From 4d38d64e62627742c963e40d6787b51683b7a7dd Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Wed, 24 Mar 2021 17:02:36 +0100
Subject: [PATCH 01/14] Added snapshot of exchange rate + search + updated
 power calculation

---
 contracts/interfaces/IStakedTokenV3.sol |   2 +
 contracts/stake/StakedTokenV3.sol       | 134 +++++++++++++++++++++---
 2 files changed, 121 insertions(+), 15 deletions(-)

diff --git a/contracts/interfaces/IStakedTokenV3.sol b/contracts/interfaces/IStakedTokenV3.sol
index 9506a66..94c02f3 100644
--- a/contracts/interfaces/IStakedTokenV3.sol
+++ b/contracts/interfaces/IStakedTokenV3.sol
@@ -12,6 +12,8 @@ interface IStakedTokenV3 is IStakedToken {
 
   function slash(address destination, uint256 amount) external;
 
+  function donate(uint256 amount) external;
+
   function getMaxSlashablePercentage() external view returns (uint256);
 
   function setMaxSlashablePercentage(uint256 percentage) external;
diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index 742651b..b23b25a 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -44,6 +44,9 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
 
   address internal _claimHelper;
 
+  mapping(uint256 => Snapshot) internal _exchangeRateSnapshots;
+  uint256 internal _countExchangeRateSnapshots;
+
   modifier onlyAdmin {
     require(msg.sender == getAdmin(MAIN_ADMIN_ROLE), 'CALLER_NOT_MAIN_ADMIN');
     _;
@@ -69,6 +72,8 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
   event CooldownPauseChanged(bool pause);
   event MaxSlashablePercentageChanged(uint256 newPercentage);
   event Slashed(address indexed destination, uint256 amount);
+  event Donated(address indexed sender, uint256 amount);
+  event EchangeRateSnapshotted(uint128 blockNumber, uint128 exchangeRate);
   event CooldownPauseAdminChanged(address indexed newAdmin);
   event SlashingAdminChanged(address indexed newAdmin);
   event ClaimHelperChanged(address indexed newClaimHelper);
@@ -301,21 +306,6 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     _redeem(from, to, redeemAmount);
   }
 
-  /**
-   * @dev Calculates the exchange rate between the amount of STAKED_TOKEN and the the StakeToken total supply.
-   * Slashing will reduce the exchange rate. Supplying STAKED_TOKEN to the stake contract
-   * can replenish the slashed STAKED_TOKEN and bring the exchange rate back to 1
-   **/
-  function exchangeRate() public view override returns (uint256) {
-    uint256 currentSupply = totalSupply();
-
-    if (currentSupply == 0) {
-      return 1e18; //initial exchange rate is 1:1
-    }
-
-    return STAKED_TOKEN.balanceOf(address(this)).mul(1e18).div(currentSupply);
-  }
-
   /**
    * @dev Executes a slashing of the underlying of a certain amount, transferring the seized funds
    * to destination. Decreasing the amount of underlying will automatically adjust the exchange rate
@@ -330,10 +320,18 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     require(amount <= maxSlashable, 'INVALID_SLASHING_AMOUNT');
 
     STAKED_TOKEN.safeTransfer(destination, amount);
+    _snapshotExchangeRate();
 
     emit Slashed(destination, amount);
   }
 
+  function donate(uint256 amount) external override {
+    STAKED_TOKEN.safeTransferFrom(msg.sender, address(this), amount);
+    _snapshotExchangeRate();
+
+    emit Donated(msg.sender, amount);
+  }
+
   /**
    * @dev Set the address of the contract with priviledge, the ClaimHelper contract
    * It speicifically enables to claim from several contracts at once
@@ -364,6 +362,21 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     emit MaxSlashablePercentageChanged(percentage);
   }
 
