🔄 SwapTokensApp – ERC20 Token Swapping via Uniswap V2

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📌 Description

SwapTokensApp is a lightweight smart contract written in Solidity that enables ERC20 token swapping using a Uniswap V2-compatible router. It demonstrates secure integration with an external DEX protocol, safe token handling via SafeERC20, and complete test coverage using the Foundry toolchain.

This project is ideal as a foundational primitive for DeFi applications, enabling token swaps with customizable routes, slippage controls, and deadlines — all while maintaining security and minimal gas usage.

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🔧 Features

• ✅ Swap arbitrary ERC20 tokens via Uniswap V2 router
• 🔒 Safe token transfer using SafeERC20 utilities
• 📦 Parametric input for amount, slippage, token route, and deadline
• ⚙️ Designed with extensibility and integration in mind
• 🧪 Tested with real token contracts on Arbitrum Mainnet

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🧱 Contract Overview

SwapTokensApp.sol

function swapTokens(
    uint256 amountIn,
    uint256 amountOutMin,
    address[] memory path,
    uint256 deadline
) external;

Parameters:

• amountIn: amount of input tokens to swap
• amountOutMin: minimum output tokens expected (slippage control)
• path: array of token addresses representing swap route (e.g., [USDT, DAI])
• deadline: UNIX timestamp after which the transaction will revert

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📁 Project Structure

├── src/
│   ├── SwapTokensApp.sol           # Main smart contract
│   └── interfaces/
│       └── IV2Router02.sol         # Uniswap V2 router interface
├── test/
│   └── SwapTokensApp.t.sol         # Full Foundry test suite

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🧪 Testing Details

• ✅ Deployed with real mainnet token addresses (USDT, DAI) on Arbitrum
• 🔄 Simulates swaps using a real Uniswap V2 router
• 📉 Validates token balance changes pre- and post-swap
• 🛠 Built using forge-std/Test.sol utilities

IERC20(USDT).approve(address(swapApp), amountIn);
swapApp.swapTokens(amountIn, amountOutMin, path, deadline);

NOTE: Ensure the test account is funded and impersonation is enabled via vm.startPrank().

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🔐 Security & Best Practices

• Uses SafeERC20 from OpenZeppelin to prevent faulty token behavior
• Validates router approval and input token transfer
• Emits a detailed SwapTokens event on every operation
• Clean separation of concerns with external IV2Router02 interface

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📄 License

This project is licensed under the GNU Lesser General Public License v3.0. For more information, see the LICENSE file.

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🙋 Author

Created with a focus on clean architecture, DeFi interoperability, and real-world usability. Contributions, suggestions, and forks are welcome.