The Future of Web3

// Account Abstraction with Permissionless.js and Pimlico
// Install: npm install permissionless viem

import { createSmartAccountClient } from 'permissionless';
import { toSimpleSmartAccount } from 'permissionless/accounts';
import { createPublicClient, http } from 'viem';
import { sepolia } from 'viem/chains';
import { createPimlicoClient } from 'permissionless/clients/pimlico';

// Create a smart account
const publicClient = createPublicClient({
  chain: sepolia,
  transport: http('https://eth-sepolia.g.alchemy.com/v2/KEY'),
});

const pimlicoClient = createPimlicoClient({
  transport: http('https://api.pimlico.io/v2/sepolia/rpc?apikey=YOUR_KEY'),
  entryPoint: { address: '0x0000000071727De22E5E9d8BAf0edAc6f37da032', version: '0.7' },
});

const smartAccount = await toSimpleSmartAccount({
  client: publicClient,
  owner: localWalletOrPasskey, // Can be a passkey, social login, etc.
  entryPoint: { address: '0x0000000071727De22E5E9d8BAf0edAc6f37da032', version: '0.7' },
});

const smartAccountClient = createSmartAccountClient({
  account: smartAccount,
  chain: sepolia,
  bundlerTransport: http('https://api.pimlico.io/v2/sepolia/rpc?apikey=YOUR_KEY'),
  paymaster: pimlicoClient, // Pimlico sponsors gas!
  userOperation: {
    estimateFeesPerGas: async () => (await pimlicoClient.getUserOperationGasPrice()).fast,
  },
});

// Send a gasless transaction — the paymaster pays!
const hash = await smartAccountClient.sendTransaction({
  to: '0xRecipient...',
  value: 0n,
  data: '0x...',
});
console.log('UserOperation hash:', hash);

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

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

/// @title SoulboundToken — Non-transferable identity token
contract SoulboundToken is ERC721 {
    uint256 private _nextTokenId;
    address public issuer;

    mapping(uint256 => string) public credentials; // tokenId => credential type
    mapping(address => bool) public hasToken;

    error TokenIsSoulbound();
    error AlreadyIssued();

    constructor() ERC721("Identity SBT", "ISBT") {
        issuer = msg.sender;
    }

    function issue(address to, string calldata credential) external {
        require(msg.sender == issuer, "Only issuer");
        if (hasToken[to]) revert AlreadyIssued();

        uint256 tokenId = _nextTokenId++;
        _mint(to, tokenId);
        credentials[tokenId] = credential;
        hasToken[to] = true;
    }

    // Override transfers to make token soulbound (non-transferable)
    function _update(address to, uint256 tokenId, address auth)
        internal override returns (address)
    {
        address from = _ownerOf(tokenId);
        // Allow minting (from == address(0)) and burning (to == address(0))
        // but block transfers between users
        if (from != address(0) && to != address(0)) {
            revert TokenIsSoulbound();
        }
        return super._update(to, tokenId, auth);
    }
}