plaza_lobby 0.7.3

//! Which rooms a connection can actually play in, and in what order to offer
//! them.
//!
//! A free function over metadata rather than a method on the manager, because
//! the rule is useful without a manager. A game whose rooms are a fixed table
//! decided at startup should not have to implement a `RoomFactory` to ask this
//! question, and the manager's own
//! [`rooms_playable_at`](crate::manager::InMemoryLobbyManager::rooms_playable_at)
//! is this with its rooms filled in.

use std::fmt::Debug;

use crate::op_payloads::RoomMetadata;

/// The rooms this connection could play in, best fit first.
///
/// **Ordered tightest-schedule-first**, so a fast connection is not sent to a
/// room built for slow ones and given a delay it does not need. A room that
/// states no limit sorts last: it will take anybody, so it is the fallback.
///
/// Full rooms are dropped too, since a player cannot enter them.
pub fn playable_at<S: Clone + Debug>(one_way_ms: u32, rooms: impl IntoIterator<Item = RoomMetadata<S>>) -> Vec<RoomMetadata<S>> {
  let mut rooms: Vec<_> = rooms
    .into_iter()
    .filter(|m| m.current_players < m.max_players)
    .filter(|m| m.max_one_way_ms.is_none_or(|allowed| one_way_ms <= allowed))
    .collect();
  rooms.sort_by_key(|m| m.max_one_way_ms.unwrap_or(u32::MAX));
  rooms
}

/// The single best room for this connection, or `None` when nothing fits.
///
/// Refuse a connection only when this returns `None`; any other result is a
/// placement. This decision belongs to a lobby because a room can only accept
/// or refuse, while this picks a room.
pub fn best_for<S: Clone + Debug>(one_way_ms: u32, rooms: impl IntoIterator<Item = RoomMetadata<S>>) -> Option<RoomMetadata<S>> {
  playable_at(one_way_ms, rooms).into_iter().next()
}