add FXN Convex Escrow and test

Author: 0xtj24

src/escrows/FXNConvexEscrow.sol

@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.13;
+
+import "openzeppelin-contracts/contracts/token/ERC20/utils/SafeERC20.sol";
+
+interface IBooster {
+    function createVault(
+        uint256 _pid
+    ) external returns (address);
+}
+
+interface IVault {
+    function deposit(uint256 _amount) external;
+    function withdraw(uint256 _shares) external;
+    function stakingToken() external view returns (address);
+    function gaugeAddress() external view returns (address);
+    function getReward() external;
+}
+
+interface IGauge {
+    function getActiveRewardTokens() external view returns (address[] memory);
+}
+/**
+ * @notice Escrow contract implementation to stake Curve LP tokens in FXN Convex and claim FXN and other rewards
+ */
+
+contract FXNConvexEscrow {
+    using SafeERC20 for IERC20;
+
+    error AlreadyInitialized();
+    error OnlyMarket();
+    error OnlyBeneficiary();
+    error OnlyBeneficiaryOrAllowlist();
+
+    uint256 public immutable pid;
+
+    IBooster public immutable booster;
+    IERC20 public immutable fxn;
+
+    IERC20 public gauge;
+    IVault public vault;
+    address public market;
+    IERC20 public token;
+    address public beneficiary;
+
+    mapping(address => bool) public allowlist;
+
+    modifier onlyBeneficiary() {
+        if (msg.sender != beneficiary) revert OnlyBeneficiary();
+        _;
+    }
+
+    modifier onlyBeneficiaryOrAllowlist() {
+        if (msg.sender != beneficiary && !allowlist[msg.sender])
+            revert OnlyBeneficiaryOrAllowlist();
+        _;
+    }
+
+    event AllowClaim(address indexed allowedAddress, bool allowed);
+
+    constructor(
+        address _booster,
+        address _fxn,
+        uint256 _pid
+    ) {
+        booster = IBooster(_booster);
+        fxn = IERC20(_fxn);
+        pid = _pid;
+    }
+
+    /**
+    @notice Initialize escrow with a token
+    @dev Must be called right after proxy is created.
+    @param _token The IERC20 token representing LP token to be staked
+    @param _beneficiary The beneficiary who the token is staked on behalf
+    */
+    function initialize(IERC20 _token, address _beneficiary) public {
+        if (market != address(0)) revert AlreadyInitialized();
+        market = msg.sender;
+        token = _token;
+        beneficiary = _beneficiary;
+        vault = IVault(booster.createVault(pid));
+        token.approve(address(vault), type(uint).max);
+        require(token == IERC20(vault.stakingToken()), "Wrong token");
+        gauge = IERC20(vault.gaugeAddress()); // receipt token that goes into the vault
+    }
+
+    /**
+    @notice Withdraws the receipt token from the vault and transfers the associated ERC20 token to a recipient.
+    @dev Will first try to pay from the escrow balance, if not enough or any, will try to pay the missing amount withdrawing from the vault.
+    @param recipient The address to receive payment from the escrow
+    @param amount The amount of ERC20 token to be transferred.
+    */
+    function pay(address recipient, uint amount) public {
+        if (msg.sender != market) revert OnlyMarket();
+        uint256 tokenBal = token.balanceOf(address(this));
+
+        if (tokenBal >= amount) {
+            token.safeTransfer(recipient, amount);
+            return;
+        }
+
+        
+        uint256 gaugeBalance = gauge.balanceOf(address(vault));
+        if (gaugeBalance > 0) {
+            uint256 missingAmount = amount - tokenBal;
+            uint256 withdrawAmount = gaugeBalance > missingAmount
+                ? missingAmount
+                : gaugeBalance;
+            
+            vault.withdraw(withdrawAmount);
+        }
+
+        token.safeTransfer(recipient, amount);
+    }
+
+    /**
+    @notice Get the token balance of the escrow
+    @return Uint representing the token balance of the escrow
+    */
+    function balance() public view returns (uint256) {
+        return
+            gauge.balanceOf(address(vault)) +
+            token.balanceOf(address(this));
+    }
+
+    /**
+    @notice Function called by market on deposit. Stakes deposited collateral into FXN Convex gauge via vault
+    @dev This function should remain callable by anyone to handle direct inbound transfers.
+    */
+    function onDeposit() public {
+        uint256 tokenBal = token.balanceOf(address(this));
+        if (tokenBal == 0) return;
+        vault.deposit(tokenBal);
+    }
+
+    /**
+    @notice Claims reward tokens to the specified address. Only callable by beneficiary and allowlisted addresses
+    @param to Address to send claimed rewards to
+    */
+    function claimTo(address to) public onlyBeneficiaryOrAllowlist {
+        //Claim rewards
+        vault.getReward();
+        //Send fxn balance
+        uint256 fxnBal = fxn.balanceOf(address(this));
+        if (fxnBal != 0) fxn.safeTransfer(to, fxnBal);
+
+        //Send contract balance of extra rewards (including CRV and CVX)
+        IGauge fxnGauge = IGauge(address(gauge));
+        address[] memory extraRewards = fxnGauge.getActiveRewardTokens();
+        if (extraRewards.length == 0) return;
+        for (uint256 i; i < extraRewards.length; ++i) {
+            // Avoid sending collateral token if it is added as a reward
+            if (extraRewards[i] == address(token)) continue;
+            uint256 rewardBal = IERC20(extraRewards[i]).balanceOf(address(this));
+            if (rewardBal > 0) {
+                //Use safe transfer in case bad reward token is added
+                IERC20(extraRewards[i]).safeTransfer(to, rewardBal);
+            }
+        }
+    }
+    
+
+    /**
+    @notice Claims reward tokens to the message sender. Only callable by beneficiary
+    */
+    function claim() external onlyBeneficiary {
+        claimTo(msg.sender);
+    }
+
+    /**
+    @notice Allow address to claim on behalf of the beneficiary to any address
+    @param allowee Address that are allowed to claim on behalf of the beneficiary
+    @dev Can only be called by the beneficiary
+    */
+    function allowClaimOnBehalf(address allowee) external onlyBeneficiary {
+        allowlist[allowee] = true;
+        emit AllowClaim(allowee, true);
+    }
+
+    /**
+    @notice Disallow address to claim on behalf of the beneficiary to any address
+    @param allowee Address that are disallowed to claim on behalf of the beneficiary
+    */
+    function disallowClaimOnBehalf(address allowee) external onlyBeneficiary {
+        allowlist[allowee] = false;
+        emit AllowClaim(allowee, false);
+    }
+}