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use std::fmt::Debug;
use ecs_macros::Component;
use seq_macro::seq;
use crate::uid::Uid;
use crate::World;
pub mod initializable;
pub mod observer;
pub mod stateful;
/// Metadata of a system.
#[derive(Debug)]
#[non_exhaustive]
pub struct Metadata
{
pub ent_id: Uid,
}
pub trait System<'world, Impl>: 'static
{
type Callbacks: Callbacks;
fn finish(self) -> (TypeErased, Self::Callbacks);
}
macro_rules! impl_system {
($c: tt) => {
seq!(I in 0..$c {
impl<'world, Func, #(TParam~I,)*> System<'world, fn(#(TParam~I,)*)>
for Func
where
Func: Fn(#(TParam~I,)*) + Copy + 'static,
#(TParam~I: Param<'world, Input = ()>,)*
{
type Callbacks = NoCallbacks;
fn finish(self) -> (TypeErased, Self::Callbacks)
{
let type_erased = TypeErased {
run: Box::new(move |world, metadata| {
// SAFETY: The caller of TypeErased::run ensures the lifetime
// is correct
let world = unsafe { &*std::ptr::from_ref(world) };
self(#({
TParam~I::new(world, &metadata)
},)*);
}),
};
(type_erased, NoCallbacks)
}
}
});
};
}
seq!(C in 1..16 {
impl_system!(C);
});
pub trait Into<'world, Impl>
{
type System;
fn into_system(self) -> Self::System;
}
pub struct TypeErased
{
run: Box<TypeErasedRunFn>,
}
impl TypeErased
{
/// Runs the system.
///
/// # Safety
/// `world_data` must live at least as long as the [`World`] the system belongs to.
pub unsafe fn run(&self, world: &World, metadata: Metadata)
{
(self.run)(world, metadata);
}
}
impl Debug for TypeErased
{
fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
{
formatter.debug_struct("TypeErased").finish_non_exhaustive()
}
}
/// Function in [`TypeErased`] used to run the system.
type TypeErasedRunFn = dyn Fn(&World, Metadata);
/// A parameter to a [`System`].
pub trait Param<'world>
{
type Input;
fn new(world: &'world World, system_metadata: &Metadata) -> Self;
}
/// A type which can be used as input to a [`System`].
pub trait Input: 'static {}
pub trait Callbacks
{
fn on_created(&mut self, world: &mut World, metadata: Metadata);
}
pub struct NoCallbacks;
impl Callbacks for NoCallbacks
{
fn on_created(&mut self, _world: &mut World, _metadata: Metadata) {}
}
#[derive(Debug, Component)]
pub(crate) struct SystemComponent
{
pub(crate) system: TypeErased,
}
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