feat: presence updates

src/database/global_edus.rs

@@ -0,0 +1,68 @@
+use crate::Result;
+use ruma_events::{collections::only::Event as EduEvent, EventJson};
+use ruma_identifiers::UserId;
+
+pub struct GlobalEdus {
+    pub(super) globallatestid_globallatest: sled::Tree, // Presence, GlobalLatestId = Count + UserId
+                                                        //pub globalallid_globalall: sled::Tree, // ToDevice, GlobalAllId = UserId + Count
+}
+
+impl GlobalEdus {
+    /// Adds a global event which will be saved until a new event replaces it (e.g. presence updates).
+    pub fn update_globallatest(
+        &self,
+        user_id: &UserId,
+        event: EduEvent,
+        globals: &super::globals::Globals,
+    ) -> Result<()> {
+        // Remove old entry
+        if let Some(old) = self
+            .globallatestid_globallatest
+            .iter()
+            .keys()
+            .rev()
+            .filter_map(|r| r.ok())
+            .find(|key| {
+                key.rsplit(|&b| b == 0xff).next().unwrap() == user_id.to_string().as_bytes()
+            })
+        {
+            // This is the old global_latest
+            self.globallatestid_globallatest.remove(old)?;
+        }
+
+        let mut global_latest_id = globals.next_count()?.to_be_bytes().to_vec();
+        global_latest_id.push(0xff);
+        global_latest_id.extend_from_slice(&user_id.to_string().as_bytes());
+
+        self.globallatestid_globallatest
+            .insert(global_latest_id, &*serde_json::to_string(&event)?)?;
+
+        Ok(())
+    }
+
+    /// Returns an iterator over the most recent presence updates that happened after the event with id `since`.
+    pub fn globallatests_since(
+        &self,
+        since: u64,
+    ) -> Result<impl Iterator<Item = Result<EventJson<EduEvent>>>> {
+        let first_possible_edu = since.to_be_bytes().to_vec();
+
+        Ok(self
+            .globallatestid_globallatest
+            .range(&*first_possible_edu..)
+            // Skip the first pdu if it's exactly at since, because we sent that last time
+            .skip(
+                if self
+                    .globallatestid_globallatest
+                    .get(first_possible_edu)?
+                    .is_some()
+                {
+                    1
+                } else {
+                    0
+                },
+            )
+            .filter_map(|r| r.ok())
+            .map(|(_, v)| Ok(serde_json::from_slice(&v)?)))
+    }
+}