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use std::any::type_name;
use std::marker::PhantomData;
use std::rc::{Rc, Weak};
use crate::component::{Parts as ComponentParts, Sequence as ComponentSequence};
use crate::event::component::Removed;
use crate::pair::Pair;
use crate::system::{Metadata as SystemMetadata, Param as SystemParam};
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,
world: Option<&'world World>,
}
impl Actions<'_>
{
/// Queues up a entity to spawn at the end of the current tick, returning the [`Uid`]
/// that the entity will have.
pub fn spawn<Comps: ComponentSequence>(&mut self, components: Comps) -> Uid
{
let new_entity_uid = Uid::new_unique(UidKind::Entity);
self.action_queue.push(Action::Spawn(
new_entity_uid,
components.into_parts_array().into(),
));
new_entity_uid
}
/// 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);
let Some(world) = self.world else {
self.action_queue.push(Action::Despawn(entity_uid));
return;
};
let Some(ent) = world.get_entity(entity_uid) else {
tracing::warn!("Cannot entity that doesn't exist");
return;
};
// TODO: Submit all events with a single function call to reduce overhead
for comp_id in ent.component_ids() {
if comp_id.kind() == UidKind::Pair {
continue;
}
world.event_submitter().submit_event(
&Pair::builder()
.relation::<Removed>()
.target_id(comp_id)
.build(),
entity_uid,
);
}
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);
if Comps::COUNT == 0 {
return;
}
self.action_queue.push(Action::AddComponents(
entity_uid,
components.into_parts_array().into(),
));
}
/// Queues up removing component(s) from a entity at the end of the current tick.
#[tracing::instrument(skip(self, component_ids))]
pub fn remove_components(
&mut self,
entity_uid: Uid,
component_ids: impl IntoIterator<Item = Uid>,
)
{
debug_assert_eq!(entity_uid.kind(), UidKind::Entity);
let mut component_ids = component_ids.into_iter().peekable();
if component_ids.peek().is_none() {
return;
}
let Some(world) = self.world else {
self.action_queue.push(Action::RemoveComponents(
entity_uid,
component_ids.collect(),
));
return;
};
let Some(ent) = world.get_entity(entity_uid) else {
tracing::warn!("Cannot remove components from entity that doesn't exist");
return;
};
let component_ids = component_ids
.filter(|comp_id| ent.has_component(*comp_id))
.collect::<Vec<_>>();
if component_ids.is_empty() {
return;
}
// TODO: Submit all events with a single function call to reduce overhead
for comp_id in &component_ids {
if comp_id.kind() == UidKind::Pair {
continue;
}
world.event_submitter().submit_event(
&Pair::builder()
.relation::<Removed>()
.target_id(*comp_id)
.build(),
entity_uid,
);
}
self.action_queue
.push(Action::RemoveComponents(entity_uid, component_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.
///
/// # Panics
/// This function will panic if `self` was retrieved from a [`WeakRef`].
#[must_use]
pub fn to_weak_ref(&self) -> WeakRef
{
let world = self.world.unwrap_or_else(|| {
panic!(
"This function cannot be called if the {} was retrieved from a {}",
type_name::<Self>(),
type_name::<WeakRef>()
)
});
WeakRef {
action_queue: Rc::downgrade(&world.data.action_queue),
}
}
}
impl<'world> SystemParam<'world> for Actions<'world>
{
type Input = ();
fn new(world: &'world World, _system_metadata: &SystemMetadata) -> Self
{
Self {
action_queue: &world.data.action_queue,
world: Some(world),
}
}
}
#[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: Rc<ActionQueue>,
_pd: PhantomData<&'weak_ref ()>,
}
impl Ref<'_>
{
#[must_use]
pub fn to_actions(&self) -> Actions<'_>
{
Actions {
action_queue: &self.action_queue,
world: None,
}
}
}
/// A action for a [`System`] to perform.
#[derive(Debug)]
pub(crate) enum Action
{
Spawn(Uid, Vec<ComponentParts>),
Despawn(Uid),
AddComponents(Uid, Vec<ComponentParts>),
RemoveComponents(Uid, Vec<Uid>),
Stop,
}
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