feat: Add client take rate

README.md

@@ -18,14 +18,19 @@ The following outlines principles for core protocol funcitonality.
 
 Logic:
 
--   All caught up!🙂
+-   Move PositionAdmin to services, rename
+-   [ ] Consider changing short() to add()
+-   [ ] Emit event when a position is created (get clear on whether or not an implicit event is emitted when creating a contract)
 
 Tests:
 
--   [x] Separate integration tests from unit tests (separate PR)
--   [x] Move all utils to test/common/
+-   [ ] Invariant: the clientTakeRate + userTakeRate = clientRate
+-   [ ] Invariant: the totalTokenAmt - sum(clientFeesToken) = (1 - clientRate) \* totalTokenAmt
+-   [ ] Unit test setClientTakeRate()
+-   [ ] Unit test getUserSavings()
+-   [ ] Unit test FeeLib via Test Harness
+-   [ ] Account for userSavings in all affected FeeCollector unit and integration tests
 
 Considerations:
 
--   [ ] Consider emitting Position events through another contract
--   [ ] Consider adding a function to short with signatures, via `ERCRecover`.
+-   None at the moment🙂

src/FeeCollector.sol

@@ -15,6 +15,7 @@ contract FeeCollector is Ownable {
 
     // Storage
     uint256 public clientRate;
+    mapping(address => uint256) public clientTakeRates;
     mapping(address => uint256) public totalClientBalances;
     mapping(address => mapping(address => uint256)) public balances;
 
@@ -28,7 +29,7 @@ contract FeeCollector is Ownable {
 
     /**
      * @notice Collects fees from Position contracts when collateral is added.
-     * @param _client The address, controlled by client operators, for receiving protocol fees.
+     * @param _client The address where a client operator will receive protocols fees.
      * @param _token The token to collect fees in (the collateral token of the calling Position contract).
      * @param _amt The total amount of fees to collect.
      */
@@ -59,6 +60,39 @@ contract FeeCollector is Ownable {
         SafeTransferLib.safeTransfer(ERC20(_token), msg.sender, withdrawAmt);
     }
 
+    /**
+     * @notice Allows clients to set the percentage of the clientRate they will receive each revenue-generating tx.
+     *         Amounts less than 100 will give the calling client's users a protocol fee discount:
+     *         clientTakeRateOfProtocolFee = clientRate * _clientTakeRate
+     *              ex: _clientTakeRate = 50% -> clientTakeRate = clientRate * 0.5
+     *         userTakeRateOfProtocolFee =  clientRate * (1 - _clientTakeRate)
+     *              ex: _clientTakeRate = 50% -> userTakeRate = clientRate * (1 - 0.5)
+     *         clientFee = protocolFee * clientTakeRateOfProtocolFee
+     *         userSavings = protocolFee * userTakeRateOfProtocolFee
+     * @param _clientTakeRate The percentage of the clientRate the client will receive each revenue-generating tx (100 = 100%).
+     */
+    function setClientTakeRate(uint256 _clientTakeRate) public payable {
+        if (_clientTakeRate > 100) revert OutOfRange();
+        clientTakeRates[msg.sender] = _clientTakeRate;
+    }
+
+    /**
+     * @notice Returns the amount discounted from the protocol fee by using the provided client.
+     * @param _client The address where a client operator will receive protocols fees.
+     * @param _maxFee The maximum amount of fees the protocol will collect.
+     */
+    function getUserSavings(address _client, uint256 _maxFee) public view returns (uint256 userSavings) {
+        uint256 userTakeRate = 100 - clientTakeRates[_client];
+        uint256 userPercentOfProtocolFee = (userTakeRate * clientRate) / 100;
+        userSavings = (userPercentOfProtocolFee * _maxFee) / 100;
+    }
+
+    /* ****************************************************************************
+    **
+    **  Admin Functions
+    **
+    ******************************************************************************/
+
     /**
      * @notice Allows owner to set client rate.
      * @param _clientRate The percentage of total transaction-specific protocol fee, allocated to the utilized client.

src/Position.sol

@@ -5,18 +5,14 @@ pragma solidity ^0.8.21;
 import { DebtService } from "src/services/DebtService.sol";
 import { SwapService } from "src/services/SwapService.sol";
 import { SafeTransferLib, ERC20 } from "solmate/utils/SafeTransferLib.sol";
+import { FeeLib } from "src/libraries/FeeLib.sol";
 import { IERC20 } from "src/interfaces/token/IERC20.sol";
 import { IERC20Permit } from "src/interfaces/token/IERC20Permit.sol";
-import { IFeeCollector } from "src/interfaces/IFeeCollector.sol";
 
 /// @title Position
 /// @author Chain Rule, LLC
 /// @notice Manages the owner's individual position
 contract Position is DebtService, SwapService {
-    // Constants: no SLOAD to save gas
-    uint256 public constant PROTOCOL_FEE = 3;
-    address public constant FEE_COLLECTOR = 0x7A7AbDb9E12F3a9845E2433958Eef8FB9C8489Ee;
-
     // Immutables: no SLOAD to save gas
     address public immutable B_TOKEN;
 
