import AVFoundation

class ViewController : UIViewController , ,AVCaptureMetadataOutputObjectsDelegate{

  //MARK:  - Local Variables
  var captureSession = AVCaptureSession()
  var videoPreviewLayer = AVCaptureVideoPreviewLayer()

  //MARK: - View Life Cycle
  Override func ViewDidLoad(){
     loadQRCapture()
  }

  func loadQRCapture(){
        // Get an instance of the AVCaptureDevice class to initialize a device object and provide the video
        // as the media type parameter.
        let captureDevice = AVCaptureDevice.default(for: AVMediaType.video)

        // Initialize the captureSession object.
        captureSession = AVCaptureSession()

        // Get an instance of the AVCaptureDeviceInput class using the previous device object.
        do{
            let input = try AVCaptureDeviceInput(device: captureDevice!)

            // Set the input device on the capture session.
            captureSession.addInput(input as AVCaptureInput)
        }
        catch{
            if (error != nil) {
                // If any error occurs, simply log the description of it and don't continue any more.
                print("\(error.localizedDescription)")
                return
            }
        }

        // Initialize a AVCaptureMetadataOutput object and set it as the output device to the capture session.
        let captureMetadataOutput = AVCaptureMetadataOutput()
        captureSession.addOutput(captureMetadataOutput)

        // Set delegate and use the default dispatch queue to execute the call back
        captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
        captureMetadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.qr]

        // Initialize the video preview layer and add it as a sublayer to the viewPreview view's layer.
        videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        videoPreviewLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill
        videoPreviewLayer.frame = view.layer.bounds
        view.layer.addSublayer(videoPreviewLayer)
        // To show Square Box inside camara for scanning.
        //Add ImageView as squareImgView and insert a scaning box image to imageView
        self.view.bringSubviewToFront(squareImgView)
        // Start video capture.
        captureSession.startRunning()
    }
}