use ecs::event::{Event, Id as EventId};
use ecs::{Component, Query, World};

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

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

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

#[derive(Debug)]
struct Start;

impl Event for Start
{
    fn id(&self) -> EventId
    {
        EventId::of::<Self>()
    }
}

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

    world.register_system(&Start, say_hello);

    world.create_entity((
        SomeData { num: 987_654 },
        Greeting {
            greeting: "Good afternoon".to_string(),
        },
    ));

    world.create_entity((
        SomeData { num: 345 },
        Greeting { greeting: "Good evening".to_string() },
    ));

    world.emit(&Start);
}