DeFi protocol templates

--- name: defi-protocol-templates description: Implement DeFi protocols with production-ready templates for staking, AMMs, governance, and lending systems. Use when building decentralized finance applications or smart contract protocols. --- # DeFi Protocol Templates Production-ready templates for common DeFi protocols including staking, AMMs, governance, lending, and flash loans. ## When to Use This Skill - Building staking platforms with reward distribution - Implementing AMM (Automated Market Maker) protocols - Creating governance token systems - Developing lending/borrowing protocols - Integrating flash loan functionality - Launching yield farming platforms ## Staking Contract ``solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.0; import "@openzeppelin/contracts/token/ERC20/IERC20.sol"; import "@openzeppelin/contracts/security/ReentrancyGuard.sol"; import "@openzeppelin/contracts/access/Ownable.sol"; contract StakingRewards is ReentrancyGuard, Ownable { IERC20 public stakingToken; IERC20 public rewardsToken; uint256 public rewardRate = 100; // Rewards per second uint256 public lastUpdateTime; uint256 public rewardPerTokenStored; mapping(address => uint256) public userRewardPerTokenPaid; mapping(address => uint256) public rewards; mapping(address => uint256) public balances; uint256 private _totalSupply; event Staked(address indexed user, uint256 amount); event Withdrawn(address indexed user, uint256 amount); event RewardPaid(address indexed user, uint256 reward); constructor(address _stakingToken, address _rewardsToken) { stakingToken = IERC20(_stakingToken); rewardsToken = IERC20(_rewardsToken); } modifier updateReward(address account) { rewardPerTokenStored = rewardPerToken(); lastUpdateTime = block.timestamp; if (account != address(0)) { rewards[account] = earned(account); userRewardPerTokenPaid[account] = rewardPerTokenStored; } _; } function rewardPerToken() public view returns (uint256) { if (_totalSupply == 0) { return rewardPerTokenStored; } return rewardPerTokenStored + ((block.timestamp - lastUpdateTime) * rewardRate * 1e18) / _totalSupply; } function earned(address account) public view returns (uint256) { return (balances[account] * (rewardPerToken() - userRewardPerTokenPaid[account])) / 1e18 + rewards[account]; } function stake(uint256 amount) external nonReentrant updateReward(msg.sender) { require(amount > 0, "Cannot stake 0"); _totalSupply += amount; balances[msg.sender] += amount; stakingToken.transferFrom(msg.sender, address(this), amount); emit Staked(msg.sender, amount); } function withdraw(uint256 amount) public nonReentrant updateReward(msg.sender) { require(amount > 0, "Cannot withdraw 0"); _totalSupply -= amount; balances[msg.sender] -= amount; stakingToken.transfer(msg.sender, amount); emit Withdrawn(msg.sender, amount); } function getReward() public nonReentrant updateReward(msg.sender) { uint256 reward = rewards[msg.sender]; if (reward > 0) { rewards[msg.sender] = 0; rewardsToken.transfer(msg.sender, reward); emit RewardPaid(msg.sender, reward); } } function exit() external { withdraw(balances[msg.sender]); getReward(); } } ` ## AMM (Automated Market Maker) ``solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.0; import "@openzeppelin/contracts/token/ERC20/IERC20.sol"; contract SimpleAMM { IERC20 public token0; IERC20 public token1; uint256 public reserve0; uint256 public reserve1; uint256 public totalSupply; mapping(address => uint256) public balanceOf; event Mint(address indexed to, uint256 amount); event Burn(address indexed from, uint256 amount); event Swap(address indexed trader, uint256 amount0In, uint256 amount1In, uint256 amount0Out, uint256 amount1Out); constructor(address token0, address token1) { token0 = IERC20(token0); token1 = IERC20(token1); } function addLiquidity(uint256 amount0, uint256 amount1) external returns (uint256 shares) { token0.transferFrom(msg.sender, address(this), amount0); token1.transferFrom(msg.sender, address(this), amount1); if (totalSupply == 0) { shares = sqrt(amount0 amount1); } else { shares = min( (amount0 totalSupply) / reserve0, (amount1 * totalSupply) / reserve1 ); } require(shares > 0, "Shares = 0"); mint(msg.sender, shares); update( token0.balanceOf(address(this)), token1.balanceOf(address(this)) ); emit Mint(msg.