games/src/bin/flappy/main.rs

// Bevy basically forces "complex types" with Querys
#![allow(clippy::type_complexity)]

use games::physics2d::*;
use games::*;

fn main() {
    App::new()
        .add_plugins((
            BaseGamePlugin {
                name: "flappy bird (with rewind)".into(),
                game_type: GameType::Two,
            },
            Physics2dPlugin,
        ))
        .insert_resource(Gravity(Vec2::NEG_Y * 9.8 * 100.0))
        .init_resource::<PipeComponents>()
        .init_resource::<GroundComponents>()
        .init_resource::<Score>()
        .init_resource::<RewindFrames>()
        .init_resource::<Flaps>()
        .init_resource::<Deaths>()
        .init_state::<PlayerState>()
        .add_systems(
            Startup,
            (
                init_bird,
                // init_obstacles,
                init_obstacle_assets,
                init_first_batches.after(init_obstacle_assets),
                init_ui,
                tweak_camera.after(create_camera_2d),
            ),
        )
        .add_systems(OnEnter(PlayerState::Alive), alive_bird)
        .add_systems(OnEnter(PlayerState::Pause), pause_bird)
        .add_systems(OnEnter(PlayerState::Stasis), pause_bird)
        // .add_systems(OnEnter(PlayerState::Rewind), pause_bird)
        .add_systems(
            Update,
            (
                // Systems to run when player state changes
                (
                    // Print out when this state changes for debugging purposes
                    debug_state_changes::<PlayerState>,
                    // Toggle (UI) elements when the player dies/alives
                    toggle_state_visibility::<PlayerState>,
                )
                    .run_if(state_changed::<PlayerState>),
                // Detect if the bird is "dead" by checking if it is visible
                // from the point of view of the camera
                detect_dead.run_if(in_state(PlayerState::Alive)),
                // Toggle rewinding state when "R" is pressed/released
                toggle_rewind.run_if(
                    input_just_pressed(KeyCode::KeyR).or(input_just_released(KeyCode::KeyR)),
                ),
                // Systems to run in the "play" state
                (
                    // Only flap when we press the space key
                    flap_kb.run_if(input_just_pressed(KeyCode::Space)),
                    // Rewinding systems
                    record.run_if(any_component_changed::<Transform>),
                )
                    .run_if(in_state(PlayerState::Alive)),
                // Rewinding systems
                rewind.run_if(in_state(PlayerState::Rewind)),
                // Camera follows when bird moves regardless of player state
                camera_follow_bird.run_if(any_component_changed::<Transform>),
                // Pause when the player presses Escape
                pause_game.run_if(input_just_pressed(KeyCode::Escape)),
                // Transition out of the pause screen if the player presses space
                un_pause_game
                    .run_if(input_just_pressed(KeyCode::Space))
                    .run_if(in_state(PlayerState::Pause)),
                // Stats that get synced to the UI
                (
                    sync_resource_to_ui::<Score>.run_if(resource_changed::<Score>),
                    sync_resource_to_ui::<Flaps>.run_if(resource_changed::<Flaps>),
                    sync_resource_to_ui::<Deaths>.run_if(resource_changed::<Deaths>),
                    sync_resource_to_ui::<RewindFrames>.run_if(resource_changed::<RewindFrames>),
                ),
                update_batch_position.run_if(any_component_changed::<Batch>),
                update_tooltip.run_if(in_state(DebuggingState::On)),
                (
                    // Temp debugging systems
                    debug_collision_events.run_if(on_event::<CollisionEnded>),
                ),
            ),
        )
        .add_observer(debug_collision_start_observations)
        .add_observer(debug_collision_end_observations)
        .add_observer(flap)
        .add_observer(populate_batch)
        .add_observer(populate_pipe)
        .add_observer(populate_ground)
        .add_observer(populate_hitbox)
        .add_observer(manage_batches)
        .add_observer(manage_score)
        .run();
}

fn tweak_camera(camera: Single<&mut Camera>) {
    debug!("Tweaking camera");
    let mut c = camera.into_inner();
    c.clear_color = ClearColorConfig::Custom(WHITE.into());
}

