README.md

description
Making use of hooks that run before or after an agreement is called

Super App Callbacks

Super App Callbacks

Super App callbacks are run when a Super App is on the receiving end of a transaction that creates, updates, or deletes an agreement in relation to that app.

When Will Super App Callbacks Run?

The Constant Flow Agreement and Instant Distribution Agreement activate different callbacks in different scenarios. In the following table, the Constant Flow Agreement is referred to as CFAv1 and the Instant Distribution Agreement is referred to as IDAv1.

Agreement	Callback	Condition
CFAv1	beforeAgreementCreated, afterAgreementCreated	A stream to a Super App is created.
CFAv1	beforeAgreementUpdated, afterAgreementUpdated	A stream to a Super App is updated.
CFAv1	beforeAgreementTerminated, afterAgreementTerminated	A stream to a Super App is deleted.
IDAv1	beforeAgreementCreated, afterAgreementCreated	A subscription (with zero units) to an index published by a Super App is approved.
IDAv1	beforeAgreementUpdated, afterAgreementUpdated	A subscription (with units) to an index published by a Super App is approved.
IDAv1	beforeAgreementTerminated, afterAgreementTerminated	A subscription to an index published by a Super App is revoked.
IDAv1	beforeAgreementUpdated, afterAgreementUpdated	A subscription to an index published by a Super App is claimed
IDAv1	beforeAgreementCreated, afterAgreementCreated	Units of an index are issued to a Super App if the units were previously zero.
IDAv1	beforeAgreementUpdated, afterAgreementUpdated	Units of an index are issued to a Super App if the units were previously non-zero.
IDAv1	beforeAgreementTerminated, afterAgreementTerminated	Units of an index issued to a Super App are deleted.

Who is Calling the Super App Callback?

Callbacks are called entirely on chain by the Superfluid protocol in response to events. Each time an action is taken inside of the Constant Flow Agreement contract, the protocol will check the Super App registry to determine whether or not the stream will be sent to a Super App (or if the stream being deleted involves a Super App in the event of deletion). If it doesn't involve a Super App, there are no callbacks to run, so the stream is created, updated, or deleted without any other operation. However, if the protocol finds that the stream indeed does involve a Super App after a check to the Superfluid Super App manifest, it will call the necessary callback(s).

The Anatomy of Super App Callbacks:

function beforeAgreementCreated(
        ISuperToken /*superToken*/,
        address /*agreementClass*/,
        bytes32 /*agreementId*/,
        bytes calldata /*agreementData*/,
        bytes calldata /*ctx*/
    )
        external
        view
        virtual
        override
        returns (bytes memory /*cbdata*/)
    {
        revert("Unsupported callback - Before Agreement Created");
    }

    function afterAgreementCreated(
        ISuperToken /*superToken*/,
        address /*agreementClass*/,
        bytes32 /*agreementId*/,
        bytes calldata /*agreementData*/,
        bytes calldata /*cbdata*/,
        bytes calldata /*ctx*/
    )
        external
        virtual
        override
        returns (bytes memory /*newCtx*/)
    {
        revert("Unsupported callback - After Agreement Created");
    }

A beforeAgreement callback will be run before the call to the agreement contract will be run. For example, if there is logic inside of the beforeAgreementCreated callback within of a Super App, and a user opens a stream into that Super App contract, the logic inside of beforeAgreementCreated will run before the stream is created.

Similarly, an afterAgreement callback will be run after the call to the agreement contract is run. For example, if there is logic inside of the afterAgreementCreated callback within a Super App, and a user opens a stream into that Super App contract, the logic inside of afterAgreementCreated will run after the stream is created.

One additional thing to note about the beforeAgreement callbacks is that they are view functions. So, if you want to, for example, save a variable to state in response to something that happens in the beforeAgreement callback, you should do the following:

1. Return the data that you want to save inside the beforeAgreement callback (this returned value will be passed to the afterAgreement callback as cbdata, which we explain below)
2. Save the variable to state inside of the afterAgreement callback
3. Make sure that you have an implementation for both the beforeAgreement and afterAgreement callbacks

Breaking Down Each Variable

ISuperToken - the protocol will pass the Super Token that's being used in the call to the constant flow agreement contract here.

address - this will be the address of the Constant Flow Agreement contract on the network you're interacting with. You can find more details around these networks inside of the Superfluid network directory.

agreementId - a bytes32 value that is a hash of the sender and receiver's address of the flow that was created, updated, or deleted.

agreementData - the address of the sender and receiver of the flow that was created, updated, or deleted - encoded using solidity's abi.encode() built in function

cbdata - this contains data that was returned by the beforeAgreement callback if it was run prior to the calling of afterAgreement callback. Note: this is only passed to the afterAgreement callback

ctx - this contains data about the call to the constant flow agreement contract itself. 'Ctx' is short for 'context' and is explained in depth inside of our tutorial on userData (which you can access inside of the ctx value).