Feat/claim st rewards (#482)

* Claim strewards and tests (#481)

* chore: remove beneficiary and minor improvements

* test: add modifier tests

* chore: reformat comment

* chore: reorder stTokenStaked increase

---------

Co-authored-by: addiaddiaddi <34423634+addiaddiaddi@users.noreply.github.com>

contracts/interfaces/IAddressHolder.sol

@@ -38,5 +38,7 @@ interface IAddressHolder {
 
     function getUnstakingAddresses() external view returns (address, address);
 
+    function getStFlip() external view returns (address);
+
     function getGovernor() external view returns (address);
 }

contracts/interfaces/ITokenVestingStaking.sol

@@ -23,6 +23,8 @@ interface ITokenVestingStaking {
 
     function unstakeFromStProvider(uint256 amount) external returns (uint256);
 
+    function claimStProviderRewards(uint256 amount_) external;
+
     function release(IERC20 token) external;
 
     function revoke(IERC20 token) external;

contracts/mocks/MockStProvider.sol

@@ -96,4 +96,8 @@ contract stFLIP is ERC20 {
         emit Burn(msg.sender, value, refundee);
         _burn(msg.sender, value);
     }
+
+    function mockSlash(address account, uint256 amount) public {
+        _burn(account, amount);
+    }
 }

contracts/utils/AddressHolder.sol

@@ -88,6 +88,10 @@ contract AddressHolder is IAddressHolder, Shared {
         return (stBurner, stFLIP);
     }
 
+    function getStFlip() external view override returns (address) {
+        return stFLIP;
+    }
+
     /// @dev    Getter function for the governor address
     function getGovernor() external view override returns (address) {
         return governor;

contracts/utils/TokenVestingStaking.sol

@@ -46,6 +46,12 @@ contract TokenVestingStaking is ITokenVestingStaking, Shared {
 
     bool public revoked;
 
+    // Cumulative counter for amount staked to the st provider
+    uint256 public stTokenStaked;
+
+    // Cumulative counter for amount unstaked from the st provider
+    uint256 public stTokenUnstaked;
+
     /**
      * @param beneficiary_ address of the beneficiary to whom vested tokens are transferred
      * @param revoker_   the person with the power to revoke the vesting. Address(0) means it is not revocable.
@@ -100,6 +106,9 @@ contract TokenVestingStaking is ITokenVestingStaking, Shared {
         address stMinter = addressHolder.getStakingAddress();
 
         FLIP.approve(stMinter, amount);
+
+        stTokenStaked += amount;
+
         require(IMinter(stMinter).mint(address(this), amount));
     }
 
@@ -111,9 +120,27 @@ contract TokenVestingStaking is ITokenVestingStaking, Shared {
         (address stBurner, address stFlip) = addressHolder.getUnstakingAddresses();
 
         IERC20(stFlip).approve(stBurner, amount);
+
+        stTokenUnstaked += amount;
+
         return IBurner(stBurner).burn(address(this), amount);
     }
 
+    /**
+     * @notice Claims the liquid staking provider rewards.
+     * @param amount_ the amount of rewards to claim. If greater than `totalRewards`, then all rewards are claimed.
+     * @dev `stTokenCounter` updates after staking/unstaking operation to keep track of the st token principle. Any
+     *       amount above the principle is considered rewards and thus can be claimed by the beneficiary.
+     */
+    function claimStProviderRewards(uint256 amount_) external override onlyBeneficiary notRevoked {
+        address stFlip = addressHolder.getStFlip();
+        uint256 totalRewards = stFLIP(stFlip).balanceOf(address(this)) + stTokenUnstaked - stTokenStaked;
+
+        uint256 amount = amount_ > totalRewards ? totalRewards : amount_;
+
+        stFLIP(stFlip).transfer(beneficiary, amount);
+    }
+
     /**
      * @notice Transfers vested tokens to beneficiary.
      * @param token ERC20 token which is being vested.
@@ -128,9 +155,9 @@ contract TokenVestingStaking is ITokenVestingStaking, Shared {
     }
 
     /**
-     * @notice Allows the revoker to revoke the vesting and stop the beneficiary from releasing
-     * any tokens if the vesting period has not bene completed. Any staked tokens at the time of
-     * revoking can be retrieved by the revoker upon unstaking via `retrieveRevokedFunds`.
+     * @notice Allows the revoker to revoke the vesting and stop the beneficiary from releasing any
+     *         tokens if the vesting period has not bene completed. Any staked tokens at the time of
+     *         revoking can be retrieved by the revoker upon unstaking via `retrieveRevokedFunds`.
      * @param token ERC20 token which is being vested.
      */
     function revoke(IERC20 token) external override onlyRevoker notRevoked {

tests/token_vesting/stakeStProvider/test_stProvider.py

@@ -18,15 +18,17 @@ def test_stakeToStProvider(addrs, tokenVestingStaking, cf, mockStProvider):
     assert stFLIP.balanceOf(staking_address) == 0
 
