Introducing KodeSherpa: Build DeFi Smart Contracts with Ease

If you’ve ever wanted to create DeFi smart contracts but struggled with tricky Solidity patterns like pull payments, staking rewards, or token accounting, Kode Sherpa is here to simplify your journey.

Exploration by Example

Recently, I explored building a staking contract with the pull-payment pattern, and here’s how Kode Sherpa helped streamline the process:

I came up with the analogous requirements for the contract

• ERC20 token

• Same as staked token

• Fixed APR of 5% (500 bps)

• Pull pattern for both principal and rewards

• stake() and unstake() only update internal balances

• withdraw() is the only function that transfers tokens to the user

Every step was based upon questions that was asked by the bot to reach for the proper spefications for the project.

KodeSherpa Exploration

Using Kode Sherpa, I was able to:

• Define staking and rewards logic without worrying about unsafe direct transfers

• Implement per-user checkpointing for accurate reward accrual

• Apply the pull-payment pattern to protect against reentrancy issues

• Lock APR immutably at deployment for predictable yield

Pull-Payment Pattern Benefits

• Users pull their rewards and principal at their convenience

• Protects against reentrancy and gas-limit attacks

• Makes staking contracts safer and more modular

This is the contract which got generated

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

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

contract FixedAprSingleTokenStakingPullPayments is ReentrancyGuard {
    IERC20 public immutable stakingToken;
    uint256 public immutable aprBps; // 500 = 5%
    uint256 private constant YEAR = 365 * 24 * 60 * 60;

    struct StakeInfo {
        uint256 principal;
        uint256 owedRewards;
        uint256 lastAccrualTime;
    }

    mapping(address => StakeInfo) public stakes;
    mapping(address => uint256) public owedBalance;

    constructor(IERC20 _stakingToken) {
        stakingToken = _stakingToken;
        aprBps = 500; // 5%
    }

    function stake(uint256 amount) external {
        require(amount > 0, "Amount must be > 0");

        _accrue(msg.sender);

        stakes[msg.sender].principal += amount;
        stakingToken.transferFrom(msg.sender, address(this), amount);
    }

    function unstake(uint256 amount) external {
        require(amount > 0, "Amount must be > 0");
        _accrue(msg.sender);

        StakeInfo storage info = stakes[msg.sender];
        require(info.principal >= amount, "Not enough staked");
        info.principal -= amount;
        owedBalance[msg.sender] += amount;
    }

    function withdraw() external nonReentrant {
        _accrue(msg.sender);

        uint256 payment = owedBalance[msg.sender];
        require(payment > 0, "Nothing to withdraw");
        owedBalance[msg.sender] = 0;
        stakingToken.transfer(msg.sender, payment);
    }

    function _accrue(address user) internal {
        StakeInfo storage info = stakes[user];
        if (info.principal == 0) {
            info.lastAccrualTime = block.timestamp;
            return;
        }
        uint256 elapsed = block.timestamp - info.lastAccrualTime;
        uint256 reward = (info.principal * aprBps * elapsed) / (YEAR * 10_000);
        info.owedRewards += reward;
        owedBalance[user] += info.owedRewards;
        info.owedRewards = 0;
        info.lastAccrualTime = block.timestamp;
    }
}

Possibilies with Kode Sherpa

With the above example, this will enable user to

• Explore smart contract templates for DeFi, NFTs, and more

• Test ideas quickly without starting from scratch

• Generate production-ready Solidity code with best practices like pull payments built-in.

You can start building your Defi project through the KodeSherpa today.