Add middleware for UserOperation lifecycle management

[ch4r10t33r]

Title

Add middleware for UserOperation lifecycle management

Labels

enhancement, account-abstraction, middleware, ux

Description

Create middleware to automate the complete UserOperation workflow, making it as easy to use as regular transactions.

Requirements

UserOperation Builder

• Implement builder pattern for creating UserOperations:

  pub const UserOperationBuilder = struct {
      allocator: Allocator,
      sender: ?Address,
      call_data: ?[]u8,
      // ... partial fields
      
      pub fn init(allocator: Allocator) UserOperationBuilder;
      pub fn setSender(self: *Self, address: Address) *Self;
      pub fn setCallData(self: *Self, data: []u8) *Self;
      pub fn setValue(self: *Self, value: u256) *Self;
      pub fn usePaymaster(self: *Self, service: *Paymaster) *Self;
      pub fn estimateGas(self: *Self, provider: *Provider) *Self;
      pub fn build(self: *Self) !UserOperation;
  };

Nonce Management

• UserOpNonceMiddleware:
  • Track nonces per smart account
  • Support nonce keys for parallel operations
  • Handle sequential and parallel nonce modes
  • Auto-increment after submission

Gas Management

• UserOpGasMiddleware:
  • Automatic gas estimation
  • Gas price suggestions (maxFeePerGas, maxPriorityFeePerGas)
  • Safety margins and multipliers
  • Network-specific optimizations

Signing Middleware

• UserOpSignerMiddleware:
  • Automatic UserOp signing
  • Support multiple signer types
  • EIP-712 structured data signing
  • Multi-sig coordination

Submission & Confirmation

• UserOpSubmissionMiddleware:

  • Automatic bundler selection
  • Retry logic for failed submissions
  • Wait for confirmation with timeout
  • Status polling

• waitForUserOperation(hash: Hash, timeout_ms: u64) UserOperationReceipt

Complete Workflow Chain

• Combine all middleware:

  const aa_provider = try provider
      .withSmartAccount(account)
      .withPaymaster(paymaster_service)
      .withUserOpMiddleware(.{
          .auto_estimate_gas = true,
          .auto_nonce = true,
          .auto_sign = true,
      });
  
  // Simple as a regular transaction!
  const receipt = try aa_provider.sendUserOperation(.{
      .to = recipient,
      .value = @as(u256, 1_000_000),
      .data = &[_]u8{},
  });

Error Recovery

• Handle common AA errors:
  • Nonce mismatch recovery
  • Gas estimation failures
  • Paymaster rejections
  • Signature issues
  • Account not deployed

File Structure

src/account_abstraction/middleware/
  ├── builder.zig              # UserOperation builder
  ├── nonce.zig                # Nonce management
  ├── gas.zig                  # Gas estimation
  ├── signer.zig               # Signing
  ├── submission.zig           # Submission & confirmation
  └── root.zig                 # Combined middleware

Example Usage

// Simple sponsored transaction
const aa_provider = try provider
    .withSmartAccount(my_account)
    .withPaymaster(pimlico);

// Send like a normal transaction!
const receipt = try aa_provider.sendTransaction(.{
    .to = recipient,
    .value = @as(u256, 1_000_000_000_000_000_000), // 1 ETH
    .data = &[_]u8{},
});

std.debug.print("✅ Gasless transaction confirmed!\n", .{});
std.debug.print("   Hash: {}\n", .{receipt.userOpHash});
std.debug.print("   Gas paid by: {}\n", .{receipt.paymaster.?});

References

• Viem middleware: https://github.com/wevm/viem/tree/main/src/account-abstraction
• ERC-4337: https://eips.ethereum.org/EIPS/eip-4337