bevy_panorbit_camera 0.10.0

use crate::PanOrbitCamera;
use bevy::input::Input;
use bevy::math::{Quat, Vec3};
use bevy::prelude::{KeyCode, MouseButton, Res, Transform};
use bevy_easings::Lerp;

const EPSILON: f32 = 0.001;

pub fn calculate_from_translation_and_focus(translation: Vec3, focus: Vec3) -> (f32, f32, f32) {
    let comp_vec = translation - focus;
    let mut radius = comp_vec.length();
    if radius == 0.0 {
        radius = 0.05; // Radius 0 causes problems
    }
    let alpha = if comp_vec.x == 0.0 && comp_vec.z >= 0.0 {
        0.0
    } else {
        (comp_vec.z / (comp_vec.x.powi(2) + comp_vec.z.powi(2)).sqrt()).acos()
    };
    let beta = (comp_vec.y / radius).asin();
    (alpha, beta, radius)
}

pub fn orbit_pressed(
    pan_orbit: &PanOrbitCamera,
    mouse_input: &Res<Input<MouseButton>>,
    key_input: &Res<Input<KeyCode>>,
) -> bool {
    let is_pressed = pan_orbit
        .modifier_orbit
        .map_or(true, |modifier| key_input.pressed(modifier))
        && mouse_input.pressed(pan_orbit.button_orbit);

    is_pressed
        && pan_orbit
            .modifier_pan
            .map_or(true, |modifier| !key_input.pressed(modifier))
}

pub fn orbit_just_pressed(
    pan_orbit: &PanOrbitCamera,
    mouse_input: &Res<Input<MouseButton>>,
    key_input: &Res<Input<KeyCode>>,
) -> bool {
    let just_pressed = pan_orbit
        .modifier_orbit
        .map_or(true, |modifier| key_input.pressed(modifier))
        && (mouse_input.just_pressed(pan_orbit.button_orbit));

    just_pressed
        && pan_orbit
            .modifier_pan
            .map_or(true, |modifier| !key_input.pressed(modifier))
}

pub fn orbit_just_released(
    pan_orbit: &PanOrbitCamera,
    mouse_input: &Res<Input<MouseButton>>,
    key_input: &Res<Input<KeyCode>>,
) -> bool {
    let just_released = pan_orbit
        .modifier_orbit
        .map_or(true, |modifier| key_input.pressed(modifier))
        && (mouse_input.just_released(pan_orbit.button_orbit));

    just_released
        && pan_orbit
            .modifier_pan
            .map_or(true, |modifier| !key_input.pressed(modifier))
}

pub fn pan_pressed(
    pan_orbit: &PanOrbitCamera,
    mouse_input: &Res<Input<MouseButton>>,
    key_input: &Res<Input<KeyCode>>,
) -> bool {
    let is_pressed = pan_orbit
        .modifier_pan
        .map_or(true, |modifier| key_input.pressed(modifier))
        && mouse_input.pressed(pan_orbit.button_pan);

    is_pressed
        && pan_orbit
            .modifier_orbit
            .map_or(true, |modifier| !key_input.pressed(modifier))
}

pub fn pan_just_pressed(
    pan_orbit: &PanOrbitCamera,
    mouse_input: &Res<Input<MouseButton>>,
    key_input: &Res<Input<KeyCode>>,
) -> bool {
    let just_pressed = pan_orbit
        .modifier_pan
        .map_or(true, |modifier| key_input.pressed(modifier))
        && (mouse_input.just_pressed(pan_orbit.button_pan));

    just_pressed
        && pan_orbit
            .modifier_orbit
            .map_or(true, |modifier| !key_input.pressed(modifier))
}

/// Update `transform` based on alpha, beta, and the camera's focus and radius
pub fn update_orbit_transform(
    alpha: f32,
    beta: f32,
    radius: f32,
    focus: Vec3,
    transform: &mut Transform,
) {
    let mut rotation = Quat::from_rotation_y(alpha);
    rotation *= Quat::from_rotation_x(-beta);
    transform.rotation = rotation;

    // Update the translation of the camera so we are always rotating 'around'
    // (orbiting) rather than rotating in place
    transform.translation = focus + transform.rotation * Vec3::new(0.0, 0.0, radius);
}

pub fn apply_limits(value: f32, upper_limit: Option<f32>, lower_limit: Option<f32>) -> f32 {
    let mut new_val = value;
    if let Some(zoom_upper) = upper_limit {
        new_val = f32::min(new_val, zoom_upper);
    }
    if let Some(zoom_lower) = lower_limit {
        new_val = f32::max(new_val, zoom_lower);
    }
    new_val
}

pub fn approx_equal(a: f32, b: f32) -> bool {
    (a - b).abs() < EPSILON
}

pub fn lerp_and_snap_f32(from: f32, to: f32, smoothness: f32) -> f32 {
    let t = 1.0 - smoothness;
    let mut new_value = from.lerp(&to, &t);
    if smoothness < 1.0 && approx_equal(new_value, to) {
        new_value = to;
    }
    new_value
}

pub fn lerp_and_snap_vec3(from: Vec3, to: Vec3, smoothness: f32) -> Vec3 {
    let t = 1.0 - smoothness;
    let mut new_value = from.lerp(to, t);
    if smoothness < 1.0 && approx_equal((new_value - to).length(), 0.0) {
        new_value.x = to.x;
    }
    new_value
}

#[cfg(test)]
mod calculate_from_translation_and_focus_tests {
    use super::*;
    use float_cmp::approx_eq;
    use std::f32::consts::PI;

