use bevy::{
    prelude::*,
    transform::TransformSystem,
    window::{CursorGrabMode, PrimaryWindow, Window, WindowMode},
};
use big_space::{
    camera::{CameraController, CameraInput},
    FloatingOrigin, GridCell,
};

fn main() {
    App::new()
        .add_plugins((
            DefaultPlugins.build().disable::<TransformPlugin>(),
            big_space::FloatingOriginPlugin::<i128>::default(),
            big_space::debug::FloatingOriginDebugPlugin::<i128>::default(),
            big_space::camera::CameraControllerPlugin::<i128>::default(),
            bevy_framepace::FramepacePlugin,
        ))
        .insert_resource(ClearColor(Color::BLACK))
        .add_systems(Startup, (setup, ui_setup))
        .add_systems(Update, (cursor_grab_system, ui_text_system))
        .add_systems(
            PostUpdate,
            highlight_nearest_sphere.after(TransformSystem::TransformPropagate),
        )
        .run()
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    // camera
    commands.spawn((
        Camera3dBundle {
            transform: Transform::from_xyz(0.0, 0.0, 8.0)
                .looking_at(Vec3::new(0.0, 0.0, 0.0), Vec3::Y),
            projection: Projection::Perspective(PerspectiveProjection {
                near: 1e-16,
                ..default()
            }),
            ..default()
        },
        GridCell::<i128>::default(), // All spatial entities need this component
        FloatingOrigin, // Important: marks this as the entity to use as the floating origin
        CameraController::default()
            .with_max_speed(10e35)
            .with_smoothness(0.9, 0.8), // Built-in camera controller
    ));

    let mesh_handle = meshes.add(
        shape::Icosphere {
            radius: 0.5,
            subdivisions: 32,
        }
        .try_into()
        .unwrap(),
    );
    let matl_handle = materials.add(StandardMaterial {
        base_color: Color::BLUE,
        perceptual_roughness: 0.8,
        reflectance: 1.0,
        ..default()
    });

    let mut translation = Vec3::ZERO;
    for i in -12..=27 {
        let j = 10_f32.powf(i as f32);
        translation.x += j;
        commands.spawn((
            PbrBundle {
                mesh: mesh_handle.clone(),
                material: matl_handle.clone(),
                transform: Transform::from_scale(Vec3::splat(j)).with_translation(translation),
                ..default()
            },
            GridCell::<i128>::default(),
        ));
    }

    // light
    commands.spawn((DirectionalLightBundle {
        directional_light: DirectionalLight {
            illuminance: 100_000.0,
            ..default()
        },
        ..default()
    },));
}

#[derive(Component, Reflect)]
pub struct BigSpaceDebugText;

fn ui_setup(mut commands: Commands) {
    commands.spawn((
        TextBundle::from_section(
            "",
            TextStyle {
                font_size: 28.0,
                color: Color::WHITE,
                ..default()
            },
        )
        .with_text_alignment(TextAlignment::Left)
        .with_style(Style {
            position_type: PositionType::Absolute,
            top: Val::Px(10.0),
            left: Val::Px(10.0),
            ..default()
        }),
        BigSpaceDebugText,
    ));
}

fn highlight_nearest_sphere(
    cameras: Query<&CameraController>,
    objects: Query<&GlobalTransform>,
    mut gizmos: Gizmos,
) {
    let Some((entity, _)) = cameras.single().nearest_object() else { return };
    let Ok(transform) = objects.get(entity) else { return };
    let (scale, rotation, translation) = transform.to_scale_rotation_translation();
    gizmos
        .sphere(translation, rotation, scale.x * 0.505, Color::RED)
        .circle_segments(128);
}

fn ui_text_system(
    mut text: Query<&mut Text, With<BigSpaceDebugText>>,
    time: Res<Time>,
    origin: Query<(&GridCell<i128>, &Transform), With<FloatingOrigin>>,
    camera: Query<&CameraController>,
    objects: Query<&Transform, With<Handle<Mesh>>>,
) {
    let (cell, transform) = origin.single();
    let translation = transform.translation;

    let grid_text = format!("Origin GridCell: {}x, {}y, {}z", cell.x, cell.y, cell.z);

    let translation_text = format!(
        "Origin Transform: {:>8.2}x, {:>8.2}y, {:>8.2}z",
        translation.x, translation.y, translation.z
    );

    let velocity = camera.single().velocity();
    let speed = velocity.0.length() / time.delta_seconds_f64();
    let camera_text = if speed > 3.0e8 {
        format!("Camera Speed: {:.0e} * speed of light", speed / 3.0e8)
    } else {
        format!("Camera Speed: {:.2e} m/s", speed)
    };

    let nearest_text = if let Some(nearest) = camera.single().nearest_object() {
        let dia = objects.get(nearest.0).unwrap().scale.max_element();
        let (fact_dia, fact) = closest(dia);
        let dist = nearest.1;
        let multiple = dia / fact_dia;
        format!("\nNearest sphere distance: {dist:.0e} m\nNearest sphere diameter: {dia:.0e} m\n{multiple:.1}x {fact}",)
    } else {
        "".into()
    };

    text.single_mut().sections[0].value =
        format!("{grid_text}\n{translation_text}\n{camera_text}\n{nearest_text}");
}

fn closest<'a>(diameter: f32) -> (f32, &'a str) {
    let items = vec![
        (8.8e26, "diameter of the observable universe"),
        (9e25, "length of the Hercules-Corona Borealis Great Wall"),
        (1e24, "diameter of the Local Supercluster"),
        (9e22, "diameter of the Local Group"),
        (1e21, "diameter of the Milky Way galaxy"),
        (5e16, "length of the Pillars of Creation"),
        (1.8e14, "diameter of Messier 87"),
        (7e12, "diameter of Pluto's orbit"),
        (24e9, "diameter of Sagittarius A"),
        (1.4e9, "diameter of the Sun"),
        (1.4e8, "diameter of Jupiter"),
        (12e6, "diameter of Earth"),
        (3e6, "diameter of the Moon"),
        (9e3, "height of Mt. Everest"),
        (2e0, "height of a human"),
        (1e-1, "size of a cat"),
        (1e-3, "size of an insect"),
        (1e-4, "diameter of a eukaryotic cell"),
        (1e-6, "diameter of a bacteria"),
        (50e-9, "size of a phage"),
        (5e-9, "size of a transistor"),
        (100e-12, "diameter of a carbon atom"),
        (40e-12, "diameter of a hydrogen atom"),
        (4e-12, "diameter of an electron"),
    ];

    let mut min = items[0];
    for item in items.iter() {
        if (item.0 - diameter).abs() < (min.0 - diameter).abs() {
            min = item.to_owned();
        }
    }
    min
}

fn cursor_grab_system(
    mut windows: Query<&mut Window, With<PrimaryWindow>>,
    mut cam: ResMut<CameraInput>,
    btn: Res<Input<MouseButton>>,
    key: Res<Input<KeyCode>>,
) {
    let Some(mut window) = windows.get_single_mut().ok() else {
        return;
    };

    if btn.just_pressed(MouseButton::Left) {
        window.cursor.grab_mode = CursorGrabMode::Locked;
        window.cursor.visible = false;
        window.mode = WindowMode::BorderlessFullscreen;
        cam.defaults_disabled = false;
    }

    if key.just_pressed(KeyCode::Escape) {
        window.cursor.grab_mode = CursorGrabMode::None;
        window.cursor.visible = true;
        window.mode = WindowMode::Windowed;
        cam.defaults_disabled = true;
    }
}