#[derive(Component)]
struct Bird;

#[derive(States, Clone, Eq, PartialEq, Debug, Hash, Default, Component)]
enum PlayerState {
    Alive,
    Rewind,
    Stasis,
    // Kind of a hack, but we need a state for this
    Credits,
    #[default]
    Pause,
}

// A tape tracking the bird's state every frame
#[derive(Component, Default)]
struct Tape {
    accumulated_translations: Vec<AccumulatedTranslation>,
    linear_velocities: Vec<LinearVelocity>,
    angular_velocities: Vec<AngularVelocity>,
    external_angular_impulses: Vec<ExternalAngularImpulse>,
    external_forces: Vec<ExternalForce>,
    external_impulses: Vec<ExternalImpulse>,
    external_torques: Vec<ExternalTorque>,
    positions: Vec<Position>,
    rotations: Vec<Rotation>,
}

fn init_bird(
    mut commands: Commands,
    server: Res<AssetServer>,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<ColorMaterial>>,
) {
    let material = MeshMaterial2d(materials.add(ColorMaterial {
        texture: Some(server.load("kenny.nl/1-bit-platformer-pack/tile_0380.png")),
        color: ORANGE.into(),
        alpha_mode: AlphaMode2d::Blend,
        ..default()
    }));

    let mesh = Mesh2d(meshes.add(Rectangle::new(1.0, 1.0)));

    let name = Name::new("bird");

    let t = Transform::from_xyz(0.0, 0.0, 0.0).with_scale(Vec3::splat(100.0));

    let physics = (
        RigidBody::Static,
        Collider::circle(0.5),
        Mass(10.0),
        ExternalImpulse::default().with_persistence(false),
        MaxLinearSpeed(500.0),
    );

    let tape = Tape::default();

    commands.spawn((
        name,
        mesh,
        material,
        physics,
        t,
        Bird,
        tape,
        CollisionEventsEnabled,
    ));
}

#[derive(Component, Clone)]
struct Ground(isize);

#[derive(Component, Clone)]
enum Pipe {
    Top,
    Bottom,
}

#[derive(Component, Clone)]
struct Hitbox;

#[derive(Component, Clone)]
struct Batch(usize);

fn init_first_batches(mut commands: Commands) {
    commands.spawn(Batch(0));
    commands.spawn(Batch(1));
    commands.spawn(Batch(2));
    commands.spawn(Batch(3));
    commands.spawn(Batch(4));
}

/// We have the concept of an environment "batch" which contains:
/// * The ground obstacle
/// * The pipe obstacle
/// * The pipe scoring sensor
///
/// These are all populated via `OnAdd` observers for the respected components.
/// This makes it much more concise to spawn each part of the environment.
fn populate_batch(
    trigger: Trigger<OnAdd, Batch>,
    batches: Query<&Batch>,
    children: Query<&ChildOf>,
    mut commands: Commands,
) {
    // Only run this for top level batch entities,
    // not children containing a reference to their batch, like hitboxes
    if !children.contains(trigger.target()) {
        let Batch(batch_id) = batches.get(trigger.target()).unwrap();
        commands
            .entity(trigger.target())
            .insert((
                Transform::from_xyz(500.0 * (*batch_id) as f32, 0.0, 0.0),
                Visibility::Inherited,
            ))
            .with_children(|parent| {
                parent.spawn(Ground(-2));
                parent.spawn(Ground(-1));
                parent.spawn(Ground(0));
                parent.spawn(Ground(1));
                parent.spawn(Ground(2));
                if *batch_id > 0 {
                    parent.spawn((Pipe::Top, Batch(*batch_id)));
                    parent.spawn((Pipe::Bottom, Batch(*batch_id)));
                    parent.spawn((Hitbox, Batch(*batch_id)));
                }
            });
    }
}

fn update_batch_position(
    mut root_changes: Query<(&mut Transform, &Batch), (Changed<Batch>, Without<ChildOf>)>,
) {
    root_changes.iter_mut().for_each(|(mut t, Batch(idx))| {
        info!("Updating batch {:?}", idx);
        t.translation.x = 500.0 * (*idx) as f32;
    });
    // todo!("Adjust pipe positions");
}

