ERC-1337 - Subscriptions on the blockchain

/// @title Enum - Collection of enums
/// Original concept from Richard Meissner - <richard@gnosis.pm> Gnosis safe contracts
contract Enum {
    enum Operation {
        Call,
        DelegateCall,
        Create,
        ERC20, 
        ERC20Approve
    }
    enum SubscriptionStatus {
        ACTIVE,
        PAUSED,
        CANCELLED,
        EXPIRED
    }

    enum Period {
        INIT,
        DAY,
        WEEK,
        MONTH
    }
}

interface ERC165 {
  /**
   * @notice Query if a contract implements an interface
   * @param interfaceID The interface identifier, as specified in ERC-165
   * @dev Interface identification is specified in ERC-165. This function
   * uses less than 30,000 gas.
   * @return `true` if the contract implements `interfaceID` and
   * `interfaceID` is not 0xffffffff, `false` otherwise
   **/
  function supportsInterface(bytes4 interfaceID) external view returns (bool);
}

/** @dev Checks if the subscription is valid.
  * @param bytes subscriptionHash is the identifier of the customer's subscription with its relevant details.
  * @return success is the result of whether the subscription is valid or not.
  **/

function isValidSubscription(
            uint256 subscriptionHash
        ) 
        public 
        view 
        returns (
            bool success
        )

/** @dev returns the value of the subscription
  * @param bytes subscriptionHash is the identifier of the customer's subscription with its relevant details.
  * @return status is the enumerated status of the current subscription, 0 expired, 1 active, 2 paused, 3 cancelled
  **/
function getSubscriptionStatus(
        uint256 subscriptionHash
    )
    public 
    view 
    returns (
        uint256 status, 
        uint256 nextWithdraw
    )

/** @dev returns the hash of cocatenated inputs to the address of the contract holding the logic.,
  * the owner would sign this hash and then provide it to the party for execution at a later date,
  * this could be viewed like a cheque, with the exception that unless you specifically
  * capture the hash on chain a valid signature will be executable at a later date, capturing the hash lets you modify the status to cancel or expire it.
  * @param address recipient the address of the person who is getting the funds.
  * @param uint256 value the value of the transaction
  * @param bytes data the data the user is agreeing to
  * @param uint256 txGas the cost of executing one of these transactions in gas(probably safe to pad this)
  * @param uint256 dataGas the cost of executing the data portion of the transaction(delegate calls etc)
  * @param uint 256 gasPrice the agreed upon gas cost of Execution of this subscription(cost incurment is up to implementation, ie, sender or receiver)
  * @param address gasToken address of the token in which gas will be compensated by, address(0) is ETH, only works in the case of an enscrow implementation)
  * @param bytes meta dynamic bytes array with 4 slots, 2 required, 2 optional // address refundAddress / uint256 period / uint256 offChainID / uint256 expiration (uinx timestamp)
  * @return bytes32, return the hash input arguments concatenated to the address of the contract that holds the logic.
  **/
function getSubscriptionHash(
        address recipient,
        uint256 value,
        bytes data,
        Enum.Operation operation,
        uint256 txGas,
        uint256 dataGas,
        uint256 gasPrice,
        address gasToken,
        bytes meta
    )
    public
    view
    returns (
        bytes32 subscriptionHash
    )

/** @dev returns the hash of concatenated inputs that the owners user would sign with their public keys
  * @param address recipient the address of the person who is getting the funds.
  * @param uint256 value the value of the transaction
  * @return bytes32 returns the hash of concatenated inputs with the address of the contract holding the subscription hash
  **/
function getModifyStatusHash(
        bytes32 subscriptionHash
        Enum.SubscriptionStatus status
    )
    public
    view
    returns (
        bytes32 modifyStatusHash
    )

/** @dev modifys the current subscription status
  * @param uint256 subscriptionHash is the identifier of the customer's subscription with its relevant details.
  * @param Enum.SubscriptionStatus status the new status of the subscription
  * @param bytes signatures of the requested method being called
  * @return success is the result of the subscription being paused
  **/
function modifyStatus(
        uint256 subscriptionHash, 
        Enum.SubscriptionStatus status, 
        bytes signatures
    ) 
    public 
    returns (
        bool success
    )

/** @dev returns the hash of cocatenated inputs to the address of the contract holding the logic.,
  * the owner would sign this hash and then provide it to the party for execution at a later date,
  * this could be viewed like a cheque, with the exception that unless you specifically
  * capture the hash on chain a valid signature will be executable at a later date, capturing the hash lets you modify the status to cancel or expire it.
  * @param address recipient the address of the person who is getting the funds.
  * @param uint256 value the value of the transaction
  * @param bytes data the data the user is agreeing to
  * @param uint256 txGas the cost of executing one of these transactions in gas(probably safe to pad this)
  * @param uint256 dataGas the cost of executing the data portion of the transaction(delegate calls etc)
  * @param uint 256 gasPrice the agreed upon gas cost of Execution of this subscription(cost incurment is up to implementation, ie, sender or receiver)
  * @param address gasToken address of the token in which gas will be compensated by, address(0) is ETH, only works in the case of an enscrow implementation)
  * @param bytes meta dynamic bytes array with 4 slots, 2 required, 2 optional // address refundAddress / uint256 period / uint256 offChainID / uint256 expiration (uinx timestamp)
  * @param bytes signatures signatures concatenated that have signed the inputs as proof of valid execution
  * @return bool success something to note that a failed execution will still pay the issuer of the transaction for their gas costs.
  **/
function executeSubscription(
        address to,
        uint256 value,
        bytes data,
        Enum.Operation operation,
        uint256 txGas,
        uint256 dataGas,
        uint256 gasPrice,
        address gasToken,
        bytes meta,
        bytes signatures
    )
    public 
    returns (
        bool success
    )