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|
use chrono::TimeDelta;
use futures::{
future,
stream::{self, StreamExt as _},
Stream,
};
use sqlx::sqlite::SqlitePool;
use super::{
broadcaster::Broadcaster,
repo::message::Provider as _,
types::{self, ChannelEvent},
};
use crate::{
channel::{self, repo::Provider as _},
clock::DateTime,
db::NotFound as _,
event::{repo::Provider as _, Sequence},
login::Login,
};
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 send(
&self,
login: &Login,
channel: &channel::Id,
body: &str,
sent_at: &DateTime,
) -> Result<types::ChannelEvent, EventsError> {
let mut tx = self.db.begin().await?;
let channel = tx
.channels()
.by_id(channel)
.await
.not_found(|| EventsError::ChannelNotFound(channel.clone()))?;
let sent = tx.sequence().next(sent_at).await?;
let event = tx
.message_events()
.create(login, &channel, &sent, body)
.await?;
tx.commit().await?;
self.events.broadcast(&event);
Ok(event)
}
pub async fn expire(&self, relative_to: &DateTime) -> Result<(), sqlx::Error> {
// Somewhat arbitrarily, expire after 90 days.
let expire_at = relative_to.to_owned() - TimeDelta::days(90);
let mut tx = self.db.begin().await?;
let expired = tx.message_events().expired(&expire_at).await?;
let mut events = Vec::with_capacity(expired.len());
for (channel, message) in expired {
let deleted = tx.sequence().next(relative_to).await?;
let event = tx
.message_events()
.delete(&channel, &message, &deleted)
.await?;
events.push(event);
}
tx.commit().await?;
for event in events {
self.events.broadcast(&event);
}
Ok(())
}
pub async fn subscribe(
&self,
resume_at: Option<Sequence>,
) -> Result<impl Stream<Item = types::ChannelEvent> + 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
.into_iter()
.map(ChannelEvent::created)
.filter(move |event| {
resume_at.map_or(true, |resume_at| Sequence::from(event) > resume_at)
});
let message_events = tx.message_events().replay(resume_at).await?;
let mut replay_events = channel_events
.into_iter()
.chain(message_events.into_iter())
.collect::<Vec<_>>();
replay_events.sort_by_key(|event| Sequence::from(event));
let resume_live_at = replay_events.last().map(Sequence::from);
let replay = stream::iter(replay_events);
// no skip_expired or resume transforms for stored_messages, as it's
// constructed not to contain messages meeting either criterion.
//
// * skip_expired is redundant with the `tx.broadcasts().expire(…)` call;
// * resume is redundant with the resume_at argument to
// `tx.broadcasts().replay(…)`.
let live_messages = live_messages
// Filtering on the broadcast resume point filters out messages
// before resume_at, and filters out messages duplicated from
// stored_messages.
.filter(Self::resume(resume_live_at));
Ok(replay.chain(live_messages))
}
fn resume(
resume_at: Option<Sequence>,
) -> impl for<'m> FnMut(&'m types::ChannelEvent) -> future::Ready<bool> {
move |event| future::ready(resume_at < Some(Sequence::from(event)))
}
}
#[derive(Debug, thiserror::Error)]
pub enum EventsError {
#[error("channel {0} not found")]
ChannelNotFound(channel::Id),
#[error(transparent)]
DatabaseError(#[from] sqlx::Error),
}
|