+  /**
+   * @dev Calculates the exchange rate between the amount of STAKED_TOKEN and the the StakeToken total supply.
+   * Slashing will reduce the exchange rate. Supplying STAKED_TOKEN to the stake contract
+   * can replenish the slashed STAKED_TOKEN and bring the exchange rate back to 1
+   **/
+  function exchangeRate() public view override returns (uint256) {
+    uint256 currentSupply = totalSupply();
+
+    if (currentSupply == 0) {
+      return 1e18; //initial exchange rate is 1:1
+    }
+
+    return STAKED_TOKEN.balanceOf(address(this)).mul(1e18).div(currentSupply);
+  }
+
   /**
    * @dev returns the current address of the claimHelper Contract, contract with priviledge
    * It speicifically enables to claim from several contracts at once
@@ -394,6 +407,43 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     return REVISION();
   }
 
+  function getPowerAtBlock(
+    address user,
+    uint256 blockNumber,
+    DelegationType delegationType
+  ) external view override returns (uint256) {
+    (
+      mapping(address => mapping(uint256 => Snapshot)) storage snapshots,
+      mapping(address => uint256) storage snapshotsCounts,
+
+    ) = _getDelegationDataByType(delegationType);
+
+    return (
+      _searchByBlockNumber(snapshots, snapshotsCounts, user, blockNumber)
+        .mul(_searchExchangeRateByBlockNumber(blockNumber))
+        .div(1e18)
+    );
+  }
+
+  function getPowerCurrent(address user, DelegationType delegationType)
+    external
+    view
+    override
+    returns (uint256)
+  {
+    (
+      mapping(address => mapping(uint256 => Snapshot)) storage snapshots,
+      mapping(address => uint256) storage snapshotsCounts,
+
+    ) = _getDelegationDataByType(delegationType);
+
+    return (
+      _searchByBlockNumber(snapshots, snapshotsCounts, user, block.number).mul(exchangeRate()).div(
+        1e18
+      )
+    );
+  }
+
   function _claimRewards(
     address from,
     address to,
@@ -479,4 +529,58 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
 
     emit Redeem(from, to, amountToRedeem, underlyingToRedeem);
   }
+
+  function _snapshotExchangeRate() internal {
+    uint128 currentBlock = uint128(block.number);
+    uint128 newExchangeRate = uint128(exchangeRate());
+
+    // Doing multiple operations in the same block
+    if (
+      _countExchangeRateSnapshots != 0 &&
+      _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].blockNumber == currentBlock
+    ) {
+      _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].value = newExchangeRate;
+    } else {
+      _exchangeRateSnapshots[_countExchangeRateSnapshots] = Snapshot(currentBlock, newExchangeRate);
+      _countExchangeRateSnapshots = _countExchangeRateSnapshots + 1;
+    }
+    emit EchangeRateSnapshotted(currentBlock, newExchangeRate);
+  }
+
+  /**
+   * @dev searches a exchange Rate by block number. Uses binary search.
+   * @param blockNumber the block number being searched
+   **/
+  function _searchExchangeRateByBlockNumber(uint256 blockNumber) internal view returns (uint256) {
+    require(blockNumber <= block.number, 'INVALID_BLOCK_NUMBER');
+
+    if (_countExchangeRateSnapshots == 0) {
+      return exchangeRate();
+    }
+
+    // First check most recent balance
+    if (_exchangeRateSnapshots[_countExchangeRateSnapshots - 1].blockNumber <= blockNumber) {
+      return _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].value;
+    }
+
+    // Next check implicit zero balance
+    if (_exchangeRateSnapshots[0].blockNumber > blockNumber) {
+      return 1e18; //initial exchange rate is 1:1
+    }
+
+    uint256 lower = 0;
+    uint256 upper = _countExchangeRateSnapshots - 1;
+    while (upper > lower) {
+      uint256 center = upper - (upper - lower) / 2; // ceil, avoiding overflow
+      Snapshot memory snapshot = _exchangeRateSnapshots[center];
+      if (snapshot.blockNumber == blockNumber) {
+        return snapshot.value;
+      } else if (snapshot.blockNumber < blockNumber) {
+        lower = center;
+      } else {
+        upper = center - 1;
+      }
+    }
+    return _exchangeRateSnapshots[lower].value;
+  }
 }

From 0d685435d8bd648e9c722d33f22ceacbc496d3e3 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Wed, 24 Mar 2021 17:15:55 +0100
Subject: [PATCH 02/14] Made the snapshotExchangeRate function public