/// The ground population spawns a center peace and two pieces of ground
/// to the left and right of the center.
fn populate_ground(
    trigger: Trigger<OnAdd, Ground>,
    grounds: Query<&Ground>,
    ground_assets: Res<GroundComponents>,
    mut commands: Commands,
) {
    let Ground(idx) = grounds.get(trigger.target()).unwrap();
    debug!("populating ground {:?}", idx);
    commands.entity(trigger.target()).insert((
        ground_assets.material.clone(),
        ground_assets.mesh.clone(),
        Name::new("ground"),
        RigidBody::Static,
        Collider::rectangle(1.0, 1.0),
        Transform::from_xyz(100.0 * (*idx) as f32, -300.0, -1.0).with_scale(Vec3::splat(100.0)),
    ));
}

/// Based on if this is a Top or Bottom pipe the placement changes
/// Otherwise this just spawns in the center of the batch.
fn populate_pipe(
    trigger: Trigger<OnAdd, Pipe>,
    pipes: Query<&Pipe>,
    pipe_assets: Res<PipeComponents>,
    mut commands: Commands,
) {
    let pipe_t = match pipes.get(trigger.target()).unwrap() {
        Pipe::Top => Transform::from_xyz(0.0, 200.0, -1.0).with_scale(Vec3::splat(100.0)),
        Pipe::Bottom => Transform::from_xyz(0.0, -200.0, -1.0).with_scale(Vec3::splat(100.0)),
    };
    commands.entity(trigger.target()).insert((
        pipe_t,
        pipe_assets.material.clone(),
        pipe_assets.mesh.clone(),
        RigidBody::Static,
        Collider::rectangle(1.0, 1.0),
        Name::new("pipe"),
    ));
}

/// The hitbox should cover the entire height of the screen so if the player
/// passes between the pipes it registers a point
fn populate_hitbox(trigger: Trigger<OnAdd, Hitbox>, mut commands: Commands) {
    commands.entity(trigger.target()).insert((
        RigidBody::Static,
        Collider::rectangle(1.0, 10.0),
        Sensor,
        CollisionEventsEnabled,
        Name::new("hitbox"),
        Transform::from_xyz(0.0, 0.0, 0.0).with_scale(Vec3::splat(100.0)),
    ));
}

#[derive(Resource, Default)]
struct GroundComponents {
    material: MeshMaterial2d<ColorMaterial>,
    mesh: Mesh2d,
}

#[derive(Resource, Default)]
struct PipeComponents {
    material: MeshMaterial2d<ColorMaterial>,
    mesh: Mesh2d,
}

/// Initialize some materials and meshes used by the environment obstacles
fn init_obstacle_assets(
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<ColorMaterial>>,
    mut pipe_assets: ResMut<PipeComponents>,
    mut ground_assets: ResMut<GroundComponents>,
    server: Res<AssetServer>,
) {
    pipe_assets.material = MeshMaterial2d(materials.add(ColorMaterial {
        texture: Some(server.load("kenny.nl/1-bit-platformer-pack/tile_0247.png")),
        color: GREEN.into(),
        ..default()
    }));
    pipe_assets.mesh = Mesh2d(meshes.add(Rectangle::new(1.0, 1.0)));

    ground_assets.material = MeshMaterial2d(materials.add(ColorMaterial {
        texture: Some(server.load("kenny.nl/1-bit-platformer-pack/tile_0088.png")),
        color: BLACK.into(),
        ..default()
    }));