    #[test]
    fn zero() {
        let translation = Vec3::new(0.0, 0.0, 0.0);
        let focus = Vec3::ZERO;
        let (alpha, beta, radius) = calculate_from_translation_and_focus(translation, focus);
        assert_eq!(alpha, 0.0);
        assert_eq!(beta, 0.0);
        assert_eq!(radius, 0.05);
    }

    #[test]
    fn in_front() {
        let translation = Vec3::new(0.0, 0.0, 5.0);
        let focus = Vec3::ZERO;
        let (alpha, beta, radius) = calculate_from_translation_and_focus(translation, focus);
        assert_eq!(alpha, 0.0);
        assert_eq!(beta, 0.0);
        assert_eq!(radius, 5.0);
    }

    #[test]
    fn to_the_side() {
        let translation = Vec3::new(5.0, 0.0, 0.0);
        let focus = Vec3::ZERO;
        let (alpha, beta, radius) = calculate_from_translation_and_focus(translation, focus);
        assert!(approx_eq!(f32, alpha, PI / 2.0));
        assert_eq!(beta, 0.0);
        assert_eq!(radius, 5.0);
    }

    #[test]
    fn above() {
        let translation = Vec3::new(0.0, 5.0, 0.0);
        let focus = Vec3::ZERO;
        let (alpha, beta, radius) = calculate_from_translation_and_focus(translation, focus);
        assert_eq!(alpha, 0.0);
        assert!(approx_eq!(f32, beta, PI / 2.0));
        assert_eq!(radius, 5.0);
    }

    #[test]
    fn arbitrary() {
        let translation = Vec3::new(0.92563736, 3.864204, -1.0105048);
        let focus = Vec3::ZERO;
        let (alpha, beta, radius) = calculate_from_translation_and_focus(translation, focus);
        assert!(approx_eq!(f32, alpha, 2.4));
        assert!(approx_eq!(f32, beta, 1.23));
        assert_eq!(radius, 4.1);
    }
}

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

    #[test]
    fn both_limits_are_some() {
        let upper_limit = Some(10.0);
        let lower_limit = Some(5.0);
        assert_eq!(apply_limits(7.0, upper_limit, lower_limit), 7.0);
        assert_eq!(apply_limits(1.0, upper_limit, lower_limit), 5.0);
    }

    #[test]
    fn lower_limit_is_some() {
        let upper_limit = None;
        let lower_limit = Some(5.0);
        assert_eq!(apply_limits(500.0, upper_limit, lower_limit), 500.0);
        assert_eq!(apply_limits(1.0, upper_limit, lower_limit), 5.0);
    }

    #[test]
    fn upper_limit_is_some() {
        let upper_limit = Some(10.0);
        let lower_limit = None;
        assert_eq!(apply_limits(15.0, upper_limit, lower_limit), 10.0);
        assert_eq!(apply_limits(-500.0, upper_limit, lower_limit), -500.0);
    }
}

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

    #[test]
    fn same_value_is_approx_equal() {
        assert!(approx_equal(1.0, 1.0));
    }

    #[test]
    fn value_within_threshold_is_approx_equal() {
        assert!(approx_equal(1.0, 1.0000001));
    }

    #[test]
    fn value_outside_threshold_is_not_approx_equal() {
        assert!(!approx_equal(1.0, 1.01));
    }
}

#[cfg(test)]
mod lerp_and_snap_f32_tests {
    use super::*;

    #[test]
    fn lerps_when_output_outside_snap_threshold() {
        let out = lerp_and_snap_f32(1.0, 2.0, 0.5);
        assert_eq!(out, 1.5);
    }

    #[test]
    fn snaps_to_target_when_inside_threshold() {
        let out = lerp_and_snap_f32(1.9991, 2.0, 0.5);
        assert_eq!(out, 2.0);
        let out = lerp_and_snap_f32(1.9991, 2.0, 0.1);
        assert_eq!(out, 2.0);
        let out = lerp_and_snap_f32(1.9991, 2.0, 0.9);
        assert_eq!(out, 2.0);
    }

    #[test]
    fn does_not_snap_if_smoothness_is_one() {
        // Smoothness of one results in the value not changing, so it doesn't make sense to snap
        let out = lerp_and_snap_f32(1.9991, 2.0, 1.0);
        assert_eq!(out, 1.9991);
    }
}

#[cfg(test)]
mod lerp_and_snap_vec3_tests {
    use super::*;

    #[test]
    fn lerps_when_output_outside_snap_threshold() {
        let out = lerp_and_snap_vec3(Vec3::ZERO, Vec3::X, 0.5);
        assert_eq!(out, Vec3::X * 0.5);
    }

    #[test]
    fn snaps_to_target_when_inside_threshold() {
        let out = lerp_and_snap_vec3(Vec3::X * 0.9991, Vec3::X, 0.5);
        assert_eq!(out, Vec3::X);
        let out = lerp_and_snap_vec3(Vec3::X * 0.9991, Vec3::X, 0.1);
        assert_eq!(out, Vec3::X);
        let out = lerp_and_snap_vec3(Vec3::X * 0.9991, Vec3::X, 0.9);
        assert_eq!(out, Vec3::X);
    }

    #[test]
    fn does_not_snap_if_smoothness_is_one() {
        // Smoothness of one results in the value not changing, so it doesn't make sense to snap
        let out = lerp_and_snap_vec3(Vec3::X * 0.9991, Vec3::X, 1.0);
        assert_eq!(out, Vec3::X * 0.9991);
    }
}