bevy_lunex 0.3.0

use std::cmp::Reverse;

use bevy::math::{FloatExt, FloatOrd};
use bevy::window::PrimaryWindow;
use bevy::picking::backend::prelude::*;
use bevy::picking::{backend::PointerHits, PickingBehavior};

use crate::*;


// #===============#
// #=== BACKEND ===#

/// Adds picking support for Lunex.
#[derive(Clone)]
pub struct UiLunexPickingPlugin;
impl Plugin for UiLunexPickingPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(PreUpdate, lunex_picking.in_set(PickSet::Backend));
    }
}

/// Checks if any Dimension entities are under a pointer.
pub fn lunex_picking(
    pointers: Query<(&PointerId, &PointerLocation)>,
    cameras: Query<(Entity, &Camera, &GlobalTransform, &OrthographicProjection)>,
    primary_window: Query<Entity, With<PrimaryWindow>>,
    sprite_query: Query<(
        Entity,
        &Dimension,
        &GlobalTransform,
        Option<&PickingBehavior>,
        &ViewVisibility,
    )>,
    mut output: EventWriter<PointerHits>,
) {
    let mut sorted_sprites: Vec<_> = sprite_query.iter().filter_map(|(entity, dimension, transform, picking_behavior, vis)| {
        if !transform.affine().is_nan() && vis.get() {
            Some((entity, dimension, transform, picking_behavior))
        } else {
            None
        }
    }).collect();

    sorted_sprites.sort_by_key(|x| Reverse(FloatOrd(x.2.translation().z)));

    let primary_window = primary_window.get_single().ok();

    for (pointer, location) in pointers.iter().filter_map(|(pointer, pointer_location)| {
        pointer_location.location().map(|loc| (pointer, loc))
    }) {
        let mut blocked = false;
        let Some((cam_entity, camera, cam_transform, cam_ortho)) = cameras
            .iter()
            .filter(|(_, camera, _, _)| camera.is_active)
            .find(|(_, camera, _, _)| {
                camera
                    .target
                    .normalize(primary_window)
                    .map(|x| x == location.target)
                    .unwrap_or(false)
            })
        else {
            continue;
        };

        let viewport_pos = camera
            .logical_viewport_rect()
            .map(|v| v.min)
            .unwrap_or_default();
        let pos_in_viewport = location.position - viewport_pos;

        let Ok(cursor_ray_world) = camera.viewport_to_world(cam_transform, pos_in_viewport) else {
            continue;
        };
        let cursor_ray_len = cam_ortho.far - cam_ortho.near;
        let cursor_ray_end = cursor_ray_world.origin + cursor_ray_world.direction * cursor_ray_len;
        
        let picks: Vec<(Entity, HitData)> = sorted_sprites
            .iter()
            .copied()
            .filter_map(|(entity, dimension, node_transform, picking_behavior)| {
                if blocked {
                    return None;
                }

                let rect = Rect::from_center_size(Vec2::ZERO, **dimension);

                // Transform cursor line segment to sprite coordinate system
                let world_to_sprite = node_transform.affine().inverse();
                let cursor_start_sprite = world_to_sprite.transform_point3(cursor_ray_world.origin);
                let cursor_end_sprite = world_to_sprite.transform_point3(cursor_ray_end);

                // Find where the cursor segment intersects the plane Z=0 (which is the sprite's
                // plane in sprite-local space). It may not intersect if, for example, we're
                // viewing the sprite side-on
                if cursor_start_sprite.z == cursor_end_sprite.z {
                    // Cursor ray is parallel to the sprite and misses it
                    return None;
                }
                let lerp_factor =
                    f32::inverse_lerp(cursor_start_sprite.z, cursor_end_sprite.z, 0.0);
                if !(0.0..=1.0).contains(&lerp_factor) {
                    // Lerp factor is out of range, meaning that while an infinite line cast by
                    // the cursor would intersect the sprite, the sprite is not between the
                    // camera's near and far planes
                    return None;
                }
                // Otherwise we can interpolate the xy of the start and end positions by the
                // lerp factor to get the cursor position in sprite space!
                let cursor_pos_sprite = cursor_start_sprite
                    .lerp(cursor_end_sprite, lerp_factor)
                    .xy();

                let is_cursor_in_sprite = rect.contains(cursor_pos_sprite);

                blocked = is_cursor_in_sprite
                    && picking_behavior
                        .map(|p| p.should_block_lower)
                        .unwrap_or(true);

                is_cursor_in_sprite.then(|| {
                    let hit_pos_world =
                        node_transform.transform_point(cursor_pos_sprite.extend(0.0));
                    // Transform point from world to camera space to get the Z distance
                    let hit_pos_cam = cam_transform
                        .affine()
                        .inverse()
                        .transform_point3(hit_pos_world);
                    // HitData requires a depth as calculated from the camera's near clipping plane
                    let depth = -cam_ortho.near - hit_pos_cam.z;
                    (
                        entity,
                        HitData::new(
                            cam_entity,
                            depth,
                            Some(hit_pos_world),
                            Some(*node_transform.back()),
                        ),
                    )
                })
            })
            .collect();

        let order = camera.order as f32;
        output.send(PointerHits::new(*pointer, picks, order));
    }
}

