refactor(indexeddb): add type to represent time-based lock on event cache

Signed-off-by: Michael Goldenberg <m@mgoldenberg.net>

crates/matrix-sdk-indexeddb/src/event_cache_store/types.rs

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License
 
+use std::time::Duration;
+
 use matrix_sdk_base::{
     deserialized_responses::TimelineEvent, event_cache::store::extract_event_relation,
     linked_chunk::ChunkIdentifier,
@@ -19,6 +21,22 @@ use matrix_sdk_base::{
 use ruma::{OwnedEventId, OwnedRoomId, RoomId};
 use serde::{Deserialize, Serialize};
 
+/// Representation of a time-based lock on the entire
+/// [`IndexeddbEventCacheStore`](crate::event_cache_store::IndexeddbEventCacheStore)
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Lease {
+    pub key: String,
+    pub holder: String,
+    pub expiration: Duration,
+}
+
+impl Lease {
+    /// Determines whether the lease is expired at a given time `t`
+    pub fn expired_at(&self, t: Duration) -> bool {
+        self.expiration < t
+    }
+}
+
 /// Representation of a [`Chunk`](matrix_sdk_base::linked_chunk::Chunk)
 /// which can be stored in IndexedDB.
 #[derive(Debug, Serialize, Deserialize)]