use bevy::prelude::*;

#[derive(Resource, Clone)]
pub struct PlanetData {
    pub lod_focus: Vec3,
    // add radius, noise params, max lod, etc
}

#[derive(Component)]
pub struct Planet;

#[derive(Component)]
pub struct PlanetMeshFace {
    pub normal: Vec3,
    pub name: &'static str,
}

const PLANET_FACES: [(Vec3, &str); 6] = [
    (Vec3::Y, "Top"),
    (-Vec3::Y, "Bot"),
    (-Vec3::X, "Left"),
    (Vec3::X, "Right"),
    (-Vec3::Z, "Back"),
    (Vec3::Z, "Front"),
];

pub fn spawn_planet(
    mut commands: Commands,
) {
    commands
        .spawn((
            Planet,
            Transform::default(),
            GlobalTransform::default(),
        ))
        .with_children(|parent| {
            for (normal, name) in PLANET_FACES {
                parent.spawn((
                    PlanetMeshFace { normal, name },
                    Transform::default(),
                    GlobalTransform::default(),
                ));
            }
        });
}

pub fn regenerate_faces_on_planet_data_change(
    planet_data: Res<PlanetData>,
    mut faces: Query<&PlanetMeshFace>,
) {
    if !planet_data.is_changed() {
        return;
    }

    for face in &mut faces {
        regenerate_mesh(face, &planet_data);
    }
}

fn regenerate_mesh(face: &PlanetMeshFace, planet_data: &PlanetData) {
    // Equivalent of:
    // child._regenerate_mesh(planet_data)

    // Typical steps:
    // - Build quadtree
    // - Project cube → sphere
    // - LOD based on planet_data.lod_focus
    // - Write Mesh
}

#[derive(Component)]
pub struct Player;

pub fn update_lod_focus_from_player(
    player: Query<&GlobalTransform, With<Player>>,
    mut planet_data: ResMut<PlanetData>,
) {
    if let Ok(player_transform) = player.get_single() {
        planet_data.lod_focus = player_transform.translation();
    }
}
pub struct PlanetPlugin;

impl Plugin for PlanetPlugin {
    fn build(&self, app: &mut App) {
        app
            .insert_resource(PlanetData {
                lod_focus: Vec3::ZERO,
            })
            .add_startup_system(spawn_planet)
            .add_system(update_lod_focus_from_player)
            .add_system(regenerate_faces_on_planet_data_change);
    }
}