全端Defi平台

本文最後更新於：2022年2月8日 晚上

全端DeFi平台

目的: 建立一個全端的defi平台

  • 待更新部分: 前端建立

1. 建立代幣合約 DappToken.sol

  • 目的: 當作平台的治理幣
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pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
contract DappToken is ERC20 {
    constructor() public ERC20("Dapp Token", "DAPP"){
        _mint(msg.sender, 1000000000000000000000000);
    }
}

2. 建立平台交易合約TokenFarm.sol

1. 先決定交易規則

  • 你可以質押哪一種代幣?
  • 你可以質押多少代幣?

stakeTokens()

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function stakeTokens(uint256 _amount, address _token) public {
        require(_amount > 0, "Amount must be more than 0");
        require(tokenIsAllowed(_token), "Token is currently no allowed");//來自下方兩個函數!
        IERC20(_token).transferFrom(msg.sender, address(this), _amount);//把用戶的代幣轉移到平台合約(我們自己的合約)中
        updateUniqueTokensStaked(msg.sender, _token);
        stakingBalance[_token][msg.sender] = //更新合約中的用戶餘額
            stakingBalance[_token][msg.sender] +
            _amount;
        if (uniqueTokensStaked[msg.sender] == 1) {
            stakers.push(msg.sender);
        }
    }

tokenIsAllowed(address _token)

  • 目的: 篩選可接受的代幣種類
    • loop through 可接受的代幣list 
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address[] public allowedTokens;
function tokenIsAllowed(address _token) public returns (bool) {
        for (
            uint256 allowedTokensIndex = 0;
            allowedTokensIndex < allowedTokens.length;
            allowedTokensIndex++
        ) {
            if (allowedTokens[allowedTokensIndex] == _token) {
                return true;
            }
        }
        return false;
    }

addAllowedTokens()

  • 目的: 把可以交易的代幣推到允許名單「allowedTokens」上
    • 因為只有合約主人可以使用， 函式要加onlyOwner + contract要加 Ownable
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contract TokenFarm is Ownable {  .....
function addAllowedTokens(address _token) public onlyOwner {
        allowedTokens.push(_token);
    }
}

2. 轉移代幣 transferFrom

  • 和 transfer 的不同?
  • 目的: 接受用戶的動作請求
    • 從msg.sender(呼叫此合約的人)到address(this)這個合約
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import "@openzeppelin/contracts/token/ERC20/IERC20.sol";//匯入ERC20的接口

//IERC20(_token)會回傳 abi
function stakeTokens(uint256 _amount, address _token) public {
... //從msg.sender(呼叫此合約的人)到address(this)這個合約
IERC20(_token).transferFrom(msg.sender, address(this), _amount);
...
}

補充: 我們可以使用 ERC20合約的兩個方法(method)來傳送代幣(token)

contract development - Send tokens using approve and transferFrom vs only transfer - Ethereum Stack Exchange

  1. approve() and transferFrom() 他人想要動用自己錢包內的代幣
    • The approve + transferFrom is for a ==3 party transfer,== usually, but not necessarily that of an exchange, where the ==sender wishes to authorize a second party to transfer some tokens on their behalf.==
      • Sender ➜ approve(exchange, amount)
      • Buyer ➜ executes trade on the Exchange
      • Exchange ➜ transferFrom(sender, buyer, amount)
      • user cannot call “transferFrom” directly because otherwise he/she can use anyone else’s token without the corresponding private key or wallet, so he need get approved by the original token owner to use a certain amount of their token
  2. transfer() 自己想要交易’
    • The transfer method is for a ==2 party transfer==, where a sender wishes to transfer some tokens to a receiver.
      • Sender ➜ transfer(receiver, amount)
      • user can unlock his wallet and call “transfer” to transfer his/her own token

mapping stakingBalance

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contract TokenFarm is Ownable { ...
// mapping token address -> staker address -> amount
    mapping(address => mapping(address => uint256)) public stakingBalance;
    }

3. 分配治理幣issueToken

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address[] public stakers; //紀錄質押名單

function stakeTokens(uint256 _amount, address _token) public {
        ...
        updateUniqueTokensStaked(msg.sender, _token);
        stakingBalance[_token][msg.sender] =
            stakingBalance[_token][msg.sender] +
            _amount;
        if (uniqueTokensStaked[msg.sender] == 1) {//如果只有一種代幣，才會該用戶加入質押名單  `stakers`
            stakers.push(msg.sender);
        }
    }

