maintain list of events in db. must convert allh handlers to use it.

src/bot/event_handlers.rs

@@ -1,10 +1,11 @@
+use crate::db::Database;
 use crate::error::BotError;
 use async_trait::async_trait;
 use log::{debug, error, info, warn};
 use matrix_sdk::{
     self,
     events::{
-        room::member::{MemberEventContent, MembershipState},
+        room::member::{MemberEventContent, MembershipChange},
         room::message::{MessageEventContent, TextMessageEventContent},
         StrippedStateEvent, SyncMessageEvent, SyncStateEvent,
     },
@@ -73,35 +74,51 @@ async fn should_process<'a>(
     Ok((msg_body, sender_username))
 }
 
+fn should_process_event(db: &Database, room_id: &str, event_id: &str) -> bool {
+    db.rooms
+        .should_process(room_id, event_id)
+        .unwrap_or_else(|e| {
+            error!(
+                "Database error when checking if we should process an event: {}",
+                e.to_string()
+            );
+            false
+        })
+}
+
 /// This event emitter listens for messages with dice rolling commands.
 /// Originally adapted from the matrix-rust-sdk examples.
 #[async_trait]
 impl EventEmitter for DiceBot {
-    async fn on_room_member(
-        &self,
-        room: SyncRoom,
-        room_member: &SyncStateEvent<MemberEventContent>,
-    ) {
-        if let SyncRoom::Joined(room) = room {
+    async fn on_room_member(&self, room: SyncRoom, event: &SyncStateEvent<MemberEventContent>) {
+        if let SyncRoom::Joined(room) | SyncRoom::Left(room) = room {
+            //Clone to avoid holding lock.
+            let room = room.read().await.clone();
+            let (room_id, username) = (room.room_id.as_str(), &event.state_key);
+
+            if !should_process_event(&self.db, room_id, event.event_id.as_str()) {
+                return;
+            }
+
             let event_affects_us = if let Some(our_user_id) = self.client.user_id().await {
-                room_member.state_key == our_user_id
+                event.state_key == our_user_id
             } else {
                 false
             };
 
-            let adding_user = match room_member.content.membership {
-                MembershipState::Join => true,
-                MembershipState::Leave | MembershipState::Ban => false,
+            use MembershipChange::*;
+            let adding_user = match event.membership_change() {
+                Joined => true,
+                Banned | Left | Kicked | KickedAndBanned => false,
                 _ => return,
             };
 
-            //Clone to avoid holding lock.
-            let room = room.read().await.clone();
-            let (room_id, username) = (room.room_id.as_str(), &room_member.state_key);
-
             let result = if event_affects_us && !adding_user {
                 info!("Clearing all information for room ID {}", room_id);
                 self.db.rooms.clear_info(room_id)
+            } else if event_affects_us && adding_user {
+                info!("Joined room {}; recording user information", room_id);
+                Ok(())
             } else if !event_affects_us && adding_user {
                 info!("Adding user {} to room ID {}", username, room_id);
                 self.db.rooms.add_user_to_room(username, room_id)
@@ -109,7 +126,7 @@ impl EventEmitter for DiceBot {
                 info!("Removing user {} from room ID {}", username, room_id);
                 self.db.rooms.remove_user_from_room(username, room_id)
             } else {
-                debug!("Ignoring a room member event: {:#?}", room_member);
+                debug!("Ignoring a room member event: {:#?}", event);
                 Ok(())
             };
 

src/db/rooms.rs

@@ -1,9 +1,13 @@
 use crate::db::errors::DataError;
+use byteorder::LittleEndian;
 use sled::transaction::TransactionalTree;
 use sled::Transactional;
-use sled::Tree;
+use sled::{CompareAndSwapError, Tree};
 use std::collections::HashSet;
 use std::str;
+use std::time::{SystemTime, UNIX_EPOCH};
+use zerocopy::byteorder::U64;
+use zerocopy::AsBytes;
 
 #[derive(Clone)]
 pub struct Rooms {
@@ -15,6 +19,9 @@ pub struct Rooms {
 
     /// Username -> list of room IDs user is in.
     pub(in crate::db) username_roomids: Tree,
+
+    /// Room ID 0xff event ID -> received timestamp.
+    pub(in crate::db) roomeventid_timestamp: Tree,
 }
 
 #[derive(Clone, Copy)]
@@ -76,9 +83,38 @@ impl Rooms {
             roomid_roominfo: db.open_tree("roomid_roominfo")?,
             roomid_usernames: db.open_tree("roomid_usernames")?,
             username_roomids: db.open_tree("username_roomids")?,
+            roomeventid_timestamp: db.open_tree("roomeventid_timestamp")?,
         })
     }
 
+    /// Determine if an event in a room should be processed. The event
+    /// is atomically recorded and true returned if the database has
+    /// not seen tis event yet. If the event already exists in the
+    /// database, the function returns false. Events are recorded by
+    /// this function by inserting the (system-local) timestamp in
+    /// epoch seconds.
+    pub fn should_process(&self, room_id: &str, event_id: &str) -> Result<bool, DataError> {
+        let mut key = room_id.as_bytes().to_vec();
+        key.push(0xff);
+        key.extend_from_slice(event_id.as_bytes());
+
+        let timestamp: U64<LittleEndian> = U64::new(
+            SystemTime::now()
+                .duration_since(UNIX_EPOCH)
+                .expect("Clock has gone backwards")
+                .as_secs(),
+        );
+
+        match self.roomeventid_timestamp.compare_and_swap(
+            key,
+            None as Option<&[u8]>,
+            Some(timestamp.as_bytes()),
+        )? {
+            Ok(()) => Ok(true),
+            Err(CompareAndSwapError { .. }) => Ok(false),
+        }
+    }
+
     pub fn get_rooms_for_user(&self, username: &str) -> Result<HashSet<String>, DataError> {
         get_set(&self.username_roomids, username.as_bytes())
     }

src/db/schema.rs

@@ -1,6 +1,6 @@
 use crate::db::errors::DataError;
 use byteorder::LittleEndian;
-use zerocopy::byteorder::{I32, U32};
+use zerocopy::byteorder::{I32, U32, U64};
 use zerocopy::LayoutVerified;
 
 /// User variables are stored as little-endian 32-bit integers in the
@@ -10,6 +10,9 @@ type LittleEndianI32Layout<'a> = LayoutVerified<&'a [u8], I32<LittleEndian>>;
 
 type LittleEndianU32Layout<'a> = LayoutVerified<&'a [u8], U32<LittleEndian>>;
 
+#[allow(dead_code)]
+type LittleEndianU64Layout<'a> = LayoutVerified<&'a [u8], U64<LittleEndian>>;
+
 /// Convert bytes to an i32 with zero-copy deserialization. An error
 /// is returned if the bytes do not represent an i32.
 pub(super) fn convert_i32(raw_value: &[u8]) -> Result<i32, DataError> {
@@ -33,3 +36,15 @@ pub(super) fn convert_u32(raw_value: &[u8]) -> Result<u32, DataError> {
         Err(DataError::I32SchemaViolation)
     }
 }
+
+#[allow(dead_code)]
+pub(super) fn convert_u64(raw_value: &[u8]) -> Result<u64, DataError> {
+    let layout = LittleEndianU64Layout::new_unaligned(raw_value.as_ref());
+
+    if let Some(layout) = layout {
+        let value: U64<LittleEndian> = *layout;
+        Ok(value.get())
+    } else {
+        Err(DataError::I32SchemaViolation)
+    }
+}