bevy_seedling 0.4.2

//! Spatial audio components.
//!
//! To enable spatial audio, three conditions are required:
//!
//! 1. The spatial audio node, [`SpatialBasicNode`], must have
//!    a transform.
//! 2. The spatial listener entity must have a [`SpatialListener2D`]
//!    or [`SpatialListener3D`].
//! 3. The spatial listener entity must have a transform.
//!
//! Typically, you'll want to include a [`SpatialBasicNode`] as an effect.
//!
//! ```
//! # use bevy_seedling::prelude::*;
//! # use bevy::prelude::*;
//! fn spawn_spatial(mut commands: Commands, server: Res<AssetServer>) {
//!     // Spawn a player with a transform (1).
//!     commands.spawn((
//!         SamplePlayer::new(server.load("my_sample.wav")),
//!         Transform::default(),
//!         sample_effects![SpatialBasicNode::default()],
//!     ));
//!
//!     // Then, spawn a listener (2), which automatically inserts
//!     // a transform if it doesn't already exist (3).
//!     commands.spawn(SpatialListener2D);
//! }
//! ```
//!
//! Multiple listeners are supported. `bevy_seedling` will
//! simply select the closest listener for distance
//! calculations.

use bevy::prelude::*;
use firewheel::nodes::spatial_basic::SpatialBasicNode;

use crate::pool::sample_effects::EffectOf;

/// A scaling factor applied to the distance between spatial listeners and emitters.
///
/// To override the [global spatial scaling][DefaultSpatialScale] for an entity,
/// simply insert [`SpatialScale`].
///
/// ```
/// # use bevy::prelude::*;
/// # use bevy_seedling::prelude::*;
/// fn set_scale(mut commands: Commands, server: Res<AssetServer>) {
///     commands.spawn((
///         SamplePlayer::new(server.load("my_sample.wav")),
///         Transform::default(),
///         sample_effects![(SpatialBasicNode::default(), SpatialScale(Vec3::splat(0.25)))],
///     ));
/// }
/// ```
///
/// By default, a spatial signal's amplitude will be cut in half at 10 units. Then,
/// for each doubling in distance, the signal will be successively halved.
///
/// | Distance | Amplitude |
/// | -------- | --------- |
/// | 10       | -6dB      |
/// | 20       | -12dB     |
/// | 40       | -18dB     |
/// | 80       | -24dB     |
///
/// When one unit corresponds to one meter, this is a good default. If
/// your game's scale differs significantly, however, you may need
/// to adjust the spatial scaling.
///
/// The distance between listeners and emitters is multiplied by this
/// factor, so if a meter in your game corresponds to more than one unit, you
/// should provide a spatial scale of less than one to compensate.
#[derive(Component, Debug, Clone, Copy)]
pub struct SpatialScale(pub Vec3);

impl Default for SpatialScale {
    fn default() -> Self {
        Self(Vec3::ONE)
    }
}

/// The global default spatial scale.
///
/// For more details on spatial scaling, see [`SpatialScale`].
///
/// The default scaling is 1 in every direction, [`Vec3::ONE`].
#[derive(Resource, Debug, Default, Clone)]
pub struct DefaultSpatialScale(SpatialScale);

impl core::ops::Deref for DefaultSpatialScale {
    type Target = SpatialScale;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl core::ops::DerefMut for DefaultSpatialScale {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

/// A 2D spatial listener.
///
/// When this component is added to an entity with a transform,
/// this transform is used to calculate spatial offsets for all
/// emitters. An emitter is an entity with [`SpatialBasicNode`]
/// and transform components.
///
/// Multiple listeners are supported. `bevy_seedling` will
/// simply select the closest listener for distance
/// calculations.
#[derive(Debug, Default, Component)]
#[require(Transform)]
pub struct SpatialListener2D;

/// A 3D spatial listener.
///
/// When this component is added to an entity with a transform,
/// this transform is used to calculate spatial offsets for all
/// emitters. An emitter is an entity with [`SpatialBasicNode`]
/// and transform components.
///
/// Multiple listeners are supported. `bevy_seedling` will
/// simply select the closest listener for distance
/// calculations.
#[derive(Debug, Default, Component)]
#[require(Transform)]
pub struct SpatialListener3D;

pub(crate) fn update_2d_emitters(
    listeners: Query<&GlobalTransform, With<SpatialListener2D>>,
    mut emitters: Query<(
        &mut SpatialBasicNode,
        Option<&SpatialScale>,
        &GlobalTransform,
    )>,
    default_scale: Res<DefaultSpatialScale>,
) {
    for (mut spatial, scale, transform) in emitters.iter_mut() {
        let emitter_pos = transform.translation();
        let closest_listener = find_closest_listener(
            emitter_pos,
            listeners.iter().map(GlobalTransform::translation),
        );

