lavina/src/core/room.rs

//! Domain of rooms — chats with multiple participants.
use std::{
    collections::HashMap,
    hash::Hash,
    sync::{Arc, RwLock},
};

use prometheus::{IntGauge, Registry as MetricRegistry};
use tokio::sync::RwLock as AsyncRwLock;

use crate::{
    core::player::{PlayerHandle, PlayerId, Updates},
    prelude::*,
};

/// Opaque room id
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct RoomId(ByteVec);
impl RoomId {
    pub fn from_bytes(bytes: ByteVec) -> Result<RoomId> {
        if bytes.len() > 32 {
            return Err(anyhow::Error::msg(
                "Room name cannot be longer than 32 symbols",
            ));
        }
        if bytes.contains(&b' ') {
            return Err(anyhow::Error::msg("Room name cannot contain spaces"));
        }
        Ok(RoomId(bytes))
    }
    pub fn as_bytes(&self) -> &ByteVec {
        &self.0
    }
}

/// Shared datastructure for storing metadata about rooms.
#[derive(Clone)]
pub struct RoomRegistry(Arc<RwLock<RoomRegistryInner>>);
impl RoomRegistry {
    pub fn empty(metrics: &mut MetricRegistry) -> Result<RoomRegistry> {
        let metric_active_rooms =
            IntGauge::new("chat_rooms_active", "Number of alive room actors")?;
        metrics.register(Box::new(metric_active_rooms.clone()))?;
        let inner = RoomRegistryInner {
            rooms: HashMap::new(),
            metric_active_rooms,
        };
        Ok(RoomRegistry(Arc::new(RwLock::new(inner))))
    }

    pub fn get_or_create_room(&mut self, room_id: RoomId) -> RoomHandle {
        let mut inner = self.0.write().unwrap();
        if let Some(room_handle) = inner.rooms.get(&room_id) {
            room_handle.clone()
        } else {
            let room = Room {
                room_id: room_id.clone(),
                subscriptions: HashMap::new(),
                topic: b"New room".to_vec(),
            };
            let room_handle = RoomHandle(Arc::new(AsyncRwLock::new(room)));
            inner.rooms.insert(room_id, room_handle.clone());
            inner.metric_active_rooms.inc();
            room_handle
        }
    }

    pub fn get_room(&self, room_id: &RoomId) -> Option<RoomHandle> {
        let inner = self.0.read().unwrap();
        let res = inner.rooms.get(room_id);
        res.map(|r| r.clone())
    }
}

struct RoomRegistryInner {
    rooms: HashMap<RoomId, RoomHandle>,
    metric_active_rooms: IntGauge,
}

#[derive(Clone)]
pub struct RoomHandle(Arc<AsyncRwLock<Room>>);
impl RoomHandle {
    pub async fn subscribe(&self, player_id: PlayerId, player_handle: PlayerHandle) {
        let mut lock = self.0.write().await;
        lock.add_subscriber(player_id, player_handle).await;
    }

    pub async fn send_message(&self, player_id: PlayerId, body: String) {
        let lock = self.0.read().await;
        lock.send_message(player_id, body).await;
    }

    pub async fn get_room_info(&self) -> RoomInfo {
        let lock = self.0.read().await;
        RoomInfo {
            id: lock.room_id.clone(),
            members: lock
                .subscriptions
                .keys()
                .map(|x| x.clone())
                .collect::<Vec<_>>(),
            topic: lock.topic.clone(),
        }
    }

    pub async fn set_topic(&mut self, changer_id: PlayerId, new_topic: ByteVec) {
        let mut lock = self.0.write().await;
        lock.topic = new_topic.clone();
        let update = Updates::RoomTopicChanged {
            room_id: lock.room_id.clone(),
            new_topic: new_topic.clone(),
        };
        lock.broadcast_update(update, &changer_id).await;
    }
}

struct Room {
    room_id: RoomId,
    subscriptions: HashMap<PlayerId, PlayerHandle>,
    topic: ByteVec,
}
impl Room {
    async fn add_subscriber(&mut self, player_id: PlayerId, player_handle: PlayerHandle) {
        tracing::info!("Adding a subscriber to room");
        self.subscriptions.insert(player_id.clone(), player_handle);
        let update = Updates::RoomJoined {
            room_id: self.room_id.clone(),
            new_member_id: player_id.clone(),
        };
        self.broadcast_update(update, &player_id).await;
    }

    async fn send_message(&self, author_id: PlayerId, body: String) {
        tracing::info!("Adding a message to room");
        let update = Updates::NewMessage {
            room_id: self.room_id.clone(),
            author_id: author_id.clone(),
            body,
        };
        self.broadcast_update(update, &author_id).await;
    }

    async fn broadcast_update(&self, update: Updates, except: &PlayerId) {
        for (player_id, sub) in &self.subscriptions {
            if player_id == except {
                continue;
            }
            log::info!("Sending a message from room to player");
            sub.update(update.clone()).await;
        }
    }
}

pub struct RoomInfo {
    pub id: RoomId,
    pub members: Vec<PlayerId>,
    pub topic: ByteVec,
}