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.

  • Pharos Devnet/Testnet Access: Access to a Pharos node (local or remote) for interacting with the blockchain.

Setup 1: Install Foundry

Setup 2: Set Up the Project

Clone the example repo:

git clone https://github.com/PharosNetwork/examples
cd examples/uniswap/foundry/contract

Install OpenZeppelin Contracts:

  • Foundry uses forge to manage dependencies. Install OpenZeppelin contracts:

forge install OpenZeppelin/openzeppelin-contracts --no-git --no-commit

Step 3: Write the Uniswap Contract

Create a New Solidity File:

  • Create a new file for your uniswap contract:

touch src/Uniswap.sol

Write the uniswap Contract:

  • Open src/Uniswap.sol in your favorite text editor and add the following code:

// 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:

forge build

Test the Smart Contract

  • Use forge to test the contract:

forge test

Step 4: Deploy the Uniswap Contract

Create a Deployment Script:

  • Create a new file for the deployment script:

touch script/DeployUniswap.s.sol

Write the Deployment Script:

  • Open script/DeployUniswap.s.sol and add the following code:

// 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:

export PRIVATE_KEY=<your private key>

Deploy the Contract:

  • Use forge to deploy the contract to the Pharos Testnet:

forge script script/DeployUniswap.s.sol --rpc-url <PHAROS_RPC_URL> --broadcast

Step 5: Interact with the Uniswap Contract

Open script/InteractUniswap.s.sol and add the following code:

// 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:

forge script script/InteractUniswap.s.sol --rpc-url <PHAROS_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. If you encounter any issues, refer to the Foundry documentation or the troubleshooting section. Happy building! 🚀

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