---
 contracts/stake/StakedTokenV3.sol | 41 +++++++++++++++++--------------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index b23b25a..54cf9cc 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -320,14 +320,14 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     require(amount <= maxSlashable, 'INVALID_SLASHING_AMOUNT');
 
     STAKED_TOKEN.safeTransfer(destination, amount);
-    _snapshotExchangeRate();
+    snapshotExchangeRate();
 
     emit Slashed(destination, amount);
   }
 
   function donate(uint256 amount) external override {
     STAKED_TOKEN.safeTransferFrom(msg.sender, address(this), amount);
-    _snapshotExchangeRate();
+    snapshotExchangeRate();
 
     emit Donated(msg.sender, amount);
   }
@@ -362,6 +362,26 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     emit MaxSlashablePercentageChanged(percentage);
   }
 
+  /**
+   * @dev Snapshots the current exchange rate
+   */
+  function snapshotExchangeRate() public {
+    uint128 currentBlock = uint128(block.number);
+    uint128 newExchangeRate = uint128(exchangeRate());
+
+    // Doing multiple operations in the same block
+    if (
+      _countExchangeRateSnapshots != 0 &&
+      _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].blockNumber == currentBlock
+    ) {
+      _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].value = newExchangeRate;
+    } else {
+      _exchangeRateSnapshots[_countExchangeRateSnapshots] = Snapshot(currentBlock, newExchangeRate);
+      _countExchangeRateSnapshots = _countExchangeRateSnapshots + 1;
+    }
+    emit EchangeRateSnapshotted(currentBlock, newExchangeRate);
+  }
+
   /**
    * @dev Calculates the exchange rate between the amount of STAKED_TOKEN and the the StakeToken total supply.
    * Slashing will reduce the exchange rate. Supplying STAKED_TOKEN to the stake contract
@@ -530,23 +550,6 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     emit Redeem(from, to, amountToRedeem, underlyingToRedeem);
   }
 
-  function _snapshotExchangeRate() internal {
-    uint128 currentBlock = uint128(block.number);
-    uint128 newExchangeRate = uint128(exchangeRate());
-
-    // Doing multiple operations in the same block
-    if (
-      _countExchangeRateSnapshots != 0 &&
-      _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].blockNumber == currentBlock
-    ) {
-      _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].value = newExchangeRate;
-    } else {
-      _exchangeRateSnapshots[_countExchangeRateSnapshots] = Snapshot(currentBlock, newExchangeRate);
-      _countExchangeRateSnapshots = _countExchangeRateSnapshots + 1;
-    }
-    emit EchangeRateSnapshotted(currentBlock, newExchangeRate);
-  }
-
   /**
    * @dev searches a exchange Rate by block number. Uses binary search.
    * @param blockNumber the block number being searched

From d36a81cac3716c374f955a53b5b19c1603446598 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Wed, 24 Mar 2021 17:28:36 +0100
Subject: [PATCH 03/14] Added natspec commenst

---
 contracts/stake/StakedTokenV3.sol | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index 54cf9cc..395cabb 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -325,6 +325,10 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     emit Slashed(destination, amount);
   }
 
+  /**
+   * @dev Function that pull funds to be staked as a donation to the pool of staked tokens.
+   * @param amount the amount to send
+   **/
   function donate(uint256 amount) external override {
     STAKED_TOKEN.safeTransferFrom(msg.sender, address(this), amount);
     snapshotExchangeRate();
@@ -427,6 +431,12 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     return REVISION();
   }
 
+  /**
+   * @dev returns the delegated power of a user at a certain block
+   * @param user the user
+   * @param blockNumber the blockNumber at which to evalute the power
+   * @param delegationType 0 for Voting, 1 for proposition
+   **/
   function getPowerAtBlock(
     address user,
     uint256 blockNumber,
@@ -445,6 +455,12 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     );
   }
 
+  /**
+   * @dev returns the current delegated power of a user. The current power is the
+   * power delegated at the time of the last snapshot
+   * @param user the user
+   * @param delegationType 0 for Voting, 1 for proposition
+   **/
   function getPowerCurrent(address user, DelegationType delegationType)
     external
     view

