Orderflow observability spec

SUAVE
1

Proposing some standard events for SUAPPs to signal orderflow via logs. The idea is to emit these events from various SUAPPs, so we have a standard interface for observing orderflow in L1/L2/block-builder/etc applications.

design

The goal was to emit logs automatically in response to calling functions like sendBundle in suave-std but I couldn’t work out how to do it, since emitting logs changes state. We only change state in the callback of a CCR; not in the first step, which is where those functions are called.
So this is an opt-in design. Following that idea, we could host some standard events like this:

Events are defined in an abstract contract (ideally in suave-std):

abstract contract ObservableOrderflow {
    event SentTransaction(bytes32 txHash);
}

Then SUAPP developers import and emit those events in their own callbacks:

contract Suapp is ObservableOrderflow {
    event MySuappEvent(uint256 x);
    modifier confidential() {
        require(Suave.isConfidential(), "must be called confidentially");
        _;
    }
    function didSomething(bytes32[] memory txHashes, uint256 x) public confidential {
        emit MySuappEvent(x);
        emit SentTransactions(txHashes);
    }
    function doSomething() public confidential returns (bytes memory) {
        // pretend these are tx hashes that we're handling in our SUAPP
        bytes32[] memory txHashes = new bytes32[](3);
        for (uint256 i = 0; i < txHashes.length; i++) {
            txHashes[i] = keccak256(abi.encode("tx", i));
        }
        return abi.encodeWithSelector(this.didSomethingWithTxs.selector, txHashes, 9001);
    }
}

This would be easier if we didn’t have to do this in a callback.
Mateusz’ idea for async chain state transitions has the potential resolve this constraint.

h/t @dmarz for coming up with the idea

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