cooldown.rs

//! Demonstrates implementing a cooldown in UI.
//!
//! You might want a system like this for abilities, buffs or consumables.
//! We create four food buttons to eat with 2, 1, 10, and 4 seconds cooldown.

use bevy::{color::palettes::tailwind, ecs::spawn::SpawnIter, prelude::*};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .add_systems(
            Update,
            (
                activate_ability,
                animate_cooldowns.run_if(any_with_component::<ActiveCooldown>),
            ),
        )
        .run();
}

fn setup(
    mut commands: Commands,
    mut texture_atlas_layouts: ResMut<Assets<TextureAtlasLayout>>,
    asset_server: Res<AssetServer>,
) {
    commands.spawn(Camera2d);
    let texture = asset_server.load("textures/food_kenney.png");
    let layout = TextureAtlasLayout::from_grid(UVec2::splat(64), 7, 7, None, None);
    let texture_atlas_layout = texture_atlas_layouts.add(layout);
    commands.spawn((
        Node {
            width: percent(100),
            height: percent(100),
            align_items: AlignItems::Center,
            justify_content: JustifyContent::Center,
            column_gap: px(15),
            ..default()
        },
        Children::spawn(SpawnIter(
            [
                FoodItem {
                    name: "an apple",
                    cooldown: 2.,
                    index: 2,
                },
                FoodItem {
                    name: "a burger",
                    cooldown: 1.,
                    index: 23,
                },
                FoodItem {
                    name: "chocolate",
                    cooldown: 10.,
                    index: 32,
                },
                FoodItem {
                    name: "cherries",
                    cooldown: 4.,
                    index: 41,
                },
            ]
            .into_iter()
            .map(move |food| build_ability(food, texture.clone(), texture_atlas_layout.clone())),
        )),
    ));
    commands.spawn((
        Text::new("*Click some food to eat it*"),
        Node {
            position_type: PositionType::Absolute,
            top: px(12),
            left: px(12),
            ..default()
        },
    ));
}

struct FoodItem {
    name: &'static str,
    cooldown: f32,
    index: usize,
}

fn build_ability(
    food: FoodItem,
    texture: Handle<Image>,
    layout: Handle<TextureAtlasLayout>,
) -> impl Bundle {
    let FoodItem {
        name,
        cooldown,
        index,
    } = food;
    let name = Name::new(name);

    // Every food item is a button with a child node.
    // The child node's height will be animated to be at 100% at the beginning
    // of a cooldown, effectively graying out the whole button, and then getting smaller over time.
    (
        Node {
            width: px(80),
            height: px(80),
            flex_direction: FlexDirection::ColumnReverse,
            ..default()
        },
        BackgroundColor(tailwind::SLATE_400.into()),
        Button,
        ImageNode::from_atlas_image(texture, TextureAtlas { layout, index }),
        Cooldown(Timer::from_seconds(cooldown, TimerMode::Once)),
        name,
        children![(
            Node {
                width: percent(100),
                height: percent(0),
                ..default()
            },
            BackgroundColor(tailwind::SLATE_50.with_alpha(0.5).into()),
        )],
    )
}

#[derive(Component)]
struct Cooldown(Timer);

#[derive(Component)]
#[component(storage = "SparseSet")]
struct ActiveCooldown;

fn activate_ability(
    mut commands: Commands,
    mut interaction_query: Query<
        (
            Entity,
            &Interaction,
            &mut Cooldown,
            &Name,
            Option<&ActiveCooldown>,
        ),
        (Changed<Interaction>, With<Button>),
    >,
    mut text: Query<&mut Text>,
) -> Result {
    for (entity, interaction, mut cooldown, name, on_cooldown) in &mut interaction_query {
        if *interaction == Interaction::Pressed {
            if on_cooldown.is_none() {
                cooldown.0.reset();
                commands.entity(entity).insert(ActiveCooldown);
                **text.single_mut()? = format!("You ate {name}");
            } else {
                **text.single_mut()? = format!(
                    "You can eat {name} again in {} seconds.",
                    cooldown.0.remaining_secs().ceil()
                );
            }
        }
    }

    Ok(())
}

fn animate_cooldowns(
    time: Res<Time>,
    mut commands: Commands,
    buttons: Query<(Entity, &mut Cooldown, &Children), With<ActiveCooldown>>,
    mut nodes: Query<&mut Node>,
) -> Result {
    for (entity, mut timer, children) in buttons {
        timer.0.tick(time.delta());
        let cooldown = children.first().ok_or("No child")?;
        if timer.0.just_finished() {
            commands.entity(entity).remove::<ActiveCooldown>();
            nodes.get_mut(*cooldown)?.height = percent(0);
        } else {
            nodes.get_mut(*cooldown)?.height = percent((1. - timer.0.fraction()) * 100.);
        }
    }

    Ok(())
}