//! Domain of chat participants.
//!
//! Player is a single user account, which is used to participate in chats,
//! including sending messages, receiving messaged, retrieving history and running privileged actions.
//! A player corresponds to a single user account. Usually a person has only one account,
//! but it is possible to have multiple accounts for one person and therefore multiple player entities.
//!
//! A player actor is a serial handler of commands from a single player. It is preferable to run all per-player validations in the player actor,
//! so that they don't overload the room actor.
use std::{
    collections::HashMap,
    sync::{Arc, RwLock},
};

use prometheus::{IntGauge, Registry as MetricsRegistry};
use tokio::{
    sync::mpsc::{channel, Receiver, Sender},
    task::JoinHandle,
};

use crate::{
    core::room::{RoomId, RoomRegistry},
    prelude::*,
    util::table::AnonTable,
};

/// Opaque player identifier.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct PlayerId(pub ByteVec);

/// Handle to a player actor.
#[derive(Clone)]
pub struct PlayerHandle {
    tx: Sender<PlayerCommand>,
}
impl PlayerHandle {
    pub async fn subscribe(&mut self) -> Receiver<Updates> {
        let (sender, rx) = channel(32);
        self.tx.send(PlayerCommand::AddSocket { sender }).await;
        rx
    }

    pub async fn send_message(&mut self, room_id: RoomId, body: String) {
        self.tx
            .send(PlayerCommand::SendMessage { room_id, body })
            .await;
    }

    pub async fn join_room(&mut self, room_id: RoomId) {
        self.tx.send(PlayerCommand::JoinRoom { room_id }).await;
    }

    pub async fn receive_message(&mut self, room_id: RoomId, author: PlayerId, body: String) {
        self.tx
            .send(PlayerCommand::IncomingMessage {
                room_id,
                author,
                body,
            })
            .await;
    }
}

/// Player update event type which is sent to a connection handler.
pub enum Updates {
    RoomJoined { room_id: RoomId },
    NewMessage { room_id: RoomId, body: String },
}
enum PlayerCommand {
    AddSocket {
        sender: Sender<Updates>,
    },
    JoinRoom {
        room_id: RoomId,
    },
    SendMessage {
        room_id: RoomId,
        body: String,
    },
    IncomingMessage {
        room_id: RoomId,
        author: PlayerId,
        body: String,
    },
}

/// Handle to a player registry — a shared data structure containing information about players.
#[derive(Clone)]
pub struct PlayerRegistry(Arc<RwLock<PlayerRegistryInner>>);
impl PlayerRegistry {
    pub fn empty(
        room_registry: RoomRegistry,
        metrics: &mut MetricsRegistry,
    ) -> Result<PlayerRegistry> {
        let metric_active_players =
            IntGauge::new("chat_players_active", "Number of alive player actors")?;
        metrics.register(Box::new(metric_active_players.clone()))?;
        let inner = PlayerRegistryInner {
            room_registry,
            players: HashMap::new(),
            metric_active_players,
        };
        Ok(PlayerRegistry(Arc::new(RwLock::new(inner))))
    }

    pub async fn get_or_create_player(&mut self, id: PlayerId) -> PlayerHandle {
        let player = Player {
            sockets: AnonTable::new(),
        };
        let mut inner = self.0.write().unwrap();
        let (handle, fiber) = player.launch(id.clone(), inner.room_registry.clone());
        inner.players.insert(id, (handle.clone(), fiber));
        inner.metric_active_players.inc();
        handle
    }
}

/// The player registry state representation.
struct PlayerRegistryInner {
    room_registry: RoomRegistry,
    players: HashMap<PlayerId, (PlayerHandle, JoinHandle<Player>)>,
    metric_active_players: IntGauge,
}

/// Player actor inner state representation.
struct Player {
    sockets: AnonTable<Sender<Updates>>,
}
impl Player {
    fn launch(
        mut self,
        player_id: PlayerId,
        mut rooms: RoomRegistry,
    ) -> (PlayerHandle, JoinHandle<Player>) {
        let (tx, mut rx) = channel(32);
        let handle = PlayerHandle { tx };
        let handle_clone = handle.clone();
        let fiber = tokio::task::spawn(async move {
            while let Some(cmd) = rx.recv().await {
                match cmd {
                    PlayerCommand::AddSocket { sender } => {
                        self.sockets.insert(sender);
                    }
                    PlayerCommand::JoinRoom { room_id } => {
                        let mut room = rooms.get_or_create_room(room_id);
                        room.subscribe(player_id.clone(), handle.clone()).await;
                    }
                    PlayerCommand::SendMessage { room_id, body } => {
                        let room = rooms.get_room(room_id);
                        match room {
                            Some(mut room) => {
                                room.send_message(player_id.clone(), body).await;
                            }
                            None => {
                                tracing::info!("no room found");
                            }
                        }
                    }
                    PlayerCommand::IncomingMessage {
                        room_id,
                        author,
                        body,
                    } => {
                        tracing::info!("Handling incoming message");
                        for socket in &self.sockets {
                            socket
                                .send(Updates::NewMessage {
                                    room_id: room_id.clone(),
                                    body: body.clone(),
                                })
                                .await;
                        }
                    }
                }
            }
            self
        });
        (handle_clone, fiber)
    }
}