查看用戶質押多少種不同代幣updateUniqueTokensStaked()

mapping uniqueTokensStaked

  • 如果只有一種，就把該用戶加入質押名單 stakers
    • 如果大於一種，就不加入
  • internal : 只有這個合約可以調用該函數
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mapping(address => uint256) public uniqueTokensStaked;

function updateUniqueTokensStaked(address _user, address _token) internal {
// mapping(address => mapping(address => uint256)) public stakingBalance;
    if (stakingBalance[_token][_user] <= 0) {//如果這個user之前不存在
       uniqueTokensStaked[_user] = uniqueTokensStaked[_user] + 1;//就幫她更新名單，回頭在 stakeTokens()被推入 stakers(質押名單)中
        }
    }

3.1 真的要開始分配了…

  1. 設定 constructor + 宣告狀態變數，才能在合約中公開使用我們的 dappToken 合約地址
    1. 能夠使用dappToken 合約的函數!
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IERC20 public dappToken;
constructor(address _dappTokenAddress) public {
        dappToken = IERC20(_dappTokenAddress);
    }
    
function issueTokens() public onlyOwner {
        // Issue tokens to all stakers
        for (
            uint256 stakersIndex = 0;
            stakersIndex < stakers.length;
            stakersIndex++
        ) {
        // 「基於目前質押的"全部"代幣數量」+「送出獎勵代幣」
            address recipient = stakers[stakersIndex];
            uint256 userTotalValue = getUserTotalValue(recipient);
            dappToken.transfer(recipient, userTotalValue);
        }
    }

getUserTotalValue() ~~!!gas expensive!!

  • 目的: 取得用戶在「全部」代幣上質押多少?
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function getUserTotalValue(address _user) public view returns (uint256) {
        uint256 totalValue = 0;
        require(uniqueTokensStaked[_user] > 0, "No tokens staked!"); //確保用戶在名單上
        for (
            uint256 allowedTokensIndex = 0;
            allowedTokensIndex < allowedTokens.length;
            allowedTokensIndex++
        ) {
            totalValue =
                totalValue +
                getUserSingleTokenValue(
                    _user,
                    allowedTokens[allowedTokensIndex]
                );
        }
        return totalValue;
    }

✔COMMENT: 目前市場上有些protocal不使用getUserTotalValue()這種會花費昂貴的gas-fee的方式來分配代幣。他們直接用空投airdrop的方式讓用戶端送出請求!

getUserSingleTokenValue()

  • 目的: 取得用戶在「某一種特定代幣」上質押多少?
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function getUserSingleTokenValue(address _user, address _token)
        public
        view
        returns (uint256)
    {
        if (uniqueTokensStaked[_user] <= 0) {
            return 0;
        }
        // price of the token * stakingBalance[_token][user]
        (uint256 price, uint256 decimals) = getTokenValue(_token);
        return // 10000000000000000000 ETH
        // ETH/USD -> 10000000000
        // 10 * 100 = 1,000
        ((stakingBalance[_token][_user] * price) / (10**decimals));
    }

getTokenValue() setPriceFeedContract() mapping tokenPriceFeedMapping

  • 目的: 透過和chainlink連結獲取pricefeed的資訊，得到匯率
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dependencies:
  - smartcontractkit/chainlink-brownie-contracts@0.2.1
compiler:
  solc:
    remappings:
      - "@chainlink=smartcontractkit/chainlink-brownie-contracts@0.2.1"
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import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
mapping(address => address) public tokenPriceFeedMapping;//map the token to the associated pricefeed
function setPriceFeedContract(address _token, address _priceFeed)
        public
        onlyOwner //只能讓合約主人設定
    {
        tokenPriceFeedMapping[_token] = _priceFeed; //map the token to the pricewfeed
    }
function getTokenValue(address _token)
        public
        view
        returns (uint256, uint256)
    {
        // priceFeedAddress
        address priceFeedAddress = tokenPriceFeedMapping[_token];
        AggregatorV3Interface priceFeed = AggregatorV3Interface(
            priceFeedAddress
        );
        (, int256 price, , , ) = priceFeed.latestRoundData();
        uint256 decimals = uint256(priceFeed.decimals());
        return (uint256(price), decimals);
    }

