use bevy::{
    ecs::{system::Command, world::EntityMut},
    prelude::*,
};

struct RunIfExistsCommand<F>(Entity, F);

impl<F: FnOnce(EntityMut) + Send + Sync + 'static> Command for RunIfExistsCommand<F> {
    fn write(self, world: &mut World) {
        world.get_entity_mut(self.0).map(self.1);
    }
}

pub trait RunIfExistsExt {
    fn run_if_exists(&mut self, entity: Entity, f: impl FnOnce(EntityMut) + Send + Sync + 'static);
}

impl RunIfExistsExt for Commands<'_, '_> {
    fn run_if_exists(&mut self, entity: Entity, f: impl FnOnce(EntityMut) + Send + Sync + 'static) {
        self.add(RunIfExistsCommand(entity, f));
    }
}