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|
use std::fmt::Debug;
use seq_macro::seq;
use crate::error::Error;
use crate::event::Emitted as EmittedEvent;
use crate::uid::Uid;
use crate::{Component, 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, Ret, #(TParam~I,)*> System<'world, fn(#(TParam~I,)*) -> Ret>
for Func
where
Func: Fn(#(TParam~I,)*) -> Ret + Copy + 'static,
Ret: ReturnValue,
#(TParam~I: Param<'world, Input = ()>,)*
{
type Callbacks = NoCallbacks;
fn finish(self) -> (TypeErased, Self::Callbacks)
{
#![allow(unused)]
crate::util::const_assert!(
size_of::<Func>() == 0,
"System function is not zero-sized (not function pointer)"
);
let type_erased = TypeErased {
run: |world, metadata, _| {
// SAFETY: The caller of TypeErased::run ensures the lifetime
// is correct
let world = unsafe { &*std::ptr::from_ref(world) };
let func = unsafe { std::mem::zeroed::<Func>() };
func(#({
TParam~I::new(world, &metadata)
},)*).into_result()
},
name: std::any::type_name::<Self>()
};
(type_erased, NoCallbacks)
}
}
});
};
}
seq!(C in 0..16 {
impl_system!(C);
});
pub trait Into<'world, Impl>
{
type System;
fn into_system(self) -> Self::System;
}
pub struct TypeErased
{
pub run: TypeErasedRunFn,
pub name: &'static str,
}
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,
evt: Option<EmittedEvent<'_>>,
) -> Result<(), Error>
{
(self.run)(world, metadata, evt)
}
pub fn name(&self) -> &'static str
{
self.name
}
}
impl Debug for TypeErased
{
fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
{
formatter.debug_struct("TypeErased").finish_non_exhaustive()
}
}
pub trait ReturnValue
{
fn into_result(self) -> Result<(), Error>;
}
impl ReturnValue for ()
{
fn into_result(self) -> Result<(), Error>
{
Ok(())
}
}
impl ReturnValue for Result<(), Error>
{
fn into_result(self) -> Result<(), Error>
{
self
}
}
/// 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,
}
type TypeErasedRunFn =
fn(&World, Metadata, Option<EmittedEvent<'_>>) -> Result<(), Error>;
|
