//
//  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 {}