openzeppelin-contracts/contracts/GSN/IRelayRecipient.sol

pragma solidity ^0.5.0;

/*
 * @dev Interface for a contract that will be called via the GSN from RelayHub.
 */
contract IRelayRecipient {
    /**
     * @dev Returns the address of the RelayHub instance this recipient interacts with.
     */
    function getHubAddr() public view returns (address);

    function acceptRelayedCall(
        address relay,
        address from,
        bytes calldata encodedFunction,
        uint256 transactionFee,
        uint256 gasPrice,
        uint256 gasLimit,
        uint256 nonce,
        bytes calldata approvalData,
        uint256 maxPossibleCharge
    )
        external
        view
        returns (uint256, bytes memory);

    function preRelayedCall(bytes calldata context) external returns (bytes32);

    function postRelayedCall(bytes calldata context, bool success, uint actualCharge, bytes32 preRetVal) external;
}