From 294e256dcde38b841d8b9c77d175bc84d1280850 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Thu, 25 Mar 2021 09:52:16 +0100
Subject: [PATCH 04/14] Added getExchangeRate

---
 contracts/stake/StakedTokenV3.sol | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index 395cabb..c31fe63 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -480,6 +480,16 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     );
   }
 
+  /**
+   * @notice Searches the exchange rate for a blocknumber
+   * @param blockNumber blockNumber to search
+   * @return The last exchangeRate recorded before the blockNumber
+   * @dev not all exchangeRates are recorded, so this value might not be exact. Use archive node for exact value
+   **/
+  function getExchangeRate(uint256 blockNumber) external view returns (uint256) {
+    return _searchExchangeRateByBlockNumber(blockNumber);
+  }
+
   function _claimRewards(
     address from,
     address to,

From 3456c2920c2edc3f515d43bfd42a2fbbab966c52 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Thu, 25 Mar 2021 14:27:04 +0100
Subject: [PATCH 05/14] Added test for power with exchange rates

---
 test/StakedAaveV3/stakedAave-V3.spec.ts | 52 ++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 6 deletions(-)

diff --git a/test/StakedAaveV3/stakedAave-V3.spec.ts b/test/StakedAaveV3/stakedAave-V3.spec.ts
index 550be98..9be2d68 100644
--- a/test/StakedAaveV3/stakedAave-V3.spec.ts
+++ b/test/StakedAaveV3/stakedAave-V3.spec.ts
@@ -213,8 +213,14 @@ makeSuite('StakedAave V3 slashing tests', (testEnv: TestEnv) => {
 
   it('Verifies that the initial exchange rate is 1:1', async () => {
     const currentExchangeRate = await stakeV3.exchangeRate();
+    const searchedExchangeRate = await stakeV3.getExchangeRate(
+      await DRE.ethers.provider.getBlockNumber()
+    );
+    const searchedExchangeRateBlockZero = await stakeV3.getExchangeRate(0);
 
     expect(currentExchangeRate.toString()).to.be.equal(WAD);
+    expect(searchedExchangeRateBlockZero.toString()).to.be.equal(WAD);
+    expect(searchedExchangeRate.toString()).to.be.equal(WAD);
   });
 
   it('Verifies that after a deposit the initial exchange rate is still 1:1', async () => {
@@ -233,29 +239,55 @@ makeSuite('StakedAave V3 slashing tests', (testEnv: TestEnv) => {
   });
 
   it('Executes a slash of 20% of the asset', async () => {
-    const { aaveToken, users } = testEnv;
-
-    const fundsReceiver = users[3].address;
+    const {
+      aaveToken,
+      users: [admin, staker, , fundsReceiver],
+    } = testEnv;
 
     const userBalanceBeforeSlash = new BigNumber(
-      (await aaveToken.balanceOf(fundsReceiver)).toString()
+      (await aaveToken.balanceOf(fundsReceiver.address)).toString()
     );
 
+    const stakerBalanceBeforeSlash = await aaveToken.balanceOf(staker.address);
+    const votingPowerBeforeSlash = await stakeV3.getPowerCurrent(staker.address, 0);
+    const propPowerBeforeSlash = await stakeV3.getPowerCurrent(staker.address, 1);
+
     const currentStakeBalance = new BigNumber(
       (await aaveToken.balanceOf(stakeV3.address)).toString()
     );
 
     const amountToSlash = currentStakeBalance.times(0.2).toFixed(0);
 
-    await stakeV3.connect(users[0].signer).slash(fundsReceiver, amountToSlash);
+    await stakeV3.connect(admin.signer).slash(fundsReceiver.address, amountToSlash);
 
     const newStakeBalance = new BigNumber((await aaveToken.balanceOf(stakeV3.address)).toString());
 
     const userBalanceAfterSlash = new BigNumber(
-      (await aaveToken.balanceOf(fundsReceiver)).toString()
+      (await aaveToken.balanceOf(fundsReceiver.address)).toString()
     );
 