/* /// Checks if any Dimension entities are under a pointer
fn lunex_picking(
    pointers: Query<(&PointerId, &PointerLocation)>,
    cameras: Query<(Entity, &Camera, &GlobalTransform, &Projection)>,
    primary_window: Query<Entity, With<PrimaryWindow>>,
    sprite_query: Query<(
        Entity,
        &Dimension,
        &GlobalTransform,
        Option<&PickingBehavior>,
        &ViewVisibility,
    )>,
    mut output: EventWriter<PointerHits>,
) {
    let mut sorted_sprites: Vec<_> = sprite_query.iter().filter_map(|(entity, dimension, transform, pickable, vis)| {
        if !transform.affine().is_nan() && vis.get() {
            Some((entity, dimension, transform, pickable))
        } else {
            None
        }
    }).collect();

    // radsort is a stable radix sort that performed better than `slice::sort_by_key`
    radsort::sort_by_key(&mut sorted_sprites, |(_, _, transform, _)| {
        -transform.translation().z
    });

    let primary_window = primary_window.get_single().ok();

    for (pointer, location) in pointers.iter().filter_map(|(pointer, pointer_location)| {
        pointer_location.location().map(|loc| (pointer, loc))
    }) {
        let mut blocked = false;
        let Some((cam_entity, camera, cam_transform, Projection::Orthographic(cam_ortho))) =
            cameras.iter().filter(|(_, camera, _, _)| camera.is_active).find(|(_, camera, _, _)| {
                camera.target.normalize(primary_window).is_some_and(|x| x == location.target)
            })
        else { continue; };

        let viewport_pos = camera
            .logical_viewport_rect()
            .map(|v| v.min)
            .unwrap_or_default();
        let pos_in_viewport = location.position - viewport_pos;

        let Ok(cursor_ray_world) = camera.viewport_to_world(cam_transform, pos_in_viewport) else {
            continue;
        };
        let cursor_ray_len = cam_ortho.far - cam_ortho.near;
        let cursor_ray_end = cursor_ray_world.origin + cursor_ray_world.direction * cursor_ray_len;

        let picks: Vec<(Entity, HitData)> = sorted_sprites
            .iter()
            .copied()
            .filter_map(|(entity, dimension, node_transform, pickable)| {
                if blocked {
                    return None;
                }


                // Transform cursor line segment to node coordinate system
                let world_to_sprite = node_transform.affine().inverse();
                let cursor_start_sprite = world_to_sprite.transform_point3(cursor_ray_world.origin);
                let cursor_end_sprite = world_to_sprite.transform_point3(cursor_ray_end);

                // Find where the cursor segment intersects the plane Z=0 (which is the sprite's
                // plane in sprite-local space). It may not intersect if, for example, we're
                // viewing the sprite side-on
                if cursor_start_sprite.z == cursor_end_sprite.z {
                    // Cursor ray is parallel to the sprite and misses it
                    return None;
                }
                let lerp_factor =
                    f32::inverse_lerp(cursor_start_sprite.z, cursor_end_sprite.z, 0.0);
                if !(0.0..=1.0).contains(&lerp_factor) {
                    // Lerp factor is out of range, meaning that while an infinite line cast by
                    // the cursor would intersect the sprite, the sprite is not between the
                    // camera's near and far planes
                    return None;
                }
                // Otherwise we can interpolate the xy of the start and end positions by the
                // lerp factor to get the cursor position in sprite space!
                let cursor_pos_sprite = cursor_start_sprite
                    .lerp(cursor_end_sprite, lerp_factor)
                    .xy();

                /* let Ok(cursor_pixel_space) = sprite.compute_pixel_space_point(
                    cursor_pos_sprite,
                    &images,
                    &texture_atlas_layout,
                ) else {
                    return None;
                }; */

                let rect = Rect::from_center_size(Vec2::ZERO, **dimension);
                let is_cursor_in_sprite = rect.contains(cursor_pos_sprite);
                blocked = is_cursor_in_sprite && pickable.map(|p| p.should_block_lower) != Some(false);

                // HitData requires a depth as calculated from the camera's near clipping plane
                let depth = -cam_ortho.near - node_transform.translation().z;


                is_cursor_in_sprite.then_some((entity, HitData::new(cam_entity, depth, None, None)))

            })
            .collect();

        let order = camera.order as f32;
        output.send(PointerHits::new(*pointer, picks, order));
    }
} */