chore: refactor VCs to use a watch channel internally (but I'm going to rework this in the next commit anyway)

src/track_vcs.rs

@@ -2,6 +2,7 @@ use std::collections::BTreeMap;
 
 use dashmap::DashMap;
 use futures::{StreamExt, stream::FuturesUnordered};
+use tokio::sync::watch;
 use twilight_model::{
     gateway::payload::incoming::VoiceStateUpdate,
     id::{
@@ -16,7 +17,37 @@ pub type GuildVoiceChannelToTextChannel =
     BTreeMap<Id<GuildMarker>, OneToOneBTreeMap<Id<ChannelMarker>, Id<ChannelMarker>>>;
 
 type VCsInGuild = OneToManyUniqueBTreeMapWithData<Id<ChannelMarker>, Id<UserMarker>, UserInVCData>;
-pub type VCs = DashMap<Id<GuildMarker>, VCsInGuild>;
+
+#[derive(Debug, Default)]
+pub struct VCs(DashMap<Id<GuildMarker>, watch::Sender<VCsInGuild>>);
+
+impl Extend<(Id<GuildMarker>, VCsInGuild)> for VCs {
+    fn extend<T: IntoIterator<Item = (Id<GuildMarker>, VCsInGuild)>>(&mut self, iter: T) {
+        for (id, guild_vcs) in iter {
+            self.0.insert(id, watch::Sender::new(guild_vcs));
+        }
+    }
+}
+
+impl VCs {
+    pub fn with_guild<R>(&self, id: Id<GuildMarker>, f: impl FnOnce(&VCsInGuild) -> R) -> R {
+        f(&*self.0.entry(id).or_default().borrow())
+    }
+
+    pub fn update_guild<R>(&self, id: Id<GuildMarker>, f: impl FnOnce(&mut VCsInGuild) -> R) -> R {
+        let mut ret_opt = None;
+        self.0.entry(id).or_default().send_modify(|guild_vcs| {
+            let ret = f(guild_vcs);
+            _ = ret_opt.insert(ret);
+        });
+        let ret = ret_opt.unwrap();
+        ret
+    }
+
+    pub fn subscribe_to_guild<R>(&self, id: Id<GuildMarker>) -> watch::Receiver<VCsInGuild> {
+        self.0.entry(id).or_default().subscribe()
+    }
+}
 
 #[tracing::instrument(skip(discord_client), ret)]
 async fn initialize_user_in_vc(
@@ -107,9 +138,9 @@ pub fn update_vcs(voice_state_update: &VoiceStateUpdate, vcs: &VCs) {
                     .build();
                 let user_in_vc_data = voice_status.into();
 
-                vcs.entry(guild_id)
-                    .or_default()
-                    .insert(channel_id, user_id, user_in_vc_data);
+                vcs.update_guild(guild_id, |guild_vcs| {
+                    guild_vcs.insert(channel_id, user_id, user_in_vc_data)
+                });
 
                 tracing::info!(
                     ?guild_id,
@@ -120,9 +151,7 @@ pub fn update_vcs(voice_state_update: &VoiceStateUpdate, vcs: &VCs) {
             }
 
             None => {
-                if let Some(mut channel_vcers) = vcs.get_mut(&guild_id) {
-                    channel_vcers.remove_right(&user_id);
-                }
+                vcs.update_guild(guild_id, |guild_vcs| guild_vcs.remove_right(&user_id));
 
                 tracing::info!(?guild_id, ?user_id, "disconnected");
             }