games/src/bin/flappy/main.rs

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

use games::physics3d::*;
use games::*;

fn main() {
    App::new()
        .add_plugins((
            BaseGamePlugin {
                name: "flappy bird (with rewind)".into(),
                ..default()
            },
            Physics3dPlugin,
        ))
        .init_state::<PlayerState>()
        .add_systems(
            Startup,
            (
                init_bird,
                init_obstacles,
                init_ui,
                tweak_camera.after(create_camera_3d),
            ),
        )
        .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.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)),
            ),
        )
        .run();
}

fn tweak_camera(mut camera: Query<(&mut Camera, &mut AmbientLight, &mut Transform), With<Camera>>) {
    camera.iter_mut().for_each(|(mut c, mut al, mut t)| {
        c.clear_color = ClearColorConfig::Custom(WHITE.into());
        al.brightness = 100.0;
        // move the camera "back" so everything else is at 0 on the Z axis
        t.translation.z = 10.0;
    });
}

#[derive(Component)]
struct Bird;

#[derive(States, Clone, Eq, PartialEq, Debug, Hash, Default, Component)]
enum PlayerState {
    Alive,
    Rewind,
    Stasis,
    #[default]
    Pause,
}

// A tape tracking the bird's state every frame
#[derive(Component, Default)]
struct Tape {
    translations: Vec<Vec3>,
    rotations: Vec<Quat>,
    linear_velocities: Vec<LinearVelocity>,
    angular_velocities: Vec<AngularVelocity>,
}

fn init_bird(
    mut commands: Commands,
    server: Res<AssetServer>,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    let material = MeshMaterial3d(materials.add(StandardMaterial {
        base_color_texture: Some(server.load("flappy/bevy.png")),
        base_color: WHITE.into(),
        alpha_mode: AlphaMode::Blend,
        ..default()
    }));

    let mesh = Mesh3d(meshes.add(Plane3d::new(Vec3::Y, Vec2::splat(1.0))));

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

    let t = Transform::from_xyz(0.0, 0.0, 0.0).with_rotation(Quat::from_rotation_x(PI / 2.0));

    let physics = (
        RigidBody::Static,
        Collider::capsule(1.0, 1.0),
        Mass(1.0),
        ExternalImpulse::default().with_persistence(false),
        LockedAxes::ROTATION_LOCKED.lock_translation_z(),
    );

    let tape = Tape::default();

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

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

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

fn init_obstacles(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    let ground = {
        let material = MeshMaterial3d(materials.add(StandardMaterial {
            base_color: LIGHT_GREEN.into(),
            ..default()
        }));

        let mesh = Mesh3d(meshes.add(Cuboid::new(10.0, 1.0, 1.0)));

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

        let physics = (RigidBody::Static, Collider::cuboid(1.0, 1.0, 1.0));

        (name, mesh, material, physics, Ground)
    };
    let pipe = {
        let material = MeshMaterial3d(materials.add(StandardMaterial {
            base_color: GREEN.into(),
            ..default()
        }));

        let mesh = Mesh3d(meshes.add(Cuboid::new(1.0, 3.0, 1.0)));
        let physics = (RigidBody::Static, Collider::cuboid(1.0, 3.0, 1.0));
        let name = Name::new("pipe");

        (
            name.clone(),
            mesh.clone(),
            material.clone(),
            physics.clone(),
            Pipe,
        )
    };

    // TODO: Instead of spawning infinite floor/pipes, we should instead spawn enough for 1-3 a few
    // screens and then "move" them around.
    // This is considerably more complexity so can be implemented later, but would keep memory
    // overhead fairly static.
    (1..99).for_each(|i| {
        // TODO: Jitter up/down/close/far of pipes for challenge
        let above = Transform::from_xyz(5.0 * i as f32, 4.0, 0.0);
        let below = Transform::from_xyz(5.0 * i as f32, -4.0, 0.0);
        let floor = Transform::from_xyz(1.0 * i as f32, -4.0, 0.0);

        commands.spawn((pipe.clone(), above));
        commands.spawn((pipe.clone(), below));
        commands.spawn((ground.clone(), floor));
    });
}

fn init_ui(mut commands: Commands) {
    commands.spawn((
        Node {
            align_self: AlignSelf::Center,
            justify_self: JustifySelf::Center,
            flex_direction: FlexDirection::Column,
            ..default()
        },
        PlayerState::Stasis,
        children![Text::new("You Died"), Text::new("Press R to Rewind"),],
    ));

    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);

    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);
    }

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

/// 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);
}

// TODO: Create floor (and ceiling?)
// Q: Move bird + camera or move world around bird & camera?
// TODO: Obstacles

fn flap(
    #[cfg(debug_assertions)] state: Res<State<PlayerState>>,
    #[cfg(debug_assertions)] keycode: Res<ButtonInput<KeyCode>>,
    mut bird: Query<(&Transform, &mut ExternalImpulse), With<Bird>>,
) {
    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"
    );

    bird.iter_mut().for_each(|(t, mut f)| {
        f.apply_impulse(t.rotation * Vec3::NEG_Z * 5.0 + t.rotation * Vec3::X);
    });
}

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<(&Transform, &LinearVelocity, &AngularVelocity, &mut Tape), With<Bird>>,
) {
    debug_assert!(
        matches!(state.get(), PlayerState::Alive),
        "Only record in the alive state"
    );

    birds.iter_mut().for_each(|(transform, linear_velocity, angular_velocity, mut tape)| {
        tape.translations.push(transform.translation);
        tape.rotations.push(transform.rotation);
        tape.linear_velocities.push(*linear_velocity);
        tape.angular_velocities.push(*angular_velocity);
    });
}

fn rewind(
    #[cfg(debug_assertions)] state: Res<State<PlayerState>>,
    mut birds: Query<(&mut Transform, &mut AngularVelocity, &mut LinearVelocity, &mut Tape), With<Bird>>,
) {
    debug_assert!(
        matches!(state.get(), PlayerState::Rewind),
        "Only rewind in the rewinding state"
    );

    birds.iter_mut().for_each(|(mut transform, mut angular_velocity, mut linear_velocity, mut tape)| {
        if let Some(t) = tape.translations.pop() {
            transform.translation = t;
        }
        if let Some(r) = tape.rotations.pop() {
            transform.rotation = r;
        }
        if let Some(av) = tape.angular_velocities.pop() {
            *angular_velocity = av;
        }
        if let Some(lv) = tape.linear_velocities.pop() {
            *linear_velocity = lv;
        }
    });
}

// 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(
    #[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 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;
}