Aggregation API: Local echo for reactions

[manuroe]

Update the SDK to improve UX responsiveness by using local echo for reactions.

[manuroe]

Kamino cloned this issue to vector-im/riotX-android

[SBiOSoftWhare]

Reaction local echo TODO:

• Queue reaction local echoes from MXAggregatedReactionsUpdater (or in MXRoom.outgoingMessages ?).
• When receiving a reaction remote echo verify if a local echo reaction is matching by checking if:
  • Event sender id are equals
  • m.relates_to properties are equals
• When a local echo reaction is added or removed -[MXAggregatedReactionsUpdater notifyReactionCountChangeListenersOfRoom:event:reactionCount:isNewReaction:] should be called.
• Handle resend and cancel of reaction local echoes. Currently message local echoes are handled in MXKRoomDataSource with resendEventWithEventId:success:failure: and removeEventWithEventId: methods.
• When asking for aggregated reactions on an event we should return remote and local echoes. -[MXAggregatedReactions aggregatedReactionsOnEvent:inRoom:] method should be updated.
• User interaction on a reaction should be disabled if it contains a pending local echo. A property hasLocalEcho could be added on MXReactionCount. We could use an alpha of 30% on the reaction to show this disabled status. To limit react/unreact burst we could also debounce and wait until user stop to tap on a reaction during 1 sec.
• React on a local echo event should be avoided.

Note: Reaction aggregation MXEvent.unsignedData.relations are not used for the moment to avoid counting issue.