QR code: Ability to add tunnels with a QR code scan

Signed-off-by: Eric Kuck <eric@bluelinelabs.com>

WireGuard/WireGuard/UI/iOS/QRScanViewController.swift

@@ -0,0 +1,107 @@
+//
+//  QRScanViewController.swift
+//  WireGuard
+//
+//  Created by Eric Kuck on 8/20/18.
+//  Copyright © 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All rights reserved.
+//
+
+import AVFoundation
+import CoreData
+import UIKit
+
+protocol QRScanViewControllerDelegate: class {
+    func didSave(tunnel: Tunnel, qrScanViewController: QRScanViewController)
+}
+
+class QRScanViewController: UIViewController {
+
+    private var viewContext: NSManagedObjectContext!
+    private weak var delegate: QRScanViewControllerDelegate?
+    var captureSession: AVCaptureSession? = AVCaptureSession()
+    let metadataOutput = AVCaptureMetadataOutput()
+    var previewLayer: AVCaptureVideoPreviewLayer!
+
+    func configure(context: NSManagedObjectContext, delegate: QRScanViewControllerDelegate? = nil) {
+        viewContext = context
+        self.delegate = delegate
+    }
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        guard let videoCaptureDevice = AVCaptureDevice.default(for: .video),
+            let videoInput = try? AVCaptureDeviceInput(device: videoCaptureDevice),
+            let captureSession = captureSession,
+            captureSession.canAddInput(videoInput),
+            captureSession.canAddOutput(metadataOutput) else {
+                scanDidEncounterError(title: "Scanning Not Supported", message: "This device does not have the ability to scan QR codes.")
+                return
+        }
+
+        captureSession.addInput(videoInput)
+        captureSession.addOutput(metadataOutput)
+
+        metadataOutput.setMetadataObjectsDelegate(self, 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)
+
+        if captureSession?.isRunning == false {
+            captureSession?.startRunning()
+        }
+    }
+
+    override func viewWillDisappear(_ animated: Bool) {
+        super.viewWillDisappear(animated)
+
+        if captureSession?.isRunning == true {
+            captureSession?.stopRunning()
+        }
+    }
+
+    func scanDidComplete(withCode code: String) {
+        do {
+            let tunnel = try Tunnel.fromConfig(code, context: viewContext)
+            delegate?.didSave(tunnel: tunnel, qrScanViewController: self)
+        } catch {
+            scanDidEncounterError(title: "Invalid Code", message: "The scanned code is not a valid WireGuard config file.")
+        }
+    }
+
+    func scanDidEncounterError(title: String, message: String) {
+        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
+        alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { [weak self] _ in
+            self?.navigationController?.popViewController(animated: true)
+        }))
+        present(alertController, animated: true)
+        captureSession = nil
+    }
+
+}
+
+extension QRScanViewController: AVCaptureMetadataOutputObjectsDelegate {
+    func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
+        captureSession?.stopRunning()
+
+        guard let metadataObject = metadataObjects.first,
+            let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject,
+            let stringValue = readableObject.stringValue else {
+                scanDidEncounterError(title: "Invalid Code", message: "The scanned code could not be read.")
+                return
+        }
+
+        AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
+        scanDidComplete(withCode: stringValue)
+    }
+
+}
+
+extension QRScanViewController: Identifyable {}