// Copyright © 2022 Rangeproof Pty Ltd. All rights reserved.

import UIKit
import AVFoundation
import Curve25519Kit
import SessionUIKit
import SessionUtilitiesKit

final class QRCodeVC : BaseVC, UIPageViewControllerDataSource, UIPageViewControllerDelegate, QRScannerDelegate {
    private let pageVC = UIPageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
    private var pages: [UIViewController] = []
    private var targetVCIndex: Int?
    private var tabBarTopConstraint: NSLayoutConstraint!
    
    // MARK: - Components
    
    private lazy var tabBar: TabBar = {
        let tabs = [
            TabBar.Tab(title: "vc_qr_code_view_my_qr_code_tab_title".localized()) { [weak self] in
                guard let self = self else { return }
                self.pageVC.setViewControllers([ self.pages[0] ], direction: .forward, animated: false, completion: nil)
            },
            TabBar.Tab(title: "vc_qr_code_view_scan_qr_code_tab_title".localized()) { [weak self] in
                guard let self = self else { return }
                self.pageVC.setViewControllers([ self.pages[1] ], direction: .forward, animated: false, completion: nil)
            }
        ]
        return TabBar(tabs: tabs)
    }()
    
    private lazy var viewMyQRCodeVC: ViewMyQRCodeVC = {
        let result = ViewMyQRCodeVC()
        result.qrCodeVC = self
        
        return result
    }()
    
    private lazy var scanQRCodePlaceholderVC: ScanQRCodePlaceholderVC = {
        let result = ScanQRCodePlaceholderVC()
        result.qrCodeVC = self
        
        return result
    }()
    
    private lazy var scanQRCodeWrapperVC: ScanQRCodeWrapperVC = {
        let message = "vc_qr_code_view_scan_qr_code_explanation".localized()
        let result = ScanQRCodeWrapperVC(message: message)
        result.delegate = self
        
        return result
    }()
    
    // MARK: - Lifecycle
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setNavBarTitle("vc_qr_code_title".localized())
        
        // Set up page VC
        let hasCameraAccess = (AVCaptureDevice.authorizationStatus(for: .video) == .authorized)
        pages = [ viewMyQRCodeVC, (hasCameraAccess ? scanQRCodeWrapperVC : scanQRCodePlaceholderVC) ]
        pageVC.dataSource = self
        pageVC.delegate = self
        pageVC.setViewControllers([ viewMyQRCodeVC ], direction: .forward, animated: false, completion: nil)
        
        // Set up tab bar
        view.addSubview(tabBar)
        tabBar.pin(.leading, to: .leading, of: view)
        tabBarTopConstraint = tabBar.autoPinEdge(toSuperviewSafeArea: .top)
        view.pin(.trailing, to: .trailing, of: tabBar)
        
        // Set up page VC constraints
        let pageVCView = pageVC.view!
        view.addSubview(pageVCView)
        
        pageVCView.pin(.leading, to: .leading, of: view)
        pageVCView.pin(.top, to: .bottom, of: tabBar)
        view.pin(.trailing, to: .trailing, of: pageVCView)
        view.pin(.bottom, to: .bottom, of: pageVCView)
        
        let screen = UIScreen.main.bounds
        pageVCView.set(.width, to: screen.width)
        
        let height: CGFloat = ((navigationController?.view.bounds.height ?? 0) - (navigationController?.navigationBar.height() ?? 0) - TabBar.snHeight)
        pageVCView.set(.height, to: height)
        viewMyQRCodeVC.constrainHeight(to: height)
        scanQRCodePlaceholderVC.constrainHeight(to: height)
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        tabBarTopConstraint.constant = navigationController!.navigationBar.height()
    }
    
    // MARK: - General
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        guard let index = pages.firstIndex(of: viewController), index != 0 else { return nil }
        return pages[index - 1]
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        guard let index = pages.firstIndex(of: viewController), index != (pages.count - 1) else { return nil }
        return pages[index + 1]
    }
    
    fileprivate func handleCameraAccessGranted() {
        pages[1] = scanQRCodeWrapperVC
        pageVC.setViewControllers([ scanQRCodeWrapperVC ], direction: .forward, animated: false, completion: nil)
    }
    
    // MARK: - Updating
    
    func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {
        guard let targetVC = pendingViewControllers.first, let index = pages.firstIndex(of: targetVC) else { return }
        targetVCIndex = index
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating isFinished: Bool, previousViewControllers: [UIViewController], transitionCompleted isCompleted: Bool) {
        guard isCompleted, let index = targetVCIndex else { return }
        tabBar.selectTab(at: index)
    }
    
