lyra-engine/lyra-ecs/src/resource.rs

use std::{any::{Any, TypeId}, sync::Arc};

use atomic_refcell::{AtomicRef, AtomicRefCell, AtomicRefMut};

use crate::{Tick, TickTracker};

/// Shorthand for `Send + Sync + 'static`, so it never needs to be implemented manually.
pub trait ResourceObject: Send + Sync + Any {
    fn as_any(&self) -> &dyn Any;
    fn as_any_mut(&mut self) -> &mut dyn Any;
}

impl<T: Send + Sync + Any> ResourceObject for T {
    fn as_any(&self) -> &dyn Any {
        self
    }

    fn as_any_mut(&mut self) -> &mut dyn Any {
        self
    }
}

pub struct TrackedResource<T: ?Sized> {
    pub tick: Tick,
    pub res: T,
}

/// A type erased storage for a Resource.
#[derive(Clone)]
pub struct ResourceData {
    pub(crate) data: Arc<AtomicRefCell<TrackedResource<dyn ResourceObject>>>,
    type_id: TypeId,
}

impl ResourceData {
    pub fn new<T: ResourceObject>(data: T, tick: Tick) -> Self {

        Self {
            data: Arc::new(AtomicRefCell::new(TrackedResource { tick, res: data })),
            type_id: TypeId::of::<T>(),
        }
    }

    /// Returns a boolean indicating whether or not `T`` is of the same type of the Resource
    pub fn is<T: ResourceObject>(&self) -> bool {
        self.type_id == TypeId::of::<T>()
    }

    /// Borrow the data inside of the resource.
    /// 
    /// # Panics
    /// 
    /// * If the data is already borrowed mutably, this will panic.
    /// * If the type of `T` is not the same as the resource type.
    pub fn get<T: ResourceObject>(&self) -> AtomicRef<T> {
        AtomicRef::map(self.data.borrow(), |a| a.res.as_any().downcast_ref().unwrap())
    }

    /// Mutably borrow the data inside of the resource.
    /// 
    /// # Panics
    /// 
    /// * If the data is already borrowed mutably, this will panic.
    /// * If the type of `T` is not the same as the resource type.
    pub fn get_mut<T: ResourceObject>(&self) -> AtomicRefMut<T> {
        AtomicRefMut::map(self.data.borrow_mut(), |a| a.res.as_any_mut().downcast_mut().unwrap())
    }

    /// Borrow the data inside of the resource.
    /// 
    /// # Panics
    /// 
    /// * If the type of `T` is not the same as the resource type.
    pub fn try_get<T: ResourceObject>(&self) -> Option<AtomicRef<T>> {
        self.data.try_borrow()
            .map(|r| AtomicRef::map(r, |a| a.res.as_any().downcast_ref().unwrap()))
            .ok()
    }

    /// Mutably borrow the data inside of the resource.
    /// 
    /// # Panics
    /// 
    /// * If the type of `T` is not the same as the resource type.
    pub fn try_get_mut<T: ResourceObject>(&self) -> Option<AtomicRefMut<T>> {
        self.data.try_borrow_mut()
            .map(|r| AtomicRefMut::map(r, |a| a.res.as_any_mut().downcast_mut().unwrap()))
            .ok()
    }

    pub fn changed(&self, tick: Tick) -> bool {
        self.data.borrow().tick >= tick
    }
}