use bevy::prelude::*;

struct Rotator;

fn main() {
    AppBuilder::new()
        .add_defaults()
        .setup_world(setup)
        .add_system(build_rotator_system())
        .run();
}

fn build_rotator_system() -> Box<dyn Schedulable> {
    SystemBuilder::new("Rotator")
        .read_resource::<Time>()
        .with_query(<(Write<Rotator>, Write<Rotation>)>::query())
        .build(move |_, world, time, light_query| {
            for (_, mut rotation) in light_query.iter_mut(world) {
                rotation.0 = rotation.0 * Quat::from_rotation_x(3.0 * time.delta_seconds);
            }
        })
}

fn setup(world: &mut World) {
    let cube = Mesh::load(MeshType::Cube);
    let plane = Mesh::load(MeshType::Plane { size: 10.0 });

    let (cube_handle, plane_handle) = {
        let mut mesh_storage = world.resources.get_mut::<AssetStorage<Mesh>>().unwrap();
        (mesh_storage.add(cube), mesh_storage.add(plane))
    };

    // plane
    world.insert(
        (),
        vec![(
            plane_handle.clone(),
            StandardMaterial {
                albedo: math::vec4(0.1, 0.2, 0.1, 1.0).into(),
            },
            LocalToWorld::identity(),
            Translation::new(0.0, 0.0, -5.0),
        )],
    );

    // cube
    let parent_cube = *world
        .insert(
            (),
            vec![(
                cube_handle.clone(),
                StandardMaterial {
                    albedo: math::vec4(0.5, 0.3, 0.3, 1.0).into(),
                },
                LocalToWorld::identity(),
                Translation::new(0.0, 0.0, 1.0),
                Rotation::from_euler_angles(0.0, 0.0, 0.0),
                Rotator,
            )],
        )
        .first()
        .unwrap();

    // cube
    world.insert(
        (),
        vec![(
            cube_handle,
            StandardMaterial {
                albedo: math::vec4(0.5, 0.3, 0.3, 1.0).into(),
            },
            LocalToWorld::identity(),
            Translation::new(0.0, 0.0, 3.0),
            Parent(parent_cube),
            LocalToParent::identity(),
        )],
    );

    // light
    world.insert(
        (),
        vec![(
            Light::default(),
            LocalToWorld::identity(),
            Translation::new(4.0, -4.0, 5.0),
            Rotation::from_euler_angles(0.0, 0.0, 0.0),
        )],
    );

    // camera
    world.insert(
        (),
        vec![(
            Camera::new(CameraType::Projection {
                fov: std::f32::consts::PI / 4.0,
                near: 1.0,
                far: 1000.0,
                aspect_ratio: 1.0,
            }),
            ActiveCamera,
            LocalToWorld(Mat4::look_at_rh(
                Vec3::new(3.0, -15.0, 8.0),
                Vec3::new(0.0, 0.0, 0.0),
                Vec3::new(0.0, 0.0, 1.0),
            )),
        )],
    );
}