feat(p2p/webrtc): randomize discovered peers based on time

re: #772

Author: binier

p2p/src/channels/signaling/mod.rs

@@ -31,6 +31,7 @@ impl crate::P2pState {
     pub(super) fn webrtc_discovery_respond_with_availble_peers<Action, State>(
         &self,
         dispatcher: &mut redux::Dispatcher<Action, State>,
+        time: redux::Timestamp,
     ) where
         State: crate::P2pStateTrait,
         Action: crate::P2pActionTrait<State>,
@@ -50,9 +51,17 @@ impl crate::P2pState {
             },
         );
 
-        // TODO(binier): maybe randomize
+        /// random shuffle available peers
+        use rand::{seq::SliceRandom, SeedableRng};
+        let mut rng = rand::rngs::StdRng::seed_from_u64(time.into());
+        let mut available_peers_ordered = available_peers.iter().copied().collect::<Vec<_>>();
+        available_peers_ordered.shuffle(&mut rng);
+
         for requester in requests {
-            if let Some(target_peer_id) = available_peers.iter().find(|&&id| id != requester) {
+            if let Some(target_peer_id) = available_peers_ordered
+                .iter()
+                .find(|&&id| id != requester && available_peers.contains(id))
+            {
                 let target_peer_id = *target_peer_id;
                 dispatcher.push(P2pChannelsSignalingDiscoveryAction::DiscoveredSend {
                     peer_id: *requester,