// Copyright 2020 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SRC_CONNECTIVITY_BLUETOOTH_CORE_BT_HOST_SM_SC_STAGE_1_H_
#define SRC_CONNECTIVITY_BLUETOOTH_CORE_BT_HOST_SM_SC_STAGE_1_H_

#include <lib/fit/function.h>
#include <lib/fpromise/result.h>

#include "src/connectivity/bluetooth/core/bt-host/common/uint256.h"
#include "src/connectivity/bluetooth/core/bt-host/hci/connection.h"
#include "src/connectivity/bluetooth/core/bt-host/sm/error.h"
#include "src/connectivity/bluetooth/core/bt-host/sm/smp.h"
#include "src/connectivity/bluetooth/core/bt-host/sm/types.h"
#include "src/lib/fxl/memory/weak_ptr.h"

namespace bt::sm {

// Pure abstract interface to be implemented by classes that execute Authentication Stage 1 of
// Phase 2 of SMP Secure Connections. The owning class will use the abstract OnPairingConfirm and
// OnPairingRandom methods of this class to handle any inbound Pairing Confirm / Random values.
// Concrete Stage 1 classes are responsible for tracking the state associated with their Pairing
// Method. See spec V5.0 Vol. 3 Part H 2.3.5.6.2-4 (aka "the spec section") for more details.
class ScStage1 {
 public:
  // This object contains the values generated/exchanged during Stage 1 which are needed to finish
  // SC pairing. An ScStage1 returns an |Output| through its callback upon successful completion.
  struct Output {
    bool operator==(const Output& other) const {
      return initiator_r == other.initiator_r && responder_r == other.responder_r &&
             initiator_rand == other.initiator_rand && responder_rand == other.responder_rand;
    }

    // `ra` in the spec, associated with the initiator. Used to generate DHKey check E in SC Phase
    // 2 Stage 2. Meaning depends on the pairing method used, see "the spec section" for details.
    UInt128 initiator_r;

    // `rb` in the spec, associated with the responder. Used to generate DHKey check E in SC Phase
    // 2 Stage 2. Meaning depends on the pairing method used, see "the spec section" for details.
    UInt128 responder_r;

    // 'Na' in the spec; the Pairing Random value sent by the initiator. Used during SC Phase 2
    // Stage 2 to generate the MacKey/LTK and the DHKey check E values.
    UInt128 initiator_rand;

    // 'Na' in the spec; the Pairing Random value sent by the initiator. Used during SC Phase 2
    // Stage 2 to generate the MacKey/LTK and the DHKey check E values.
    UInt128 responder_rand;
  };

  // Used by Stage 1 classes to notify their owning class that they have finished. A successful
  // Stage 1 notifies its owner with `Output`, or that it has failed due to `ErrorCode`.
  using Stage1CompleteCallback = fit::function<void(fpromise::result<Output, ErrorCode>)>;

  virtual void Run() = 0;
  virtual void OnPairingConfirm(PairingConfirmValue) = 0;
  virtual void OnPairingRandom(PairingRandomValue) = 0;
  virtual ~ScStage1() = default;
};

}  // namespace bt::sm

#endif  // SRC_CONNECTIVITY_BLUETOOTH_CORE_BT_HOST_SM_SC_STAGE_1_H_