> For the complete documentation index, see [llms.txt](https://docs.pharos.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.pharos.xyz/developer-guide/foundry/write-your-first-uniswap-contract.md). # Write Your First Uniswap Contract This guide will walk you through the process of creating and deploying a simple Uniswap-like decentralized exchange (DEX) contract on the Pharos blockchain. By the end of this guide, you will have a basic understanding of how automated market makers (AMMs) work and how to implement a simple DEX. ### Prerequisites Before you begin, ensure you have the following: * Git: Used for code management and obtain examples. * Node.js: Install it from [nodejs.org](https://nodejs.org/). * Pharos Devnet/Testnet Access: Access to a Pharos node (local or remote) for interacting with the blockchain. ### Setup 1: Install Foundry * [Foundry](https://book.getfoundry.sh/getting-started/installation) ### Setup 2: Set Up the Project Clone the example repo: ```shell git clone https://github.com/PharosNetwork/examples cd examples/uniswap/foundry/contract ``` Install OpenZeppelin Contracts: * Foundry uses forge to manage dependencies. Install OpenZeppelin contracts: ```shell forge install OpenZeppelin/openzeppelin-contracts --no-git ``` ### Step 3: Write the Uniswap Contract Create a New Solidity File: * Create a new file for your uniswap contract: ```shell touch src/Uniswap.sol ``` Write the uniswap Contract: * Open `src/Uniswap.sol` in your favorite text editor and add the following code: ```solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.0; import "openzeppelin-contracts/contracts/token/ERC20/IERC20.sol"; contract Uniswap { address public tokenA; address public tokenB; uint256 public reserveA; uint256 public reserveB; constructor(address _tokenA, address _tokenB) { tokenA = _tokenA; tokenB = _tokenB; } function addLiquidity(uint256 amountA, uint256 amountB) external { require(IERC20(tokenA).transferFrom(msg.sender, address(this), amountA), "Transfer failed"); require(IERC20(tokenB).transferFrom(msg.sender, address(this), amountB), "Transfer failed"); reserveA += amountA; reserveB += amountB; } function removeLiquidity(uint256 amountA, uint256 amountB) external { require(reserveA >= amountA && reserveB >= amountB, "Insufficient reserves"); reserveA -= amountA; reserveB -= amountB; require(IERC20(tokenA).transfer(msg.sender, amountA), "Transfer failed"); require(IERC20(tokenB).transfer(msg.sender, amountB), "Transfer failed"); } function swapAToB(uint256 amountA) external { uint256 amountB = (amountA * reserveB) / reserveA; require(IERC20(tokenA).transferFrom(msg.sender, address(this), amountA), "Transfer failed"); require(IERC20(tokenB).transfer(msg.sender, amountB), "Transfer failed"); reserveA += amountA; reserveB -= amountB; } function swapBToA(uint256 amountB) external { uint256 amountA = (amountB * reserveA) / reserveB; require(IERC20(tokenB).transferFrom(msg.sender, address(this), amountB), "Transfer failed"); require(IERC20(tokenA).transfer(msg.sender, amountA), "Transfer failed"); reserveB += amountB; reserveA -= amountA; } } ``` Compile the Smart Contract: * Use forge to compile the contract: ```shell forge build ``` Test the Smart Contract * Use forge to test the contract: ```shell forge test ``` ### Step 4: Deploy the Uniswap Contract Create a Deployment Script: * Create a new file for the deployment script: ```shell touch script/DeployUniswap.s.sol ``` Write the Deployment Script: * Open script/DeployUniswap.s.sol and add the following code: ```solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.0; import "forge-std/Script.sol"; import "../src/Uniswap.sol"; contract DeployUniswap is Script { function run() external { uint256 deployerPrivateKey = vm.envUint("PRIVATE_KEY"); vm.startBroadcast(deployerPrivateKey); address tokenA = address(0xAA); // Replace with the address of token A address tokenB = address(0xBB); // Replace with the address of token B Uniswap uniswap = new Uniswap(tokenA, tokenB); vm.stopBroadcast(); } } ``` Set the private key: ```shell export PRIVATE_KEY= ``` Deploy the Contract: * Use forge to deploy the contract to the Pharos Testnet: ```shell forge script script/DeployUniswap.s.sol --rpc-url --broadcast ``` ### Step 5: Interact with the Uniswap Contract Open `script/InteractUniswap.s.sol` and add the following code: ```solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.0; import "forge-std/Script.sol"; import "../src/Uniswap.sol"; import "../test/Uniswap.t.sol"; contract DeployUniswap is Script { function run() external { uint256 deployerPrivateKey = vm.envUint("PRIVATE_KEY"); vm.startBroadcast(deployerPrivateKey); MockERC20 tokenA = new MockERC20("TokenA", "TKA"); MockERC20 tokenB = new MockERC20("TokenB", "TKB"); Uniswap uniswap = new Uniswap(address(tokenA), address(tokenB)); console.log("TokenA deployed at:", address(tokenA)); console.log("TokenB deployed at:", address(tokenB)); console.log("Uniswap deployed at:", address(uniswap)); vm.stopBroadcast(); } } ``` Execute the script using forge: ```shell forge script script/InteractUniswap.s.sol --rpc-url --broadcast ``` ### Troubleshooting * **Contract Deployment Fails**: Ensure you have enough testnet tokens to cover the deployment cost. * **Interaction Issues**: Verify that the contract address and ABI are correct. * **Test Failures**: Check the test output for detailed error messages and adjust the tests accordingly. ### Conclusion This guide provides a comprehensive introduction to creating and deploying a Uniswap-like contract on the Pharos blockchain using Foundry. 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