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|
use futures::{
future,
stream::{self, StreamExt as _},
Stream,
};
use itertools::Itertools as _;
use sqlx::sqlite::SqlitePool;
use super::{broadcaster::Broadcaster, Event, Sequence, Sequenced};
use crate::{
channel::{self, repo::Provider as _},
message::{self, repo::Provider as _},
};
pub struct Events<'a> {
db: &'a SqlitePool,
events: &'a Broadcaster,
}
impl<'a> Events<'a> {
pub const fn new(db: &'a SqlitePool, events: &'a Broadcaster) -> Self {
Self { db, events }
}
pub async fn subscribe(
&self,
resume_at: Option<Sequence>,
) -> Result<impl Stream<Item = Event> + std::fmt::Debug, sqlx::Error> {
// Subscribe before retrieving, to catch messages broadcast while we're
// querying the DB. We'll prune out duplicates later.
let live_messages = self.events.subscribe();
let mut tx = self.db.begin().await?;
let channels = tx.channels().replay(resume_at).await?;
let channel_events = channels
.iter()
.map(channel::History::events)
.kmerge_by(|a, b| a.instant.sequence < b.instant.sequence)
.filter(Sequence::after(resume_at))
.map(Event::from);
let messages = tx.messages().replay(resume_at).await?;
let message_events = messages
.iter()
.map(message::History::events)
.kmerge_by(|a, b| a.instant.sequence < b.instant.sequence)
.filter(Sequence::after(resume_at))
.map(Event::from);
let replay_events = channel_events
.merge_by(message_events, |a, b| {
a.instant.sequence < b.instant.sequence
})
.collect::<Vec<_>>();
let resume_live_at = replay_events.last().map(Sequenced::sequence);
let replay = stream::iter(replay_events);
let live_messages = live_messages
// Filtering on the broadcast resume point filters out messages
// before resume_at, and filters out messages duplicated from
// `replay_events`.
.filter(Self::resume(resume_live_at));
Ok(replay.chain(live_messages))
}
fn resume(resume_at: Option<Sequence>) -> impl for<'m> FnMut(&'m Event) -> future::Ready<bool> {
let filter = Sequence::after(resume_at);
move |event| future::ready(filter(event))
}
}
|
