# 第 3 次讀書會主題實作練習 - 建立一個 Bank 銀行

Dapp_陳其駿_Jim

<h3>
Staking Token
</h3>

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract testERC20 is ERC20 {
    constructor() ERC20("testERC20", "tERC") {
        // _mint(msg.sender, 10 ** (9 + 18));
        _mint(msg.sender, 1_000_000_000 * 1e18);
    }
}

<h3>
Bank
</h3>

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract BasicBank {
    
    IERC20 public stakingToken;
    uint256 public totalStakedToken;
    mapping(address => uint256) public balanceOf;
    
    uint256 public withdrawDeadline = 10 seconds;

    uint256 public rewardRate = 1;
    mapping(address => uint256) public rewardOf;

    struct Deposit {
        uint256 amount; 
        uint256 startTime; 
        uint256 endTime; 
    }

    mapping(address => Deposit[]) public depositOf;

    constructor(IERC20 _stakingToken) {
        stakingToken = _stakingToken;
    }

    function updateTotalStakenToken() internal {
        totalStakedToken = stakingToken.balanceOf(address(this));
    }
    function deposit(uint256 _amount) external  {
        stakingToken.transferFrom(msg.sender, address(this), _amount);

        totalStakedToken += _amount;
        balanceOf[msg.sender] += _amount;

        depositOf[msg.sender].push(
            Deposit({
                amount: _amount,
                startTime: block.timestamp,
                endTime: block.timestamp + withdrawDeadline
            })
        );
    }

    function withdraw(uint256 _depositId) external {
        require(balanceOf[msg.sender] > 0, "You have no balance to withdraw");

        Deposit[] storage deposits = depositOf[msg.sender];
        require(block.timestamp >= deposits[_depositId].endTime, "Withdrawal Period is not reached yet");
        require(_depositId <= deposits.length, "Deposit ID not exist!!");

        uint256 currentReward = deposits[_depositId].amount + getInterest(_depositId);
        updateTotalStakenToken();
        
        require(totalStakedToken >= currentReward, "Tokens in the pool is insufficient for the withdrawal");

        rewardOf[msg.sender] += currentReward;

        stakingToken.transfer(msg.sender, currentReward);
        totalStakedToken -= currentReward;
        balanceOf[msg.sender] -= deposits[_depositId].amount;

        deposits[_depositId] = deposits[deposits.length - 1];
        deposits.pop();
    }

    function getInterest(uint256 _depositId) public view returns (uint256) {
        uint256 start = depositOf[msg.sender][_depositId].startTime;
        uint256 _amount = depositOf[msg.sender][_depositId].amount;
        return (block.timestamp - start) * rewardRate * _amount;
    }

    function getAllInterest() public view returns (uint256){
        uint256 N = depositOf[msg.sender].length;
        uint256 allRewards;

        for (uint256 i = 0; i < N; i++) {
            allRewards += getInterest(i);
        }
        return allRewards;
    }
}

<h3>屬性與方法</h3>

>mapping
>>balanceOf：查詢地址的餘額
>>rewardOf：查詢地址領取的總額
>>depositOf：查詢地址的存款狀況

>function
>>deposit：存款方法
>>getInterest：取得存款的利息
>>getAllInterest：取得所有存款的利息
>>withdraw：提領方法