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use core::any::TypeId;
use core::ops::{Deref, DerefMut};
use core::ptr::NonNull;
use crate::archetype::Archetype;
use crate::{Component, Entity, MissingComponent, Query, QueryOne};
/// Handle to an entity with any component types
#[derive(Copy, Clone)]
pub struct EntityRef<'a> {
archetype: &'a Archetype,
entity: Entity,
index: u32,
}
impl<'a> EntityRef<'a> {
pub(crate) unsafe fn new(archetype: &'a Archetype, entity: Entity, index: u32) -> Self {
Self {
archetype,
entity,
index,
}
}
/// Get the [`Entity`] handle associated with this entity
#[inline]
pub fn entity(&self) -> Entity {
self.entity
}
/// Determine whether this entity has a `T` component without borrowing it
pub fn has<T: Component>(&self) -> bool {
self.archetype.has::<T>()
}
/// Borrow the component of type `T`, if it exists
///
/// Panics if the component is already uniquely borrowed from another entity with the same
/// components.
pub fn get<T: Component>(&self) -> Option<Ref<'a, T>> {
Some(unsafe { Ref::new(self.archetype, self.index).ok()? })
}
/// Uniquely borrow the component of type `T`, if it exists
///
/// Panics if the component is already borrowed from another entity with the same components.
pub fn get_mut<T: Component>(&self) -> Option<RefMut<'a, T>> {
Some(unsafe { RefMut::new(self.archetype, self.index).ok()? })
}
/// Run a query against this entity
///
/// Equivalent to invoking [`World::query_one`](crate::World::query_one) on the entity. May
/// outlive `self`.
///
/// # Example
/// ```
/// # use hecs::*;
/// let mut world = World::new();
/// let a = world.spawn((123, true, "abc"));
/// // The returned query must outlive the borrow made by `get`
/// let mut query = world.entity(a).unwrap().query::<(&mut i32, &bool)>();
/// let (number, flag) = query.get().unwrap();
/// if *flag { *number *= 2; }
/// assert_eq!(*number, 246);
/// ```
pub fn query<Q: Query>(&self) -> QueryOne<'a, Q> {
unsafe { QueryOne::new(self.archetype, self.index) }
}
/// Enumerate the types of the entity's components
///
/// Convenient for dispatching component-specific logic for a single entity. For example, this
/// can be combined with a `HashMap<TypeId, Box<dyn Handler>>` where `Handler` is some
/// user-defined trait with methods for serialization, or to be called after spawning or before
/// despawning to maintain secondary indices.
pub fn component_types(&self) -> impl Iterator<Item = TypeId> + 'a {
self.archetype.types().iter().map(|ty| ty.id())
}
/// Number of components in this entity
pub fn len(&self) -> usize {
self.archetype.types().len()
}
/// Shorthand for `self.len() == 0`
pub fn is_empty(&self) -> bool {
self.len() == 0
}
}
unsafe impl<'a> Send for EntityRef<'a> {}
unsafe impl<'a> Sync for EntityRef<'a> {}
/// Shared borrow of an entity's component
#[derive(Clone)]
pub struct Ref<'a, T: Component> {
archetype: &'a Archetype,
/// State index for `T` in `archetype`
state: usize,
target: NonNull<T>,
}
impl<'a, T: Component> Ref<'a, T> {
pub(crate) unsafe fn new(
archetype: &'a Archetype,
index: u32,
) -> Result<Self, MissingComponent> {
let state = archetype
.get_state::<T>()
.ok_or_else(MissingComponent::new::<T>)?;
let target =
NonNull::new_unchecked(archetype.get_base::<T>(state).as_ptr().add(index as usize));
archetype.borrow::<T>(state);
Ok(Self {
archetype,
state,
target,
})
}
}
unsafe impl<T: Component> Send for Ref<'_, T> {}
unsafe impl<T: Component> Sync for Ref<'_, T> {}
impl<'a, T: Component> Drop for Ref<'a, T> {
fn drop(&mut self) {
self.archetype.release::<T>(self.state);
}
}
impl<'a, T: Component> Deref for Ref<'a, T> {
type Target = T;
fn deref(&self) -> &T {
unsafe { self.target.as_ref() }
}
}
/// Unique borrow of an entity's component
pub struct RefMut<'a, T: Component> {
archetype: &'a Archetype,
/// State index for `T` in `archetype`
state: usize,
target: NonNull<T>,
}
impl<'a, T: Component> RefMut<'a, T> {
pub(crate) unsafe fn new(
archetype: &'a Archetype,
index: u32,
) -> Result<Self, MissingComponent> {
let state = archetype
.get_state::<T>()
.ok_or_else(MissingComponent::new::<T>)?;
let target =
NonNull::new_unchecked(archetype.get_base::<T>(state).as_ptr().add(index as usize));
archetype.borrow_mut::<T>(state);
Ok(Self {
archetype,
state,
target,
})
}
}
unsafe impl<T: Component> Send for RefMut<'_, T> {}
unsafe impl<T: Component> Sync for RefMut<'_, T> {}
impl<'a, T: Component> Drop for RefMut<'a, T> {
fn drop(&mut self) {
self.archetype.release_mut::<T>(self.state);
}
}
impl<'a, T: Component> Deref for RefMut<'a, T> {
type Target = T;
fn deref(&self) -> &T {
unsafe { self.target.as_ref() }
}
}
impl<'a, T: Component> DerefMut for RefMut<'a, T> {
fn deref_mut(&mut self) -> &mut T {
unsafe { self.target.as_mut() }
}
}