// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;

contract MagicNum {

  address public solver;

  constructor() public {}

  function setSolver(address _solver) public {
    solver = _solver;
  }

  /*
    ____________/\\\_______/\\\\\\\\\_____        
     __________/\\\\\_____/\\\///////\\\___       
      ________/\\\/\\\____\///______\//\\\__      
       ______/\\\/\/\\\______________/\\\/___     
        ____/\\\/__\/\\\___________/\\\//_____    
         __/\\\\\\\\\\\\\\\\_____/\\\//________   
          _\///////////\\\//____/\\\/___________  
           ___________\/\\\_____/\\\\\\\\\\\\\\\_ 
            ___________\///_____\///////////////__
  */
}

// SPDX-License-Identifier: MIT
pragma solidity >=0.8.0 <0.9.0;

import "openzeppelin-contracts-08/utils/Address.sol";

contract GoodSamaritan {
    Wallet public wallet;
    Coin public coin;

    constructor() {
        wallet = new Wallet();
        coin = new Coin(address(wallet));

        wallet.setCoin(coin);
    }

    function requestDonation() external returns(bool enoughBalance){
        // donate 10 coins to requester
        try wallet.donate10(msg.sender) {
            return true;
        } catch (bytes memory err) {
            if (keccak256(abi.encodeWithSignature("NotEnoughBalance()")) == keccak256(err)) {
                // send the coins left
                wallet.transferRemainder(msg.sender);
                return false;
            }
        }
    }
}

contract Coin {
    using Address for address;

    mapping(address => uint256) public balances;

    error InsufficientBalance(uint256 current, uint256 required);

    constructor(address wallet_) {
        // one million coins for Good Samaritan initially
        balances[wallet_] = 10**6;
    }

    function transfer(address dest_, uint256 amount_) external {
        uint256 currentBalance = balances[msg.sender];

        // transfer only occurs if balance is enough
        if(amount_ <= currentBalance) {
            balances[msg.sender] -= amount_;
            balances[dest_] += amount_;

            if(dest_.isContract()) {
                // notify contract 
                INotifyable(dest_).notify(amount_);
            }
        } else {
            revert InsufficientBalance(currentBalance, amount_);
        }
    }
}

contract Wallet {
    // The owner of the wallet instance
    address public owner;

    Coin public coin;

    error OnlyOwner();
    error NotEnoughBalance();

    modifier onlyOwner() {
        if(msg.sender != owner) {
            revert OnlyOwner();
        }
        _;
    }

    constructor() {
        owner = msg.sender;
    }

    function donate10(address dest_) external onlyOwner {
        // check balance left
        if (coin.balances(address(this)) < 10) {
            revert NotEnoughBalance();
        } else {
            // donate 10 coins
            coin.transfer(dest_, 10);
        }
    }

    function transferRemainder(address dest_) external onlyOwner {
        // transfer balance left
        coin.transfer(dest_, coin.balances(address(this)));
    }

    function setCoin(Coin coin_) external onlyOwner {
        coin = coin_;
    }
}

interface INotifyable {
    function notify(uint256 amount) external;
}

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.14;

import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import {Address} from "@openzeppelin/contracts/utils/Address.sol";
import {SafeERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

// Some ideas for this challenge were taken from damn vulnerable defi
contract InSecureumLenderPool {
    using Address for address;
    using SafeERC20 for IERC20;

    /// @dev Token contract address to be used for lending.
    //IERC20 immutable public token;
    IERC20 public token;
    /// @dev Internal balances of the pool for each user.
    mapping(address => uint) public balances;

    // flag to notice contract is on a flashloan
    bool private _flashLoan;

    /// @param _token Address of the token to be used for the lending pool.
    constructor (address _token) {
        token = IERC20(_token);
    }

    /// @dev Deposit the given amount of tokens to the lending 
    ///      pool. This will add _amount to balances[msg.sender] and
    ///      transfer _amount tokens to the lending pool.
    /// @param _amount Amount of token to deposit in the lending pool
    function deposit(uint256 _amount) external {
        require(!_flashLoan, "Cannot deposit while flash loan is active");
        token.safeTransferFrom(msg.sender, address(this), _amount);
        balances[msg.sender] += _amount;
    }
    
    /// @dev Withdraw the given amount of tokens from the lending pool.
    function withdraw(uint256 _amount) external {
        require(!_flashLoan, "Cannot withdraw while flash loan is active");
        balances[msg.sender] -= _amount;
        token.safeTransfer(msg.sender, _amount);
    }   

    /// @dev Give borrower all the tokens to make a flashloan.
    ///      For this with get the amount of tokens in the lending pool before, then we give
    ///      control to the borrower to make the flashloan. After the borrower makes the flashloan
    ///      we check if the lending pool has the same amount of tokens as before.
    /// @param borrower The contract that will have access to the tokens
    /// @param data Function call data to be used by the borrower contract.
    function flashLoan(
        address borrower,
        bytes calldata data
    )
        external
    {
        uint256 balanceBefore = token.balanceOf(address(this));
        
        _flashLoan = true;
        
        borrower.functionDelegateCall(data);

        _flashLoan = false;

        uint256 balanceAfter = token.balanceOf(address(this));
        require(balanceAfter >= balanceBefore, "Flash loan hasn't been paid back");
    }
}

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.14;

import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract InSecureumToken is ERC20 {

    // Decimals are set to 18 by default in `ERC20`
    constructor(uint256 _supply) ERC20("InSecureumToken", "ISEC") {
        _mint(msg.sender, _supply);
    }

}