//! Use bevy's split screen example to test viewports with this plugin.

use bevy::prelude::*;
use bevy_mod_picking::prelude::*;

fn main() {
    App::new()
        .add_plugins((
            DefaultPlugins.set(low_latency_window_plugin()),
            DefaultPickingPlugins,
            bevy_egui::EguiPlugin,
        ))
        .insert_resource(DebugPickingMode::Normal)
        .add_systems(Startup, setup)
        .add_systems(Update, set_camera_viewports)
        .run();
}

/// set up a simple 3D scene
fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    commands.spawn((
        PbrBundle {
            mesh: meshes.add(bevy_render::mesh::PlaneMeshBuilder::from_length(5.0)),
            material: materials.add(Color::srgb(0.3, 0.5, 0.3)),
            ..default()
        },
        PickableBundle::default(), // <- Makes the mesh pickable.
    ));
    commands.spawn((
        PbrBundle {
            mesh: meshes.add(Cuboid::default()),
            material: materials.add(Color::srgb(0.8, 0.7, 0.6)),
            transform: Transform::from_xyz(0.0, 0.5, 0.0),
            ..default()
        },
        PickableBundle::default(), // <- Makes the mesh pickable.
    ));
    commands.spawn(PointLightBundle {
        point_light: PointLight {
            shadows_enabled: true,
            ..default()
        },
        transform: Transform::from_xyz(4.0, 8.0, -4.0),
        ..default()
    });

    // Left Camera
    commands.spawn((
        Camera3dBundle {
            transform: Transform::from_xyz(0.0, 20.0, -10.0).looking_at(Vec3::ZERO, Vec3::Y),
            ..default()
        },
        LeftCamera,
    ));

    // Right Camera
    commands.spawn((
        Camera3dBundle {
            transform: Transform::from_xyz(10.0, 10., 15.0).looking_at(Vec3::ZERO, Vec3::Y),
            camera: Camera {
                // don't clear on the second camera because the first camera already cleared the window
                clear_color: ClearColorConfig::None,
                // Renders the right camera after the left camera, which has a default priority of 0
                order: 1,
                ..default()
            },
            ..default()
        },
        RightCamera,
    ));
}

#[derive(Component)]
struct LeftCamera;

#[derive(Component)]
struct RightCamera;

fn set_camera_viewports(
    windows: Query<&Window>,
    mut resize_events: EventReader<bevy::window::WindowResized>,
    mut left_camera: Query<&mut Camera, (With<LeftCamera>, Without<RightCamera>)>,
    mut right_camera: Query<&mut Camera, With<RightCamera>>,
) {
    // We need to dynamically resize the camera's viewports whenever the window size changes so then
    // each camera always takes up half the screen. A resize_event is sent when the window is first
    // created, allowing us to reuse this system for initial setup.
    for resize_event in resize_events.read() {
        let window = windows.get(resize_event.window).unwrap();
        let mut left_camera = left_camera.single_mut();
        left_camera.viewport = Some(bevy::render::camera::Viewport {
            physical_position: UVec2::new(0, 0),
            physical_size: UVec2::new(
                window.resolution.physical_width() / 2,
                window.resolution.physical_height(),
            ),
            ..default()
        });

        let mut right_camera = right_camera.single_mut();
        right_camera.viewport = Some(bevy::render::camera::Viewport {
            physical_position: UVec2::new(window.resolution.physical_width() / 2, 0),
            physical_size: UVec2::new(
                window.resolution.physical_width() / 2,
                window.resolution.physical_height(),
            ),
            ..default()
        });
    }
}