// SPDX-License-Identifier: MIT pragma solidity ^0.8.0; import "@openzeppelin/contracts/token/ERC20/IERC20.sol"; import "./AccountLocks.sol"; abstract contract Collateral is AccountLocks { IERC20 public immutable token; CollateralFunds private funds; mapping(address => uint256) private balances; constructor(IERC20 _token) collateralInvariant { token = _token; } function balanceOf(address account) public view returns (uint256) { return balances[account]; } function add(address account, uint256 amount) private { balances[account] += amount; funds.balance += amount; } function subtract(address account, uint256 amount) private { balances[account] -= amount; funds.balance -= amount; } function transferFrom(address sender, uint256 amount) internal { address receiver = address(this); require(token.transferFrom(sender, receiver, amount), "Transfer failed"); } function deposit(uint256 amount) public collateralInvariant { transferFrom(msg.sender, amount); funds.deposited += amount; add(msg.sender, amount); } // TODO: remove AccountLocks function isWithdrawAllowed() internal virtual returns (bool) { _unlockAccount(); return true; } function withdraw() public collateralInvariant { require(isWithdrawAllowed(), "Account locked"); uint256 amount = balanceOf(msg.sender); funds.withdrawn += amount; subtract(msg.sender, amount); assert(token.transfer(msg.sender, amount)); } function _slashAmount(address account, uint256 percentage) internal view returns (uint256) { return (balanceOf(account) * percentage) / 100; } function _slash(address account, uint256 percentage) internal collateralInvariant { uint256 amount = _slashAmount(account, percentage); funds.slashed += amount; subtract(account, amount); } modifier collateralInvariant() { CollateralFunds memory oldFunds = funds; _; assert(funds.deposited >= oldFunds.deposited); assert(funds.withdrawn >= oldFunds.withdrawn); assert(funds.slashed >= oldFunds.slashed); assert(funds.deposited == funds.balance + funds.withdrawn + funds.slashed); } struct CollateralFunds { uint256 balance; uint256 deposited; uint256 withdrawn; uint256 slashed; } }