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use std::any::Any;
use std::marker::PhantomData;
use std::sync::{Arc, Weak};
use crate::component::{
Component,
Metadata as ComponentMetadata,
Sequence as ComponentSequence,
};
use crate::entity::Uid as EntityUid;
use crate::lock::{Lock, WriteGuard};
use crate::system::{NoInitParamFlag, Param as SystemParam, System};
use crate::{ActionQueue, World};
/// Used to to queue up actions for a [`World`] to perform.
#[derive(Debug)]
pub struct Actions<'world>
{
action_queue: WriteGuard<'world, ActionQueue>,
action_queue_weak: Weak<Lock<ActionQueue>>,
}
impl<'world> Actions<'world>
{
/// Adds a spawning a new entity to the action queue.
pub fn spawn<Comps: ComponentSequence>(&mut self, components: Comps)
{
self.action_queue.push(Action::Spawn(components.into_vec()));
}
/// Adds component(s) to a entity.
pub fn add_components<Comps>(&mut self, entity_uid: EntityUid, components: Comps)
where
Comps: ComponentSequence,
{
self.action_queue
.push(Action::AddComponents(entity_uid, components.into_vec()));
}
/// Removes component(s) from a entity.
pub fn remove_components<Comps>(&mut self, entity_uid: EntityUid)
where
Comps: ComponentSequence,
{
self.action_queue
.push(Action::RemoveComponents(entity_uid, Comps::metadata()));
}
/// Adds stopping the loop in [`Engine::event_loop`] at the next opportune time to the
/// action queue.
pub fn stop(&mut self)
{
self.action_queue.push(Action::Stop);
}
/// Returns a struct which holds a weak reference to the [`World`] that `Actions`
/// references and that can be used to aquire a new `Actions` instance if the
/// referenced [`World`] is still alive.
#[must_use]
pub fn to_weak_ref(&self) -> WeakRef
{
WeakRef {
action_queue: self.action_queue_weak.clone(),
}
}
fn new(action_queue: &'world Arc<Lock<ActionQueue>>) -> Self
{
Self {
action_queue: action_queue
.write_nonblock()
.expect("Failed to aquire read-write action queue lock"),
action_queue_weak: Arc::downgrade(action_queue),
}
}
}
unsafe impl<'world> SystemParam<'world> for Actions<'world>
{
type Flags = NoInitParamFlag;
type Input = ();
fn initialize<SystemImpl>(
_system: &mut impl System<'world, SystemImpl>,
_input: Self::Input,
)
{
}
fn new<SystemImpl>(
_system: &'world impl System<'world, SystemImpl>,
world: &'world World,
) -> Self
{
Self::new(&world.data.action_queue)
}
fn is_compatible<Other: SystemParam<'world>>() -> bool
{
let other_comparable = Other::get_comparable();
other_comparable.downcast_ref::<Comparable>().is_none()
}
fn get_comparable() -> Box<dyn Any>
{
Box::new(())
}
}
#[derive(Debug, Clone)]
pub struct WeakRef
{
action_queue: Weak<Lock<ActionQueue>>,
}
impl WeakRef
{
/// Returns a struct which can be used to retrieve a [`Actions`].
///
/// Returns [`None`] if the referenced [`World`] has been dropped.
#[must_use]
pub fn access(&self) -> Option<Ref<'_>>
{
Some(Ref {
action_queue: self.action_queue.upgrade()?,
_pd: PhantomData,
})
}
}
/// Intermediate between [`Actions`] and [`WeakRef`]. Contains a strong reference to
/// a world which is not allowed direct access to.
#[derive(Debug, Clone)]
pub struct Ref<'weak_ref>
{
action_queue: Arc<Lock<ActionQueue>>,
_pd: PhantomData<&'weak_ref ()>,
}
impl<'weak_ref> Ref<'weak_ref>
{
#[must_use]
pub fn to_actions(&self) -> Actions<'_>
{
Actions::new(&self.action_queue)
}
}
/// A action for a [`System`] to perform.
#[derive(Debug)]
pub(crate) enum Action
{
Spawn(Vec<Box<dyn Component>>),
AddComponents(EntityUid, Vec<Box<dyn Component>>),
RemoveComponents(EntityUid, Vec<ComponentMetadata>),
Stop,
}
struct Comparable;
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