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// Copyright 2023 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use async_rx::StreamExt as _;
use async_stream::stream;
use futures_core::Stream;
use futures_util::{StreamExt as _, pin_mut};
use matrix_sdk::event_cache::{PaginationStatus, RoomPagination};
use tracing::instrument;
use super::Error;
use crate::timeline::{PaginationError::NotSupported, controller::TimelineFocusKind};
impl super::Timeline {
/// Add more events to the start of the timeline.
///
/// Returns whether we hit the start of the timeline.
#[instrument(skip_all, fields(room_id = ?self.room().room_id()))]
pub async fn paginate_backwards(&self, mut num_events: u16) -> Result<bool, Error> {
match self.controller.focus() {
TimelineFocusKind::Live { event_cache, .. } => {
match self.controller.live_lazy_paginate_backwards(num_events).await {
Some(needed_num_events) => {
num_events = needed_num_events.try_into().expect(
"failed to cast `needed_num_events` (`usize`) into `num_events` (`usize`)",
);
}
None => {
// We could adjust the skip count to a lower value, while passing the
// requested number of events. We *may* have reached the start of the
// timeline, but since we're fulfilling the caller's request, assume it's
// not the case and return false here. A subsequent call will go to the
// `Some()` arm of this match, and cause a call to the event cache's
// pagination.
return Ok(false);
}
}
Ok(self.live_paginate_backwards(&event_cache.pagination(), num_events).await?)
}
TimelineFocusKind::Event { event_cache, .. } => {
Ok(event_cache.paginate_backwards(num_events).await?.hit_end_of_timeline)
}
TimelineFocusKind::Thread { event_cache, .. } => Ok(event_cache
.pagination()
.run_backwards_once(num_events)
.await
.map(|outcome| outcome.reached_start)?),
TimelineFocusKind::PinnedEvents { .. } => Err(Error::PaginationError(NotSupported)),
}
}
/// Add more events to the end of the timeline.
///
/// Returns whether we hit the end of the timeline.
#[instrument(skip_all, fields(room_id = ?self.room().room_id()))]
pub async fn paginate_forwards(&self, num_events: u16) -> Result<bool, Error> {
match self.controller.focus() {
TimelineFocusKind::Live { .. } => Ok(true),
TimelineFocusKind::Event { event_cache, .. } => {
Ok(event_cache.paginate_forwards(num_events).await?.hit_end_of_timeline)
}
TimelineFocusKind::Thread { .. } | TimelineFocusKind::PinnedEvents { .. } => {
Err(Error::PaginationError(NotSupported))
}
}
}
/// Paginate backwards in live mode.
///
/// This can only be called when the timeline is in live mode, not focused
/// on a specific event.
///
/// Returns whether we hit the start of the timeline.
async fn live_paginate_backwards(
&self,
event_cache_pagination: &RoomPagination,
batch_size: u16,
) -> Result<bool, Error> {
loop {
match event_cache_pagination.run_backwards_once(batch_size).await {
Ok(outcome) => {
if outcome.reached_start {
self.controller.insert_timeline_start_if_missing().await;
return Ok(true);
}
if !outcome.events.is_empty() {
return Ok(false);
}
// Fallthrough: as a special contract, restart pagination,
// if it returned 0 events.
}
// Propagate errors as such.
Err(err) => return Err(err.into()),
}
}
}
/// Subscribe to the back-pagination status of a live timeline.
///
/// This will return `None` if the timeline is in the focused mode.
///
/// Note: this may send multiple Paginating/Idle sequences during a single
/// call to [`Self::paginate_backwards()`].
pub async fn live_back_pagination_status(
&self,
) -> Option<(PaginationStatus, impl Stream<Item = PaginationStatus> + use<>)> {
let TimelineFocusKind::Live { event_cache, .. } = self.controller.focus() else {
return None;
};
let pagination = event_cache.pagination();
let mut status = pagination.status();
let current_value = self.controller.map_pagination_status(status.next_now()).await;
let controller = self.controller.clone();
let stream = Box::pin(stream! {
let status_stream = status.dedup();
pin_mut!(status_stream);
while let Some(state) = status_stream.next().await {
let state = controller.map_pagination_status(state).await;
match state {
PaginationStatus::Idle { hit_timeline_start } => {
if hit_timeline_start {
controller.insert_timeline_start_if_missing().await;
}
}
PaginationStatus::Paginating => {}
}
yield state;
}
});
Some((current_value, stream))
}
}