    ground_assets.mesh = Mesh2d(meshes.add(Rectangle::new(1.0, 1.0)));
}

fn init_ui(mut commands: Commands) {
    commands
        .spawn((
            Node {
                align_self: AlignSelf::Center,
                justify_self: JustifySelf::Center,
                flex_direction: FlexDirection::Column,
                ..default()
            },
            PlayerState::Stasis,
        ))
        .with_children(|parent| {
            parent.spawn((
                Text::new("Game Over...?"),
                TextLayout::new_with_justify(JustifyText::Center),
            ));
            parent.spawn((
                SyncResource::<Score>::default(),
                Text::default(),
                TextLayout::new_with_justify(JustifyText::Center),
            ));
            parent.spawn((
                SyncResource::<Flaps>::default(),
                Text::default(),
                TextLayout::new_with_justify(JustifyText::Center),
            ));
            parent.spawn((
                SyncResource::<RewindFrames>::default(),
                Text::default(),
                TextLayout::new_with_justify(JustifyText::Center),
            ));
            parent.spawn((
                SyncResource::<Deaths>::default(),
                Text::default(),
                TextLayout::new_with_justify(JustifyText::Center),
            ));
            parent.spawn((
                Text::new("Press R to Rewind"),
                TextLayout::new_with_justify(JustifyText::Center),
            ));
            parent
                .spawn((Node {
                    flex_direction: FlexDirection::Row,
                    justify_content: JustifyContent::SpaceEvenly,
                    ..default()
                },))
                .with_children(|parent| {
                    fn quit_game(
                        _trigger: Trigger<Pointer<Click>>,
                        mut exit: EventWriter<AppExit>,
                    ) {
                        warn!("Quitting game");
                        exit.write(AppExit::Success);
                    }

                    fn show_credits(
                        _trigger: Trigger<Pointer<Click>>,
                        mut state: ResMut<NextState<PlayerState>>,
                    ) {
                        state.set(PlayerState::Credits);
                    }

                    parent
                        .spawn((
                            Button,
                            Node { ..default() },
                            children![Text::new("Credits")],
                        ))
                        .observe(show_credits);
                    parent
                        .spawn((Button, Node { ..default() }, children![Text::new("Quit"),]))
                        .observe(quit_game);
                });
        });

    fn hide_credits(_trigger: Trigger<Pointer<Click>>, mut state: ResMut<NextState<PlayerState>>) {
        state.set(PlayerState::Stasis)
    }

    let credits_str = include_str!("../../../assets/flappy/CREDITS");

    commands
        .spawn((
            Node {
                align_self: AlignSelf::Center,
                justify_self: JustifySelf::Center,
                flex_direction: FlexDirection::Column,
                ..default()
            },
            PlayerState::Credits,
            children![(Text::new(credits_str), TextLayout::new_with_justify(JustifyText::Center))],
        ))
        .with_children(|parent| {
            parent.spawn((Node {
                align_self: AlignSelf::End,
                justify_self: JustifySelf::End,
                ..default()
            }, Button, children![Text::new("Close")]));
        }).observe(hide_credits);

    fn start_game(_trigger: Trigger<Pointer<Click>>, mut next: ResMut<NextState<PlayerState>>) {
        next.set(PlayerState::Alive);
    }

    commands
        .spawn((
            Node {
                align_self: AlignSelf::Center,
                justify_self: JustifySelf::Center,
                flex_direction: FlexDirection::Column,
                ..default()
            },
            Button,
            // TODO: Add Pause (basically Stasis) state
            PlayerState::Pause,
            children![Text::new("Go!"),],
        ))
        .observe(start_game);

    commands
        .spawn(Node {
            align_self: AlignSelf::End,
            justify_self: JustifySelf::Center,
            flex_direction: FlexDirection::Row,
            ..default()
        })
        .with_children(|parent| {
            parent
                .spawn((
                    Node { ..default() },
                    Button,
                    children![Text::new("Rewind!"),],
                ))
                .observe(start_rewind)
                .observe(end_rewind);

            parent
                .spawn((Node { ..default() }, Button, children![Text::new("Flap!"),]))
                .observe(flap_button);
        });

