LoopAndGestureViewController.swift

//
//  LoopAndGestureViewController.swift
//  
//
//  Created by Dennis Ippel on 02/04/2021.
//

import UIKit
import RealityKit
import Combine

class LoopAndGestureViewController: UIViewController {
    
    var arView: ARView!
    var animUpdateSubscription: Cancellable?
    var cubeMaterial: SimpleMaterial!
    var cubeEntity: ModelEntity!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        arView = ARView(frame: view.frame,
                        cameraMode: .nonAR,
                        automaticallyConfigureSession: false)
        view.addSubview(arView)
        
        let skyboxResource = try! EnvironmentResource.load(named: "decor_shop_2k")
        arView.environment.lighting.resource = skyboxResource
        arView.environment.background = .skybox(skyboxResource)
        
        let cubeMaterial = SimpleMaterial(color: .blue, isMetallic: true)
        cubeEntity = ModelEntity(mesh: .generateBox(size: 1),
                         materials: [cubeMaterial])
        let cubeAnchor = AnchorEntity(world: .zero)
        cubeAnchor.addChild(cubeEntity)
        
        arView.scene.anchors.append(cubeAnchor)
        
        animate(entity: cubeAnchor,
                angle: .pi,
                axis: [1, 0, 0],
                duration: 4,
                loop: true)
        
        cubeEntity.generateCollisionShapes(recursive: false)
        arView.installGestures(.all, for: cubeEntity).forEach {
            gestureRecognizer in
            gestureRecognizer.addTarget(self, action: #selector(handleGesture(_:)))
        }
    }
    
    func animate(entity: HasTransform,
                 angle: Float,
                 axis: SIMD3<Float>,
                 duration: TimeInterval,
                 loop: Bool)
    {
        var transform = entity.transform
        transform.rotation *= simd_quatf(angle: angle, axis: axis)
        entity.move(to: transform, relativeTo: entity.parent, duration: duration)
        
        guard loop,
              animUpdateSubscription == nil
        else { return }
        
        animUpdateSubscription = arView.scene.subscribe(to: AnimationEvents.PlaybackCompleted.self,
                                                        on: entity,
        { _ in
            self.animate(entity: entity,
                         angle: angle,
                         axis: axis,
                         duration: duration,
                         loop: loop)
        })
    }
    
    @objc private func handleGesture(_ recognizer: UIGestureRecognizer) {
        guard let rotationGesture = recognizer as? EntityRotationGestureRecognizer else { return }
        
        switch rotationGesture.state {
        case .began:
            var component: ModelComponent = cubeEntity.components[ModelComponent]!.self
            component.materials = [SimpleMaterial(color: .orange, isMetallic: true)]
            cubeEntity.components.set(component)
        case .ended:
            var component: ModelComponent = cubeEntity.components[ModelComponent]!.self
            component.materials = [SimpleMaterial(color: .white, isMetallic: true)]
            cubeEntity.components.set(component)
        default:
            break
        }
    }
}