    // MARK: - Interaction
    
    @objc private func close() {
        dismiss(animated: true, completion: nil)
    }
    
    func controller(_ controller: QRCodeScanningViewController, didDetectQRCodeWith string: String) {
        let hexEncodedPublicKey = string
        startNewPrivateChatIfPossible(with: hexEncodedPublicKey)
    }
    
    fileprivate func startNewPrivateChatIfPossible(with hexEncodedPublicKey: String) {
        if !ECKeyPair.isValidHexEncodedPublicKey(candidate: hexEncodedPublicKey) {
            let alert = UIAlertController(
                title: "invalid_session_id".localized(),
                message: "INVALID_SESSION_ID_MESSAGE".localized(), preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "BUTTON_OK".localized(), style: .default, handler: nil))
            presentAlert(alert)
        }
        else {
            let maybeThread: SessionThread? = Storage.shared.write { db in
                try SessionThread.fetchOrCreate(db, id: hexEncodedPublicKey, variant: .contact)
            }
            
            guard maybeThread != nil else { return }
            
            presentingViewController?.dismiss(animated: true, completion: nil)
            
            SessionApp.presentConversation(for: hexEncodedPublicKey, action: .compose, animated: false)
        }
    }
}

private final class ViewMyQRCodeVC : UIViewController {
    weak var qrCodeVC: QRCodeVC!
    private var bottomConstraint: NSLayoutConstraint!
    
    // MARK: - Lifecycle
    
    override func viewDidLoad() {
        // Remove background color
        view.themeBackgroundColor = .clear
        
        // Set up title label
        let titleLabel = UILabel()
        titleLabel.font = .boldSystemFont(ofSize: isIPhone5OrSmaller ? CGFloat(40) : Values.massiveFontSize)
        titleLabel.text = "Scan Me"
        titleLabel.themeTextColor = .textPrimary
        titleLabel.textAlignment = .center
        titleLabel.lineBreakMode = .byWordWrapping
        titleLabel.numberOfLines = 1
        titleLabel.set(.height, to: isIPhone5OrSmaller ? CGFloat(40) : Values.massiveFontSize)
        
        // Set up QR code image view
        let qrCodeImageView = UIImageView(
            image: QRCode.generate(for: getUserHexEncodedPublicKey(), hasBackground: false)
                .withRenderingMode(.alwaysTemplate)
        )
        qrCodeImageView.set(.height, to: isIPhone5OrSmaller ? 180 : 240)
        qrCodeImageView.set(.width, to: isIPhone5OrSmaller ? 180 : 240)
        
#if targetEnvironment(simulator)
#else
        // Note: For some reason setting this seems to stop the QRCode from rendering on the
        // simulator so only doing it on device
        qrCodeImageView.contentMode = .scaleAspectFit
#endif
        
        let qrCodeImageViewBackgroundView = UIView()
        qrCodeImageViewBackgroundView.layer.cornerRadius = 8
        qrCodeImageViewBackgroundView.addSubview(qrCodeImageView)
        qrCodeImageView.pin(
            to: qrCodeImageViewBackgroundView,
            withInset: 5    // The QRCode image has about 6pt of padding and we want 11 in total
        )
        
        ThemeManager.onThemeChange(observer: qrCodeImageView) { theme, _ in
            switch theme.interfaceStyle {
                case .light:
                    qrCodeImageView.themeTintColorForced = .theme(theme, color: .textPrimary)
                    qrCodeImageViewBackgroundView.themeBackgroundColorForced = nil
                    
                default:
                    qrCodeImageView.themeTintColorForced = .theme(theme, color: .backgroundPrimary)
                    qrCodeImageViewBackgroundView.themeBackgroundColorForced = .color(.white)
            }
            
        }
        
        // Set up QR code image view container
        let qrCodeImageViewContainer = UIView()
        qrCodeImageViewContainer.accessibilityLabel = "Your QR code"
        qrCodeImageViewContainer.isAccessibilityElement = true
        qrCodeImageViewContainer.addSubview(qrCodeImageViewBackgroundView)
        qrCodeImageViewBackgroundView.center(.horizontal, in: qrCodeImageViewContainer)
        qrCodeImageViewBackgroundView.pin(.top, to: .top, of: qrCodeImageViewContainer)
        qrCodeImageViewBackgroundView.pin(.bottom, to: .bottom, of: qrCodeImageViewContainer)
        
        // Set up explanation label
        let explanationLabel = UILabel()
        explanationLabel.font = .systemFont(ofSize: Values.mediumFontSize)
        explanationLabel.text = "vc_view_my_qr_code_explanation".localized()
        explanationLabel.themeTextColor = .textPrimary
        explanationLabel.textAlignment = .center
        explanationLabel.lineBreakMode = .byWordWrapping
        explanationLabel.numberOfLines = 0
        
        // Set up share button
        let shareButton = OutlineButton(style: .regular, size: .large)
        shareButton.setTitle("share".localized(), for: .normal)
        shareButton.addTarget(self, action: #selector(shareQRCode), for: .touchUpInside)
        
