Add ERC-4337 UserOperation type and encoding #27

Title

Add ERC-4337 UserOperation type and encoding

Labels

enhancement, account-abstraction, erc-4337

Description

Implement the core UserOperation struct according to ERC-4337 specification to enable account abstraction functionality, similar to viem's implementation.

Requirements

Core Type

• Define UserOperation struct with all ERC-4337 required fields:
  • sender: Address - Account making the operation
  • nonce: u256 - Anti-replay parameter (now using native u256!)
  • init_code: []u8 - Account creation code (for first tx)
  • call_data: []u8 - Data to pass to sender during execution
  • call_gas_limit: u256 - Gas limit for main execution call
  • verification_gas_limit: u256 - Gas for account validation
  • pre_verification_gas: u256 - Fixed gas overhead
  • max_fee_per_gas: u256 - Max fee per gas unit (EIP-1559)
  • max_priority_fee_per_gas: u256 - Max priority fee (EIP-1559)
  • paymaster_and_data: []u8 - Paymaster address and extra data
  • signature: []u8 - Signature over the userOp hash

Encoding & Hashing

• Implement packed ABI encoding for UserOperation
• Add getUserOpHash(op: UserOperation, entry_point: Address, chain_id: u64) Hash
• Add packUserOp(op: UserOperation) []u8 for encoding

Helper Methods

• init() - Create new UserOperation
• deinit() - Free allocated memory
• isDeployment() - Check if this deploys a new account (has init_code)

File Structure

src/account_abstraction/
  ├── user_operation.zig    # Core UserOperation type
  ├── types.zig             # AA-related types
  └── root.zig              # Module exports

References

• ERC-4337: https://eips.ethereum.org/EIPS/eip-4337
• Viem: https://github.com/wevm/viem/tree/main/src/account-abstraction
• Account Abstraction contracts: https://github.com/eth-infinitism/account-abstraction

Benefits

• Enable gasless transactions
• Smart contract wallet support
• Batch operations
• Session keys and permissions
• Social recovery