# OUTDATED: BLSWallet 4337 Interop

## Summary

- Create a 4337 `EntryPoint` contract which converts the 4337 `UserOperation` to a `Bundle` and calls `processBundle` on the `VerificationGateway`
- Include `simulateValidation` by doing the same thing, include `require(msg.sender == address(0))`, and just return `(0,0)` for `(preOpGas,prefund)`
- This way, when a wallet makes an `eth_sendUserOperation` call, the node can accept it into the 4337 `UserOperation` mempool
- Once in the `UserOperation` mempool, participants that are aware of our 4337 `EntryPoint` can convert these `UserOperation`s into bundles, aggregate them (taking advantage of BLS signature aggregation), and submit the `processBundle` call if it is profitable for them to do so

## How Wallets Can Integrate BLSWallet This Way

Wallets still need to know how to convert an `eth_sendTransaction` call into a BLSWallet appropriate `eth_sendUserOperation` call. We can provide a module to help with this. It's expected that a wallet will write something like this:

async function handle_eth_sendTransaction(tx) {
  const blsPrivateKey = lookupBlsPrivateKey(tx.from);

  if (blsPrivateKey === undefined) {
    // Error / handle non-BLSWallet account
  }

  const userOperation = blsWallet4337.txToUserOperation(tx, blsPrivateKey);

  return await request({
    method: 'eth_sendUserOperation',
    params: [userOperation, blsWallet4337.entryPointAddress],
  });
}

There's also a setup requirement. Transactions and `UserOperation`s use an address to identify the contract wallet and `processBundle` requires the BLS public key instead. The Wallet will need to explicitly initialize the contract wallet so that the `VerificationGateway` will store the mapping:

async function initWallet(privateKey) {
  const wallet = await BlsWalletWrapper.connect(
    privateKey,
    verificationGateway.address,
    provider,
  );
  
  const bundle = wallet.sign({
    nonce: 0,
    actions: [],
  });
  
  await verificationGateway.processBundle(bundle);
}

## Draft of BLSWallet's 4337 `EntryPoint`

contract EntryPoint {
  function handleOps(
    UserOperation[] calldata ops,
    address payable beneficiary
  ) public {
    for (uint i = 0; i < ops.length; i++) {
      _handleOp(ops[i]);
    }
  }

  function simulateValidation(
    UserOperation calldata op
  ) external returns (uint preOpGas, uint prefund) {
    require(msg.sender == address(0), "must be called off-chain with from=zero-addr");

    _handleOp(op);

    preOpGas = 0;
    prefund = 0;
  }

  function _handleOp(
    UserOperation calldata op
  ) private {
    uint[BLS_KEY_LEN][] memory senderPublicKeys = new uint[BLS_KEY_LEN][](1);

    senderPublicKeys[0] = verificationGateway.walletFromHash[
      verificationGateway.hashFromWallet[op.sender]
    ];

    IWallet.Operation[] memory operations = new IWallet.Operation[](1);
    operations[0].nonce = op.nonce;
    operations[0].actions = op.callData; // TODO: bytes->actions conversion

    Bundle memory bundle = Bundle({
      signature: op.signature, // TODO: bytes->uint[2] conversion
      senderPublicKeys: senderPublicKeys,
    });

    verificationGateway.processBundle(toBundle(ops[i]));
  }
}

## Work to Be Done

1. `EntryPoint` contract
2. `blsWallet4337` npm module to assist wallet integration (or extend `bls-wallet-clients`)
3. Add to aggregator or create aggregator-like node that participates in the `UserOperation` mempool to submit bundles

## Potential Issues
- 4337 is prescriptive about how the `EntryPoint` and associated wallets work (in ways that don't fit BLS Wallet). These don't seem to be necessary, but could cause adoption concerns.

## Links

- [EIP-4337](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-4337.md)
- [Reference implementation of 4337 `EntryPoint`](https://github.com/eth-infinitism/account-abstraction/blob/develop/contracts/core/EntryPoint.sol)