Pay delegate

Before implementing, learn about delegates here. Also see snow-delegate-template.

Specs

A contract can become a treasury pay delegate by adhering to ISNWPayDelegate3_1_1:

interface ISNWPayDelegate3_1_1 is IERC165 {
  function didPay(SNWDidPayData3_1_1 calldata data) external payable;
}

When extending pay functionality with a delegate, the protocol will pass a SNWDidPayData3_1_1 to the didPay(...) function:

struct SNWDidPayData3_1_1 {
    address payer;
    uint256 projectId;
    uint256 currentFundingCycleConfiguration;
    SNWTokenAmount amount;
    SNWTokenAmount forwardedAmount;
    uint256 projectTokenCount;
    address beneficiary;
    bool preferClaimedTokens;
    string memo;
    bytes dataSourceMetadata;
    bytes payerMetadata;
}

struct SNWTokenAmount {
  address token;
  uint256 value;
  uint256 decimals;
  uint256 currency;
}

The msg.sender to the delegate will be the payment terminal that facilitated the payment.

In payment terminals based on the SNWPayoutRedemptionPaymentTerminal3_1_1, such as SNWETHPaymentTerminal3_1_1's and SNWERC20PaymentTerminal3_1_1's, the pay delegate hook gets called after the project's tokens have been minted and distributed. View the docs.

Make sure to only allow trusted contracts to access the didPay(...) transaction.

Attaching

New delegate contracts should be deployed independently. Once deployed, its address can be returned from a data source hook. See how to build a data source for more.

Examples

import '@openzeppelin/contracts/token/ERC721/ERC721.sol';
import '@snx-protocol/contracts-v2/contracts/interfaces/ISNWFundingCycleDataSource.sol';
import '@snx-protocol/contracts-v2/contracts/interfaces/ISNWPayDelegate.sol';
import '@snx-protocol/contracts-v2/contracts/structs/SNWTokenAmount.sol';

contract NFTPayDelegate is ERC721, ISNWFundingCycleDataSource, ISNWPayDelegate {
  error INVALID_PAYMENT_EVENT();

  ISNWDirectory directory;
  uint256 projectId;
  SNWTokenAmount contributionThreshold;
  uint256 supply;

  // This contract can be used as a funding cycle data source to ensure its didPay function is called once the payment has gone through.
  function payParams(SNWPayParamsData calldata _data)
    external
    view
    override
    returns (
      uint256 weight,
      string memory memo,
      ISNWPayDelegate delegate
    )
  {
    // Forward the received weight and memo, and use this contract as a pay delegate.
    return (_data.weight, _data.memo, ISNWPayDelegate(address(this)));
  }

  // This is unused but needs to be included to fulfill ISNWFundingCycleDataSource.
  function redeemParams(SNWRedeemParamsData calldata _data)
    external
    pure
    override
    returns (
      uint256 reclaimAmount,
      string memory memo,
      ISNWRedemptionDelegate delegate
    )
  {
    // Return the default values.
    return (_data.reclaimAmount.value, _data.memo, ISNWRedemptionDelegate(address(0)));
  }

  constructor(ISNWDirectory _directory, uint256 _projectId, SNWTokenAmount _contributionThreshold, string calldata _name, string calldata _symbol) ERC721(_name, _symbol) {
    directory = _directory;
    projectId = _projectId;
  },

  // Called once the payment has gone through if the project's current funding cycle is using a data source that returns this delegate.
  function didPay(SNWDidPayData calldata _data) external override {
    // Make sure the caller is a terminal of the project, and the call is being made on behalf of an interaction with the correct project.
    if (
      !directory.isTerminalOf(projectId, ISNWPaymentTerminal(msg.sender)) ||
      _data.projectId != projectId
    ) revert INVALID_PAYMENT_EVENT();

    // Make the contribution is being made in the expected token.
    if (_data.amount.token != contributionThreshold.token) return;

    // Make sure the values use the same number of decimals.
    if (_data.amount.decimals < contributionThreshold.decimals) return;

    // Make sure the threshold is met.
    if (_data.amount.value < contributionThreshold.value) return;

    uint256 _tokenId = ++supply;

    _mint(_data.beneficiary, _tokenId);
  }
}