Pay delegate

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);
  }
}