SunARViewController

import UIKit
import ARKit
import CoreLocation

class ViewController: UIViewController, ARSCNViewDelegate, CLLocationManagerDelegate {

    let arView = ARSCNView()
    let locationManager = CLLocationManager()
    var sunNode: SCNNode?

    override func viewDidLoad() {
        super.viewDidLoad()

        // AR setup
        arView.frame = view.bounds
        arView.delegate = self
        view.addSubview(arView)

        // Request location
        locationManager.delegate = self
        locationManager.requestWhenInUseAuthorization()
        locationManager.startUpdatingLocation()

        // Set up AR scene
        let configuration = ARWorldTrackingConfiguration()
        arView.session.run(configuration)

        // Initial render of the sun
        renderSun()
    }

    func renderSun() {
        guard let currentLocation = locationManager.location else { return }
        let sunData = SunCalculation.sun(date: Date(), latitude: currentLocation.coordinate.latitude, longitude: currentLocation.coordinate.longitude)
        
        let sunPosition = positionFromAzimuthAndAltitude(azimuth: sunData.azimuth, altitude: sunData.altitude)

        if sunNode == nil {
            sunNode = SCNNode(geometry: SCNSphere(radius: 0.05))
            sunNode?.geometry?.firstMaterial?.diffuse.contents = UIColor.yellow
            arView.scene.rootNode.addChildNode(sunNode!)
        }

        sunNode?.position = sunPosition
    }

    func positionFromAzimuthAndAltitude(azimuth: Double, altitude: Double) -> SCNVector3 {
        let azimuthRadians = azimuth * .pi / 180.0
        let altitudeRadians = altitude * .pi / 180.0
        let x = cos(altitudeRadians) * cos(azimuthRadians)
        let y = sin(altitudeRadians)
        let z = cos(altitudeRadians) * sin(azimuthRadians)
        return SCNVector3(x, y, z)
    }

    func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
        renderSun()
    }
    
    func updateSunPosition() {
        renderSun() // Calculate and update sun's position
    }


    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        arView.session.pause()
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        // Only reset tracking if necessary; this provides a smoother experience for the user.
        let configuration = ARWorldTrackingConfiguration()
        arView.session.run(configuration, options: [.removeExistingAnchors])
        
        updateSunPosition() // Calculate and update sun's position every time the view appears
    }
}