@@ -36,7 +32,7 @@ contract Position is DebtService, SwapService {
      * @param _ltv The desired loan-to-value ratio for this transaction-specific loan (ex: 75 is 75%).
      * @param _swapAmtOutMin The minimum amount of output tokens from swap for the tx to go through.
      * @param _poolFee The fee of the Uniswap pool.
-     * @param _client The address, controlled by client operators, for receiving protocol fees (use address(0) if no client).
+     * @param _client The address where a client operator will receive protocols fees. (use address(0) if no client).
      */
     function short(uint256 _cAmt, uint256 _ltv, uint256 _swapAmtOutMin, uint24 _poolFee, address _client)
         public
@@ -47,10 +43,7 @@ contract Position is DebtService, SwapService {
         SafeTransferLib.safeTransferFrom(ERC20(C_TOKEN), msg.sender, address(this), _cAmt);
 
         // 2. Take protocol fee
-        uint256 protocolFee = (_cAmt * PROTOCOL_FEE) / 1000;
-        uint256 cAmtNet = _cAmt - protocolFee;
-        SafeTransferLib.safeApprove(ERC20(C_TOKEN), FEE_COLLECTOR, protocolFee);
-        IFeeCollector(FEE_COLLECTOR).collectFees(_client, C_TOKEN, protocolFee);
+        uint256 cAmtNet = FeeLib.takeProtocolFee(C_TOKEN, _cAmt, _client);
 
         // 3. Borrow debt token
         uint256 dAmt = _borrow(cAmtNet, _ltv);
@@ -68,7 +61,7 @@ contract Position is DebtService, SwapService {
      * @param _ltv The desired loan-to-value ratio for this transaction-specific loan (ex: 75 is 75%).
      * @param _swapAmtOutMin The minimum amount of output tokens from swap for the tx to go through.
      * @param _poolFee The fee of the Uniswap pool.
-     * @param _client The address, controlled by client operators, for receiving protocol fees (use address(0) if no client).
+     * @param _client The address where a client operator will receive protocols fees. (use address(0) if no client).
      * @param _deadline The deadline timestamp that the permit is valid.
      * @param _v The V parameter of ERC712 permit signature.
      * @param _r The R parameter of ERC712 permit signature.

src/interfaces/IFeeCollector.sol

@@ -35,7 +35,7 @@ interface IFeeCollector {
 
     /**
      * @notice Collects fees from Position contracts when collateral is added.
-     * @param _client The address, controlled by client operators, for receiving protocol fees.
+     * @param _client The address where a client operator will receive protocols fees.
      * @param _token The token to collect fees in (the collateral token of the calling Position contract).
      * @param _amt The total amount of fees to collect.
      */
@@ -46,6 +46,26 @@ interface IFeeCollector {
      */
     function clientWithdraw(address _token) external payable;
 
+    /**
+     * @notice Allows clients to set the percentage of the clientRate they will receive each revenue-generating tx.
+     *         Amounts less than 100 will give the calling client's users a protocol fee discount:
+     *         clientTakeRateOfProtocolFee = clientRate * _clientTakeRate
+     *              ex: _clientTakeRate = 50% -> clientTakeRate = clientRate * 0.5
+     *         userTakeRateOfProtocolFee =  clientRate * (1 - _clientTakeRate)
+     *              ex: _clientTakeRate = 50% -> userTakeRate = clientRate * (1 - 0.5)
+     *         clientFee = protocolFee * clientTakeRateOfProtocolFee
+     *         userSavings = protocolFee * userTakeRateOfProtocolFee
+     * @param _clientTakeRate The percentage of the clientRate the client will receive each revenue-generating tx (100 = 100%).
+     */
+    function setClientTakeRate(uint256 _clientTakeRate) external payable;
+
+    /**
+     * @notice Returns the amount discounted from the protocol fee by using the provided client.
+     * @param _client The address where a client operator will receive protocols fees.
+     * @param _protocolFee The maximum amount of fees the protocol will collect.
+     */
+    function getUserSavings(address _client, uint256 _protocolFee) external view returns (uint256 userSavings);
+
     /* ****************************************************************************
     **
     **  ADMIN FUNCTIONS