        // Set up share button container
        let shareButtonContainer = UIView()
        shareButtonContainer.addSubview(shareButton)
        shareButton.pin(.leading, to: .leading, of: shareButtonContainer, withInset: 80)
        shareButton.pin(.top, to: .top, of: shareButtonContainer)
        shareButtonContainer.pin(.trailing, to: .trailing, of: shareButton, withInset: 80)
        shareButtonContainer.pin(.bottom, to: .bottom, of: shareButton, withInset: isIPhone6OrSmaller ? Values.largeSpacing : Values.onboardingButtonBottomOffset)
        let spacing = isIPhone5OrSmaller ? Values.mediumSpacing : Values.largeSpacing
        
        // Set up stack view
        let stackView = UIStackView(arrangedSubviews: [ titleLabel, UIView.spacer(withHeight: spacing), qrCodeImageViewContainer, UIView.spacer(withHeight: spacing),
            explanationLabel, UIView.vStretchingSpacer(), shareButtonContainer ])
        stackView.axis = .vertical
        stackView.alignment = .fill
        stackView.layoutMargins = UIEdgeInsets(top: Values.largeSpacing, left: Values.largeSpacing, bottom: 0, right: Values.largeSpacing)
        stackView.isLayoutMarginsRelativeArrangement = true
        view.addSubview(stackView)
        stackView.pin(.leading, to: .leading, of: view)
        stackView.pin(.top, to: .top, of: view)
        view.pin(.trailing, to: .trailing, of: stackView)
        bottomConstraint = view.pin(.bottom, to: .bottom, of: stackView)
        
        // Set up width constraint
        view.set(.width, to: UIScreen.main.bounds.width)
    }
    
    // MARK: - General
    
    func constrainHeight(to height: CGFloat) {
        view.set(.height, to: height)
    }
    
    // MARK: - Interaction
    
    @objc private func shareQRCode() {
        let qrCode = QRCode.generate(for: getUserHexEncodedPublicKey(), hasBackground: true)
        let shareVC = UIActivityViewController(activityItems: [ qrCode ], applicationActivities: nil)
        if UIDevice.current.isIPad {
            shareVC.excludedActivityTypes = []
            shareVC.popoverPresentationController?.permittedArrowDirections = []
            shareVC.popoverPresentationController?.sourceView = self.view
            shareVC.popoverPresentationController?.sourceRect = self.view.bounds
        }
        qrCodeVC.navigationController!.present(shareVC, animated: true, completion: nil)
    }
}

private final class ScanQRCodePlaceholderVC : UIViewController {
    weak var qrCodeVC: QRCodeVC!
    
    override func viewDidLoad() {
        // Remove background color
        view.themeBackgroundColor = .clear
        
        // Set up explanation label
        let explanationLabel = UILabel()
        explanationLabel.font = .systemFont(ofSize: Values.smallFontSize)
        explanationLabel.text = "vc_scan_qr_code_camera_access_explanation".localized()
        explanationLabel.themeTextColor = .textPrimary
        explanationLabel.textAlignment = .center
        explanationLabel.lineBreakMode = .byWordWrapping
        explanationLabel.numberOfLines = 0
        
        // Set up call to action button
        let callToActionButton = UIButton()
        callToActionButton.titleLabel?.font = .boldSystemFont(ofSize: Values.mediumFontSize)
        callToActionButton.setTitle("vc_scan_qr_code_grant_camera_access_button_title".localized(), for: UIControl.State.normal)
        callToActionButton.setThemeTitleColor(.primary, for: .normal)
        callToActionButton.addTarget(self, action: #selector(requestCameraAccess), for: UIControl.Event.touchUpInside)
        
        // Set up stack view
        let stackView = UIStackView(arrangedSubviews: [ explanationLabel, callToActionButton ])
        stackView.axis = .vertical
        stackView.spacing = Values.mediumSpacing
        stackView.alignment = .center
        
        // Set up constraints
        view.set(.width, to: UIScreen.main.bounds.width)
        view.addSubview(stackView)
        stackView.pin(.leading, to: .leading, of: view, withInset: Values.massiveSpacing)
        view.pin(.trailing, to: .trailing, of: stackView, withInset: Values.massiveSpacing)
        let verticalCenteringConstraint = stackView.center(.vertical, in: view)
        verticalCenteringConstraint.constant = -16 // Makes things appear centered visually
    }
    
    func constrainHeight(to height: CGFloat) {
        view.set(.height, to: height)
    }
    
    @objc private func requestCameraAccess() {
        ows_ask(forCameraPermissions: { [weak self] hasCameraAccess in
            if hasCameraAccess {
                self?.qrCodeVC.handleCameraAccessGranted()
            } else {
                // Do nothing
            }
        })
    }
}