import MetalKit
import ARKit

extension MTKView : RenderDestinationProvider {}

class ViewController: UIViewController, MTKViewDelegate, ARSessionDelegate {
    
    var session: ARSession!
    var renderer: Renderer!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        session = ARSession()
        session.delegate = self
        if let view = self.view as? MTKView {
            view.device = MTLCreateSystemDefaultDevice()
            view.delegate = self
            renderer = Renderer(session: session, metalDevice: view.device!, renderDestination: view)
            renderer.drawRectResized(size: view.bounds.size)
        }
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(ViewController.handleTap(gestureRecognize:)))
        view.addGestureRecognizer(tapGesture)
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        let configuration = ARWorldTrackingConfiguration()
        configuration.planeDetection = .horizontal
        session.run(configuration)
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        session.pause()
    }
    
    @objc
    func handleTap(gestureRecognize: UITapGestureRecognizer) {
        if let currentFrame = session.currentFrame {
            var translation = matrix_identity_float4x4
            translation.columns.3.z = -0.2
            let transform = simd_mul(currentFrame.camera.transform, translation)
            let anchor = ARAnchor(transform: transform)
            session.add(anchor: anchor)
        }
    }
    
    func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {
        renderer.drawRectResized(size: size)
    }
    
    func draw(in view: MTKView) {
        renderer.update()
    }
    
    func session(_ session: ARSession, didAdd anchors: [ARAnchor]) {
        print(anchors)
    }
    
    func session(_ session: ARSession, didFailWithError error: Error) {}
    
    func sessionWasInterrupted(_ session: ARSession) {}
    
    func sessionInterruptionEnded(_ session: ARSession) {}
}