     const exchangeRate = new BigNumber((await stakeV3.exchangeRate()).toString()).toString();
+    const searchedExchangeRate = await stakeV3.getExchangeRate(
+      await DRE.ethers.provider.getBlockNumber()
+    );
+    const searchedExchangeRateBlockBefore = await stakeV3.getExchangeRate(
+      (await DRE.ethers.provider.getBlockNumber()) - 1
+    );
+    const searchedExchangeRateBlockZero = await stakeV3.getExchangeRate(0);
+
+    const stakerBalanceAfterSlash = await aaveToken.balanceOf(staker.address);
+    const votingPowerAfterSlash = await stakeV3.getPowerCurrent(staker.address, 0);
+    const propPowerAfterSlash = await stakeV3.getPowerCurrent(staker.address, 1);
+    const searchedVotingPowerBeforeSlash = await stakeV3.getPowerAtBlock(
+      staker.address,
+      (await DRE.ethers.provider.getBlockNumber()) - 1,
+      0
+    );
+    const searchedPropPowerBeforeSlash = await stakeV3.getPowerAtBlock(
+      staker.address,
+      (await DRE.ethers.provider.getBlockNumber()) - 1,
+      1
+    );
 
     expect(newStakeBalance.toString()).to.be.equal(
       currentStakeBalance.minus(amountToSlash).toFixed(0)
@@ -264,6 +296,14 @@ makeSuite('StakedAave V3 slashing tests', (testEnv: TestEnv) => {
       userBalanceBeforeSlash.plus(amountToSlash).toFixed(0)
     );
     expect(exchangeRate).to.be.equal(ethers.utils.parseEther('0.8'));
+    expect(searchedExchangeRate).to.be.equal(ethers.utils.parseEther('0.8'));
+    expect(searchedExchangeRateBlockBefore).to.be.equal(ethers.utils.parseEther('1.0'));
+    expect(searchedExchangeRateBlockZero).to.be.equal(ethers.utils.parseEther('1.0'));
+    expect(stakerBalanceAfterSlash).to.be.equal(stakerBalanceBeforeSlash);
+    expect(searchedVotingPowerBeforeSlash).to.be.equal(votingPowerBeforeSlash);
+    expect(searchedPropPowerBeforeSlash).to.be.equal(propPowerBeforeSlash);
+    expect(votingPowerAfterSlash).to.be.equal(votingPowerBeforeSlash.mul(8).div(10));
+    expect(propPowerAfterSlash).to.be.equal(propPowerBeforeSlash.mul(8).div(10));
   });
 
   it('Redeems 1 stkAAVE after slashing - expected to receive 0.8 AAVE', async () => {

From 251640aeba94c82f1b8bc7631f17a05e7c425c72 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Tue, 6 Apr 2021 17:48:45 +0200
Subject: [PATCH 06/14] removed test aave v3 from npm run test, issue with
 hardhat block number mngt

---
 package.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package.json b/package.json
index e87eeb2..6b42be1 100644
--- a/package.json
+++ b/package.json
@@ -16,7 +16,7 @@
     "compile": "SKIP_LOAD=true hardhat compile",
     "compile:force": "npm run compile -- --force",
     "compile:force:quiet": "npm run compile:force -- --quiet",
-    "test": "npm run compile:force:quiet && hardhat test test/__setup.spec.ts test/AaveIncentivesController/*.spec.ts test/StakedAave/*.spec.ts test/StakedAaveV2/*.spec.ts test/StakedAaveV3/*.spec.ts",
+    "test": "npm run compile:force:quiet && hardhat test test/__setup.spec.ts test/AaveIncentivesController/*.spec.ts test/StakedAave/*.spec.ts test/StakedAaveV2/*.spec.ts && hardhat test test/__setup.spec.ts test/StakedAaveV3/*.spec.ts",
     "test:ci": "npm run compile:force:quiet && npm run test-pei && npm run test-psi && npm run test-psi2 && npm run test-bpt",
     "test-pei": "npm run test test/__setup.spec.ts test/AaveIncentivesController/*.spec.ts",
     "test-psi": "npm run test test/__setup.spec.ts test/StakedAave/*.spec.ts",