    commands.spawn((
        Node {
            align_self: AlignSelf::Start,
            justify_self: JustifySelf::Center,
            ..default()
        },
        BackgroundColor(WHITE.into()),
        SyncResource::<Score>::default(),
        Text::default(),
        TextLayout::new_with_justify(JustifyText::Center),
    ));
}

fn start_rewind(_trigger: Trigger<Pointer<Pressed>>, mut next: ResMut<NextState<PlayerState>>) {
    next.set(PlayerState::Rewind);
}

fn end_rewind(_trigger: Trigger<Pointer<Released>>, mut next: ResMut<NextState<PlayerState>>) {
    next.set(PlayerState::Alive);
}

fn flap_button(
    _trigger: Trigger<Pointer<Pressed>>,
    mut commands: Commands,
    bird: Single<Entity, With<Bird>>,
) {
    let e = *bird;
    debug!("Flapping {:?}", e);
    commands.trigger_targets(Flap, e);
}

/// Pause the game when the player presses "Escape"
fn pause_game(mut next: ResMut<NextState<PlayerState>>) {
    next.set(PlayerState::Pause);
}

fn un_pause_game(mut next: ResMut<NextState<PlayerState>>) {
    next.set(PlayerState::Alive);
}

#[derive(Component, Clone, Event)]
struct Flap;

// Observer for flapping
fn flap(
    trigger: Trigger<Flap>,
    mut bird: Query<&mut ExternalImpulse, With<Bird>>,
    mut flaps: ResMut<Flaps>,
) {
    debug!("real flap for {:?}", trigger.target());
    // Increment flap stat
    flaps.0 += 1;

    // Flap birds wings
    if let Ok(mut f) = bird.get_mut(trigger.target()) {
        f.apply_impulse(Vec2::Y * 5000.0 + Vec2::X * 1000.0);
    }
}

fn flap_kb(
    #[cfg(debug_assertions)] state: Res<State<PlayerState>>,
    #[cfg(debug_assertions)] keycode: Res<ButtonInput<KeyCode>>,
    birds: Query<Entity, With<Bird>>,
    mut commands: Commands,
) {
    debug_assert!(
        matches!(state.get(), PlayerState::Alive),
        "Only flap when playing"
    );
    debug_assert!(
        keycode.just_pressed(KeyCode::Space),
        "Only flap when space is just pressed"
    );

    birds.iter().for_each(|e| {
        debug!("Flapping {:?}", e);
        commands.trigger_targets(Flap, e);
    });
}

fn toggle_rewind(keycode: Res<ButtonInput<KeyCode>>, mut next: ResMut<NextState<PlayerState>>) {
    debug_assert!(
        keycode.just_pressed(KeyCode::KeyR) || keycode.just_released(KeyCode::KeyR),
        "Only toggle rewind when R is pressed"
    );

    if keycode.just_pressed(KeyCode::KeyR) {
        debug!("Toggling rewind ON");
        next.set(PlayerState::Rewind)
    } else {
        debug!("Toggling rewind OFF");
        next.set(PlayerState::Alive)
    }
}

fn record(
    #[cfg(debug_assertions)] state: Res<State<PlayerState>>,
    mut birds: Query<
        (
            &AccumulatedTranslation,
            &LinearVelocity,
            &AngularVelocity,
            &ExternalAngularImpulse,
            &ExternalForce,
            &ExternalImpulse,
            &ExternalTorque,
            &Position,
            &Rotation,
            &mut Tape,
        ),
        With<Bird>,
    >,
) {
    debug_assert!(
        matches!(state.get(), PlayerState::Alive),
        "Only record in the alive state"
    );

    birds
        .iter_mut()
        .for_each(|(at, lv, av, eai, ef, ei, et, p, r, mut tape)| {
            tape.accumulated_translations.push(*at);
            tape.linear_velocities.push(*lv);
            tape.angular_velocities.push(*av);
            tape.external_angular_impulses.push(*eai);
            tape.external_forces.push(*ef);
            tape.external_impulses.push(*ei);
            tape.external_torques.push(*et);
            tape.positions.push(*p);
            tape.rotations.push(*r);
        });
}

