its 0x2D before proceeding. This step
///   never fails the attempt; see PairingEngine::run_discover_confirm_step_().
///
/// Phase 2 — Authenticated Key Exchange (0x31 → 0x3C → 0x32 → 0x33):
///   The controller sends CMD_KEY_INIT (0x31) to the device. The device challenges
///   with CMD_CHALLENGE_REQ (0x3C). The controller proves knowledge of the system
///   key with CMD_CHALLENGE_RESP (0x3D) and simultaneously sends the encrypted system
///   key via CMD_KEY_TRANSFER (0x32). The device confirms with CMD_KEY_CONFIRM (0x33).
///
/// Phase 3 — Configuration (CMD_SET_CONFIG1):
///   The controller sends a configuration frame (0x6F) to enable automatic status
///   updates from the device. This phase completes even if the config frame fails;
///   the device will still operate in polled mode.
///
/// All frames use the standard authenticated exchange flow (state types in
/// hub_exchange.h, implementation in ExchangeEngine). PairingEngine serializes these
/// phases, logs the YAML metadata the user should add, and keeps the paired device
/// in the current runtime registry until reboot.
 
#include "proto_device_model.h"
#include "proto_frame.h"
#include "radio_interface.h"
#include <cstdint>
#include <string>
 
namespace esphome {
namespace home_io_control {
 
namespace pairing {
 
/// @brief State machine for the three‑phase pairing flow.
enum class PairingState : uint8_t {
  IDLE,                    ///< No pairing in progress; idle state.
  TX_DISCOVER,             ///< Discovery broadcast (0x28) sent; awaiting device response.
  WAIT_DISCOVER_RESPONSE,  ///< Listening for discovery response (0x29) from a device in pairing mode.
  TX_DISCOVER_CONFIRM,     ///< Discovery-confirm (0x2C) sent to the discovered device.
  WAIT_DISCOVER_CONFIRM,   ///< Listening for the device's discovery-confirm ack (0x2D).
  TX_KEY_INIT,             ///< Key‑init (0x31) sent to the discovered device.
  WAIT_KEY_CHALLENGE,      ///< Waiting for challenge (0x3C) from device as part of key transfer.
  TX_KEY_TRANSFER,         ///< Key‑transfer (0x32) sent with encrypted system key.
  WAIT_KEY_CONFIRM,        ///< Waiting for key‑confirm (0x33) from device (key receipt acknowledgement).
  REGISTER_DEVICE,         ///< Registering device in the runtime registry for the current boot.
  COMPLETE,                ///< Pairing completed successfully; device ready for use.
  FAILED,                  ///< Pairing failed (timeout, radio error, or protocol violation).
};
 
/// @brief Context object that lives for the duration of a single pairing attempt.
struct PairingContext {
  PairingState state{PairingState::IDLE};  ///< Current state machine state.
  IoDevice device{};                       ///< Resolved device metadata after discovery (node_id, type, subtype, etc.).
  IoFrame req{};                           ///< Outbound frame buffer (reused across all phases).
  IoFrame resp{};                          ///< Inbound frame buffer (holds key‑confirm response).
  IoFrame rx{};                            ///< Raw RX frame during waiting phases (discovery, challenge, confirm).
  IoFrame key_init{};                      ///< Key‑init frame retained for key‑transfer IV derivation.
  RadioRxPacket packet{};                  ///< Raw radio capture for the current phase.
  std::string device_id;                   ///< Hex string representation of the paired node ID.
  bool discovery_metadata_complete{false};  ///< True when discovery carried type/subtype bytes.
  bool discovery_low_power{false};          ///< True when discovery reported POWER_SAVE_LOW_POWER.
};
 
/// @brief What PairingEngine::run_discover_confirm_step_() actually observed.
///
/// Not stored in PairingContext — nothing downstream reads it, so it is returned directly to the
/// caller, which logs the details (reply channel, try number, elapsed time) and otherwise ignores
/// the result: the step never fails a pairing attempt (see run_discover_confirm_step_()'s doc).
enum class DiscoverConfirmResult : uint8_t {
  SKIPPED,      ///< `pairing_discover_confirm` tuning mode is `skip` — no 0x2C was sent.
  ACKED,        ///< The device answered with CMD_DISCOVER_CONFIRM_ACK (0x2D).
  ERROR_REPLY,  ///< The device answered with CMD_ERROR_RESP.
  NO_REPLY,     ///< Every try was silent (or every transmit failed).
};
 
}  // namespace pairing
 
/// @brief Get a short, log/telemetry-friendly name for a pairing state.
/// @param state Pairing state.
/// @return Null-terminated lowercase string such as "wait_key_challenge".
inline const char *pairing_stage_name(pairing::PairingState state) {
  switch (state) {
    case pairing::PairingState::IDLE:
      return "idle";
    case pairing::PairingState::TX_DISCOVER:
      return "tx_discover";
    case pairing::PairingState::WAIT_DISCOVER_RESPONSE:
      return "wait_discover_response";
    case pairing::PairingState::TX_DISCOVER_CONFIRM:
      return "tx_discover_confirm";
    case pairing::PairingState::WAIT_DISCOVER_CONFIRM:
      return "wait_discover_confirm";
    case pairing::PairingState::TX_KEY_INIT:
      return "tx_key_init";
    case pairing::PairingState::WAIT_KEY_CHALLENGE:
      return "wait_key_challenge";
    case pairing::PairingState::TX_KEY_TRANSFER:
      return "tx_key_transfer";
    case pairing::PairingState::WAIT_KEY_CONFIRM:
      return "wait_key_confirm";
    case pairing::PairingState::REGISTER_DEVICE:
      return "register_device";
    case pairing::PairingState::COMPLETE:
      return "complete";
    case pairing::PairingState::FAILED:
    default:
      return "failed";
  }
}
 
}  // namespace home_io_control
}  // namespace esphome