Implement Payment Settlement Smart Contract

.github/workflows/smart_contracts.yml

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+name: Smart Contracts CI
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+
+jobs:
+  hardhat:
+    strategy:
+      fail-fast: true
+
+    name: Hardhat project
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./contracts
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+
+      - name: Setup Node 16
+        uses: actions/setup-node@v3
+        with:
+          node-version: "16.x"
+          cache: "npm"
+          cache-dependency-path: "contracts/yarn.lock"
+
+      - name: Install Node dependencies
+        run: |
+          yarn install
+
+      - name: Run Hardhat tests
+        run: |
+          yarn test
+        id: hardhat-test

contracts/.gitignore

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+node_modules
+.env
+coverage
+coverage.json
+typechain
+typechain-types
+
+# Hardhat files
+cache
+artifacts
+
+deployments/localhost
+

contracts/README.md

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-# GHOPAY
+# GHOPAY - Smart Contracts
+This directory contains the smart contracts related tests, utilities and deployment addresses for the Payment Settlement.
+
+## How does it work ?
+The smart contracts themselves have essentially three tasks:
+1. Verify the user signature that was passed in by the Gelato relay in terms of amount and receiver
+2. Use user signature to pull in GHO
+3. Swap a fraction of the GHO for gas fee token (usually eth / native token) expected by relay
+4. Pay the relay
+5. Transfer remaining Gho to the receiver
+
+
+## Installation
+`yarn install`
+
+## Run tests
+`yarn test`
+
+
+## Sepolia Deployment
+
+### Warning:
+Note that on Sepolia we have deployed the [PaymentSettlementTestHarness](contracts/contracts/test/PaymentSettlementTestHarness.sol) contract which extends the [PaymentSettlement](contracts/contracts/PaymentSettlement.sol) with some unsafe methods added for testing purposes.
+One should NEVER deploy this version of the contract on a network were it will handle actual value.
+
+
+### Run Deploy:
+Delete deployment outputs of previous deployment if you want to redeploy:
+`rm -rf deployments/sepolia`
+
+Deploy on actual sepolia:
+`deploy:sepolia --network sepolia`
+
+Test deploy on local fork:
+`deploy:sepolia --network localhost`
+
+## Send Payment (on Sepolia)
+
+You can use the [payment script](contracts/scripts/sendPayment.ts) to send a GHO payment gaslessly via the Gelato relay.
+For this you will have to:
+1. Adjust the `receiver` and `amount` variables in the script to your liking
+2. Make sure you have set the `SEPOLIA_PRIVATE_KEY` environment variable to the private key of an account with sufficient GHO tokens on sepolia
+3. Run `yarn send-payment:sepolia` to make the payment
+4. Wait for the script to finish. In the success case the last emitted logs should llook something like this:
+```
+Task Status {
+  chainId: 11155111,
+  taskId: '0xaa31e9ec7dc88958e8d263b59575b2c22452985815552c4e189baa11e7141104',
+  taskState: 'ExecSuccess',
+  creationDate: '2024-01-14T06:51:54.367Z',
+  transactionHash: '0xa38b90e8af1f66425961e3e09deca5bc184b94cf10be95535893338ce7dcf1c9',
+  executionDate: '2024-01-14T06:52:01.839Z',
+  blockNumber: 5083156,
+  gasUsed: '295101',
+  effectiveGasPrice: '153284042'
+}
+```
+
+
+

contracts/constants/addresses.ts

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+export const ghoAddress = "0xc4bF5CbDaBE595361438F8c6a187bDc330539c60";
+export const ghoWhale = "0xCb3404A4288182303fE4df9bb8F9D239447E5781";
+export const uniV3PoolAddress ="0xba09E75749973Ce095121dfc02ec8D8364eE1AC9";
+export const paymentSettlementAddress = "0x62E028A0FeE5925de63F9bAb1a31Fb922C51386C";
+export const wethAddress = "0xfFf9976782d46CC05630D1f6eBAb18b2324d6B14";
+export const ethAddress = "0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE";

