update buffer feature

contracts/TapETH.sol

@@ -24,6 +24,7 @@ error InsufficientBalance(uint256 currentBalance, uint256 amount);
 contract TapETH is Initializable, ITapETH {
  using Math for uint256;
  uint256 internal constant INFINITE_ALLOWANCE = ~uint256(0);
+ uint256 public constant BUFFER_DENOMINATOR = 10 ** 10;
 
  uint256 private totalShares;
  uint256 private _totalSupply;
@@ -256,12 +257,13 @@ contract TapETH is Initializable, ITapETH {
  }
 
  /**
- * @notice This function is called by the governance to set the buffer.
+ * @notice This function is called by the governance to set the buffer rate.
  */
- function setBuffer(uint256 _amount) external {
+ function setBuffer(uint256 _buffer) external {
  require(msg.sender == governance, "TapETH: no governance");
- buffer = _amount;
- emit SetBuffer(_amount);
+ require(_buffer <= BUFFER_DENOMINATOR, "TapETH: out of range");
+ buffer = _buffer;
+ emit SetBuffer(_buffer);
  }
 
  /**
@@ -271,10 +273,8 @@ contract TapETH is Initializable, ITapETH {
  function setTotalSupply(uint256 _amount) external {
  require(pools[msg.sender], "TapETH: no pool");
  require(_amount != 0, "TapETH: no pool");
- uint256 _deltaBuffer = Math.min(buffer, _amount);
+ uint256 _deltaBuffer = (buffer * _amount) / BUFFER_DENOMINATOR;
  _totalSupply += _amount - _deltaBuffer;
- totalRewards += _amount;
- buffer -= _deltaBuffer;
  }
 
  /**