//  Created by shishir sapkota on 1/17/18.
//  Copyright © 2018 ccr. All rights reserved.
//
//  QRCodeScannerViewController.swift
//  Created by Iccr
// https://github.com/Iccr

import UIKit
import AVFoundation

class VedaQRScannerViewController: UIViewController {
    // Mark:- Properties
    var captureSession: AVCaptureSession?
    var videoPreviewLayer: AVCaptureVideoPreviewLayer?
    var qrCodeFrameView: UIView?
    var onObtained: ((VedaQRScannerViewController, String) -> ())?

    // Mark:- Outlets
    @IBOutlet weak var closeButton: UIButton!
    @IBOutlet weak var messageLabel: UILabel!

    // Mark:- Life cycle
    override func viewDidLoad() {
        super.viewDidLoad()
    }

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

    // Mark:- @IBActions
    @IBAction func close(_ sender: Any?) {
        self.captureSession?.stopRunning()
        self.dismiss(animated: true, completion: nil)
    }

    // Mark:- Other functions
    private func checkPermission() {
        PermissionHelper.isAllowedToRecordVideo { (isAllowed) in
            if isAllowed {
                self.openQr()
            }else {
                self.alertWithOkCancel(message: "Camera access denied. Do you want to change the permission from settings?", okAction: {
                    let url = URL(string: UIApplicationOpenSettingsURLString)!
                    UIApplication.shared.open(url, options: [:], completionHandler: nil)
                }, cancelAction: {
                    self.close(nil)
                })
            }
        }
    }

    private func openQr() {
        if self.setupAvCapture() {
            setupOutput()
            setupVideoLayer()
            captureSession?.startRunning()
            setupQRCodeFrameView()
            self.view.bringSubview(toFront: messageLabel)
            self.view.bringSubview(toFront: closeButton)
        }
    }

    func setupAvCapture() -> Bool {
        let captureDevice = AVCaptureDevice.default(for: AVMediaType.video)
        do {
            // Get an instance of the AVCaptureDeviceInput class using the previous device object.
            guard let captureDevice = captureDevice else {return false}
            let input = try AVCaptureDeviceInput(device: captureDevice)
            captureSession = AVCaptureSession()
            // Set the input device on the capture session.
            captureSession?.addInput(input)
            return true
        } catch {
            // If any error occurs, simply print it out and don't continue any more.
            print(error)
            return false
        }
    }

    func setupOutput() {
        // Initialize a AVCaptureMetadataOutput object and set it as the output device to the capture session.
        let captureMetadataOutput = AVCaptureMetadataOutput()
        captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
        captureSession?.addOutput(captureMetadataOutput)
        captureMetadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.qr]
    }

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

    func setupQRCodeFrameView() {
        // Initialize QR Code Frame to highlight the QR code
        qrCodeFrameView = UIView()
        qrCodeFrameView!.layer.borderColor = UIColor.green.cgColor
        qrCodeFrameView!.layer.borderWidth = 2
        view.addSubview(qrCodeFrameView!)
        view.bringSubview(toFront: qrCodeFrameView!)
    }
}

extension VedaQRScannerViewController: AVCaptureMetadataOutputObjectsDelegate {
    func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
        if metadataObjects.count == 0 {
            qrCodeFrameView?.frame = CGRect.zero
            messageLabel.text = "noQR"
            return
        }
        // Get the metadata object.
        let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
        if metadataObj.type == AVMetadataObject.ObjectType.qr {
            let qrCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
            qrCodeFrameView?.frame = qrCodeObject!.bounds
            if metadataObj.stringValue != nil {
                messageLabel.text = metadataObj.stringValue
                self.captureSession?.stopRunning()
                self.dismiss(animated: true, completion: nil)
                self.onObtained?(self, metadataObj.stringValue!)
            }
        }
    }
}

struct PermissionHelper {
    static func isAllowedToRecordVideo(completion: @escaping (Bool) -> ()) {
        let status = AVCaptureDevice.authorizationStatus(for: AVMediaType.video)
        completion(status != .denied && status != .restricted)
    }
}