fn rewind(
    #[cfg(debug_assertions)] state: Res<State<PlayerState>>,
    mut birds: Query<
        (
            &mut AccumulatedTranslation,
            &mut LinearVelocity,
            &mut AngularVelocity,
            &mut ExternalAngularImpulse,
            &mut ExternalForce,
            &mut ExternalImpulse,
            &mut ExternalTorque,
            &mut Position,
            &mut Rotation,
            &mut Tape,
        ),
        With<Bird>,
    >,
    mut frames: ResMut<RewindFrames>,
) {
    debug_assert!(
        matches!(state.get(), PlayerState::Rewind),
        "Only rewind in the rewinding state"
    );

    birds.iter_mut().for_each(
        |(mut at, mut lv, mut av, mut eai, mut ef, mut ei, mut et, mut p, mut r, mut tape)| {
            if !tape.positions.is_empty() {
                at.0 = tape.accumulated_translations.pop().unwrap().0;
                lv.0 = tape.linear_velocities.pop().unwrap().0;
                av.0 = tape.angular_velocities.pop().unwrap().0;
                eai.set_impulse(tape.external_angular_impulses.pop().unwrap().impulse());
                ef.set_force(tape.external_forces.pop().unwrap().force());
                ei.set_impulse(tape.external_impulses.pop().unwrap().impulse());
                et.set_torque(tape.external_torques.pop().unwrap().torque());
                p.0 = tape.positions.pop().unwrap().0;
                *r = {
                    let curr = tape.rotations.pop().unwrap();
                    Rotation {
                        cos: curr.cos,
                        sin: curr.sin,
                    }
                };
                frames.0 += 1;
            }
        },
    );
}

// PERF: May run more than necessary, should be event-driven on aabb intersection
fn detect_dead(
    #[cfg(debug_assertions)] state: Res<State<PlayerState>>,
    bird: Single<&ColliderAabb, With<Bird>>,
    obstacles: Query<&ColliderAabb, Or<(With<Ground>, With<Pipe>)>>,
    mut next: ResMut<NextState<PlayerState>>,
) {
    debug_assert!(
        matches!(state.get(), PlayerState::Alive),
        "Only check if dead while alive"
    );

    if obstacles.iter().any(|obstacle| bird.intersects(obstacle)) {
        next.set(PlayerState::Stasis);
    }
}

fn alive_bird(
    #[cfg(debug_assertions)] state: Res<State<PlayerState>>,
    mut bird: Single<&mut RigidBody, With<Bird>>,
) {
    debug_assert!(matches!(state.get(), PlayerState::Alive));
    debug!("Setting bird to Dynamic");
    **bird = RigidBody::Dynamic;
}

fn pause_bird(
    state: Res<State<PlayerState>>,
    mut bird: Single<&mut RigidBody, With<Bird>>,
    mut deaths: ResMut<Deaths>,
) {
    debug_assert!(!matches!(state.get(), PlayerState::Alive));

    // Increment death count
    if state.get() == &PlayerState::Stasis {
        deaths.0 += 1
    }

    debug!("Setting bird to Static");
    **bird = RigidBody::Static;
}

fn camera_follow_bird(
    bird: Single<&Transform, (With<Bird>, Changed<Transform>)>,
    mut camera: Single<&mut Transform, (With<Camera>, Without<Bird>)>,
) {
    camera.translation.x = bird.translation.x;
}

/// How many pipes the player has passed
#[derive(Resource, Default)]
struct Score(usize);

impl Display for Score {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        writeln!(f, "Score: {}", self.0)
    }
}

/// Number of frames that were rewound
#[derive(Resource, Default)]
struct RewindFrames(usize);

impl Display for RewindFrames {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        writeln!(f, "Frames Rewound: {}", self.0)
    }
}

