aave-protocol-v2/contracts/tokenization/VariableDebtToken.sol

151 lines
4.5 KiB
Solidity

// SPDX-License-Identifier: agpl-3.0
pragma solidity ^0.6.8;
import {Context} from '@openzeppelin/contracts/GSN/Context.sol';
import {IERC20} from '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import {SafeMath} from '@openzeppelin/contracts/math/SafeMath.sol';
import {DebtTokenBase} from './base/DebtTokenBase.sol';
import {WadRayMath} from '../libraries/math/WadRayMath.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;
uint256 public constant DEBT_TOKEN_REVISION = 0x1;
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
);
constructor(
address pool,
address underlyingAsset,
string memory name,
string memory symbol
) public DebtTokenBase(pool, underlyingAsset, name, symbol) {}
/**
* @dev gets the revision of the stable debt token implementation
* @return the debt token implementation revision
**/
function getRevision() internal virtual override pure returns (uint256) {
return DEBT_TOKEN_REVISION;
}
/**
* @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) {
uint256 userBalance = _balances[user];
if (userBalance == 0) {
return 0;
}
return
userBalance
.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) external 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) external override onlyLendingPool {
(
uint256 previousBalance,
uint256 currentBalance,
uint256 balanceIncrease
) = _calculateBalanceIncrease(user);
_mint(user, amount.add(balanceIncrease));
uint256 newUserIndex = _pool.getReserveNormalizedVariableDebt(_underlyingAssetAddress);
_userIndexes[user] = newUserIndex;
emit MintDebt(user, amount, previousBalance, currentBalance, balanceIncrease, newUserIndex);
}
/**
* @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) external override onlyLendingPool {
(
uint256 previousBalance,
uint256 currentBalance,
uint256 balanceIncrease
) = _calculateBalanceIncrease(user);
if (balanceIncrease > amount) {
_mint(user, balanceIncrease.sub(amount));
} else {
_burn(user, amount.sub(balanceIncrease));
}
uint256 newUserIndex = 0;
//if user not repaid everything
if (currentBalance != amount) {
newUserIndex = _pool.getReserveNormalizedVariableDebt(_underlyingAssetAddress);
}
_userIndexes[user] = newUserIndex;
emit BurnDebt(user, amount, previousBalance, currentBalance, balanceIncrease, newUserIndex);
}
}