use std::{any::{Any, TypeId}, ptr::NonNull};

use lyra_ecs::{AtomicRef, AtomicRefMut, ResourceObject, World};

use crate::{Reflect, FromType};

#[derive(Clone)]
pub struct ReflectedResource {
    pub type_id: TypeId,

    fn_reflect: for<'a> fn (world: &'a World) -> Option<AtomicRef<'a, dyn Reflect>>,
    fn_reflect_mut: for<'a> fn (world: &'a mut World) -> Option<AtomicRefMut<'a, dyn Reflect>>,
    fn_reflect_ptr: fn (world: &mut World) -> Option<NonNull<u8>>,
    fn_refl_insert: fn (world: &mut World, this: Box<dyn Reflect>),
}

impl ReflectedResource {
    /// Retrieves the reflected resource from the world.
    pub fn reflect<'a>(&self, world: &'a World) -> Option<AtomicRef<'a, dyn Reflect>> {
        (self.fn_reflect)(world)
    }

    /// Retrieves a mutable reflected resource from the world.
    pub fn reflect_mut<'a>(&self, world: &'a mut World) -> Option<AtomicRefMut<'a, dyn Reflect>> {
        (self.fn_reflect_mut)(world)
    }

    pub fn reflect_ptr(&self, world: &mut World) ->  Option<NonNull<u8>> {
        (self.fn_reflect_ptr)(world)
    }

    /// Insert the resource into the world.
    pub fn insert(&self, world: &mut World, this: Box<dyn Reflect>) {
        (self.fn_refl_insert)(world, this)
    }
}

impl<T: ResourceObject + Reflect> FromType<T> for ReflectedResource {
    fn from_type() -> Self {
        Self {
            type_id: TypeId::of::<T>(),
            fn_reflect: |world: &World| {
                world.get_resource::<T>()
                    .map(|r| {
                        // TODO: figure out change tracking for reflected resource
                        let r = r.get_inner();
                        AtomicRef::map(r, |r| r as &dyn Reflect)
                    })
            },
            fn_reflect_mut: |world: &mut World| {
                world.get_resource_mut::<T>()
                    .map(|r| {
                        // TODO: figure out change tracking for reflected resource
                        let r = r.get_inner();
                        AtomicRefMut::map(r, |r| r as &mut dyn Reflect)
                    })
            },
            fn_reflect_ptr: |world: &mut World| unsafe {
                world.get_resource_ptr::<T>()
                    .map(|ptr| ptr.cast::<u8>())
            },
            fn_refl_insert: |world: &mut World, this: Box<dyn Reflect>| {
                let res = this as Box<dyn Any>;
                let res = res.downcast::<T>()
                    .expect("Provided a non-matching type to ReflectedResource insert method!");
                let res = *res;
                world.add_resource(res);
            }
        }
    }
}