hydrogen-web/doc/impl-thoughts/REPLIES.md

If we were to render replies in a smart way (instead of relying on the fallback), we would need to manually find entries that are pointed to be in_reply_to. Consulting the timeline code, it seems appropriate to add a _replyingTo field to a BaseEventEntry (much like we have _pendingAnnotations and pendingRedactions). We can then:

• use TilesCollection's _findTileIdx to find the tile of the message being replied to, and put a reference to its tile into the new tile being created (?).
  • It doesn't seem appropriate to add an additional argument to TileCreator, but we may want to re-use tiles instead of creating duplicate ones. Otherwise, of course, tileCreator can create more than one tile from an entry's _replyingTo field.
• Resolve _replyingTo much like we resolve redactingEntry in timeline: search by relatedTxnId and relatedEventId if our entry is a reply (we can add an isReply flag there).
  • This works fine for local entries, which are loaded via an AsyncMappedList, but what about remote entries? They are not loaded asynchronously, and the fact that they are not a derived collection is used throughout Timeline.
• Entries that don't have replies that are loadeded (but that are replies) probably need to be tracked somehow?
  • Then, on timeline add, check new IDs and update corresponding entries