use rapier_testbed3d::TestbedViewer;
use rapier3d::prelude::*;

pub async fn run(viewer: &mut TestbedViewer) -> anyhow::Result<()> {
    /*
     * World
     */
    let mut world = PhysicsWorld::new();

    /*
     * Ground.
     */
    let ground_size = 20.0;
    let ground_height = 0.1;

    let rigid_body = RigidBodyBuilder::fixed().translation(Vector::new(0.0, -ground_height, 0.0));
    let collider = ColliderBuilder::cuboid(ground_size, ground_height, 0.4)
        .friction(0.15)
        // .restitution(0.5)
        ;
    let (ground_handle, _) = world.insert(rigid_body, collider);

    /*
     * Rolling ball
     */
    let ball_rad = 0.1;
    let rb = RigidBodyBuilder::dynamic()
        .translation(Vector::new(0.0, 0.2, 0.0))
        .linvel(Vector::new(10.0, 0.0, 0.0));
    let collider = ColliderBuilder::ball(ball_rad).density(100.0);
    let (ball_handle, _) = world.insert(rb, collider);

    let mut linvel = Vector::ZERO;
    let mut angvel = AngVector::ZERO;
    let mut pos = Pose::IDENTITY;
    let mut step = 0;
    let mut extra_colliders = Vec::new();
    let snapped_frame = 51;

    /*
     * Set up the testbed.
     */
    viewer.set_world(&mut world);
    viewer.look_at(Vec3::new(10.0, 10.0, 10.0), Vec3::ZERO);

    while viewer.render_frame(&mut world).await {
        if viewer.simulating() {
            world.step();

            step += 1;

            // Add a bigger ball collider
            let collider = ColliderBuilder::ball(ball_rad + 0.01 * (step as f32)).density(100.0);
            let new_ball_collider_handle =
                world
                    .colliders
                    .insert_with_parent(collider, ball_handle, &mut world.bodies);

            viewer.add_collider(new_ball_collider_handle, &world);

            extra_colliders.push(new_ball_collider_handle);

            // Snap the ball velocity or restore it.
            let ball = world.bodies.get_mut(ball_handle).unwrap();

            if step == snapped_frame {
                linvel = ball.linvel();
                angvel = ball.angvel();
                pos = *ball.position();
            }

            if step == 100 {
                ball.set_linvel(linvel, true);
                ball.set_angvel(angvel, true);
                ball.set_position(pos, true);
                step = snapped_frame;

                for handle in &extra_colliders {
                    viewer.remove_collider(*handle);

                    world
                        .colliders
                        .remove(*handle, &mut world.islands, &mut world.bodies, true);
                }

                extra_colliders.clear();
            }

            // Remove then re-add the ground collider.
            // let ground = world.bodies.get_mut(ground_handle).unwrap();
            // ground.set_position(Pose::from_translation(Vector::new(0.0, step as f32 * 0.001, 0.0)), false);
            // let coll = world
            //     .colliders
            //     .remove(ground_collider_handle, &mut world.bodies, true)
            //     .unwrap();
            let coll =
                ColliderBuilder::cuboid(ground_size, ground_height + step as f32 * 0.01, 0.4)
                    .friction(0.15);
            let new_ground_collider_handle =
                world
                    .colliders
                    .insert_with_parent(coll, ground_handle, &mut world.bodies);

            viewer.add_collider(new_ground_collider_handle, &world);

            extra_colliders.push(new_ground_collider_handle);
        }
    }
    Ok(())
}
