use engine_ecs::pair::ChildOf;
use engine_ecs::phase::START as START_PHASE;
use engine_ecs::query::term::{Traverse, TraverseSelfOrUp};
use engine_ecs::{pair, Component, Query, World};

#[derive(Component)]
struct SomeData
{
    num: u64,
}

#[derive(Component)]
struct Greeting
{
    greeting: String,
}

fn say_hello(query: Query<(Traverse<(&Greeting,), TraverseSelfOrUp, ChildOf>, &SomeData)>)
{
    for (greeting, data) in &query {
        println!("{}: {}", greeting.greeting, data.num);
    }
}

fn main()
{
    let mut world = World::new();

    world.register_system(*START_PHASE, say_hello);

    let parent_ent = world.spawn((Greeting {
        greeting: "Good afternoon".to_string(),
    },));

    world.spawn((SomeData { num: 345 }, pair!(ChildOf, { parent_ent })));

    world.spawn((
        SomeData { num: 123 },
        Greeting { greeting: "Good evening".to_string() },
        pair!(ChildOf, { parent_ent }),
    ));

    world.step();
}