Generate Production-Ready DeFi Protocol Smart Contracts

DeFi Protocol Templates provides production-ready Solidity templates for common DeFi protocols: staking, AMMs, governance, lending, and flash loans. The Staking Contract (StakingRewards) implements OpenZeppelin's ReentrancyGuard and Ownable, tracking per-second reward accrual via rewardPerToken()/earned() and exposing stake(), withdraw(), getReward(), and a combined exit() function. The AMM (SimpleAMM) implements constant-product liquidity pools with addLiquidity()/removeLiquidity() share-minting via the sqrt-of-product formula on first deposit, and a swap() function that applies a 0.3% fee before computing output via the constant-product formula. The Governance Token template pairs an ERC20Votes/ERC20Permit token (GovernanceToken) with a Governor contract implementing propose() (gated by a proposal threshold of past votes), vote() (weighted by getPastVotes() at the proposal's start block), and execute() (requiring forVotes to exceed againstVotes after the roughly 3-day voting period). The Flash Loan template (FlashLoanProvider/IFlashLoanReceiver) charges a 0.09% fee, transfers funds to the receiver, invokes its executeOperation() callback, and verifies the post-loan balance covers principal plus fee before completing:

    function flashLoan(
        address receiver,
        uint256 amount,
        bytes calldata params
    ) external {
        uint256 balanceBefore = token.balanceOf(address(this));
        require(balanceBefore >= amount, "Insufficient liquidity");

        uint256 fee = (amount * feePercentage) / 10000;

        // Send tokens to receiver
        token.transfer(receiver, amount);

        // Execute callback
        require(
            IFlashLoanReceiver(receiver).executeOperation(
                address(token),
                amount,
                fee,
                params
            ),
            "Flash loan failed"
        );

        // Verify repayment
        uint256 balanceAfter = token.balanceOf(address(this));
        require(balanceAfter >= balanceBefore + fee, "Flash loan not repaid");

        emit FlashLoan(receiver, amount, fee);
    }

Use this skill when building staking platforms with reward distribution, implementing AMM protocols, creating governance token systems, developing lending/borrowing protocols, integrating flash loan functionality, or launching yield farming platforms. All four templates default to MIT-licensed, Solidity ^0.8.0 contracts, so it's not the right fit if the target license or compiler version differs from that baseline without adjustment.

Outputs are complete, deployable Solidity contracts - assets/staking-contract.sol, assets/amm-contract.sol, assets/governance-token.sol, assets/lending-protocol.sol - plus deeper reference guides on staking mechanics (references/staking.md), AMM mathematics and pricing (references/liquidity-pools.md), governance/voting systems (references/governance-tokens.md), lending/borrowing implementation (references/lending-protocols.md), and flash loan security (references/flash-loans.md). Named common DeFi patterns to apply on top of the templates include TWAP price oracles for manipulation resistance, liquidity mining incentives, token vesting with gradual release, multisig requirements for critical operations, and governance timelocks. Concrete default parameters ship with the templates: a 0.09% flash-loan fee, a governance proposal threshold of 100,000 tokens (100000 * 10**18), and a roughly 3-day voting period expressed as 17,280 blocks.

Built on OpenZeppelin contracts (IERC20, ReentrancyGuard, Ownable, ERC20Votes) with Solmate named as an alternative established library. The AMM's share-minting math uses a Babylonian-method sqrt() helper for the first liquidity deposit and a min() helper to bound subsequent deposits by whichever token's reserve ratio is scarcer. Seven best practices are stated: use established libraries, test thoroughly across unit, integration, and fuzzing; get a professional security audit before launch; start with an MVP and add features incrementally; monitor contract health and user activity; consider proxy patterns for upgradability; and implement emergency pause mechanisms.

Smart contract developers building DeFi protocols from scratch who want audited-pattern starting points, with events already wired for off-chain indexing (Staked/Withdrawn/RewardPaid, Mint/Burn/Swap, ProposalCreated/VoteCast/ProposalExecuted, FlashLoan) rather than writing these primitives and their event emissions from first principles, while still requiring their own security audit before launch.