contracts/contracts/PaymentSettlement.sol

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+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.17;
+
+import {
+    GelatoRelayContext
+} from "@gelatonetwork/relay-context/contracts/GelatoRelayContext.sol";
+
+import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import {IERC20Permit} from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Permit.sol";
+import {
+    SafeERC20
+} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
+import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
+import "@openzeppelin/contracts/utils/cryptography/EIP712.sol";
+import "@openzeppelin/contracts/access/Ownable.sol";
+import "@openzeppelin/contracts/security/Pausable.sol";
+
+import "./interfaces/IUniV3Pool.sol";
+import "./interfaces/IWETH.sol";
+
+
+contract PaymentSettlement is GelatoRelayContext, EIP712, Ownable, Pausable {
+
+    using SafeERC20 for IERC20;
+
+    // Copied from: https://github.com/Uniswap/v3-core/blob/d8b1c635c275d2a9450bd6a78f3fa2484fef73eb/contracts/libraries/TickMath.sol#L13
+    /// @dev The minimum value that can be returned from #getSqrtRatioAtTick. Equivalent to getSqrtRatioAtTick(MIN_TICK)
+    uint160 internal constant MIN_SQRT_RATIO = 4295128739;
+    /// @dev The maximum value that can be returned from #getSqrtRatioAtTick. Equivalent to getSqrtRatioAtTick(MAX_TICK)
+    uint160 internal constant MAX_SQRT_RATIO = 1461446703485210103287273052203988822378723970342;
+
+    bytes32 public constant PAY_TYPEHASH =
+        keccak256("Pay(address receiver,uint256 permitNonce)");
+
+    IUniV3Pool internal immutable uniV3Pool;
+    IWETH public immutable weth;
+
+    address internal constant ETH = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;
+    address internal allowedCallback;
+
+    struct Signature {
+        uint8 v;
+        bytes32 r;
+        bytes32 s;
+    }
+    struct PermitData {
+        uint256 deadline;
+        Signature signature;
+    }
+
+    struct PaymentData {
+        address token;
+        address from;
+        address to;
+        uint256 amount;
+        PermitData permitData;
+    }
+
+    event Payment(
+        address indexed token,
+        address indexed from,
+        address indexed to,
+        uint256 amount
+    );
+
+    modifier checkCallback() {
+        require(msg.sender == allowedCallback, "AuctionBot: msg.sender != allowedCallback");
+        _;
+        allowedCallback = address(0);
+    }
+
+    constructor(address payable _uniV3Pool, address payable _weth) EIP712("PaymentSettlement", "1") {
+        uniV3Pool = IUniV3Pool(_uniV3Pool);
+        weth = IWETH(_weth);
+    }
+
+    function pay(
+        PaymentData calldata _paymentData,
+        Signature calldata _signature
+    ) external whenNotPaused onlyGelatoRelay {
+        address feeToken = address(_getFeeToken());
+        uint256 fee = _getFee();
+        _settlePayment(_paymentData, _signature, feeToken, fee);
+    }
+
+    // This function is used to verify the data and revert the transaction
+    // Only call as static call to avoid wasting gas
+    function verifyData(
+        PaymentData calldata _paymentData,
+        Signature calldata _signature,
+        address _feeToken,
+        uint256 _fee
+    ) external whenNotPaused returns (bool) {
+
+        try this.verifyDataReverting(_paymentData, _signature, _feeToken, _fee) {
+            revert("PaymentSettlement: verifyDataReverting did not revert");
+        } catch Error(string memory reason) {
+            // Check that the right error was thrown
+            if (keccak256(abi.encodePacked(reason)) != keccak256(abi.encodePacked("PaymentSettlement: verification complete"))) {
+                return(false);
+            }
+        } catch {
+           return (false);
+        }
+
+        return(true);
+    }
+
+    // This function is used to verify the data and revert the transaction
+    // This will always revert and is only meant to be called by verifyData
+    function verifyDataReverting(
+        PaymentData calldata _paymentData,
+        Signature calldata _signature,
+        address _feeToken,
+        uint256 _fee
+    ) external {
+        _settlePayment(_paymentData, _signature, _feeToken, _fee);
+        revert("PaymentSettlement: verification complete");
+    }
+
+
+    function verifySignature(
+        PaymentData calldata _paymentData,
+        Signature calldata _signature
+    ) external view returns (bool) {
