deltachat-ios/deltachat-ios/QrCodeReaderController.swift

//
//  QrCodeReaderController.swift
//  deltachat-ios
//
//  Created by Friedel Ziegelmayer on 28.12.18.
//  Copyright © 2018 Jonas Reinsch. All rights reserved.
//

import AVFoundation
import UIKit

protocol QrCodeReaderDelegate: class {
  func handleQrCode(_ code: String)
}

class QrCodeReaderController: UIViewController {
  var captureSession = AVCaptureSession()

  var videoPreviewLayer: AVCaptureVideoPreviewLayer?
  var qrCodeFrameView: UIView?

  weak var delegate: QrCodeReaderDelegate?

  private let supportedCodeTypes = [
    AVMetadataObject.ObjectType.qr,
  ]

  override func viewDidLoad() {
    super.viewDidLoad()

    let deviceDiscoverySession = AVCaptureDevice.DiscoverySession(
      deviceTypes: [.builtInDualCamera],
      mediaType: AVMediaType.video,
      position: .back
    )

    guard let captureDevice = deviceDiscoverySession.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!)

    captureSession.startRunning()

    qrCodeFrameView = UIView()

    if let qrCodeFrameView = qrCodeFrameView {
      qrCodeFrameView.layer.borderColor = UIColor.green.cgColor
      qrCodeFrameView.layer.borderWidth = 2
      view.addSubview(qrCodeFrameView)
      view.bringSubviewToFront(qrCodeFrameView)
    }
  }

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

extension QrCodeReaderController: AVCaptureMetadataOutputObjectsDelegate {
  func metadataOutput(_: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from _: AVCaptureConnection) {
    if metadataObjects.isEmpty {
      qrCodeFrameView?.frame = CGRect.zero
      return
    }

    let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject

    if supportedCodeTypes.contains(metadataObj.type) {
      let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
      qrCodeFrameView?.frame = barCodeObject!.bounds

      if metadataObj.stringValue != nil {
        DispatchQueue.main.async {
          self.captureSession.stopRunning()
          self.dismiss(animated: true) {
            self.delegate?.handleQrCode(metadataObj.stringValue!)
          }
        }
      }
    }
  }
}