 
-def test_stake_unstake_rev_sender(addrs, tokenVestingStaking):
+def test_rev_sender(addrs, tokenVestingStaking):
     tv, _, total = tokenVestingStaking
     with reverts(REV_MSG_NOT_BENEFICIARY):
         tv.stakeToStProvider(total, {"from": addrs.DEPLOYER})
     with reverts(REV_MSG_NOT_BENEFICIARY):
         tv.unstakeFromStProvider(0, {"from": addrs.DEPLOYER})
+    with reverts(REV_MSG_NOT_BENEFICIARY):
+        tv.claimStProviderRewards(0, {"from": addrs.DEPLOYER})
 
 
-def test_stake_unstake_rev_amount(addrs, tokenVestingStaking):
+def test_rev_amount(addrs, tokenVestingStaking):
     tv, _, total = tokenVestingStaking
     with reverts(REV_MSG_ERC20_EXCEED_BAL):
         tv.stakeToStProvider(total + 1, {"from": addrs.BENEFICIARY})
@@ -53,6 +55,16 @@ def test_unstake_rev_revoked(addrs, tokenVestingStaking, mockStProvider):
         tv.unstakeFromStProvider(1, {"from": addrs.BENEFICIARY})
 
 
+def test_claim_rev_revoked(addrs, tokenVestingStaking, mockStProvider):
+    tv, _, _ = tokenVestingStaking
+    stFLIP, _, _, _ = mockStProvider
+
+    tv.revoke(stFLIP, {"from": addrs.REVOKER})
+
+    with reverts(REV_MSG_TOKEN_REVOKED):
+        tv.claimStProviderRewards(1, {"from": addrs.BENEFICIARY})
+
+
 def test_unstakeFromStProvider(addrs, tokenVestingStaking, cf, mockStProvider):
     tv, _, total = tokenVestingStaking
     stFLIP, _, burner, staking_address = mockStProvider
@@ -73,3 +85,138 @@ def test_unstakeFromStProvider(addrs, tokenVestingStaking, cf, mockStProvider):
     assert stFLIP.balanceOf(tv) == 0
     assert cf.flip.balanceOf(staking_address) == 0
     assert stFLIP.balanceOf(staking_address) == 0
+
+
+## Claim rewards flow possibilities
+## 1. increment stake (staked 100, unstaked 0, balance 100)
+## 2. earn rewards    (staked 100, unstaked 0, balance 103)
+## 3. claim rewards   (staked 100, unstaked 0, balance 100) 103 + 0 - 100 = 3
+## 4. receive 3 stflip
+##
+## 1. stake            (staked 100, unstaked 0, balance 100)
+## 2. earn rewards     (staked 100, unstaked 0, balance 103)
+## 3. unstake all      (staked 100, unstaked 103, balance 0)
+## 4. claim underflows (staked 100, unstaked 103, balance 0) 0 + 103 - 100 = 3
+## 5. Need to have stflip to claim
+## 1. stake            (staked 100, unstaked 0, balance 100)
+## 2. get slashed      (staked 100, unstaked 0, balance 95)
+## 3. unstake all      (staked 100, unstaked 0, balance 95)
+## 4. claim underflows (staked 100, unstaked 0, balance 95) 95 + 0 - 100 = -5
+## 5. must earn 5 stflip first before earning claimable rewards
+##
+## 1. stake            (staked 100, unstaked 0, balance 100)
+## 2. earn rewards     (staked 100, unstaked 0, balance 103)
+## 3. unstake half     (staked 50, unstaked 53, balance 50)
+## 4. claim rewards   (staked 50, unstaked 53, balance 50) 50 + 53 - 50 = 3
+## 5. Receive 3 stflip
+
+
+def test_stProviderClaimRewards(addrs, tokenVestingStaking, cf, mockStProvider):
+    tv, _, total = tokenVestingStaking
+    stFLIP, minter, _, _ = mockStProvider
+    reward_amount = 100 * 10**18
+
+    cf.flip.approve(minter, 2**256 - 1, {"from": addrs.DEPLOYER})
+    minter.mint(addrs.DEPLOYER, reward_amount, {"from": addrs.DEPLOYER})
+
+    assert cf.flip.balanceOf(tv) == total
+    assert stFLIP.balanceOf(tv) == 0
+    assert tv.stTokenStaked() == 0
+    assert tv.stTokenUnstaked() == 0
+
