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 Hardhat

• Hardhat

Setup 2: Set Up the Project

Clone the example repo:

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

Install OpenZeppelin Contracts:

npm install

Step 3: Write the Uniswap Contract

Create a New Solidity File:

• Create a new file for your uniswap contract:

touch contracts/Uniswap.sol

Write the uniswap Contract:

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

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/token/ERC20/ERC20.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:

npx hardhat compile

Test the Smart Contract

npx hardhat test

Step 4: Deploy the Uniswap Contract

Set the private key:

npx hardhat vars set PRIVATE_KEY

Deploy the Contract:

npx hardhat ignition deploy ./ignition/modules/Token.js --network pharos

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 Hardhat. If you encounter any issues, refer to the Hardhat documentation or the troubleshooting section. Happy building! 🚀