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use std::marker::PhantomData;
use std::sync::{Arc, Weak};
use crate::component::{
Component,
Metadata as ComponentMetadata,
Sequence as ComponentSequence,
};
use crate::system::{NoInitParamFlag, Param as SystemParam, System};
use crate::uid::{Kind as UidKind, Uid};
use crate::{ActionQueue, World};
/// Used to to queue up actions for a [`World`] to perform.
#[derive(Debug)]
pub struct Actions<'world>
{
action_queue: &'world ActionQueue,
action_queue_weak: Weak<ActionQueue>,
}
impl<'world> Actions<'world>
{
/// Queues up a entity to spawn at the end of the current tick.
pub fn spawn<Comps: ComponentSequence>(&mut self, components: Comps)
{
self.action_queue.push(Action::Spawn(
components.into_vec(),
EventIds { ids: Comps::added_event_ids() },
));
}
/// Queues up despawning a entity at the end of the current tick.
pub fn despawn(&mut self, entity_uid: Uid)
{
debug_assert_eq!(entity_uid.kind(), UidKind::Entity);
self.action_queue.push(Action::Despawn(entity_uid));
}
/// Queues up adding component(s) to a entity at the end of the current tick.
pub fn add_components<Comps>(&mut self, entity_uid: Uid, components: Comps)
where
Comps: ComponentSequence,
{
debug_assert_eq!(entity_uid.kind(), UidKind::Entity);
self.action_queue.push(Action::AddComponents(
entity_uid,
components.into_vec(),
EventIds { ids: Comps::added_event_ids() },
));
}
/// Queues up removing component(s) from a entity at the end of the current tick.
pub fn remove_components<Comps>(&mut self, entity_uid: Uid)
where
Comps: ComponentSequence,
{
debug_assert_eq!(entity_uid.kind(), UidKind::Entity);
self.action_queue.push(Action::RemoveComponents(
entity_uid,
Comps::metadata(),
EventIds { ids: Comps::removed_event_ids() },
));
}
/// Stops the [`World`]. The world will finish the current tick and that tick will be
/// the last.
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<ActionQueue>) -> Self
{
Self {
action_queue,
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)
}
}
#[derive(Debug, Clone)]
pub struct WeakRef
{
action_queue: Weak<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<ActionQueue>,
_pd: PhantomData<&'weak_ref ()>,
}
impl<'weak_ref> Ref<'weak_ref>
{
#[must_use]
pub fn to_actions(&self) -> Actions<'_>
{
Actions::new(&self.action_queue)
}
}
#[derive(Debug)]
pub(crate) struct EventIds
{
pub(crate) ids: Vec<Uid>,
}
/// A action for a [`System`] to perform.
#[derive(Debug)]
pub(crate) enum Action
{
Spawn(Vec<Box<dyn Component>>, EventIds),
Despawn(Uid),
AddComponents(Uid, Vec<Box<dyn Component>>, EventIds),
RemoveComponents(Uid, Vec<ComponentMetadata>, EventIds),
Stop,
}
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