From 3775176e182ae421e91cfda1adfe74845b6c06a1 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Wed, 21 Apr 2021 11:35:02 +0200
Subject: [PATCH 07/14] fix: removed Typo and not needed blockNumber in
 ExchangeRateSnapshotted event

---
 contracts/stake/StakedTokenV3.sol | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index c31fe63..71e42eb 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -73,7 +73,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
   event MaxSlashablePercentageChanged(uint256 newPercentage);
   event Slashed(address indexed destination, uint256 amount);
   event Donated(address indexed sender, uint256 amount);
-  event EchangeRateSnapshotted(uint128 blockNumber, uint128 exchangeRate);
+  event ExchangeRateSnapshotted(uint128 exchangeRate);
   event CooldownPauseAdminChanged(address indexed newAdmin);
   event SlashingAdminChanged(address indexed newAdmin);
   event ClaimHelperChanged(address indexed newClaimHelper);
@@ -383,7 +383,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
       _exchangeRateSnapshots[_countExchangeRateSnapshots] = Snapshot(currentBlock, newExchangeRate);
       _countExchangeRateSnapshots = _countExchangeRateSnapshots + 1;
     }
-    emit EchangeRateSnapshotted(currentBlock, newExchangeRate);
+    emit ExchangeRateSnapshotted(newExchangeRate);
   }
 
   /**

From 1057fe8d1eaa82ac91d2086ad5aa55a29c5c87e6 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Wed, 21 Apr 2021 11:45:37 +0200
Subject: [PATCH 08/14] fix: cached storage, syntax ++ on
 `snapshotExchangeRate()`

---
 contracts/stake/StakedTokenV3.sol | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index 71e42eb..5edefe7 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -372,16 +372,17 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
   function snapshotExchangeRate() public {
     uint128 currentBlock = uint128(block.number);
     uint128 newExchangeRate = uint128(exchangeRate());
+    uint256 count = _countExchangeRateSnapshots;
 
     // Doing multiple operations in the same block
     if (
-      _countExchangeRateSnapshots != 0 &&
-      _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].blockNumber == currentBlock
+      count != 0 &&
+      _exchangeRateSnapshots[count - 1].blockNumber == currentBlock
     ) {
-      _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].value = newExchangeRate;
+      _exchangeRateSnapshots[count - 1].value = newExchangeRate;
     } else {
-      _exchangeRateSnapshots[_countExchangeRateSnapshots] = Snapshot(currentBlock, newExchangeRate);
-      _countExchangeRateSnapshots = _countExchangeRateSnapshots + 1;
+      _exchangeRateSnapshots[count] = Snapshot(currentBlock, newExchangeRate);
+      _countExchangeRateSnapshots++;
     }
     emit ExchangeRateSnapshotted(newExchangeRate);
   }

From 46b09276048fcc6303b5cf3b6f1f16084398946b Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Wed, 21 Apr 2021 16:04:04 +0200
Subject: [PATCH 09/14] fix: added comments, added exchangeRatePrecision
 constant

---
 contracts/stake/StakedTokenV3.sol | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index 5edefe7..82b707e 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -44,6 +44,8 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
 
   address internal _claimHelper;
 
+  uint public constant EXCHANGE_RATE_PRECISION = 1e18;
+
   mapping(uint256 => Snapshot) internal _exchangeRateSnapshots;
   uint256 internal _countExchangeRateSnapshots;
 
@@ -320,6 +322,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     require(amount <= maxSlashable, 'INVALID_SLASHING_AMOUNT');
 
     STAKED_TOKEN.safeTransfer(destination, amount);
+    // We transfer tokens first: this is the event updating the exchange Rate
     snapshotExchangeRate();
 
     emit Slashed(destination, amount);
@@ -331,6 +334,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
    **/
   function donate(uint256 amount) external override {
     STAKED_TOKEN.safeTransferFrom(msg.sender, address(this), amount);
+    // We transfer tokens first: this is the event updating the exchange Rate
     snapshotExchangeRate();
 
     emit Donated(msg.sender, amount);
@@ -396,10 +400,10 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     uint256 currentSupply = totalSupply();
 
     if (currentSupply == 0) {
-      return 1e18; //initial exchange rate is 1:1
+      return uint256(1).mul(EXCHANGE_RATE_PRECISION); //initial exchange rate is 1:1
     }
 
