//! Component events.

use std::fmt::{Debug, Formatter};
use std::marker::PhantomData;

use ecs_macros::Component;

use crate::component::{Component, Id as ComponentId};
use crate::event::{Event, Id};
use crate::tuple::{ReduceElement as TupleReduceElement, With as TupleWith};

/// Event emitted when:
/// a) A entity with component `ComponentT` is spawned.
/// b) A component `ComponentT` is added to a entity.
pub struct Added<ComponentT>
where
    ComponentT: Component,
{
    _pd: PhantomData<ComponentT>,
}

impl<ComponentT> Debug for Added<ComponentT>
where
    ComponentT: Component,
{
    fn fmt(&self, formatter: &mut Formatter<'_>) -> std::fmt::Result
    {
        formatter
            .debug_struct("Added")
            .field("_pd", &self._pd)
            .finish()
    }
}

impl<ComponentT> Default for Added<ComponentT>
where
    ComponentT: Component,
{
    fn default() -> Self
    {
        Self { _pd: PhantomData }
    }
}

impl<ComponentT> Event for Added<ComponentT>
where
    ComponentT: Component,
{
    fn id() -> Id
    where
        Self: Sized,
    {
        Id::new::<Added<ComponentForId>, _>(Some(ComponentId::of::<ComponentT>()))
    }
}

pub fn create_added_id(component_id: ComponentId) -> Id
{
    Id::new::<Added<ComponentForId>, _>(Some(component_id))
}

pub struct ComponentToAddedEvent;

impl<ComponentT: Component, Accumulator>
    TupleReduceElement<Accumulator, ComponentToAddedEvent> for ComponentT
where
    Accumulator: TupleWith<Added<Self>>,
{
    type Return = Accumulator::With;
}

use crate as ecs;

#[derive(Debug, Component)]
struct ComponentForId;