feat: Add delegation for iCake

contracts/ICakeV3.sol

@@ -5,6 +5,7 @@ pragma experimental ABIEncoderV2;
 import "@openzeppelin-4.5.0/contracts/access/Ownable.sol";
 import "@openzeppelin-4.5.0/contracts/utils/math/SafeMath.sol";
 import "@openzeppelin-4.5.0/contracts/token/ERC20/utils/SafeERC20.sol";
+import "@openzeppelin-4.5.0/contracts/security/ReentrancyGuard.sol";
 
 interface IVeCake {
     function getUserInfo(address _user) external view returns (
@@ -29,7 +30,7 @@ interface IIFOInitializable {
     function endTimestamp() external view returns (uint256);
 }
 
-contract ICakeV3 is Ownable {
+contract ICakeV3 is Ownable, ReentrancyGuard {
     using SafeMath for uint256;
 
     address public admin;
@@ -43,8 +44,25 @@ contract ICakeV3 is Ownable {
 
     uint256 public constant MIN_CEILING_DURATION = 1 weeks;
 
+    /// @notice VECake delegator address in ICakeV3.
+    /// @dev User can delegate VECake to another address for boosted in ICakeV3.
+    /// Mapping from VECake account to ICakeV3 delegator account.
+    mapping(address => address) public delegator;
+
+    /// @notice The ICakeV3 account which was delegated by VECake account.
+    /// Mapping from ICakeV3 delegator account to VECake account.
+    mapping(address => address) public delegated;
+
+    /// @notice Gives permission to VECake account.
+    /// @dev Avoid malicious attacks.
+    /// The approval is cleared when the delegator was setted.
+    /// Mapping from MasterChef V3 delegator account to VECake account.
+    mapping(address => address) public delegatorApprove;
+
     event UpdateRatio(uint256 newRatio);
     event UpdateIfoDeployerAddress(address indexed newAddress);
+    event UpdateDelegator(address indexed user, address indexed oldDelegator, address indexed delegator);
+    event Approve(address indexed delegator, address indexed VECakeUser);
 
     /**
      * @notice Constructor
@@ -58,6 +76,85 @@ contract ICakeV3 is Ownable {
         ratio = 1000;
     }
 
+    struct DelegatorConfig {
+        address VECakeUser;
+        address delegator;
+    }
+
+    /// @notice set VECake delegators.
+    /// @dev In case VECake partner contract can not upgrade, owner can set delegator.
+    /// The delegator address can not have any position in ICakeV3.
+    /// The old delegator address can not have any position in ICakeV3.
+    /// @param _delegatorConfigs VECake delegator config.
+    function setDelegators(DelegatorConfig[] calldata _delegatorConfigs) external onlyOwner {
+        for (uint256 i = 0; i < _delegatorConfigs.length; i++) {
+            DelegatorConfig memory delegatorConfig = _delegatorConfigs[i];
+            require(
+                delegatorConfig.VECakeUser != address(0) && delegatorConfig.delegator != address(0),
+                "Invalid address"
+            );
+            // The delegator need to approve VECake contract.
+            require(delegatorApprove[delegatorConfig.delegator] == delegatorConfig.VECakeUser, "Not approved");
+
+            address oldDelegator = delegatorConfig.VECakeUser;
+            if (delegator[delegatorConfig.VECakeUser] != address(0)) {
+                oldDelegator = delegator[delegatorConfig.VECakeUser];
+            }
+            // clear old delegated information
+            delegated[oldDelegator] = address(0);
+
+            delegator[delegatorConfig.VECakeUser] = delegatorConfig.delegator;
+            delegated[delegatorConfig.delegator] = delegatorConfig.VECakeUser;
+            delegatorApprove[delegatorConfig.delegator] = address(0);
+            emit UpdateDelegator(delegatorConfig.VECakeUser, oldDelegator, delegatorConfig.delegator);
+        }
+    }
+
+    /// @notice Gives permission to VECake account.
+    /// @dev Only a single account can be approved at a time, so approving the zero address clears previous approvals.
+    /// The approval is cleared when the delegator is set.
+    /// @param _VECakeUser VECake account address.
+    function approveToVECakeUser(address _VECakeUser) external nonReentrant {
+        require(delegated[msg.sender] == address(0), "Delegator already has VECake account");
+
+        delegatorApprove[msg.sender] = _VECakeUser;
+        emit Approve(msg.sender, _VECakeUser);
+    }
+
+    /// @notice set VECake delegator address for ICakeV3.
+    /// @dev The delegator address can not have any position in ICakeV3.
+    /// The old delegator address can not have any position in ICakeV3.
+    /// @param _delegator MasterChef V3 delegator address.
+    function setDelegator(address _delegator) external nonReentrant {
+        require(_delegator != address(0), "Invalid address");
+        // The delegator need to approve VECake contract.
+        require(delegatorApprove[_delegator] == msg.sender, "Not approved");
+
+        address oldDelegator = msg.sender;
+        if (delegator[msg.sender] != address(0)) {
+            oldDelegator = delegator[msg.sender];
+        }
+        // clear old delegated information
+        delegated[oldDelegator] = address(0);
+
+        delegator[msg.sender] = _delegator;
+        delegated[_delegator] = msg.sender;
+        delegatorApprove[_delegator] = address(0);
+
+        emit UpdateDelegator(msg.sender, oldDelegator, _delegator);
+    }
+
+    /// @notice Remove VECake delegator address for ICakeV3.
+    /// @dev The old delegator address can not have any position in ICakeV3.
+    function removeDelegator() external nonReentrant {
+        address oldDelegator = delegator[msg.sender];
+        require(oldDelegator != address(0), "No delegator");
+
+        delegated[oldDelegator] = address(0);
+        delegator[msg.sender] = address(0);
+        emit UpdateDelegator(msg.sender, oldDelegator, address(0));
+    }
+
     /**
      * @notice calculate iCake credit per user.
      * @param _user: user address.
@@ -150,12 +247,23 @@ contract ICakeV3 is Ownable {
      * @param _endTime timestamp to calculate user's veCake amount
      */
     function _sumUserCredit(address _user, uint256 _endTime) internal view returns (uint256) {
+        // If this user has delegator , but the delegator is not the same user in MasterChef V3, use default boost factor.
+        if (delegator[_user] != address(0) && delegator[_user] != _user) {
+            return 0;
+        }
+
+        // If ICakeV3 user has delegated VECake account, use delegated VECake account balance to calculate boost factor.
+        address VEcakeUser = _user;
+        if (delegated[_user] != address(0)) {
+            VEcakeUser = delegated[_user];
+        }
+
         // get native
-        uint256 veNative = IVeCake(veCakeAddress).balanceOfAtTime(_user, _endTime);
+        uint256 veNative = IVeCake(veCakeAddress).balanceOfAtTime(VEcakeUser, _endTime);
 
         // get proxy/migrated
         uint256 veMigrate = 0;
-        ( , ,address cakePoolProxy, , , , , )  = IVeCake(veCakeAddress).getUserInfo(_user);
+        ( , ,address cakePoolProxy, , , , , )  = IVeCake(veCakeAddress).getUserInfo(VEcakeUser);
         if (cakePoolProxy != address(0)) {
             veMigrate = IVeCake(veCakeAddress).balanceOfAtTime(cakePoolProxy, _endTime);
         }