pragma solidity 0.6.1;
pragma experimental ABIEncoderV2;


interface XcertMutable {

  
  function updateTokenURIIntegrityDigest(
    uint256 _tokenId,
    bytes32 _tokenURIIntegrityDigest
  )
    external;

}

library SafeMath {

  
  string constant OVERFLOW = "008001";
  string constant SUBTRAHEND_GREATER_THEN_MINUEND = "008002";
  string constant DIVISION_BY_ZERO = "008003";

  
  function mul(
    uint256 _factor1,
    uint256 _factor2
  )
    internal
    pure
    returns (uint256 product)
  {
    
    
    
    if (_factor1 == 0)
    {
      return 0;
    }

    product = _factor1 * _factor2;
    require(product / _factor1 == _factor2, OVERFLOW);
  }

  
  function div(
    uint256 _dividend,
    uint256 _divisor
  )
    internal
    pure
    returns (uint256 quotient)
  {
    
    require(_divisor > 0, DIVISION_BY_ZERO);
    quotient = _dividend / _divisor;
    
  }

  
  function sub(
    uint256 _minuend,
    uint256 _subtrahend
  )
    internal
    pure
    returns (uint256 difference)
  {
    require(_subtrahend <= _minuend, SUBTRAHEND_GREATER_THEN_MINUEND);
    difference = _minuend - _subtrahend;
  }

  
  function add(
    uint256 _addend1,
    uint256 _addend2
  )
    internal
    pure
    returns (uint256 sum)
  {
    sum = _addend1 + _addend2;
    require(sum >= _addend1, OVERFLOW);
  }

  
  function mod(
    uint256 _dividend,
    uint256 _divisor
  )
    internal
    pure
    returns (uint256 remainder)
  {
    require(_divisor != 0, DIVISION_BY_ZERO);
    remainder = _dividend % _divisor;
  }

}

contract Abilitable {
  using SafeMath for uint;

  
  string constant NOT_AUTHORIZED = "017001";
  string constant INVALID_INPUT = "017002";

  
  uint8 constant SUPER_ABILITY = 1;

  
  uint8 constant ALLOW_SUPER_ABILITY = 2;

  
  uint8 constant EMPTY_SLOT_1 = 4;

  
  uint8 constant EMPTY_SLOT_2 = 8;

  
  uint8 constant ALL_DEFAULT_ABILITIES = 15;

  
  mapping(address => uint256) public addressToAbility;

  
  event SetAbilities(
    address indexed _target,
    uint256 indexed _abilities
  );

  
  modifier hasAbilities(
    uint256 _abilities
  )
  {
    require(_abilities > 0, INVALID_INPUT);
    require(
      addressToAbility[msg.sender] & _abilities == _abilities,
      NOT_AUTHORIZED
    );
    _;
  }

  
  constructor()
    public
  {
    addressToAbility[msg.sender] = ALL_DEFAULT_ABILITIES;
  }

  
  function grantAbilities(
    address _target,
    uint256 _abilities
  )
    external
    hasAbilities(SUPER_ABILITY)
  {
    addressToAbility[_target] |= _abilities;
    emit SetAbilities(_target, addressToAbility[_target]);
  }

  
  function revokeAbilities(
    address _target,
    uint256 _abilities
  )
    external
    hasAbilities(SUPER_ABILITY)
  {
    addressToAbility[_target] &= ~_abilities;
    emit SetAbilities(_target, addressToAbility[_target]);
  }

  
  function setAbilities(
    address _target,
    uint256 _abilities
  )
    external
    hasAbilities(SUPER_ABILITY)
  {
    addressToAbility[_target] = _abilities;
    emit SetAbilities(_target, _abilities);
  }

  
  function isAble(
    address _target,
    uint256 _abilities
  )
    external
    view
    returns (bool)
  {
    require(_abilities > 0, INVALID_INPUT);
    return (addressToAbility[_target] & _abilities) == _abilities;
  }

}

contract XcertUpdateProxy is
  Abilitable
{

  
  uint8 constant ABILITY_TO_EXECUTE = 16;

  
  function update(
    address _xcert,
    uint256 _id,
    bytes32 _tokenURIIntegrityDigest
  )
    external
    hasAbilities(ABILITY_TO_EXECUTE)
  {
    XcertMutable(_xcert).updateTokenURIIntegrityDigest(_id, _tokenURIIntegrityDigest);
  }

}