src/interfaces/IPosition.sol

@@ -36,7 +36,7 @@ interface IPosition {
      * @param _ltv The desired loan-to-value ratio for this transaction-specific loan (ex: 75 is 75%).
      * @param _swapAmtOutMin The minimum amount of output tokens from swap for the tx to go through.
      * @param _poolFee The fee of the Uniswap pool.
-     * @param _client The address, controlled by client operators, for receiving protocol fees (use address(0) if no client).
+     * @param _client The address where a client operator will receive protocols fees. (use address(0) if no client).
      */
     function short(uint256 _cAmt, uint256 _ltv, uint256 _swapAmtOutMin, uint24 _poolFee, address _client)
         external
@@ -48,7 +48,7 @@ interface IPosition {
      * @param _ltv The desired loan-to-value ratio for this transaction-specific loan (ex: 75 is 75%).
      * @param _swapAmtOutMin The minimum amount of output tokens from swap for the tx to go through.
      * @param _poolFee The fee of the Uniswap pool.
-     * @param _client The address, controlled by client operators, for receiving protocol fees (use address(0) if no client).
+     * @param _client The address where a client operator will receive protocols fees. (use address(0) if no client).
      * @param _deadline The deadline timestamp that the permit is valid.
      * @param _v The V parameter of ERC712 permit signature.
      * @param _r The R parameter of ERC712 permit signature.

src/interfaces/IPositionFactory.sol

@@ -23,7 +23,9 @@ interface IPositionFactory {
         returns (address);
 
     /**
-     * @notice Returns a list of contract addresses for the given owner.
+     * @notice Returns an indexed contract addresses from the list of contracts for the given owner.
+     *         Direct external calls to this mapping require an index to retrieve
+     *         a specific address. To get the full array, call getPositions().
      */
     function positionsLookup(address _owner) external view returns (address[] memory);
 

src/libraries/FeeLib.sol

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.21;
+
+import { SafeTransferLib, ERC20 } from "solmate/utils/SafeTransferLib.sol";
+import { IFeeCollector } from "src/interfaces/IFeeCollector.sol";
+
+/// @title FeeLib
+/// @author Chain Rule, LLC
+/// @notice Manages all protocol-fee-related interactions
+library FeeLib {
+    // Constants: no SLOAD to save gas
+    uint256 public constant PROTOCOL_FEE_RATE = 3;
+    address public constant FEE_COLLECTOR = 0x7A7AbDb9E12F3a9845E2433958Eef8FB9C8489Ee;
+
+    /**
+     * @notice Takes protocol fee from the amount of collateral supplied.
+     * @param _cAmt The amount of collateral to be supplied (units: C_DECIMALS).
+     * @param _client The address where a client operator will receive protocols fees.
+     * @return cAmtNet The resulting amount of collateral to be supplied after fees are taken.
+     */
+    function takeProtocolFee(address _token, uint256 _cAmt, address _client) internal returns (uint256 cAmtNet) {
+        uint256 maxFee = (_cAmt * PROTOCOL_FEE_RATE) / 1000;
+        uint256 userSavings = IFeeCollector(FEE_COLLECTOR).getUserSavings(_client, maxFee);
+        uint256 fee = maxFee - userSavings;
+        cAmtNet = _cAmt - fee;
+        SafeTransferLib.safeApprove(ERC20(_token), FEE_COLLECTOR, fee);
+        IFeeCollector(FEE_COLLECTOR).collectFees(_client, _token, fee);
+    }
+}

test/common/Constants.t.sol

@@ -23,7 +23,7 @@ uint256 constant PROFIT_PERCENT = 25;
 uint256 constant REPAY_PERCENT = 75;
 uint256 constant WITHDRAW_BUFFER = 100_000;
 uint256 constant REPAY_BUFFER = 2;
-uint256 constant PROTOCOL_FEE = 3;
+uint256 constant PROTOCOL_FEE_RATE = 3;
 uint256 constant CLIENT_RATE = 30;
 
 contract Assets {

test/integration/FeeCollector.short.t.sol

@@ -13,7 +13,7 @@ import {
     CONTRACT_DEPLOYER,
     FEE_COLLECTOR,
     TEST_CLIENT,
-    PROTOCOL_FEE,
+    PROTOCOL_FEE_RATE,
     CLIENT_RATE,
     USDC,
     WETH,
@@ -110,7 +110,7 @@ contract FeeCollectorShortTest is Test, TokenUtils {
             _cAmt = bound(_cAmt, assets.minCAmts(cToken), assets.maxCAmts(cToken));
 
             // Expectations
-            uint256 protocolFee = (_cAmt * PROTOCOL_FEE) / 1000;
+            uint256 protocolFee = (_cAmt * PROTOCOL_FEE_RATE) / 1000;
             uint256 clientFee = (protocolFee * CLIENT_RATE) / 100;
 
             // Fund positionOwner with _cAmt of cToken
@@ -153,7 +153,7 @@ contract FeeCollectorShortTest is Test, TokenUtils {
             _cAmt = bound(_cAmt, assets.minCAmts(cToken), assets.maxCAmts(cToken));
 
             // Expectations
-            uint256 protocolFee = (_cAmt * PROTOCOL_FEE) / 1000;
+            uint256 protocolFee = (_cAmt * PROTOCOL_FEE_RATE) / 1000;
 
             // Fund positionOwner with _cAmt of cToken
             _fund(positionOwner, cToken, _cAmt);