3. 取消質押 unstakeTokens

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function unstakeTokens(address _token) public {
        uint256 balance = stakingBalance[_token][msg.sender]; //獲取用戶目前餘額
        require(balance > 0, "Staking balance cannot be 0");
        IERC20(_token).transfer(msg.sender, balance);//用戶要返回治理幣!
        stakingBalance[_token][msg.sender] = 0;
        uniqueTokensStaked[msg.sender] = uniqueTokensStaked[msg.sender] - 1; // 去除該用戶質押的代幣種類
    }

reentrancy attacks

4. 開始建立部屬 deploy.py

影片示範

  • weth_token 和fau_token
    • 因為都不是實際存在的測試網 所以需要部屬mock合約
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KEPT_BALANCE = Web3.toWei(100, "ether")

def deploy_token_farm_and_dapp_token(front_end_update=False):
    account = get_account()
    dapp_token = DappToken.deploy({"from": account})
    token_farm = TokenFarm.deploy( #部屬合約
        dapp_token.address,
        {"from": account},
        publish_source=config["networks"][network.show_active()].get("verify",False),
    )
    tx = dapp_token.transfer(
        token_farm.address, dapp_token.totalSupply() - KEPT_BALANCE, {"from": account} #把大部分的治理幣轉去合約儲存，剩餘留給自己(KEPT_BALANCE)
    )
    tx.wait(1)
    # dapp_token, weth_token, fau_token/dai
    weth_token = get_contract("weth_token")#在本地上部屬假的weth token 回傳得到該合約的地址
    fau_token = get_contract("fau_token")#在本地上部屬假的fau token
    dict_of_allowed_tokens = { #每個合約會map到轉換地址
        dapp_token: get_contract("dai_usd_price_feed"),
        fau_token: get_contract("dai_usd_price_feed"),
        weth_token: get_contract("eth_usd_price_feed"),
    }
    add_allowed_tokens(token_farm, dict_of_allowed_tokens, account)
    if front_end_update:
        update_front_end()
    return token_farm, dapp_token

add_allowed_tokens()

目的: 讓用戶可以新增代幣種類，並抓取合約

  • contract_to_mock
    • 在helpful_script.py
    • 用來製作token名稱和地址之間的mapping
    • MockDAI和MockWETH都是「本地的偽ERC代幣合約」
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#in helpful_script.py 用來製作token名稱和地址之間的mapping
contract_to_mock = {
    "eth_usd_price_feed": MockV3Aggregator,
    "dai_usd_price_feed": MockV3Aggregator,
    "fau_token": MockDAI,
    "weth_token": MockWETH,
}
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def add_allowed_tokens(token_farm, dict_of_allowed_tokens, account):
    for token in dict_of_allowed_tokens:
        add_tx = token_farm.addAllowedTokens(token.address, {"from": account})
        add_tx.wait(1)
        set_tx = token_farm.setPriceFeedContract(
            token.address, dict_of_allowed_tokens[token], {"from": account})
        set_tx.wait(1)
    return token_farm

deploy_mocks()

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def deploy_mocks(decimals=DECIMALS, initial_value=INITIAL_PRICE_FEED_VALUE):
    """
    Use this script if you want to deploy mocks to a testnet
    """
    print(f"The active network is {network.show_active()}")
    print("Deploying Mocks...")
    account = get_account()
    print("Deploying Mock Link Token...")
    link_token = LinkToken.deploy({"from": account})
    print("Deploying Mock Price Feed...")
    mock_price_feed = MockV3Aggregator.deploy(
        decimals, initial_value, {"from": account}
    )
    print(f"Deployed to {mock_price_feed.address}")
    print("Deploying Mock DAI...")
    dai_token = MockDAI.deploy({"from": account}) #部屬偽合約
    print(f"Deployed to {dai_token.address}")
    print("Deploying Mock WETH")
    weth_token = MockWETH.deploy({"from": account})
    print(f"Deployed to {weth_token.address}")

主要參考來源:

Solidity, Blockchain, and Smart Contract Course – Beginner to Expert Python Tutorial - YouTube