use rapier_testbed2d::TestbedViewer;
use rapier2d::prelude::*;

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

    /*
     * Ground
     */
    let ground_size = Vec2::new(50.0, 1.0);
    let nsubdivs = 2000;

    let heights = (0..nsubdivs + 1)
        .map(|i| {
            if i == 0 || i == nsubdivs {
                80.0
            } else {
                (i as f32 * ground_size.x / (nsubdivs as f32)).cos() * 2.0
            }
        })
        .collect();

    let rigid_body = RigidBodyBuilder::fixed();
    let collider = ColliderBuilder::heightfield(heights, ground_size);
    let _ = world.insert(rigid_body, collider);

    /*
     * Create the cubes
     */
    let num = 26;
    let rad = 0.5;

    let shift = rad * 2.0;
    let centerx = shift * (num / 2) as f32;
    let centery = shift / 2.0;

    for i in 0..num {
        for j in 0usize..num * 5 {
            let x = i as f32 * shift - centerx;
            let y = j as f32 * shift + centery + 3.0;

            // Build the rigid body.
            let rigid_body = RigidBodyBuilder::dynamic().translation(Vec2::new(x, y));

            if j % 2 == 0 {
                let collider = ColliderBuilder::cuboid(rad, rad);
                let _ = world.insert(rigid_body, collider);
            } else {
                let collider = ColliderBuilder::ball(rad);
                let _ = world.insert(rigid_body, collider);
            }
        }
    }

    /*
     * Set up the viewer.
     */
    viewer.set_world(&mut world);
    viewer.look_at(Vec2::new(0.0, 50.0), 10.0);

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