// Track number of times player flapped their wings
#[derive(Resource, Default)]
struct Flaps(usize);

impl Display for Flaps {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        writeln!(f, "Flaps: {}", self.0)
    }
}

// Track number of times player died
#[derive(Resource, Default)]
struct Deaths(usize);

impl Display for Deaths {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        writeln!(f, "Deaths: {}", self.0)
    }
}

// TODO: Scoring is bugged, need to make it correct.
fn manage_score(
    trigger: Trigger<OnCollisionEnd>,
    state: Res<State<PlayerState>>,
    bird: Query<Entity, With<Bird>>,
    hitboxes: Query<&Batch, With<Hitbox>>,
    mut score: ResMut<Score>,
) {
    let a = trigger.target();
    let b = trigger.collider;
    if bird.contains(a) && hitboxes.contains(b) {
        debug!("Hit event while {:?}", state.get());
        let Batch(id) = hitboxes.get(b).unwrap();
        score.0 = match state.get() {
            PlayerState::Alive => *id,
            PlayerState::Rewind => *id - 1,
            _ => *id, // HOW???
        }
    }
}

fn debug_collision_events(
    mut end: EventReader<CollisionEnded>,
    mut start: EventReader<CollisionStarted>,
    state: Res<State<PlayerState>>,
) {
    start.read().for_each(|CollisionStarted(a, b)| {
        debug!("Collision started between {a} and {b} in {:?}", state.get());
    });
    end.read().for_each(|CollisionEnded(a, b)| {
        debug!("Collision ended between {a} and {b} in {:?}", state.get());
    });
}

fn debug_collision_start_observations(
    trigger: Trigger<OnCollisionStart>,
    state: Res<State<PlayerState>>,
) {
    debug!(
        "Collision started between {} and {} in {:?}",
        trigger.target(),
        trigger.collider,
        state.get()
    );
}

fn debug_collision_end_observations(
    trigger: Trigger<OnCollisionEnd>,
    state: Res<State<PlayerState>>,
) {
    debug!(
        "Collision end between {} and {} in {:?}",
        trigger.target(),
        trigger.collider,
        state.get()
    );
}

/// When the player moves forward while alive
/// spawn more batches and despawn old batches
fn manage_batches(
    trigger: Trigger<OnCollisionStart>,
    state: Res<State<PlayerState>>,
    bird: Query<Entity, With<Bird>>,
    batches: Query<(Entity, &Batch)>,
    mut commands: Commands,
) {
    debug_assert!(
        matches!(state.get(), PlayerState::Alive) || matches!(state.get(), PlayerState::Rewind)
    );
    let a = trigger.target();
    let b = trigger.collider;
    if bird.contains(a)
        && let Ok((_e, Batch(idx))) = batches.get(b)
        && *idx > 2
    {
        info!("Managing batches in player state {:?}", state.get());
        let (old_batch_idx, new_batch_idx) = match state.get() {
            PlayerState::Alive => (idx - 2, idx + 2),
            PlayerState::Rewind => (idx + 2, idx - 2),
            _ => panic!("Should not happen!"),
        };
        // Find all entities with the old batch and adjust them
        batches
            .iter()
            .filter_map(|(e, batch)| (batch.0 == old_batch_idx).then_some(e))
            .for_each(|e| {
                info!("Moving batch {} -> {}", old_batch_idx, new_batch_idx);
                commands.entity(e).insert(Batch(new_batch_idx));
            })
    }
}

fn update_tooltip(
    mut query: Query<(
        &mut ToolTip,
        Option<&LinearVelocity>,
        Option<&Batch>,
        Entity,
    )>,
) {
    query.iter_mut().for_each(|(mut tt, lv, b, _e)| {
        // Add Linear Velocity if present on entity
        lv.iter().for_each(|it| {
            tt.insert("Velocity", format!("{}", it.0));
        });
        // Add Batch ID to if present
        b.iter().for_each(|it| {
            tt.insert("Batch", format!("{}", it.0));
        });
    });
}