Hub & Spoke

iLayer smart contracts form the backbone of the iLayer network, enabling secure and trustless interactions between users and solver bots. They allow value exchange without counterparty risk through a locking mechanism similar to an atomic swap, mediated by LayerZero cross-chain messaging system.

At the core, the system is split into two main parts deployed on every supported chain:

• OrderHub: Responsible for order creation and withdrawal, input token custody and order settlement.

• OrderSpoke: Handles order filling and output token disbursement.

Each chain supported by iLayer features both a Hub contract and a Spoke contract, deployed under deterministic and consistent addresses using Create3 (on EVM-compatible chains).

The intent flow

1. Creating an Order (OrderHub):

• A user creates an order specifying:

  • Input tokens (ERC20, ERC721, ERC1155) they're willing to trade.

  • Desired output tokens on the destination chain.

  • Deadlines, destination chain ID, optional sponsored fees, and an optional execution hook (callRecipientand callData).

• The user signs the order off-chain.

• The OrderHub contract verifies the user's signature and nonce to prevent replay attacks.

• Input tokens are transferred from the user to the OrderHub for secure custody.

• Order state is marked as ACTIVE.

Key function: createOrder()

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2. Filling an Order (OrderSpoke):

• When a solver (executor bot or service) fills an order, they trigger the fillOrder() function in the OrderSpoke contract on the destination chain.

• The OrderSpoke verifies that:

  • The order hasn't expired.

  • The solver is allowed to fill it by checking if the msg.sender is the designated primary filler or the primary deadline has expired and anyone can fill it.

  • The order hasn’t already been filled.

• The solver provides output tokens to the OrderSpoke, ensuring the balance matches the amounts defined in the Order. Any positive slippage / excess is kept by the Spoke contract.

• If specified in the Order intent, the Spoke also executes an external hook via an Executor contract safely isolated to prevent malicious behavior or reentrancy.

• The OrderSpoke sends a message back to the originating chain (OrderHub) using LayerZero, signaling successful execution and settlement details.

Key function: fillOrder()

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3. Settling Orders (OrderHub receiving confirmation):

• Upon receiving a cross-chain message (_lzReceive()):

  • OrderHub marks the order status as FILLED.

  • Input tokens held in custody are released to the solver’s funding wallet.

This completes the settlement: the user gets desired assets on the destination chain, and the solver receives input tokens on the source chain.

Key function: _lzReceive()