Add Recent conversations view

[alya]

Many users find the Recent conversations view helpful in the web app, and it would be a useful feature in the mobile app as well.

Work on this will likely happen after we've implemented various other functionality, such as a navigation system we are happy with where this view can be added.

CZO discussion

[chrisbobbe]

We've had another request for this as beta feedback: https://chat.zulip.org/#narrow/channel/48-mobile/topic/Recent.20conversations/near/2000412

[chrisbobbe]

More beta feedback where this seems desired: https://chat.zulip.org/#narrow/channel/48-mobile/topic/Recent.20conversations/near/2067849

[gnprice]

Tim and I discussed this in the office yesterday. The current plan for when we go to implement this is:

• We'll try doing it with no API changes, by having the app just fetch the latest 1000 messages and then compute the "Recent conversations" view based on those. Effectively it'll take the same strategy as the web app has always taken for that view, just with fewer messages.
• There'll also be a "load more" button at the bottom of the list, causing the app to fetch another 1000 messages, etc.
• The view won't show a participants list — the mobile format is too crowded for that anyway. As a result, loading more messages can never change the items that are already in the list, making it fit well with a "load more" at the bottom.
  • (Well, it can if it results in finding more old unreads in the later conversations. That's only possible if you load past your 50,000 newest unreads, so in particular past your 50,000 newest messages. Seems OK that in that case the unread counts in the existing list items can start increasing.)
• Also on the subject of how to fit the design into the space: the channel name, topic, and unread count seem pretty indispensable, and that's already enough to make it crowded. Perhaps channel above topic, as two lines, and then unread count off on the right but vertically centered (so that it's aligned with the pair of those, not with either one).
  • Also unread icon and probably unmuted/followed icon, like in web. But try leaving out the timestamp, to save space.

I'm not 100% confident that showing "Recent conversations" based on just the 1000 latest messages will be a good UX. But we can try it out and see. If we end up needing to do more to make it work, this experiment will have cost no effort in API design and very little in data fetching; almost all the work will be in logic that we'll still equally need if we go on to implement the feature atop some other API variation instead.

If something like this does work well, a possible enhancement involving a fairly small API change:

• We could have an API feature (perhaps just a flag on the get-messages endpoint) to get a list of very stripped-down message objects: just ID, destination, and perhaps sender, timestamp, and/or flags; in particular no content. That's everything this view would need; and because it'd be a lot less data it might enable us to fetch a larger set of messages.