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

import UIKit
import AVFoundation
import SessionUIKit
import SessionUtilitiesKit
import SessionSnodeKit
import SignalUtilitiesKit

final class LinkDeviceVC: 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!
    private var activityIndicatorModal: ModalActivityIndicatorViewController?
    
    // MARK: - Components
    
    private lazy var tabBar: TabBar = {
        let tabs = [
            TabBar.Tab(title: "vc_link_device_recovery_phrase_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_link_device_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 recoveryPhraseVC: RecoveryPhraseVC = {
        let result = RecoveryPhraseVC()
        result.linkDeviceVC = self
        return result
    }()
    
    private lazy var scanQRCodePlaceholderVC: ScanQRCodePlaceholderVC = {
        let result = ScanQRCodePlaceholderVC()
        result.linkDeviceVC = self
        return result
    }()
    
    private lazy var scanQRCodeWrapperVC: ScanQRCodeWrapperVC = {
        let message = "vc_link_device_scan_qr_code_explanation".localized()
        let result = ScanQRCodeWrapperVC(message: message)
        result.delegate = self
        return result
    }()
    
    // MARK: - Lifecycle
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setNavBarTitle("vc_link_device_title".localized())
        
        // Page VC
        let hasCameraAccess = (AVCaptureDevice.authorizationStatus(for: .video) == .authorized)
        pages = [ recoveryPhraseVC, (hasCameraAccess ? scanQRCodeWrapperVC : scanQRCodePlaceholderVC) ]
        pageVC.dataSource = self
        pageVC.delegate = self
        pageVC.setViewControllers([ recoveryPhraseVC ], direction: .forward, animated: false, completion: nil)
        
        // Tab bar
        view.addSubview(tabBar)
        tabBar.pin(.leading, to: .leading, of: view)
        tabBarTopConstraint = tabBar.autoPinEdge(toSuperviewSafeArea: .top)
        view.pin(.trailing, to: .trailing, of: tabBar)
        
        // 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 statusBarHeight = UIApplication.shared.statusBarFrame.height
        let height = (navigationController?.view.bounds.height ?? 0) - (navigationController?.navigationBar.bounds.height ?? 0) - TabBar.snHeight - statusBarHeight
        pageVCView.set(.height, to: height)
        recoveryPhraseVC.constrainHeight(to: height)
        scanQRCodePlaceholderVC.constrainHeight(to: height)
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        tabBarTopConstraint.constant = navigationController!.navigationBar.height()
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    // 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() {
        DispatchQueue.main.async {
            self.pages[1] = self.scanQRCodeWrapperVC
            self.pageVC.setViewControllers([ self.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 seed = Data(hex: string)
        continueWithSeed(seed)
    }
    
    func continueWithSeed(_ seed: Data) {
        if (seed.count != 16) {
            let modal: ConfirmationModal = ConfirmationModal(
                info: ConfirmationModal.Info(
                    title: "invalid_recovery_phrase".localized(),
                    explanation: "INVALID_RECOVERY_PHRASE_MESSAGE".localized(),
                    cancelTitle: "BUTTON_OK".localized(),
                    cancelStyle: .alert_text,
                    afterClosed: { [weak self] in
                        self?.scanQRCodeWrapperVC.startCapture()
                    }
                )
            )
            present(modal, animated: true)
            return
        }
        let (ed25519KeyPair, x25519KeyPair) = try! Identity.generate(from: seed)
        Onboarding.Flow.link.preregister(with: seed, ed25519KeyPair: ed25519KeyPair, x25519KeyPair: x25519KeyPair)
        
        Identity.didRegister()
        
        // Now that we have registered get the Snode pool
        GetSnodePoolJob.run()
        
        NotificationCenter.default.addObserver(self, selector: #selector(handleInitialConfigurationMessageReceived), name: .initialConfigurationMessageReceived, object: nil)
        
        ModalActivityIndicatorViewController
            .present(
                // There was some crashing here due to force-unwrapping so just falling back to
                // using self if there is no nav controller
                fromViewController: (self.navigationController ?? self)
            ) { [weak self] modal in
                self?.activityIndicatorModal = modal
            }
    }
    
