Hooks are functions triggered at specific stages of a transaction, allowing for the integration of bespoke logic and actions before or after transfers.
These enable the customization of SuperBridge and SuperToken to meet specific requirements, such as token investments or state variable updates, by executing custom logic at predetermined points in the transaction process.
A hook can be written by following the IHook interface. It should contain the 6 functions that are called at various stages of bridging.
<aside> 💡 Hooks are part of our modular approach and allow for customizable and extendable functionality within smart contracts. Create your own hooks to change how the contract behaves in response to specific events or conditions.
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Some frequently used hooks are included in the core project. Developers can also write custom hooks tailored to their use case. Available hooks contracts include:
LimitHook [See interface here]: This hook adds logic to throttle the maximum amount that can be bridged in a day. It can be used to control the maximum damage in case of hacks. Bridged amounts can be optionally limited for risk isolation. Those limits are enforced on-chain and can be updated by your Chain/DAO. Specific function calls on the vault contracts allow real-time monitoring of limits and capacity.ExecutionHook [See interface here]: This hook adds the ability to execute arbitrary payload on the receiver when tokens are delivered on the destination chain.YieldHook: Should the bridged token continue to earn a yield on the source chain? The bridged token can continue earning yield on the original or source chain after it has been deposited on the bridge. For this, the token is deposited on a platform that generates yield on the source chain, like Aave. The YieldHook requires an additional IStrategy contract that handles the integration of the contract that provides the yield, see interface here.Different hooks are called at different times in the flow of a bridging transaction. Here is the lifecycle of the hooks:
srcPreHookCall: Executes before initiating a transfer from the source. It allows for custom logic to be applied to the source asset before the transfer begins.srcPostHookCall: Executes after a transfer from the source has been completed. This hook enables additional actions or checks to be performed after the source asset has been transferred.dstPreHookCall: Executes before initiating a transfer to the destination. Similar to srcPreHookCall, but for the destination asset, allowing for pre-transfer custom logic on the receiving end.dstPostHookCall: Executes after a transfer to the destination is completed. It allows for post-transfer actions or validations on the destination asset.preRetryHook: Executes before retrying a failed transaction. This hook provides a chance to adjust parameters or perform cleanup before attempting the transaction again.postRetryHook: Executes after retrying a failed transaction. It allows for handling the outcomes of the retry attempt, whether successful or not, and to cache or clean up data accordingly.<aside> ⚠️ For any contracts functioning as hooks, they need to follow the interface of the IHook contract.
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