feat(sdk): Find and remove duplicated events in RoomEvents.

This patch uses the new `Deduplicator` type, along with
`LinkeChunk::remove_item_at` to remove duplicated events. When a new
event is received, the older one is removed.

crates/matrix-sdk/src/event_cache/deduplicator.rs

@@ -15,11 +15,11 @@
 //! Simple but efficient types to find duplicated events. See [`Deduplicator`]
 //! to learn more.
 
-use std::{collections::BTreeSet, sync::Mutex};
+use std::{collections::BTreeSet, fmt, sync::Mutex};
 
 use growable_bloom_filter::{GrowableBloom, GrowableBloomBuilder};
 
-use super::store::{Event, RoomEvents};
+use super::room::events::{Event, RoomEvents};
 
 /// `Deduplicator` is an efficient type to find duplicated events.
 ///
@@ -34,6 +34,12 @@ pub struct Deduplicator {
     bloom_filter: Mutex<GrowableBloom>,
 }
 
+impl fmt::Debug for Deduplicator {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter.debug_struct("Deduplicator").finish_non_exhaustive()
+    }
+}
+
 impl Deduplicator {
     const APPROXIMATED_MAXIMUM_NUMBER_OF_EVENTS: usize = 800_000;
     const DESIRED_FALSE_POSITIVE_RATE: f64 = 0.001;

crates/matrix-sdk/src/event_cache/linked_chunk/mod.rs

@@ -948,6 +948,15 @@ impl Position {
     pub fn index(&self) -> usize {
         self.1
     }
+
+    /// Decrement the index part (see [`Self::index`]), i.e. subtract 1.
+    ///
+    /// # Panic
+    ///
+    /// This method will panic if it will underflow, i.e. if the index is 0.
+    pub(super) fn decrement_index(&mut self) {
+        self.1 = self.1.checked_sub(1).expect("Cannot decrement the index because it's already 0");
+    }
 }
 
 /// An iterator over a [`LinkedChunk`] that traverses the chunk in backward