contract TransferRegistry is FactRegistry, Identity {

    event LogRegisteredTransfer(
        address recipient,
        address token,
        uint256 amount,
        uint256 salt
    );

    using Addresses for address;

    function identify()
        external pure virtual override
        returns(string memory)
    {
        return "StarkWare_TransferRegistry_2020_1";
    }

    /*
      The actual transfer is extracted to a function, so that we can easily mock the contract.
    */
    function performEthTransfer(address recipient, uint256 value)
        internal
        virtual {
        recipient.performEthTransfer(value);
    }

    /*
      The actual transfer is extracted to a function, so that we can easily mock the contract.
    */
    function performErc20Transfer(address recipient, address erc20, uint256 amount)
        internal
        virtual {
        erc20.safeTokenContractCall(
            abi.encodeWithSelector(IERC20(0).transferFrom.selector, msg.sender, recipient, amount)
        );
    }

    /*
      Passes on the transaction ETH value onto the recipient address,
      and register the associated fact.
      Reverts if the fact has already been registered.
    */
    function transfer(address recipient, uint256 salt) // NOLINT: erc20-interface.
        external
        payable {
        bytes32 transferFact = keccak256(
            abi.encodePacked(recipient, msg.value, address(0x0), salt));
        require(!_factCheck(transferFact), "TRANSFER_ALREADY_REGISTERED");
        registerFact(transferFact);
        emit LogRegisteredTransfer(recipient, address(0x0), msg.value, salt);
        performEthTransfer(recipient, msg.value);
    }

    /*
      Transfer the specified amount of erc20 tokens from msg.sender balance to the recipient's
      balance.
      Pre-conditions to successful transfer are that the msg.sender has sufficient balance,
      and the the approval (for the transfer) was granted to this contract.
      A fact with the transfer details is registered upon success.
      Reverts if the fact has already been registered.
    */
    function transferERC20(address recipient, address erc20, uint256 amount, uint256 salt)
        external {
        bytes32 transferFact = keccak256(
            abi.encodePacked(recipient, amount, erc20, salt));
        require(!_factCheck(transferFact), "TRANSFER_ALREADY_REGISTERED");
        registerFact(transferFact);
        emit LogRegisteredTransfer(recipient, erc20, amount, salt);
        performErc20Transfer(recipient, erc20, amount);
    }

}
function performErc20Transfer(address recipient, address erc20, uint256 amount)
        internal
        virtual {
        erc20.safeTokenContractCall(
            abi.encodeWithSelector(IERC20(0).transferFrom.selector, msg.sender, recipient, amount)
        );
    }
/*
 The actual transfer is extracted to a function, so that we can easily mock the contract.
 */