deltachat-ios/deltachat-ios/Controller/QrCodeReaderController.swift

import AVFoundation
import UIKit

class QrCodeReaderController: UIViewController {
    var captureSession = AVCaptureSession()

    var videoPreviewLayer: AVCaptureVideoPreviewLayer?

    weak var delegate: QrCodeReaderDelegate?

    private let supportedCodeTypes = [
        AVMetadataObject.ObjectType.qr
    ]

    override func viewDidLoad() {
        super.viewDidLoad()
        self.edgesForExtendedLayout = []
        title = String.localized("qrscan_title")

        guard let captureDevice = AVCaptureDevice.DiscoverySession.init(
            deviceTypes: [AVCaptureDevice.DeviceType.builtInWideAngleCamera],
            mediaType: .video,
            position: .back).devices.first else {
            print("Failed to get the camera device")
            return
        }

        do {
            let input = try AVCaptureDeviceInput(device: captureDevice)
            captureSession.addInput(input)

            let captureMetadataOutput = AVCaptureMetadataOutput()
            captureSession.addOutput(captureMetadataOutput)

            captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            captureMetadataOutput.metadataObjectTypes = supportedCodeTypes
        } catch {
            // If any error occurs, simply print it out and don't continue any more.
            logger.error("failed to setup QR Code Scanner: \(error)")
            return
        }

        videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        videoPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
        videoPreviewLayer?.frame = view.layer.bounds
        view.layer.addSublayer(videoPreviewLayer!)

        let infoLabel = createInfoLabel()
        view.addSubview(infoLabel)
        view.addConstraint(infoLabel.constraintAlignBottomTo(view, paddingBottom: 8))
        view.addConstraint(infoLabel.constraintCenterXTo(view))
        view.bringSubviewToFront(infoLabel)
    }

    private func createInfoLabel() -> UIView {
        let label = UILabel()
        label.translatesAutoresizingMaskIntoConstraints = false
        label.text = String.localized("qrscan_hint")
        label.lineBreakMode = .byWordWrapping
        label.numberOfLines = 0
        label.textAlignment = .center
        label.textColor = .white
        return label
    }


    override func viewWillAppear(_ animated: Bool) {
        captureSession.startRunning()
    }
    override func viewWillDisappear(_ animated: Bool) {
        captureSession.stopRunning()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

extension QrCodeReaderController: AVCaptureMetadataOutputObjectsDelegate {
    func metadataOutput(_: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from _: AVCaptureConnection) {

        let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject

        if supportedCodeTypes.contains(metadataObj.type) {
            if metadataObj.stringValue != nil {
                self.delegate?.handleQrCode(metadataObj.stringValue!)
            }
        }
    }
}