engine/ecs/src/events.rs

use std::{
    any::{Any, TypeId},
    collections::HashMap,
    mem,
    ops::DerefMut,
};

pub struct Events<C> {
    events: HashMap<
        TypeId,
        (
            Vec<Box<dyn Any + Send + Sync>>,
            Vec<Box<dyn Fn(&mut C, &dyn Any) -> anyhow::Result<()> + Send + Sync>>,
        ),
    >,
}

impl<C> Default for Events<C> {
    fn default() -> Self {
        Self {
            events: HashMap::new(),
        }
    }
}

impl<C> Events<C> {
    pub(crate) fn clone_from_register(&self) -> Self {
        Self {
            events: self
                .events
                .keys()
                .map(|type_id| (*type_id, (Vec::new(), Vec::new())))
                .collect(),
        }
    }

    pub(crate) fn move_events(&mut self, other: &mut Self) {
        for (type_id, (payloads, _)) in other.events.iter_mut() {
            if !payloads.is_empty() {
                let mut tmp = Vec::new();
                mem::swap(payloads, &mut tmp);

                self.events.get_mut(type_id).unwrap().0.extend(tmp);
            }
        }
    }

    pub fn clear(&mut self) {
        for (payloads, listener) in self.events.values_mut() {
            payloads.clear();
            listener.clear();
        }
    }

    pub fn register_event<T: Any + Send + Sync>(&mut self) {
        self.events
            .insert(TypeId::of::<T>(), (Vec::new(), Vec::new()));
    }

    pub fn add_reader<T: Any + Send + Sync, F>(&mut self, f: F)
    where
        F: Fn(&mut C, &T) -> anyhow::Result<()> + Send + Sync + 'static,
    {
        match self.events.get_mut(&TypeId::of::<T>()) {
            Some((_, listener)) => listener.push(Box::new(move |c, payload| {
                let typed_payload: &T = payload.downcast_ref().unwrap();

                f(c, typed_payload)
            })),
            None => panic!("register event type first!"),
        }
    }

    pub fn write_event<T: Any + Send + Sync>(&mut self, payload: T) {
        match self.events.get_mut(&TypeId::of::<T>()) {
            Some((payloads, _)) => payloads.push(Box::new(payload)),
            None => panic!("register event type first!"),
        }
    }

    pub(crate) fn fire_events(&mut self, c: &mut C) -> anyhow::Result<()> {
        for (payloads, listeners) in self.events.values_mut() {
            for payload in payloads.iter_mut() {
                for listener in listeners.iter_mut() {
                    (listener)(c, payload.deref_mut())?;
                }
            }

            payloads.clear();
        }

        Ok(())
    }
}