feat: add operator receiver functionality to BlockRewardController

This commit adds the ability for operators to designate a receiver address for their base BGT rewards. The functionality is implemented directly in BlockRewardController to avoid requiring hard fork changes to BeaconDeposit.

Author: ZERGUCCI

src/pol/interfaces/IBlockRewardController.sol

@@ -53,6 +53,18 @@ interface IBlockRewardController is IPOLErrors {
     /// @param rewardRate The amount of BGT minted to the distributor.
     event BlockRewardProcessed(bytes indexed pubkey, uint64 nextTimestamp, uint256 baseRate, uint256 rewardRate);
 
+    /// @notice Emitted when base BGT is minted to either the operator or their receiver
+    /// @param operator The operator address that earned the base rewards
+    /// @param receiver The address that received the base rewards (operator or their set receiver)
+    /// @param amount The amount of base BGT minted
+    event BaseMinted(address indexed operator, address indexed receiver, uint256 indexed amount);
+
+    /// @notice Emitted when an operator sets or changes their receiver address
+    /// @param operator The operator address that changed their receiver
+    /// @param oldReceiver The previous receiver address (zero if first time setting)
+    /// @param newReceiver The new receiver address (zero if clearing receiver)
+    event OperatorReceiverUpdated(address indexed operator, address indexed oldReceiver, address indexed newReceiver);
+
     /// @notice Returns the constant base rate for BGT.
     /// @return The constant base amount of BGT to be minted in the current block.
     function baseRate() external view returns (uint256);
@@ -152,4 +164,11 @@ interface IBlockRewardController is IPOLErrors {
      * @param _distributor The new distributor contract.
      */
     function setDistributor(address _distributor) external;
+
+    /**
+     * @notice Sets or updates the receiver address for an operator's base BGT rewards
+     * @dev Only the operator can set their receiver
+     * @param receiver The address that will receive base BGT rewards. Set to address(0) to receive rewards directly
+     */
+    function setOperatorReceiver(address receiver) external;
 }

src/pol/rewards/BlockRewardController.sol

@@ -63,6 +63,9 @@ contract BlockRewardController is IBlockRewardController, OwnableUpgradeable, UU
     /// @notice The reward convexity param in the function, determines how fast it converges to its max, 18 dec.
     int256 public rewardConvexity;
 
+    /// @notice The mapping of operators to their receiver addresses for base rewards
+    mapping(address => address) public operatorReceivers;
+
     /// @custom:oz-upgrades-unsafe-allow constructor
     constructor() {
         _disableInitializers();
@@ -235,11 +238,34 @@ contract BlockRewardController is IBlockRewardController, OwnableUpgradeable, UU
         // Use the beaconDepositContract to fetch the operator, Its gauranteed to return a valid address.
         // Beacon Deposit contract will enforce validators to set an operator.
         address operator = beaconDepositContract.getOperator(pubkey);
-        if (base > 0) bgt.mint(operator, base);
-
+        
+        // Check if the operator has set a receiver for their base rewards
+        address receiver = operatorReceivers[operator];
+        // If no receiver is set (address(0)), mint to operator directly
+        if (base > 0) {
+            address mintTo = receiver == address(0) ? operator : receiver;
+            bgt.mint(mintTo, base);
+            emit BaseMinted(operator, mintTo, base);
+        }
+        
         // Mint the scaled rewards BGT for validator reward allocation to the distributor.
         if (reward > 0) bgt.mint(distributor, reward);
 
         return reward;
     }
+
+    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
+    /*                       OPERATOR RECEIVERS                   */
+    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/
+
+    /**
+     * @notice Sets or updates the receiver address for an operator's base BGT rewards
+     * @dev Only the operator can set their receiver
+     * @param receiver The address that will receive base BGT rewards. Set to address(0) to receive rewards directly
+     */
+    function setOperatorReceiver(address receiver) external {
+        address oldReceiver = operatorReceivers[msg.sender];
+        operatorReceivers[msg.sender] = receiver;
+        emit OperatorReceiverUpdated(msg.sender, oldReceiver, receiver);
+    }
 }

test/mock/pol/NoopBlockRewardController.sol

@@ -62,4 +62,7 @@ contract NoopBlockRewardController is IBlockRewardController {
 
     /// @inheritdoc IBlockRewardController
     function setDistributor(address _distributor) external { }
+
+    /// @inheritdoc IBlockRewardController
+    function setOperatorReceiver(address _receiver) external { }
 }

test/pol/BlockRewardController.t.sol

@@ -258,6 +258,102 @@ contract BlockRewardControllerTest is POLTest {
         assertApproxEqAbs(reward, expected, maxDelta);
     }
 
