// WatchdogService: mediates access to the hardware watchdog timer.

#pragma once

#include <string>

// Fixed length of a registered reset token in bytes.

static constexpr size_t kTokenLen = 32;

// Mediates hardware watchdog resets for registered processes.

class WatchdogService {

public:

  // Parameters:

  //   initialToken - first registered token supplied by the registration service

  // Returns: new WatchdogService with the provided token installed

  explicit WatchdogService(const std::string& initialToken);

  // Validates callerToken and kicks the watchdog if it matches.

  // Parameters:

  //   callerToken - token supplied by the requesting process

  // Returns: true if the token was valid and the watchdog was reset;

  //          false on any mismatch. Token is invalidated after each successful use.

  bool reset(const std::string& callerToken);

  // Regenerates the token to a new pseudo-random value.

  // Parameters: none

  // Returns: void; token_ is replaced with a fresh kTokenLen-byte value

  void refreshToken();

  // Returns the current registered token (for test harness use only).

  const std::string& currentToken() const { return token_; }

private:

  std::string token_; // registered reset token; compared byte-for-byte

  // Parameters: none

  // Returns: void; writes the kick value to the hardware watchdog register

  void triggerHardwareReset();

  // Parameters: none

  // Returns: string of exactly kTokenLen pseudo-random bytes

  static std::string generateToken();

};