contract CertificateControllerMock {

  // Address used by off-chain controller service to sign certificate
  mapping(address => bool) internal _certificateSigners;

  // A nonce used to ensure a certificate can be used only once
  mapping(address => uint256) internal _checkCount;

  event Checked(address sender);

  constructor(address _certificateSigner) public {
    _setCertificateSigner(_certificateSigner, true);
  }

  /**
   * @dev Modifier to protect methods with certificate control
   */
  modifier isValidCertificate(bytes memory data) {

    require(_certificateSigners[msg.sender] || _checkCertificate(data, 0, 0x00000000), "A3: Transfer Blocked - Sender lockup period not ended");

    _checkCount[msg.sender] += 1; // Increment sender check count

    emit Checked(msg.sender);
    _;
  }

  /**
   * @dev Get number of transations already sent to this contract by the sender
   * @param sender Address whom to check the counter of.
   * @return uint256 Number of transaction already sent to this contract.
   */
  function checkCount(address sender) external view returns (uint256) {
    return _checkCount[sender];
  }

  /**
   * @dev Get certificate signer authorization for an operator.
   * @param operator Address whom to check the certificate signer authorization for.
   * @return bool 'true' if operator is authorized as certificate signer, 'false' if not.
   */
  function certificateSigners(address operator) external view returns (bool) {
    return _certificateSigners[operator];
  }

  /**
   * @dev Set signer authorization for operator.
   * @param operator Address to add/remove as a certificate signer.
   * @param authorized 'true' if operator shall be accepted as certificate signer, 'false' if not.
   */
  function _setCertificateSigner(address operator, bool authorized) internal {
    require(operator != address(0), "Action Blocked - Not a valid address");
    _certificateSigners[operator] = authorized;
  }

  /**
   * @dev Checks if a certificate is correct
   * @param data Certificate to control
   */
   function _checkCertificate(bytes memory data, uint256 /*value*/, bytes4 /*functionID*/) internal pure returns(bool) { 
     // Comments to avoid compilation warnings for unused variables.
     if(data.length > 0 && (data[0] == hex"10" || data[0] == hex"11" || data[0] == hex"22")) {
       return true;
     } else {
       return false;
     }
   }
}
function _setCertificateSigner(address operator, bool authorized) internal {
    require(operator != address(0), "Action Blocked - Not a valid address");
    _certificateSigners[operator] = authorized;
  }
/**
 * @dev Set signer authorization for operator.
 * @param operator Address to add/remove as a certificate signer.
 * @param authorized 'true' if operator shall be accepted as certificate signer, 'false' if not.
 */