+    /// @dev Should process rewards with operator receiver set
+    function test_ProcessRewardsWithReceiver() public {
+        test_SetDistributor();
+        test_SetBaseRate();
+        
+        address receiver = makeAddr("receiver");
+        // Set receiver for operator
+        vm.prank(operator);
+        blockRewardController.setOperatorReceiver(receiver);
+        
+        // Verify receiver is set correctly
+        assertEq(blockRewardController.operatorReceivers(operator), receiver);
+
+        // Process rewards - should mint base rewards to receiver instead of operator
+        vm.prank(address(distributor));
+        vm.expectEmit(true, true, true, true);
+        emit IBlockRewardController.BlockRewardProcessed(valData.pubkey, DISTRIBUTE_FOR_TIMESTAMP, 1 ether, 0);
+
+        // expect call to mint BGT to the receiver instead of operator
+        vm.expectCall(address(bgt), abi.encodeCall(IBGT.mint, (receiver, 1.0 ether)));
+        blockRewardController.processRewards(valData.pubkey, DISTRIBUTE_FOR_TIMESTAMP, true);
+    }
+
+    /// @dev Should process rewards with operator receiver cleared
+    function test_ProcessRewardsWithReceiverCleared() public {
+        test_SetDistributor();
+        test_SetBaseRate();
+        
+        address receiver = makeAddr("receiver");
+        // First set a receiver
+        vm.prank(operator);
+        blockRewardController.setOperatorReceiver(receiver);
+        
+        // Then clear it by setting to address(0)
+        vm.prank(operator);
+        blockRewardController.setOperatorReceiver(address(0));
+        
+        // Verify receiver is cleared
+        assertEq(blockRewardController.operatorReceivers(operator), address(0));
+
+        // Process rewards - should mint base rewards to operator since receiver is cleared
+        vm.prank(address(distributor));
+        vm.expectEmit(true, true, true, true);
+        emit IBlockRewardController.BlockRewardProcessed(valData.pubkey, DISTRIBUTE_FOR_TIMESTAMP, 1 ether, 0);
+
+        // expect call to mint BGT to the operator since receiver is cleared
+        vm.expectCall(address(bgt), abi.encodeCall(IBGT.mint, (operator, 1.0 ether)));
+        blockRewardController.processRewards(valData.pubkey, DISTRIBUTE_FOR_TIMESTAMP, true);
+    }
+
+    /// @dev Should process rewards with no receiver set (default case)
+    function test_ProcessRewardsWithNoReceiver() public {
+        test_SetDistributor();
+        test_SetBaseRate();
+        
+        // Verify no receiver is set
+        assertEq(blockRewardController.operatorReceivers(operator), address(0));
+
+        // Process rewards - should mint base rewards to operator since no receiver set
+        vm.prank(address(distributor));
+        vm.expectEmit(true, true, true, true);
+        emit IBlockRewardController.BlockRewardProcessed(valData.pubkey, DISTRIBUTE_FOR_TIMESTAMP, 1 ether, 0);
+
+        // expect call to mint BGT to the operator since no receiver set
+        vm.expectCall(address(bgt), abi.encodeCall(IBGT.mint, (operator, 1.0 ether)));
+        blockRewardController.processRewards(valData.pubkey, DISTRIBUTE_FOR_TIMESTAMP, true);
+    }
+
+    /// @dev Should process rewards correctly when multiple operators have different receiver settings
+    function test_ProcessRewardsMultipleOperators() public {
+        test_SetDistributor();
+        test_SetBaseRate();
+        
+        // Setup second operator with mock BeaconDeposit
+        address operator2 = makeAddr("operator2");
+        bytes memory pubkey2 = bytes("validator2");
+        BeaconDepositMock(beaconDepositContract).setOperator(pubkey2, operator2);
+        
+        // Setup receivers in BlockRewardController
+        address receiver1 = makeAddr("receiver1");
+        vm.prank(operator);
+        blockRewardController.setOperatorReceiver(receiver1);
+        
+        // Don't set receiver for operator2
+        
+        // Process rewards for first operator - should go to receiver1
+        vm.prank(address(distributor));
+        vm.expectCall(address(bgt), abi.encodeCall(IBGT.mint, (receiver1, 1.0 ether)));
+        blockRewardController.processRewards(valData.pubkey, DISTRIBUTE_FOR_TIMESTAMP, true);
+        
+        // Process rewards for second operator - should go to operator2 directly
+        vm.prank(address(distributor));
+        vm.expectCall(address(bgt), abi.encodeCall(IBGT.mint, (operator2, 1.0 ether)));
+        blockRewardController.processRewards(pubkey2, DISTRIBUTE_FOR_TIMESTAMP, true);
+    }
+
     /// @dev Should bound compute rewards correctly to its theoretical limits
     function testFuzz_ComputeRewards(
         uint256 boostPower,