Time Interpreter / Slotting Arithmetic

[KtorZ]

Describe your idea, in simple words.

The local-state-query protocol provides a GetInterpreter query which returns an interface for running various queries regarding time and slotting arithmetic on Cardano. Behind the scene, the interpreter is constructed from a list of epoch summaries objects, which are also transferred over the wire. This is also how Ogmios currently provides support for this query (called eraSummaries in Ogmios).

While already useful, it does not however provide the full power of the internal TimeInterpreter abstraction from ouroboros-network. This abstraction is used to perform queries for converting times to slot, epochs and the like. It is not possible to transfer such abstraction over the wire, but, it may possible to turn it into a mini-protocol and offer a simple query/response pattern to clients.

Note that, these could be supported via both WebSocket and plain HTTP?

Why is it a good idea?

There's a lot of pitfalls and rooms for error in the time interpretation of the chain. Since a lot of this intelligence has already been put into the Haskell TimeInterpreter, providing support for it via Ogmios could be extremely useful for those looking into slot arithmetic, especially across eras. In particular, the following queries are currently available from the TimeInterpreter:

Query	Description / Effects
wallclockToSlot	Translate a UTC (relative) time to an absolute slot number
slotToWallclock	Convert an absolute slot number to a UTC (relative) time
slotToEpoch	Convert an absolute slot number to an epoch number and slot number within this epoch
epochToSlot	Translate an epoch number to the absolute slot number of the first slot of that epoch
epochToSize	Get the size (in slots) of a given epoch

Are you willing to work on it yourself?

Yes.