ecs: implement change tracking for world resources

lyra-ecs/src/resource.rs

@@ -2,6 +2,8 @@ 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;
@@ -23,14 +25,17 @@ impl<T: Send + Sync + Any> ResourceObject for T {
 pub struct ResourceData {
     pub(crate) data: Arc<AtomicRefCell<dyn ResourceObject>>,
     type_id: TypeId,
+    // use a tick tracker which has interior mutability
+    pub(crate) tick: TickTracker,
 }
 
 impl ResourceData {
-    pub fn new<T: ResourceObject>(data: T) -> Self {
+    pub fn new<T: ResourceObject>(data: T, tick: Tick) -> Self {
 
         Self {
             data: Arc::new(AtomicRefCell::new(data)),
             type_id: TypeId::of::<T>(),
+            tick: TickTracker::from(*tick),
         }
     }
 
@@ -80,4 +85,8 @@ impl ResourceData {
             .map(|r| AtomicRefMut::map(r, |a| a.as_any_mut().downcast_mut().unwrap()))
             .ok()
     }
+
+    pub fn changed(&self, tick: Tick) -> bool {
+        self.tick.current() >= tick
+    }
 }

lyra-ecs/src/world.rs

@@ -374,33 +374,65 @@ impl World {
         ViewOne::new(self, entity.id, T::Query::new())
     }
 
-    //pub fn view_one(&self, entity: EntityId) -> 
+    /// Add a resource to the world.
-
+    /// 
+    /// Ticks the world.
     pub fn add_resource<T: ResourceObject>(&mut self, data: T) {
-        self.resources.insert(TypeId::of::<T>(), ResourceData::new(data));
+        let tick = self.tick();
+        self.resources.insert(TypeId::of::<T>(), ResourceData::new(data, tick));
     }
 
+    /// Add the default value of a resource.
+    ///
+    /// Ticks the world.
+    /// 
+    /// > Note: This will replace existing values.
     pub fn add_resource_default<T: ResourceObject + Default>(&mut self) {
-        self.resources.insert(TypeId::of::<T>(), ResourceData::new(T::default()));
+        let tick = self.tick();
+        self.resources.insert(TypeId::of::<T>(), ResourceData::new(T::default(), tick));
+    }
+
+    /// Add the default value of a resource if it does not already exist.
+    /// 
+    /// Returns a boolean indicating if the resource was added. Ticks the world if the resource
+    /// was added.
+    pub fn add_resource_default_if_absent<T: ResourceObject + Default>(&mut self) -> bool {
+        let id = TypeId::of::<T>();
+        if !self.resources.contains_key(&id) {
+            let tick = self.tick();
+            self.resources.insert(id, ResourceData::new(T::default(), tick));
+            
+            true
+        } else {
+            false
+        }
     }
 
     /// Get a resource from the world, or insert it into the world with the provided
     /// `fn` and return it.
+    ///
+    /// Ticks the world.
     pub fn get_resource_or_else<T: ResourceObject, F>(&mut self, f: F) -> AtomicRefMut<T>
     where
         F: Fn() -> T + 'static
     {
-        self.resources.entry(TypeId::of::<T>())
+        let tick = self.tick();
-            .or_insert_with(|| ResourceData::new(f()))
+        let res = self.resources.entry(TypeId::of::<T>())
-            .get_mut()
+            .or_insert_with(|| ResourceData::new(f(), tick));
+        res.tick.tick_to(&tick);
+        res.get_mut()
     }
 
     /// Get a resource from the world, or insert it into the world as its default.
+    /// 
+    /// Ticks the world.
     pub fn get_resource_or_default<T: ResourceObject + Default>(&mut self) -> AtomicRefMut<T>
     {
-        self.resources.entry(TypeId::of::<T>())
+        let tick = self.tick();
-            .or_insert_with(|| ResourceData::new(T::default()))
+        let res = self.resources.entry(TypeId::of::<T>())
-            .get_mut()
+            .or_insert_with(|| ResourceData::new(T::default(), tick));
+        res.tick.tick_to(&tick);
+        res.get_mut()
     }
 
     /// Gets a resource from the World.
@@ -413,6 +445,22 @@ impl World {
             .get()
     }
 
+    /// Returns a boolean indicating if the resource changed.
+    /// 
+    /// This will return false if the resource doesn't exist.
+    pub fn has_resource_changed<T: ResourceObject>(&self) -> bool {
+        let tick = self.current_tick();
+        self.resources.get(&TypeId::of::<T>())
+            .map(|r| r.changed(tick))
+            .unwrap_or(false)
+    }
+
+    /// Returns the [`Tick`] that the resource was last modified at.
+    pub fn resource_tick<T: ResourceObject>(&self) -> Option<Tick> {
+        self.resources.get(&TypeId::of::<T>())
+            .map(|r| r.tick.current())
+    }
+
     /// Returns boolean indicating if the World contains a resource of type `T`.
     pub fn has_resource<T: ResourceObject>(&self) -> bool {
         self.resources.contains_key(&TypeId::of::<T>())
@@ -430,20 +478,29 @@ impl World {
     /// 
     /// Will panic if the resource is not in the world. See [`World::try_get_resource_mut`] for
     /// a function that returns an option.
+    /// 
+    /// Ticks the world.
     pub fn get_resource_mut<T: ResourceObject>(&self) -> AtomicRefMut<T> {
-        self.resources.get(&TypeId::of::<T>())
+        self.try_get_resource_mut::<T>()
-            .expect(&format!("World is missing resource of type '{}'", std::any::type_name::<T>()))
+            .unwrap_or_else(|| panic!("World is missing resource of type '{}'", std::any::type_name::<T>()))
-            .get_mut()
     }
 
     /// Attempts to get a mutable borrow of a resource from the World.
     /// 
-    /// Returns `None` if the resource was not found.
+    /// Returns `None` if the resource was not found. Ticks the world if the resource was found.
     pub fn try_get_resource_mut<T: ResourceObject>(&self) -> Option<AtomicRefMut<T>> {
         self.resources.get(&TypeId::of::<T>())
-            .and_then(|r| r.try_get_mut())
+            .and_then(|r| {
+                // now that the resource was retrieved, tick the world and the resource
+                let new_tick = self.tick();
+                r.tick.tick_to(&new_tick);
+                r.try_get_mut()
+            })
     }
 
+    /// Get the corresponding [`ResourceData`].
+    /// 
+    /// > Note: If you borrow the resource mutably, the world and the resource will not be ticked.
     pub fn try_get_resource_data<T: ResourceObject>(&self) -> Option<ResourceData> {
         self.resources.get(&TypeId::of::<T>())
             .map(|r| r.clone())
@@ -693,4 +750,22 @@ mod tests {
         let pos = world.view_one::<&mut Vec2>(second).get().unwrap();
         assert_eq!(*pos, Vec2::new(5.0, 5.0));
     }
+
+    /// Tests resource change checks
+     #[test]
+    fn resource_changed() {
+        let mut world = World::new();
+        world.add_resource(SimpleCounter(50));
+
+        assert!(world.has_resource_changed::<SimpleCounter>());
+
+        world.spawn(Vec2::new(50.0, 50.0));
+     
+        assert!(!world.has_resource_changed::<SimpleCounter>());
+
+        let mut counter = world.get_resource_mut::<SimpleCounter>();
+        counter.0 += 100;
+
+        assert!(world.has_resource_changed::<SimpleCounter>());
+    }
 }