use bevy::prelude::*;

fn main() {
    App::new() //
        .add_plugins(DefaultPlugins)
        .add_systems(PreStartup, pre_startup)
        .add_systems(Startup, (startup, setup))
        .add_systems(PostStartup, post_startup)
        .add_systems(First, first)
        .add_systems(PreUpdate, pre_update)
        .add_systems(Update, (update, check_space_pressed))
        .add_systems(PostUpdate, post_update)
        .run();
}

fn pre_startup() {
    info!("PreStartup");
}

fn startup() {
    info!("Startup");
}

fn post_startup() {
    info!("PostStartup");
}

fn first() {
    info!("First");
}

fn pre_update() {
    info!("PreUpdate");
}

fn update() {
    info!("Update");
}

fn post_update() {
    info!("PostUpdate");
}

fn check_space_pressed(input: Res<ButtonInput<KeyCode>>, mut commands: Commands) {
    if input.just_pressed(KeyCode::Space) {
        commands.trigger(TestEvent0);
    }
}

fn setup(mut commands: Commands) {
    commands.spawn((Observer::new(test_event_0_handler),));
    commands.spawn((Observer::new(test_event_1_handler),));
}

#[derive(Event, Debug)]
struct TestEvent0;

#[derive(Event, Debug)]
struct TestEvent1;

fn test_event_0_handler(event: On<TestEvent0>, mut commands: Commands) {
    info!("handle {:?}", event.event());
    commands.trigger(TestEvent1);
}

fn test_event_1_handler(event: On<TestEvent1>, mut commands: Commands) {
    info!("handle {:?}", event.event());
    commands.trigger(TestEvent0);
}