-    return STAKED_TOKEN.balanceOf(address(this)).mul(1e18).div(currentSupply);
+    return STAKED_TOKEN.balanceOf(address(this)).mul(EXCHANGE_RATE_PRECISION).div(currentSupply);
   }
 
   /**

From 06b6dc9af724d9cd8e81a0b82165af6765cda198 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Wed, 21 Apr 2021 16:09:42 +0200
Subject: [PATCH 10/14] fix: cached storage snapshotCount, added snapshot to
 initialize function

---
 contracts/stake/StakedTokenV3.sol | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index 82b707e..ec5dbea 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -164,6 +164,8 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     _claimHelper = claimHelper;
 
     _maxSlashablePercentage = maxSlashablePercentage;
+
+    snapshotExchangeRate();
   }
 
   /**
@@ -376,16 +378,16 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
   function snapshotExchangeRate() public {
     uint128 currentBlock = uint128(block.number);
     uint128 newExchangeRate = uint128(exchangeRate());
-    uint256 count = _countExchangeRateSnapshots;
+    uint256 snapshotsCount = _countExchangeRateSnapshots;
 
     // Doing multiple operations in the same block
     if (
-      count != 0 &&
-      _exchangeRateSnapshots[count - 1].blockNumber == currentBlock
+      snapshotsCount != 0 &&
+      _exchangeRateSnapshots[snapshotsCount - 1].blockNumber == currentBlock
     ) {
-      _exchangeRateSnapshots[count - 1].value = newExchangeRate;
+      _exchangeRateSnapshots[snapshotsCount - 1].value = newExchangeRate;
     } else {
-      _exchangeRateSnapshots[count] = Snapshot(currentBlock, newExchangeRate);
+      _exchangeRateSnapshots[snapshotsCount] = Snapshot(currentBlock, newExchangeRate);
       _countExchangeRateSnapshots++;
     }
     emit ExchangeRateSnapshotted(newExchangeRate);
@@ -588,13 +590,11 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
   function _searchExchangeRateByBlockNumber(uint256 blockNumber) internal view returns (uint256) {
     require(blockNumber <= block.number, 'INVALID_BLOCK_NUMBER');
 
-    if (_countExchangeRateSnapshots == 0) {
-      return exchangeRate();
-    }
+    uint256 snapshotsCount =_countExchangeRateSnapshots;
 
     // First check most recent balance
-    if (_exchangeRateSnapshots[_countExchangeRateSnapshots - 1].blockNumber <= blockNumber) {
-      return _exchangeRateSnapshots[_countExchangeRateSnapshots - 1].value;
+    if (_exchangeRateSnapshots[snapshotsCount - 1].blockNumber <= blockNumber) {
+      return _exchangeRateSnapshots[snapshotsCount - 1].value;
     }
 
     // Next check implicit zero balance
@@ -603,7 +603,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     }
 
     uint256 lower = 0;
-    uint256 upper = _countExchangeRateSnapshots - 1;
+    uint256 upper = snapshotsCount - 1;
     while (upper > lower) {
       uint256 center = upper - (upper - lower) / 2; // ceil, avoiding overflow
       Snapshot memory snapshot = _exchangeRateSnapshots[center];

From bdd65801b5218a92853f85df504c69e7409c4e69 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Fri, 30 Apr 2021 11:17:52 +0200
Subject: [PATCH 11/14] fix: minor readiness fix on exchange rate

---
 contracts/stake/StakedTokenV3.sol | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index ec5dbea..2579d7a 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -402,7 +402,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     uint256 currentSupply = totalSupply();
 
     if (currentSupply == 0) {
-      return uint256(1).mul(EXCHANGE_RATE_PRECISION); //initial exchange rate is 1:1
+      return EXCHANGE_RATE_PRECISION; //initial exchange rate is 1:1
     }
 
     return STAKED_TOKEN.balanceOf(address(this)).mul(EXCHANGE_RATE_PRECISION).div(currentSupply);

From 04d83f3668e100a73126a901d7755b0c7c627ec8 Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Fri, 30 Apr 2021 11:24:22 +0200
Subject: [PATCH 12/14] clean: used exchangeratePrecision variable where needed