+    tv.stakeToStProvider(total, {"from": addrs.BENEFICIARY})
+
+    assert cf.flip.balanceOf(tv) == 0
+    assert stFLIP.balanceOf(tv) == total
+    assert tv.stTokenStaked() == total
+    assert tv.stTokenUnstaked() == 0
+
+    stFLIP.transfer(tv, reward_amount, {"from": addrs.DEPLOYER})  # earn rewards
+
+    assert cf.flip.balanceOf(tv) == 0
+    assert stFLIP.balanceOf(tv) == total + reward_amount
+    assert tv.stTokenStaked() == total
+    assert tv.stTokenUnstaked() == 0
+
+    tv.claimStProviderRewards(reward_amount, {"from": addrs.BENEFICIARY})
+
+    assert cf.flip.balanceOf(tv) == 0
+    assert stFLIP.balanceOf(tv) == total
+    assert tv.stTokenStaked() == total
+    assert tv.stTokenUnstaked() == 0
+    assert stFLIP.balanceOf(addrs.BENEFICIARY) == reward_amount
+
+
+def test_stProviderClaimRewardsInsufficientStflip(
+    addrs, tokenVestingStaking, cf, mockStProvider
+):
+    tv, _, total = tokenVestingStaking
+    stFLIP, minter, _, _ = mockStProvider
+    reward_amount = 100 * 10**18
+
+    cf.flip.approve(minter, 2**256 - 1, {"from": addrs.DEPLOYER})
+    minter.mint(addrs.DEPLOYER, reward_amount, {"from": addrs.DEPLOYER})
+
+    assert cf.flip.balanceOf(tv) == total
+    assert stFLIP.balanceOf(tv) == 0
+    assert tv.stTokenStaked() == 0
+    assert tv.stTokenUnstaked() == 0
+
+    tv.stakeToStProvider(total, {"from": addrs.BENEFICIARY})
+
+    assert cf.flip.balanceOf(tv) == 0
+    assert stFLIP.balanceOf(tv) == total
+    assert tv.stTokenStaked() == total
+    assert tv.stTokenUnstaked() == 0
+
+    stFLIP.transfer(tv, reward_amount, {"from": addrs.DEPLOYER})  # earn rewards
+
+    assert cf.flip.balanceOf(tv) == 0
+    assert stFLIP.balanceOf(tv) == total + reward_amount
+    assert tv.stTokenStaked() == total
+    assert tv.stTokenUnstaked() == 0
+
+    tv.unstakeFromStProvider(total + reward_amount, {"from": addrs.BENEFICIARY})
+
+    assert cf.flip.balanceOf(tv) == 0
+    assert stFLIP.balanceOf(tv) == 0
+    assert tv.stTokenStaked() == total
+    assert tv.stTokenUnstaked() == total + reward_amount
+
+    with reverts(REV_MSG_ERC20_EXCEED_BAL):
+        tv.claimStProviderRewards(reward_amount, {"from": addrs.BENEFICIARY})
+
+
+def test_stProviderClaimRewardsSlash(addrs, tokenVestingStaking, cf, mockStProvider):
+    tv, _, total = tokenVestingStaking
+    stFLIP, _, _, _ = mockStProvider
+    slash_amount = 100 * 10**18
+
+    assert cf.flip.balanceOf(tv) == total
+    assert stFLIP.balanceOf(tv) == 0
+    assert tv.stTokenStaked() == 0
+    assert tv.stTokenUnstaked() == 0
+
+    tv.stakeToStProvider(total, {"from": addrs.BENEFICIARY})
+
+    assert cf.flip.balanceOf(tv) == 0
+    assert stFLIP.balanceOf(tv) == total
+    assert tv.stTokenStaked() == total
+    assert tv.stTokenUnstaked() == 0
+
+    stFLIP.mockSlash(tv, slash_amount, {"from": addrs.DEPLOYER})
+
+    assert cf.flip.balanceOf(tv) == 0
+    assert stFLIP.balanceOf(tv) == total - slash_amount
+    assert tv.stTokenStaked() == total
+    assert tv.stTokenUnstaked() == 0
+
+    tv.unstakeFromStProvider(total - slash_amount, {"from": addrs.BENEFICIARY})
+
+    assert cf.flip.balanceOf(tv) == 0
+    assert stFLIP.balanceOf(tv) == 0
+    assert tv.stTokenStaked() == total
+    assert tv.stTokenUnstaked() == total - slash_amount
+
+    with reverts(REV_MSG_INTEGER_OVERFLOW):
+        tv.claimStProviderRewards(2**256 - 1, {"from": addrs.BENEFICIARY})