EIP-2612-NextJS.md

# EIP-2612 Implementation in Next.js

## Overview
This implementation showcases how we can integrate the EIP-2612 standard (permit function) into a Next.js application. EIP-2612 allows for gasless approvals in Ethereum-based tokens.

## Installation
To get started, you need to have Node.js and npm installed. Then, initialize a Next.js project and install the necessary dependencies.

```bash
npx create-next-app eip2612-nextjs
cd eip2612-nextjs
npm install ethers

EIP-2612 Contract Example

Here’s a basic ERC-20 contract with the permit function that follows the EIP-2612 standard:

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/draft-ERC20Permit.sol";

contract MyToken is ERC20, ERC20Permit {
    constructor() ERC20("MyToken", "MTK") ERC20Permit("MyToken") {
        _mint(msg.sender, 1000000 * 10 ** 18);
    }
}

This smart contract allows for the permit function, enabling token approvals via signatures instead of requiring on-chain transactions for approval.

Frontend Integration

In your Next.js application, create a simple form to handle the permit function using the user's signature.

pages/index.js

import { useState } from "react";
import { ethers } from "ethers";

export default function Home() {
  const [amount, setAmount] = useState("");
  const [signature, setSignature] = useState("");
  const [spender, setSpender] = useState("");

  const handlePermit = async () => {
    const provider = new ethers.providers.Web3Provider(window.ethereum);
    const signer = provider.getSigner();
    const address = await signer.getAddress();
    
    const domain = {
      name: "MyToken",
      version: "1",
      chainId: 1,
      verifyingContract: "0xYourContractAddress",
    };

    const types = {
      Permit: [
        { name: "owner", type: "address" },
        { name: "spender", type: "address" },
        { name: "value", type: "uint256" },
        { name: "nonce", type: "uint256" },
        { name: "deadline", type: "uint256" },
      ],
    };

    const value = {
      owner: address,
      spender,
      value: ethers.utils.parseUnits(amount, 18).toString(),
      nonce: 0, // Replace with actual nonce value
      deadline: Math.floor(Date.now() / 1000) + 60 * 20, // 20 minutes from now
    };

    const signature = await signer._signTypedData(domain, types, value);
    setSignature(signature);
  };

  return (
    <div>
      <h1>EIP-2612 Permit Example</h1>
      <input
        type="text"
        placeholder="Spender Address"
        value={spender}
        onChange={(e) => setSpender(e.target.value)}
      />
      <input
        type="number"
        placeholder="Amount"
        value={amount}
        onChange={(e) => setAmount(e.target.value)}
      />
      <button onClick={handlePermit}>Sign Permit</button>
      {signature && (
        <div>
          <h3>Signature:</h3>
          <p>{signature}</p>
        </div>
      )}
    </div>
  );
}

Explanation

• Domain: This is the EIP-712 domain separator that includes the token's name, version, chainId, and contract address.
• Types: Defines the structure of the permit data according to the EIP-2612 standard.
• Value: The actual permit data containing the owner's address, spender's address, amount, nonce, and deadline.
• Signature: After signing the data with the user's private key, the resulting signature is displayed on the frontend.

Conclusion

This is a basic implementation of EIP-2612 in a Next.js app. You can extend it to include sending the signed permit to your smart contract for further processing.