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use std::any::Any;
use std::convert::Infallible;
use std::fmt::Debug;
use ecs_macros::Component;
use seq_macro::seq;
use crate::component::{Component, HandleMut as ComponentHandleMut};
use crate::tuple::{ReduceElement as TupleReduceElement, Tuple};
use crate::World;
pub mod stateful;
pub trait System<'world, Impl>: 'static
{
type Input;
#[must_use]
fn initialize(self, input: Self::Input) -> Self;
fn run<'this>(&'this self, world: &'world World)
where
'this: 'world;
fn into_type_erased(self) -> TypeErased;
fn get_local_component_mut<LocalComponent: Component>(
&self,
) -> Option<ComponentHandleMut<LocalComponent>>;
fn set_local_component<LocalComponent: Component>(
&mut self,
local_component: LocalComponent,
);
}
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 Input = Infallible;
fn initialize(self, _input: Self::Input) -> Self
{
self
}
fn run<'this>(&'this self, world: &'world World)
where
'this: 'world
{
let func = *self;
func(#({
TParam~I::new(self, world)
},)*);
}
fn into_type_erased(self) -> TypeErased
{
TypeErased {
data: Box::new(self),
run: Box::new(|data, world| {
// SAFETY: The caller of TypeErased::run ensures the lifetime
// is correct
let data = unsafe { &*std::ptr::from_ref(data) };
let me = data
.downcast_ref::<Func>()
.expect("Function downcast failed");
// SAFETY: The caller of TypeErased::run ensures the lifetime
// is correct
let world = unsafe { &*std::ptr::from_ref(world) };
me.run(world);
}),
}
}
fn get_local_component_mut<LocalComponent: Component>(
&self,
) -> Option<ComponentHandleMut<LocalComponent>>
{
panic!("System does not have any local components");
}
fn set_local_component<LocalComponent: Component>(
&mut self,
_local_component: LocalComponent,
) {
panic!("System does not have any local components");
}
}
});
};
}
seq!(C in 1..16 {
impl_system!(C);
});
pub trait Into<Impl>
{
type System;
fn into_system(self) -> Self::System;
}
pub struct TypeErased
{
data: Box<dyn Any>,
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)
{
// You have to dereference for downcasting to work for some reason
let data = &*self.data;
(self.run)(data, world);
}
}
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(&dyn Any, &World);
/// A parameter to a [`System`].
pub trait Param<'world>
{
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;
}
/// A type which can be used as input to a [`System`].
pub trait Input: 'static {}
/// Component tuple reducing operation to get the parameters that takes input.
pub struct ParamWithInputFilter;
impl<InputT: Input, Accumulator> TupleReduceElement<Accumulator, ParamWithInputFilter>
for InputT
where
Accumulator: Tuple,
{
type Return = Accumulator::WithElementAtEnd<Self>;
}
impl<Accumulator> TupleReduceElement<Accumulator, ParamWithInputFilter> for ()
{
type Return = Accumulator;
}
#[derive(Debug, Component)]
pub(crate) struct SystemComponent
{
pub(crate) system: TypeErased,
}
|
