Adding a "custom crdt"/"append-only-log" capacity to Loro

[lee-orr]

Hi,

I'm wondering whether you'd be open to accepting a contribution allowing building custom crdt or event logs with projections/a custom materializer on top of Loro's eg-walker-like implementation, versioning system, etc? And if so - what challenges you'd expect in adding such a feature to Loro?

I think adding this kind of system would open the door to using Loro in a way that enables combining some of the capabilities of some of the SQL-style local first systems (like Jazz) or event sourced ones (like LiveStore - like ease of querying, or domain-driven design for data modelling - with the capacities of more traditional CRDTs like collaborative editing of arbitrary JSON-like data and rich text. While I don't think those abilities need to be explicitly added to Loro, having some ability to create custom container & Op types would make this kind of thing much easier and more reliable. (As of now, the best way I can think of doing this without changes to Loro is building on the list, but that requires filtering out "delete" events and forcing "inserts" to the end of the local copy of the list, and doesn't expose a capacity to adjust conflict resolution while materializing - since the list sets up the order, and people can add stuff anywhere in the list)

This is one of a couple of features that I think would be helpful in creating permission/group management CRDTs on top of loro as well - I'll be writing up a separate discussion for some of the ones I feel are more specific to that.