use rand::distr::{Distribution, StandardUniform};
use rand::{SeedableRng, rngs::StdRng};
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 = 40.0;
    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, ground_size);
    let (_handle, _) = world.insert(rigid_body, collider);

    /*
     * Create the polyhedra
     */
    let num = 5;
    let scale = 2.0;
    let border_rad = 0.1;

    let shift = border_rad * 2.0 + scale;
    let centerx = shift * (num / 2) as f32;
    let centery = shift / 2.0;
    let centerz = shift * (num / 2) as f32;

    let mut rng = StdRng::seed_from_u64(0);
    let distribution = StandardUniform;

    for j in 0usize..25 {
        for i in 0..num {
            for k in 0usize..num {
                let x = i as f32 * shift - centerx;
                let y = j as f32 * shift + centery + 3.0;
                let z = k as f32 * shift - centerz;

                let mut points = Vec::new();
                for _ in 0..10 {
                    let pt: SimdPoint<f32> = distribution.sample(&mut rng);
                    points.push(Vector::new(pt.x, pt.y, pt.z) * scale);
                }

                // Build the rigid body.
                let rigid_body = RigidBodyBuilder::dynamic().translation(Vector::new(x, y, z));
                let collider = ColliderBuilder::round_convex_hull(&points, border_rad).unwrap();
                let (_handle, _) = world.insert(rigid_body, collider);
            }
        }
    }

    /*
     * Set up the testbed.
     */
    viewer.set_world(&mut world);
    viewer.look_at(Vec3::new(30.0, 30.0, 30.0), Vec3::ZERO);

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