study-univ3-on-hardhat/contracts/Flash.sol

//SPDX-License-Identifier: Unlicense
pragma solidity ^0.7.6;
pragma abicoder v2;

import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import '@uniswap/v3-core/contracts/interfaces/pool/IUniswapV3PoolActions.sol';
import './base/TransferHelper.sol';
import './base/Address.sol';

contract Flash {
    mapping(address => bool) private adminMap;
    mapping(address => mapping(address => uint256)) private approveMap;
    address private owner;

    constructor() {
        owner = msg.sender;

        adminMap[owner] = true;
        adminMap[address(this)] = true;
    }

    modifier onlyOwner() {
        require(msg.sender == owner || msg.sender == address(this), 'Not is owner.');
        _;
    }

    modifier onlyMaster() {
        require(adminMap[msg.sender], 'Not is master.');
        _;
    }

    function addAdmin(address _addr) public onlyOwner {
        adminMap[_addr] = true;
    }

    function approve(uint256 _volume, address _token, address _to) public onlyOwner {
        TransferHelper.safeApprove(_token, _to, _volume);
        approveMap[_to][_token] = _volume;
    }

    function withdraw(address _token) public onlyOwner {
        uint256 token_balance = IERC20(_token).balanceOf(address(this));
        TransferHelper.safeTransfer(_token, owner, token_balance);
    }

    struct FlashLoanParams {
        address pool;
    }

    function flashLoan(FlashLoanParams memory params) external pure returns (uint256 num){
        return 0;
    }
}