28.0.50; add IRCv3 building blocks to ERC

[J.P.]

Hi,

It's high time we explored bringing IRCv3 to ERC. I say we approach this
by focusing first on those innovations most likely to alleviate the more
pernicious problems endangering this client, such as

  * text processing bottlenecks
  * buffer association / session management / connection bookkeeping
  * maintenance debt

and leave the bells and whistles (fun stuff) for the next generation of
contributors [1].


Text processing

Perhaps most evident during history playback, sluggish message handling
looks poised to become a persistent and pervasive drag. This will likely
only worsen as the average length, complexity, and frequency of messages
increases. In the short term, I'd like to offer UI feedback indicating
the relative progress of remaining work by leveraging the heads-up that
batch provides [2].

Of course, this won't improve raw performance or relieve any I/O
pressure [3], but it will enrich the user experience overall. Also worth
prioritizing (even if it prolongs wait times, IMO) would be ensuring
some allowance for minimal interactivity (like basic navigation) while
processing is ongoing.


Bookkeeping

IRCv3 provides a much needed solution for determining and tracking
session ownership and uniqueness, and that's account awareness. While
useful for keeping tabs on other users, it also offers standardized,
real-time knowledge of a user's own authentication status [4]. This is
critical for laying to rest long festering issues [5] widely felt during
the recent move from Freenode to Libera.


Codebase

The flexibility and granularity demanded by the spec (different sets of
extensions for different sessions) forces us to make ERC more limber and
session-focused. This means ensuring the right seams and machinery exist
for adapting to context/environment at runtime. The CLOS dispatch
facility may be the obvious choice, but any combination of solutions
providing comparable flexibility would be a marked improvement over the
status quo.


A call to action
~~~~~~~~~~~~~~~~

To kick things off, I'm asking for a seasoned contributor to volunteer
their experience and elbow grease and to roll up their sleeves and get
stuck in with me down here in debbugstan. I vow to do whatever it takes
to shoulder most of the burden, whether that means cobbling together a
blueprint to get the ball rolling and/or doing the lion's share of the
intel legwork [6]. Please find it in yourself to step forward and answer
the call.

Thanks,
J.P.


Notes
~~~~~

[1] Even the traditional set of building blocks I hope to introduce
    should open the door to a wealth of opportunities. For example, by
    caching and tracking things like away statuses, idle times, and
    account IDs, we can dynamically update buffers to have nicks go dim
    or italic and otherwise react as updates arrive. (For anyone
    saying "please no": as with all things ERC, such enhancements would
    be optional/opt-in. The point is the possibilities are many.)

[2] https://ircv3.net/specs/extensions/batch

[3] Eventually, it may be nice to actually shoot for performance gains,
    perhaps by spawning child processes that ingest raw batched text and
    return structured data nearly ready for insertion. Also along these
    lines would be an optional "agent" subprocess to buffer I/O and
    wrangle PINGs while Emacs is otherwise preoccupied. (Some of the
    server-initiated message types introduced by IRCv3 are pretty
    chatty.)

[4] https://ircv3.net/specs/extensions/account-notify

[5] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=48598

[6] Actually, I've been engaged in the latter (note taking, knocking on
    doors) for the better part of a year, now. As for the former, a
    provisional/experimental (but usable) implementation may soon find
    its way to this thread, if only to kick start the conversation.


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