use bevy::{
    pbr::NotShadowCaster,
    prelude::*,
    render::render_resource::{AsBindGroup, ShaderRef},
};

use crate::camera_controller::{CameraController, CameraMotionSystem};

pub struct WorldGridPlugin;

impl Plugin for WorldGridPlugin {
    fn build(&self, app: &mut App) {
        app.add_plugins(MaterialPlugin::<ProceduralGridMaterial>::default())
            .add_systems(Startup, spawn_world_grid)
            .add_systems(PostUpdate, move_plane_with_camera.after(CameraMotionSystem));
    }
}

#[derive(Component)]
pub struct WorldGridPlane;

#[derive(Asset, AsBindGroup, TypePath, Clone)]
struct ProceduralGridMaterial {}

impl Material for ProceduralGridMaterial {
    fn fragment_shader() -> ShaderRef {
        "shaders/procedural_grid.wgsl".into()
    }

    fn alpha_mode(&self) -> AlphaMode {
        AlphaMode::Blend
    }
}

fn spawn_world_grid(
    mut cmd: Commands,
    mut ra_meshes: ResMut<Assets<Mesh>>,
    mut ra_mat_proc_grid: ResMut<Assets<ProceduralGridMaterial>>,
) {
    let plane = ra_meshes.add(Mesh::from(shape::Plane {
        size: 200.0,
        subdivisions: 0,
    }));
    let proc_grid = ra_mat_proc_grid.add(ProceduralGridMaterial {});

    cmd.spawn((
        Name::new("World Grid"),
        SpatialBundle::from_transform(Transform::IDENTITY),
        WorldGridPlane,
    ))
    .with_children(|parent| {
        parent.spawn((
            MaterialMeshBundle {
                mesh: plane.clone(),
                material: proc_grid.clone(),
                transform: Transform::IDENTITY,
                ..default()
            },
            NotShadowCaster,
        ));
        parent.spawn((
            MaterialMeshBundle {
                mesh: plane,
                material: proc_grid,
                transform: Transform::IDENTITY.looking_to(Vec3::Z, Vec3::NEG_Y),
                ..default()
            },
            NotShadowCaster,
        ));
    });
}

fn move_plane_with_camera(
    mut plane: Query<(&WorldGridPlane, &mut Transform)>,
    camera: Query<&CameraController, Changed<CameraController>>,
) {
    if let Ok(&CameraController { focus, .. }) = camera.get_single() {
        let (_, mut xform) = plane.single_mut();

        xform.translation.x = focus.x;
        xform.translation.z = focus.z;
    }
}