        let Some(listener_pos) = closest_listener else {
            continue;
        };

        let scale = scale.map(|s| s.0).unwrap_or(default_scale.0.0);

        let x_diff = (emitter_pos.x - listener_pos.x) * scale.x;
        let y_diff = (emitter_pos.y - listener_pos.y) * scale.y;

        spatial.offset.x = x_diff;
        spatial.offset.z = y_diff;
    }
}

// TODO: is there a good way to consolidate this?
pub(crate) fn update_2d_emitters_effects(
    listeners: Query<&GlobalTransform, With<SpatialListener2D>>,
    mut emitters: Query<(&mut SpatialBasicNode, Option<&SpatialScale>, &EffectOf)>,
    effect_parents: Query<&GlobalTransform>,
    default_scale: Res<DefaultSpatialScale>,
) {
    for (mut spatial, scale, effect_of) in emitters.iter_mut() {
        let Ok(transform) = effect_parents.get(effect_of.0) else {
            continue;
        };

        let emitter_pos = transform.translation();
        let closest_listener = find_closest_listener(
            emitter_pos,
            listeners.iter().map(GlobalTransform::translation),
        );

        let Some(listener_pos) = closest_listener else {
            continue;
        };

        let scale = scale.map(|s| s.0).unwrap_or(default_scale.0.0);

        let x_diff = (emitter_pos.x - listener_pos.x) * scale.x;
        let y_diff = (emitter_pos.y - listener_pos.y) * scale.y;

        spatial.offset.x = x_diff;
        spatial.offset.z = y_diff;
    }
}

pub(crate) fn update_3d_emitters(
    listeners: Query<&GlobalTransform, With<SpatialListener3D>>,
    mut emitters: Query<(
        &mut SpatialBasicNode,
        Option<&SpatialScale>,
        &GlobalTransform,
    )>,
    default_scale: Res<DefaultSpatialScale>,
) {
    for (mut spatial, scale, transform) in emitters.iter_mut() {
        let emitter_pos = transform.translation();
        let closest_listener = find_closest_listener(
            emitter_pos,
            listeners.iter().map(GlobalTransform::translation),
        );

        let Some(listener_pos) = closest_listener else {
            continue;
        };

        let scale = scale.map(|s| s.0).unwrap_or(default_scale.0.0);

        spatial.offset = (emitter_pos - listener_pos) * scale;
    }
}

pub(crate) fn update_3d_emitters_effects(
    listeners: Query<&GlobalTransform, With<SpatialListener3D>>,
    mut emitters: Query<(&mut SpatialBasicNode, Option<&SpatialScale>, &EffectOf)>,
    effect_parents: Query<&GlobalTransform>,
    default_scale: Res<DefaultSpatialScale>,
) {
    for (mut spatial, scale, effect_of) in emitters.iter_mut() {
        let Ok(transform) = effect_parents.get(effect_of.0) else {
            continue;
        };

        let emitter_pos = transform.translation();
        let closest_listener = find_closest_listener(
            emitter_pos,
            listeners.iter().map(GlobalTransform::translation),
        );

        let Some(listener_pos) = closest_listener else {
            continue;
        };

        let scale = scale.map(|s| s.0).unwrap_or(default_scale.0.0);

        spatial.offset = (emitter_pos - listener_pos) * scale;
    }
}

fn find_closest_listener(emitter_pos: Vec3, listeners: impl Iterator<Item = Vec3>) -> Option<Vec3> {
    let mut closest_listener: Option<(f32, Vec3)> = None;

    for listener_pos in listeners {
        let distance = emitter_pos.distance_squared(listener_pos);

        match &mut closest_listener {
            None => closest_listener = Some((distance, listener_pos)),
            Some((old_distance, old_pos)) => {
                if distance < *old_distance {
                    *old_distance = distance;
                    *old_pos = listener_pos;
                }
            }
        }
    }

    closest_listener.map(|l| l.1)
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_closest() {
        let positions = [Vec3::splat(5.0), Vec3::splat(4.0), Vec3::splat(6.0)];
        let emitter = Vec3::splat(0.0);
        let closest = find_closest_listener(emitter, positions.iter().copied()).unwrap();

        assert_eq!(closest, positions[1]);
    }

    #[test]
    fn test_empty() {
        let positions = [];

        let emitter = Vec3::splat(0.0);
        let closest = find_closest_listener(emitter, positions.iter().copied());

        assert!(closest.is_none());
    }
}