    @objc private func handleInitialConfigurationMessageReceived(_ notification: Notification) {
        DispatchQueue.main.async {
            self.navigationController!.dismiss(animated: true) {
                let pnModeVC = PNModeVC()
                self.navigationController!.setViewControllers([ pnModeVC ], animated: true)
            }
        }
    }
}

private final class RecoveryPhraseVC: UIViewController {
    weak var linkDeviceVC: LinkDeviceVC!
    private var spacer1HeightConstraint: NSLayoutConstraint!
    private var spacer2HeightConstraint: NSLayoutConstraint!
    private var restoreButtonBottomOffsetConstraint: NSLayoutConstraint!
    private var bottomConstraint: NSLayoutConstraint!
    
    private lazy var mnemonicTextView: TextView = {
        let result = TextView(placeholder: "vc_restore_seed_text_field_hint".localized())
        result.themeBorderColor = .textPrimary
        result.accessibilityLabel = "Enter your recovery phrase"
        
        return result
    }()
    
    // MARK: - Lifecycle
    
    override func viewDidLoad() {
        view.themeBackgroundColor = .clear
        
        // Title label
        let titleLabel = UILabel()
        titleLabel.font = .boldSystemFont(ofSize: isIPhone5OrSmaller ? Values.largeFontSize : Values.veryLargeFontSize)
        titleLabel.text = "vc_enter_recovery_phrase_title".localized()
        titleLabel.themeTextColor = .textPrimary
        titleLabel.lineBreakMode = .byWordWrapping
        titleLabel.numberOfLines = 0
        
        // Explanation label
        let explanationLabel = UILabel()
        explanationLabel.font = .systemFont(ofSize: Values.smallFontSize)
        explanationLabel.text = "vc_enter_recovery_phrase_explanation".localized()
        explanationLabel.themeTextColor = .textPrimary
        explanationLabel.lineBreakMode = .byWordWrapping
        explanationLabel.numberOfLines = 0
        
        // Spacers
        let topSpacer = UIView.vStretchingSpacer()
        let spacer1 = UIView()
        spacer1HeightConstraint = spacer1.set(.height, to: isIPhone5OrSmaller ? Values.smallSpacing : Values.veryLargeSpacing)
        let spacer2 = UIView()
        spacer2HeightConstraint = spacer2.set(.height, to: isIPhone5OrSmaller ? Values.smallSpacing : Values.veryLargeSpacing)
        let bottomSpacer = UIView.vStretchingSpacer()
        let restoreButtonBottomOffsetSpacer = UIView()
        restoreButtonBottomOffsetConstraint = restoreButtonBottomOffsetSpacer.set(.height, to: Values.onboardingButtonBottomOffset)
        
        // Continue button
        let continueButton = SessionButton(style: .filled, size: .large)
        continueButton.accessibilityLabel = "Link device"
        continueButton.setTitle("continue_2".localized(), for: UIControl.State.normal)
        continueButton.addTarget(self, action: #selector(handleContinueButtonTapped), for: UIControl.Event.touchUpInside)
        
        // Continue button container
        let continueButtonContainer = UIView(wrapping: continueButton, withInsets: UIEdgeInsets(top: 0, leading: Values.massiveSpacing, bottom: 0, trailing: Values.massiveSpacing), shouldAdaptForIPadWithWidth: Values.iPadButtonWidth)
        
        // Top stack view
        let topStackView = UIStackView(arrangedSubviews: [ titleLabel, spacer1, explanationLabel, spacer2, mnemonicTextView ])
        topStackView.axis = .vertical
        topStackView.alignment = .fill
        
        // Top stack view container
        let topStackViewContainer = UIView()
        topStackViewContainer.addSubview(topStackView)
        topStackView.pin(.leading, to: .leading, of: topStackViewContainer, withInset: Values.veryLargeSpacing)
        topStackView.pin(.top, to: .top, of: topStackViewContainer)
        topStackViewContainer.pin(.trailing, to: .trailing, of: topStackView, withInset: Values.veryLargeSpacing)
        topStackViewContainer.pin(.bottom, to: .bottom, of: topStackView)
        
