Steve Howell 2126478867 refactor: Simplify recent_senders code. ...

This reduces our dependency on message_list code (via
message_util), and it makes moving streams/topics and
deleting messages more performant.

For every single message that was being updated or
deleted, the previous code was basically re-computing
lots of things, including having to iterate through
every message in memory to find the messages matching
your topic.

Now everything basically happens in O(1) time.

The only O(N) computation is that we now lazily
re-compute the max message id every time you need it
for typeahead logic, and then we cache it for
subsequent use. The N here is the number of messages
that the particular sender has sent to the particular
stream/topic combination, so it should always be quite
small, except for certain spammy bots.

Once the max has been calculated, the common operation
of adding a message doesn't invalidate our cached
value. We only invalidate the cache on deletes.

The main change that we make here from a data
standpoint is that we just keep track of all
message_ids for all senders. The storage overhead here
should be negligible.  By keeping track of our own
messages, we don't have to punt to other code for
update/delete situations.

There is similar code in recent_topics that I think can
be improved in similar ways, and it would allow us to
eliminate functions like this one:

    export function get_messages_in_topic(stream_id, topic) {
        return message_list.all
            .all_messages()
            .filter(
                (x) =>
                    x.type === "stream" &&
                    x.stream_id === stream_id &&
                    x.topic.toLowerCase() === topic.toLowerCase(),
            );
    }

2021-04-14 16:28:07 -07:00

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