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//! Entity identity and allocation via generational keys.
use serde::{Deserialize, Serialize};
slotmap::new_key_type! {
/// Universal entity identifier used across all component storages.
/// Serialize/Deserialize provided by slotmap's `serde` feature.
pub struct EntityId;
}
/// Generates a typed newtype wrapper around [`EntityId`].
///
/// Each wrapper is `#[repr(transparent)]` with a public inner field for
/// convenient internal access via `.0`, and delegates `Display` to
/// `EntityId`'s `Debug` (since slotmap keys do not implement `Display`).
macro_rules! typed_entity_id {
($(#[$meta:meta])* $name:ident) => {
$(#[$meta])*
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
#[serde(transparent)]
#[repr(transparent)]
pub struct $name(pub EntityId);
impl $name {
/// Returns the inner [`EntityId`].
#[inline]
pub const fn entity(self) -> EntityId {
self.0
}
}
impl std::fmt::Display for $name {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "{}({:?})", stringify!($name), self.0)
}
}
impl $name {
/// Wrap an `EntityId` in this typed newtype **without** verifying
/// the entity is actually of that kind. Wrong-kind IDs surface
/// later as `EntityNotFound` / `NotAnElevator` from accessor
/// calls.
///
/// The explicit name signals the unsafety that the silent
/// [`From<EntityId>`] impl on this type also exposes — both
/// constructors are intended for callers that already hold a
/// confirmed-kind id (typed-ID accessors like
/// [`World::elevator_ids`](crate::world::World::elevator_ids),
/// snapshot deserialization, defense-in-depth tests). At host
/// boundaries, prefer [`Simulation::elevator_id`](crate::sim::Simulation::elevator_id)
/// / [`Simulation::rider_id`](crate::sim::Simulation::rider_id),
/// which return `Option` after a runtime kind check.
#[inline]
#[must_use]
pub const fn wrap_unchecked(id: EntityId) -> Self {
Self(id)
}
}
impl From<$name> for EntityId {
#[inline]
fn from(id: $name) -> Self {
id.0
}
}
impl From<EntityId> for $name {
/// Wrap an `EntityId` in this typed newtype **without** verifying
/// the entity is actually of that kind. Wrong-kind IDs surface
/// later as `EntityNotFound` / `NotAnElevator` from accessor
/// calls. Equivalent to [`wrap_unchecked`](Self::wrap_unchecked);
/// at host boundaries, prefer the verified
/// [`Simulation::elevator_id`](crate::sim::Simulation::elevator_id)
/// / [`Simulation::rider_id`](crate::sim::Simulation::rider_id)
/// accessors, which return `Option` after a runtime kind check.
#[inline]
fn from(id: EntityId) -> Self {
Self(id)
}
}
impl Default for $name {
fn default() -> Self {
Self(EntityId::default())
}
}
};
}
typed_entity_id! {
/// Typed wrapper around [`EntityId`] for elevator entities.
ElevatorId
}
typed_entity_id! {
/// Typed wrapper around [`EntityId`] for rider entities.
RiderId
}