        // Main stack view
        let mainStackView = UIStackView(arrangedSubviews: [ topSpacer, topStackViewContainer, bottomSpacer, continueButtonContainer, restoreButtonBottomOffsetSpacer ])
        mainStackView.axis = .vertical
        mainStackView.alignment = .fill
        view.addSubview(mainStackView)
        mainStackView.pin(.leading, to: .leading, of: view)
        mainStackView.pin(.top, to: .top, of: view)
        mainStackView.pin(.trailing, to: .trailing, of: view)
        bottomConstraint = mainStackView.pin(.bottom, to: .bottom, of: view)
        topSpacer.heightAnchor.constraint(equalTo: bottomSpacer.heightAnchor, multiplier: 1).isActive = true
        
        // Dismiss keyboard on tap
        let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(dismissKeyboard))
        view.addGestureRecognizer(tapGestureRecognizer)
        
        // Listen to keyboard notifications
        let notificationCenter = NotificationCenter.default
        notificationCenter.addObserver(self, selector: #selector(handleKeyboardWillChangeFrameNotification(_:)), name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
        notificationCenter.addObserver(self, selector: #selector(handleKeyboardWillHideNotification(_:)), name: UIResponder.keyboardWillHideNotification, object: nil)
        
        // Set up width constraint
        view.set(.width, to: UIScreen.main.bounds.width)
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    // MARK: - General
    
    func constrainHeight(to height: CGFloat) {
        view.set(.height, to: height)
    }
    
    @objc private func dismissKeyboard() {
        mnemonicTextView.resignFirstResponder()
    }
    
    // MARK: - Updating
    
    @objc private func handleKeyboardWillChangeFrameNotification(_ notification: Notification) {
        guard let newHeight = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue.size.height else { return }
        bottomConstraint.constant = -newHeight // Negative due to how the constraint is set up
        restoreButtonBottomOffsetConstraint.constant = isIPhone6OrSmaller ? Values.smallSpacing : Values.largeSpacing
        spacer1HeightConstraint.constant = isIPhone6OrSmaller ? Values.smallSpacing : Values.mediumSpacing
        spacer2HeightConstraint.constant = isIPhone6OrSmaller ? Values.smallSpacing : Values.mediumSpacing
        UIView.animate(withDuration: 0.25) {
            self.view.layoutIfNeeded()
        }
    }
    
    @objc private func handleKeyboardWillHideNotification(_ notification: Notification) {
        bottomConstraint.constant = 0
        restoreButtonBottomOffsetConstraint.constant = Values.onboardingButtonBottomOffset
        spacer1HeightConstraint.constant = isIPhone5OrSmaller ? Values.smallSpacing : Values.veryLargeSpacing
        spacer2HeightConstraint.constant = isIPhone5OrSmaller ? Values.smallSpacing : Values.veryLargeSpacing
        UIView.animate(withDuration: 0.25) {
            self.view.layoutIfNeeded()
        }
    }
    
    // MARK: - Interaction
    
    @objc private func handleContinueButtonTapped() {
        func showError(title: String, message: String = "") {
            let modal: ConfirmationModal = ConfirmationModal(
                targetView: self.view,
                info: ConfirmationModal.Info(
                    title: title,
                    explanation: message,
                    cancelTitle: "BUTTON_OK".localized(),
                    cancelStyle: .alert_text
                )
            )
            self.present(modal, animated: true)
        }
        let mnemonic = mnemonicTextView.text!.lowercased()
        do {
            let hexEncodedSeed = try Mnemonic.decode(mnemonic: mnemonic)
            let seed = Data(hex: hexEncodedSeed)
            mnemonicTextView.resignFirstResponder()
            linkDeviceVC.continueWithSeed(seed)
        } catch let error {
            let error = error as? Mnemonic.DecodingError ?? Mnemonic.DecodingError.generic
            showError(title: error.errorDescription!)
        }
    }
}

private final class ScanQRCodePlaceholderVC: UIViewController {
    weak var linkDeviceVC: LinkDeviceVC!
    
    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: .normal)
        callToActionButton.setThemeTitleColor(.primary, for: .normal)
        callToActionButton.addTarget(self, action: #selector(requestCameraAccess), for: .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() {
        Permissions.requestCameraPermissionIfNeeded { [weak self] in
            self?.linkDeviceVC.handleCameraAccessGranted()
        }
    }
}