bundesmessenger-ios/bwi/QRCode/ScannerView.swift

//
/*
 * Copyright (c) 2022 BWI GmbH
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import SwiftUI
import UIKit
import AVFoundation


struct ScannerView: UIViewControllerRepresentable {
    @Binding var qrCode: String
    @Binding var scanCompleted: Bool

    class Coordinator: NSObject, AVCaptureMetadataOutputObjectsDelegate {
        var parent: ScannerView

        init(_ parent: ScannerView) {
            self.parent = parent
        }

        func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {

            if let metadataObject = metadataObjects.first {
                guard let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject else { return }
                guard let stringValue = readableObject.stringValue else { return }
                AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
                DispatchQueue.main.async {
                    self.parent.qrCode = stringValue
                    self.parent.scanCompleted = true
                }
            }
        }
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    func makeUIViewController(context: Context) -> some ScannerViewController {
        let controller = ScannerViewController()
        controller.delegate = context.coordinator
        return controller
    }
    
    func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {
    }
    
}

class ScannerViewController: UIViewController {
    var captureSession: AVCaptureSession?
    var previewLayer: AVCaptureVideoPreviewLayer!
    let metadataOutput = AVCaptureMetadataOutput()
    weak var delegate: AVCaptureMetadataOutputObjectsDelegate?

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.black
        captureSession = AVCaptureSession()

        guard let videoCaptureDevice = AVCaptureDevice.default(for: .video), let videoInput = try? AVCaptureDeviceInput(device: videoCaptureDevice) else {
            captureSession = nil
            return
        }

        if let captureSession = captureSession {
            guard captureSession.canAddInput(videoInput) && captureSession.canAddOutput(metadataOutput) else {
                self.captureSession = nil
                return
            }
            
            captureSession.addInput(videoInput)
            captureSession.addOutput(metadataOutput)

            metadataOutput.setMetadataObjectsDelegate(delegate, queue: .main)
            metadataOutput.metadataObjectTypes = [.qr]

            previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
            previewLayer.frame = view.layer.bounds
            previewLayer.videoGravity = .resizeAspectFill
            view.layer.addSublayer(previewLayer)
        }
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        let dispatchQueue = DispatchQueue(label: "AVCapturesession.startRunning", qos: .background)
        dispatchQueue.async{
            if (self.captureSession?.isRunning == false) {
                self.captureSession?.startRunning()
            }
        }
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        let dispatchQueue = DispatchQueue(label: "AVCapturesession.stopRunning", qos: .background)
        dispatchQueue.async{
            if (self.captureSession?.isRunning == true) {
                self.captureSession?.stopRunning()
            }
        }
    }
}