---
 contracts/stake/StakedTokenV3.sol | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index 2579d7a..68d66f9 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -458,7 +458,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     return (
       _searchByBlockNumber(snapshots, snapshotsCounts, user, blockNumber)
         .mul(_searchExchangeRateByBlockNumber(blockNumber))
-        .div(1e18)
+        .div(EXCHANGE_RATE_PRECISION)
     );
   }
 
@@ -482,7 +482,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
 
     return (
       _searchByBlockNumber(snapshots, snapshotsCounts, user, block.number).mul(exchangeRate()).div(
-        1e18
+        EXCHANGE_RATE_PRECISION
       )
     );
   }
@@ -599,7 +599,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
 
     // Next check implicit zero balance
     if (_exchangeRateSnapshots[0].blockNumber > blockNumber) {
-      return 1e18; //initial exchange rate is 1:1
+      return EXCHANGE_RATE_PRECISION; //initial exchange rate is 1:1
     }
 
     uint256 lower = 0;

From 7ed6e975567db366fed6bb07ce6780ecabd7ff2c Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Fri, 30 Apr 2021 11:25:27 +0200
Subject: [PATCH 13/14] clean: used exchangeratePrecision variable where needed

---
 contracts/stake/StakedTokenV3.sol | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index 68d66f9..eb31ec1 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -532,7 +532,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
 
     stakersCooldowns[to] = getNextCooldownTimestamp(0, amount, to, balanceOfUser);
 
-    uint256 sharesToMint = amount.mul(1e18).div(exchangeRate());
+    uint256 sharesToMint = amount.mul(EXCHANGE_RATE_PRECISION).div(exchangeRate());
     _mint(to, sharesToMint);
 
     if (pullFunds) {
@@ -570,7 +570,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
 
     _updateCurrentUnclaimedRewards(from, balanceOfFrom, true);
 
-    uint256 underlyingToRedeem = amountToRedeem.mul(exchangeRate()).div(1e18);
+    uint256 underlyingToRedeem = amountToRedeem.mul(exchangeRate()).div(EXCHANGE_RATE_PRECISION);
 
     _burn(from, amountToRedeem);
 

From d8f7e66c4624dcbfdc22b0c24e5badb893e0a00f Mon Sep 17 00:00:00 2001
From: Hadrien Charlanes <hadrien@variabl.io>
Date: Fri, 30 Apr 2021 11:40:30 +0200
Subject: [PATCH 14/14] refactor: cached better snapshot index

---
 contracts/stake/StakedTokenV3.sol | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/contracts/stake/StakedTokenV3.sol b/contracts/stake/StakedTokenV3.sol
index eb31ec1..156427a 100644
--- a/contracts/stake/StakedTokenV3.sol
+++ b/contracts/stake/StakedTokenV3.sol
@@ -590,11 +590,11 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
   function _searchExchangeRateByBlockNumber(uint256 blockNumber) internal view returns (uint256) {
     require(blockNumber <= block.number, 'INVALID_BLOCK_NUMBER');
 
-    uint256 snapshotsCount =_countExchangeRateSnapshots;
+    uint256 lastExchangeRateSnapshotIndex =_countExchangeRateSnapshots - 1;
 
     // First check most recent balance
-    if (_exchangeRateSnapshots[snapshotsCount - 1].blockNumber <= blockNumber) {
-      return _exchangeRateSnapshots[snapshotsCount - 1].value;
+    if (_exchangeRateSnapshots[lastExchangeRateSnapshotIndex].blockNumber <= blockNumber) {
+      return _exchangeRateSnapshots[lastExchangeRateSnapshotIndex].value;
     }
 
     // Next check implicit zero balance
@@ -603,7 +603,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     }
 
     uint256 lower = 0;
-    uint256 upper = snapshotsCount - 1;
+    uint256 upper = lastExchangeRateSnapshotIndex;
     while (upper > lower) {
       uint256 center = upper - (upper - lower) / 2; // ceil, avoiding overflow
       Snapshot memory snapshot = _exchangeRateSnapshots[center];