aave-protocol-v2/contracts/tokenization/VariableDebtToken.sol
2020-07-13 11:54:08 +03:00

173 lines
4.8 KiB
Solidity

pragma solidity ^0.6.0;
import '@openzeppelin/contracts/GSN/Context.sol';
import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import '@openzeppelin/contracts/math/SafeMath.sol';
import '@openzeppelin/contracts/utils/Address.sol';
import {DebtTokenBase} from './base/DebtTokenBase.sol';
import {WadRayMath} from '../libraries/WadRayMath.sol';
import '@nomiclabs/buidler/console.sol';
import {IVariableDebtToken} from './interfaces/IVariableDebtToken.sol';
/**
* @title interface IVariableDebtToken
* @author Aave
* @notice defines the basic interface for a variable debt token.
* @dev does not inherit from IERC20 to save in contract size
**/
contract VariableDebtToken is DebtTokenBase, IVariableDebtToken {
using SafeMath for uint256;
using WadRayMath for uint256;
using Address for address;
mapping(address => uint256) private userIndexes;
/**
* @dev emitted when new variable debt is minted
* @param _user the user receiving the debt
* @param _amount the amount of debt being minted
* @param _previousBalance the previous balance of the user
* @param _currentBalance the current balance of the user
* @param _balanceIncrease the debt accumulated since the last action
* @param _index the index of the user
**/
event mintDebt(
address _user,
uint256 _amount,
uint256 _previousBalance,
uint256 _currentBalance,
uint256 _balanceIncrease,
uint256 _index
);
/**
* @dev emitted when variable debt is burnt
* @param _user the user which debt has been burned
* @param _amount the amount of debt being burned
* @param _previousBalance the previous balance of the user
* @param _currentBalance the current balance of the user
* @param _balanceIncrease the debt accumulated since the last action
* @param _index the index of the user
**/
event burnDebt(
address _user,
uint256 _amount,
uint256 _previousBalance,
uint256 _currentBalance,
uint256 _balanceIncrease,
uint256 _index
);
/**
* @dev calculates the accumulated debt balance of the user
* @return the debt balance of the user
**/
function balanceOf(address _user) public virtual override view returns (uint256) {
if (balances[_user] == 0) {
return 0;
}
return
balances[_user]
.wadToRay()
.rayMul(pool.getReserveNormalizedVariableDebt(underlyingAssetAddress))
.rayDiv(userIndexes[_user])
.rayToWad();
}
/**
* @dev returns the index of the last user action
* @return the user index
**/
function getUserIndex(address _user) public virtual override view returns (uint256) {
return userIndexes[_user];
}
/**
* @dev mints new variable debt
* @param _user the user receiving the debt
* @param _amount the amount of debt being minted
**/
function mint(address _user, uint256 _amount) public override onlyLendingPool {
(uint256 previousBalance, uint256 currentBalance, uint256 balanceIncrease) = _cumulateBalance(
_user
);
_mint(_user, _amount);
userIndexes[_user] = pool.getReserveNormalizedVariableDebt(underlyingAssetAddress);
emit mintDebt(
_user,
_amount,
previousBalance,
currentBalance,
balanceIncrease,
userIndexes[_user]
);
}
/**
* @dev burns user variable debt
* @param _user the user which debt is burnt
* @param _amount the amount of debt being burned
**/
function burn(address _user, uint256 _amount) public override onlyLendingPool {
(uint256 previousBalance, uint256 currentBalance, uint256 balanceIncrease) = _cumulateBalance(
_user
);
_burn(_user, _amount);
//if user repaid everything
if (currentBalance == _amount) {
userIndexes[_user] = 0;
} else {
userIndexes[_user] = pool.getReserveNormalizedVariableDebt(underlyingAssetAddress);
}
emit burnDebt(
_user,
_amount,
previousBalance,
currentBalance,
balanceIncrease,
userIndexes[_user]
);
}
/**
* @dev accumulates the accrued interest of the user to the principal balance
* @param _user the address of the user for which the interest is being accumulated
* @return the previous principal balance, the new principal balance, the balance increase
* and the new user index
**/
function _cumulateBalance(address _user)
internal
returns (
uint256,
uint256,
uint256
)
{
uint256 previousPrincipalBalance = balances[_user];
if (previousPrincipalBalance == 0) {
return (0, 0, 0);
}
//calculate the accrued interest since the last accumulation
uint256 balanceIncrease = balanceOf(_user).sub(previousPrincipalBalance);
//mints an _amount of tokens equivalent to the _amount accumulated
_mint(_user, balanceIncrease);
return (
previousPrincipalBalance,
previousPrincipalBalance.add(balanceIncrease),
balanceIncrease
);
}
}