+        bool result = _verifySignature(_paymentData, _signature);
+        return result;
+    }
+
+    function pause() external onlyOwner whenNotPaused {
+        _pause();
+    }
+
+    function unpause() external onlyOwner whenPaused {
+        _unpause();
+    }
+
+    function transferOwner(address _newOwner) external onlyOwner {
+        _transferOwnership(_newOwner);
+    }
+
+    // @dev Called by UniswapV3Pool after a swap
+    function uniswapV3SwapCallback(
+        int256 amount0Delta,
+        int256 amount1Delta,
+        bytes memory data
+    ) external checkCallback {
+        (address paymentToken) = abi.decode(data, (address));
+        uint256  amountToRepay = amount1Delta > 0 ? uint256(amount1Delta) : uint256(amount0Delta);
+        IERC20(paymentToken).safeTransfer(msg.sender, amountToRepay);
+    }
+
+    // ====== INTERNAL FUNCTIONS ======
+
+    function _settlePayment(
+        PaymentData calldata _paymentData,
+        Signature calldata _signature,
+        address _feeToken,
+        uint256 _fee
+    ) internal {
+
+        require(_verifySignature(_paymentData, _signature), "PaymentSettlement: invalid signature");
+
+        IERC20Permit(_paymentData.token).permit(
+            _paymentData.from,
+            address(this),
+            _paymentData.amount,
+            _paymentData.permitData.deadline,
+            _paymentData.permitData.signature.v,
+            _paymentData.permitData.signature.r,
+            _paymentData.permitData.signature.s
+        );
+
+        IERC20(_paymentData.token).safeTransferFrom(
+            _paymentData.from,
+            address(this),
+            _paymentData.amount
+        );
+
+        _obtainFeeToken(_paymentData.token, _paymentData.amount, _feeToken, _fee);
+        _transferRelayFee();
+
+        SafeERC20.safeTransfer(
+            IERC20(_paymentData.token),
+            _paymentData.to,
+            IERC20(_paymentData.token).balanceOf(address(this))
+        );
+
+        emit Payment(
+            _paymentData.token,
+            _paymentData.from,
+            _paymentData.to,
+            _paymentData.amount
+        );
+
+    }
+
+
+    function _obtainFeeToken(
+        address _paymentToken,
+        uint256 _paymentAmount,
+        address _feeToken,
+        uint256 _fee
+    ) internal {
+        if(_feeToken == _paymentToken) {
+            return;
+        }
+
+        bool isFeeTokenETH = _feeToken == ETH;
+        if(isFeeTokenETH) {
+            _feeToken = address(weth);
+        }
+
+        IUniV3Pool uniV3Pool = _getUniV3Pool();
+        IERC20(_paymentToken).approve(address(uniV3Pool), _paymentAmount);
+
+        bool zeroForOne = uniV3Pool.token0() == _paymentToken;
+        int256 amountSpecified = -int256(_fee);
+        uint160 sqrtPriceLimitX96 = 0;
+        allowedCallback = address(uniV3Pool);
+        uniV3Pool.swap(
+            address(this),
+            zeroForOne,
+            amountSpecified,
+            zeroForOne ? MIN_SQRT_RATIO + 1 : MAX_SQRT_RATIO - 1,
+            abi.encode(_paymentToken)
+        );
+
+        if(isFeeTokenETH) {
+            weth.withdraw(_fee);
+        }
+    }
+
+    function _verifySignature(
+        PaymentData calldata _paymentData,
+        Signature calldata _signature
+    ) internal view  returns(bool) {
+        uint256 userNonce = IERC20Permit(_paymentData.token).nonces(_paymentData.from);
+
+        bytes32 paymentStructHash = keccak256(abi.encode(
+            PAY_TYPEHASH,
+            _paymentData.to,
+            userNonce
+        ));
+        bytes32 hash = _hashTypedDataV4(paymentStructHash);
+        address signer = ECDSA.recover(hash, _signature.v, _signature.r, _signature.s);
+        bool result = signer == _paymentData.from;
+        return(result);
+    }
+
+    function _getUniV3Pool() internal virtual view returns(IUniV3Pool) {
+        return(uniV3Pool);
+    }
+
+    receive() external payable {
+        require(msg.sender == address(weth), "PaymentSettlement: invalid msg.sender");
+    }
+
+}

contracts/contracts/interfaces/IERC20Complete.sol

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+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.17;
+
+import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import {IERC20Permit} from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Permit.sol";
+
+interface IERC20Complete is IERC20, IERC20Permit {
+    function decimals() external view returns (uint8);
+    function name() external view returns (string memory);
+}