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// SPDX-License-Identifier: AGPL-3.0-only OR Commercial
use std::any::{Any, TypeId, type_name};
use std::cell::UnsafeCell;
use std::collections::HashMap;
#[allow(dead_code)]
/// Typed singleton storage for world-global data (e.g., delta time, tick count).
///
/// Values are wrapped in `UnsafeCell` to support interior mutability without
/// creating overlapping `&Resources` / `&mut Resources`. This eliminates the
/// Stacked Borrows aliasing UB when `UnsafeWorldCell` accesses different
/// resources concurrently (e.g., `Res<A>` + `ResMut<B>`).
pub(crate) struct Resources {
map: HashMap<TypeId, UnsafeCell<Box<dyn Any>>>,
}
#[allow(dead_code)]
impl Resources {
pub fn new() -> Self {
Self {
map: HashMap::new(),
}
}
/// Insert a resource, replacing any previous value of the same type.
pub fn insert<T: 'static>(&mut self, value: T) {
self.map
.insert(TypeId::of::<T>(), UnsafeCell::new(Box::new(value)));
}
/// Get a reference to a resource. Panics if not present.
pub fn get<T: 'static>(&self) -> &T {
let cell = self
.map
.get(&TypeId::of::<T>())
.unwrap_or_else(|| panic!("resource not found: {}", type_name::<T>()));
// SAFETY: We hold `&self`, so no `&mut self` exists — no other code
// can create a mutable reference through UnsafeCell concurrently.
let boxed: &Box<dyn Any> = unsafe { &*cell.get() };
boxed.downcast_ref::<T>().unwrap()
}
/// Get a mutable reference to a resource. Panics if not present.
pub fn get_mut<T: 'static>(&mut self) -> &mut T {
let cell = self
.map
.get(&TypeId::of::<T>())
.unwrap_or_else(|| panic!("resource not found: {}", type_name::<T>()));
// SAFETY: We hold `&mut self`, so exclusive access is guaranteed.
let boxed: &mut Box<dyn Any> = unsafe { &mut *cell.get() };
boxed.downcast_mut::<T>().unwrap()
}
/// Get a reference to a resource using only `&self`.
///
/// This is the `UnsafeWorldCell` path: both `get_unchecked` and
/// `get_mut_unchecked` take `&self`, so the caller only needs a single
/// `&Resources` — eliminating `&Resources` / `&mut Resources` overlap.
///
/// # Safety
///
/// - The resource of type `T` must exist.
/// - No mutable reference to the same resource may exist concurrently.
pub(crate) unsafe fn get_unchecked<T: 'static>(&self) -> &T {
let cell = self
.map
.get(&TypeId::of::<T>())
.unwrap_or_else(|| panic!("resource not found: {}", type_name::<T>()));
// SAFETY: Caller guarantees no mutable reference to this resource.
unsafe { &*cell.get() }.downcast_ref::<T>().unwrap()
}
/// Get a mutable reference to a resource using only `&self`.
///
/// Interior mutability via `UnsafeCell` — the caller only needs `&self`,
/// so no `&mut Resources` is created. Combined with `get_unchecked`,
/// this allows `Res<A>` + `ResMut<B>` without overlapping container refs.
///
/// # Safety
///
/// - The resource of type `T` must exist.
/// - No other reference (shared or mutable) to the same resource may
/// exist concurrently.
#[allow(clippy::mut_from_ref)] // Intentional: UnsafeCell interior mutability
pub(crate) unsafe fn get_mut_unchecked<T: 'static>(&self) -> &mut T {
let cell = self
.map
.get(&TypeId::of::<T>())
.unwrap_or_else(|| panic!("resource not found: {}", type_name::<T>()));
// SAFETY: Caller guarantees exclusive access to this resource.
// UnsafeCell allows mutation through &self.
unsafe { &mut *cell.get() }.downcast_mut::<T>().unwrap()
}
/// Try to get a reference to a resource. Returns `None` if not present.
pub fn try_get<T: 'static>(&self) -> Option<&T> {
let cell = self.map.get(&TypeId::of::<T>())?;
// SAFETY: We hold `&self`, so no mutable access exists.
let boxed: &Box<dyn Any> = unsafe { &*cell.get() };
boxed.downcast_ref::<T>()
}
/// Remove and return a resource. Panics if not present.
pub fn take<T: 'static>(&mut self) -> T {
*self
.map
.remove(&TypeId::of::<T>())
.unwrap_or_else(|| panic!("resource not found: {}", type_name::<T>()))
.into_inner()
.downcast::<T>()
.unwrap()
}
/// Try to remove and return a resource. Returns `None` if not present.
pub fn try_take<T: 'static>(&mut self) -> Option<T> {
self.map
.remove(&TypeId::of::<T>())
.and_then(|cell| cell.into_inner().downcast::<T>().ok())
.map(|b| *b)
}
/// Returns `true` if the resource exists.
pub fn contains<T: 'static>(&self) -> bool {
self.map.contains_key(&TypeId::of::<T>())
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn insert_and_get() {
let mut res = Resources::new();
res.insert(42_i32);
assert_eq!(*res.get::<i32>(), 42);
}
#[test]
fn get_mut() {
let mut res = Resources::new();
res.insert(10_u32);
*res.get_mut::<u32>() = 20;
assert_eq!(*res.get::<u32>(), 20);
}
#[test]
fn overwrite() {
let mut res = Resources::new();
res.insert(1_i32);
res.insert(2_i32);
assert_eq!(*res.get::<i32>(), 2);
}
#[test]
fn try_get_missing_returns_none() {
let res = Resources::new();
assert!(res.try_get::<f64>().is_none());
}
#[test]
#[should_panic(expected = "resource not found")]
fn get_missing_panics() {
let res = Resources::new();
let _: &f64 = res.get::<f64>();
}
#[test]
fn contains() {
let mut res = Resources::new();
assert!(!res.contains::<i32>());
res.insert(1_i32);
assert!(res.contains::<i32>());
}
#[test]
fn get_unchecked_reads_resource() {
let mut res = Resources::new();
res.insert(42_i32);
unsafe {
assert_eq!(*res.get_unchecked::<i32>(), 42);
}
}
#[test]
fn get_mut_unchecked_mutates_resource() {
let mut res = Resources::new();
res.insert(10_u32);
unsafe {
*res.get_mut_unchecked::<u32>() = 20;
}
assert_eq!(*res.get::<u32>(), 20);
}
}