I built op-stack-hooks (https://github.com/AlexBHarley/op-stack-hooks) one of the first OP Stack Mods. op-stack-hooks allows registering listeners on the L2 for events that happen on the L1. ie,
- listening and reacting to swaps made on Uniswap
- permissionless & automated Chainlink feeds on the L2.
The mod includes changes to op-node, for deriving events and an additional predeploy for registering events.
Acts as a nice demonstration for how OP Stack Mods can be written. Previously the only example I could find was Ticking Optimism (https://stack.optimism.io/docs/build/featured/#ticking-optimism) which is fairly rudimentary. This example shows event parsing, L2 state reads and L2 writes.
