//
//  MastodonRegisterViewController.swift
//  Mastodon
//
//  Created by MainasuK Cirno on 2021-2-5.
//

import AlamofireImage
import Combine
import MastodonSDK
import os.log
import PhotosUI
import UIKit

final class MastodonRegisterViewController: UIViewController, NeedsDependency, OnboardingViewControllerAppearance {
    
    static let avatarImageMaxSizeInPixel = CGSize(width: 400, height: 400)
    
    var disposeBag = Set<AnyCancellable>()
    
    weak var context: AppContext! { willSet { precondition(!isViewLoaded) } }
    weak var coordinator: SceneCoordinator! { willSet { precondition(!isViewLoaded) } }
    
    var viewModel: MastodonRegisterViewModel!

    // picker
    private(set) lazy var imagePicker: PHPickerViewController = {
        var configuration = PHPickerConfiguration()
        configuration.filter = .images
        configuration.selectionLimit = 1

        let imagePicker = PHPickerViewController(configuration: configuration)
        imagePicker.delegate = self
        return imagePicker
    }()
    private(set) lazy var imagePickerController: UIImagePickerController = {
        let imagePickerController = UIImagePickerController()
        imagePickerController.sourceType = .camera
        imagePickerController.delegate = self
        return imagePickerController
    }()
    
    private(set) lazy var documentPickerController: UIDocumentPickerViewController = {
        let documentPickerController = UIDocumentPickerViewController(forOpeningContentTypes: [.image])
        documentPickerController.delegate = self
        return documentPickerController
    }()
    
    let tapGestureRecognizer = UITapGestureRecognizer.singleTapGestureRecognizer
    
    let scrollView: UIScrollView = {
        let scrollview = UIScrollView()
        scrollview.showsVerticalScrollIndicator = false
        scrollview.keyboardDismissMode = .interactive
        scrollview.alwaysBounceVertical = true
        scrollview.clipsToBounds = false // make content could display over bleeding
        scrollview.translatesAutoresizingMaskIntoConstraints = false
        return scrollview
    }()
    
    let largeTitleLabel: UILabel = {
        let label = UILabel()
        label.font = UIFontMetrics(forTextStyle: .largeTitle).scaledFont(for: UIFont.boldSystemFont(ofSize: 34))
        label.textColor = Asset.Colors.Label.primary.color
        label.text = L10n.Scene.Register.title
        return label
    }()
    
    let avatarView: UIView = {
        let view = UIView()
        view.backgroundColor = .clear
        return view
    }()
    
    let avatarButton: UIButton = {
        let button = HighlightDimmableButton()
        let boldFont = UIFont.systemFont(ofSize: 42)
        let configuration = UIImage.SymbolConfiguration(font: boldFont)
        let image = UIImage(systemName: "person.fill.viewfinder", withConfiguration: configuration)

        button.setImage(image?.withRenderingMode(UIImage.RenderingMode.alwaysTemplate), for: UIControl.State.normal)
        button.imageView?.tintColor = Asset.Colors.Label.secondary.color
        button.backgroundColor = Asset.Colors.Background.secondaryGroupedSystemBackground.color
        button.layer.cornerRadius = 10
        button.clipsToBounds = true
        
        return button
    }()
    
    let plusIconImageView: UIImageView = {
        let icon = UIImageView()

        let image = Asset.Circles.plusCircleFill.image.withRenderingMode(.alwaysTemplate)
        icon.image = image
        icon.tintColor = Asset.Colors.Icon.plus.color
        icon.backgroundColor = Asset.Colors.Background.systemGroupedBackground.color
        return icon
    }()
    
    let domainLabel: UILabel = {
        let label = UILabel()
        label.font = .preferredFont(forTextStyle: .headline)
        label.textColor = Asset.Colors.Label.primary.color
        return label
    }()
    
    let usernameTextField: UITextField = {
        let textField = UITextField()
        
        textField.autocapitalizationType = .none
        textField.autocorrectionType = .no
        textField.backgroundColor = Asset.Colors.Background.secondaryGroupedSystemBackground.color
        textField.textColor = Asset.Colors.Label.primary.color
        textField.attributedPlaceholder = NSAttributedString(string: L10n.Scene.Register.Input.Username.placeholder,
                                                             attributes: [NSAttributedString.Key.foregroundColor: Asset.Colors.Label.secondary.color,
                                                                          NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .headline)])
        textField.borderStyle = UITextField.BorderStyle.roundedRect
        let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: 5, height: textField.frame.height))
        textField.leftView = paddingView
        textField.leftViewMode = .always
        return textField
    }()
    
    let usernameErrorPromptLabel: UILabel = {
        let label = UILabel()
        let color = Asset.Colors.danger.color
        let font = UIFont.preferredFont(forTextStyle: .caption1)
        return label
    }()
    
    let displayNameTextField: UITextField = {
        let textField = UITextField()
        textField.autocapitalizationType = .none
        textField.autocorrectionType = .no
        textField.backgroundColor = Asset.Colors.Background.secondaryGroupedSystemBackground.color
        textField.textColor = Asset.Colors.Label.primary.color
        textField.attributedPlaceholder = NSAttributedString(string: L10n.Scene.Register.Input.DisplayName.placeholder,
                                                             attributes: [NSAttributedString.Key.foregroundColor: Asset.Colors.Label.secondary.color,
                                                                          NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .headline)])
        textField.borderStyle = UITextField.BorderStyle.roundedRect
        let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: 5, height: textField.frame.height))
        textField.leftView = paddingView
        textField.leftViewMode = .always
        return textField
    }()
    
    let emailTextField: UITextField = {
        let textField = UITextField()
        textField.autocapitalizationType = .none
        textField.autocorrectionType = .no
        textField.keyboardType = .emailAddress
        textField.backgroundColor = Asset.Colors.Background.secondaryGroupedSystemBackground.color
        textField.textColor = Asset.Colors.Label.primary.color
        textField.attributedPlaceholder = NSAttributedString(string: L10n.Scene.Register.Input.Email.placeholder,
                                                             attributes: [NSAttributedString.Key.foregroundColor: Asset.Colors.Label.secondary.color,
                                                                          NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .headline)])
        textField.borderStyle = UITextField.BorderStyle.roundedRect
        let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: 5, height: textField.frame.height))
        textField.leftView = paddingView
        textField.leftViewMode = .always
        return textField
    }()
    
    let emailErrorPromptLabel: UILabel = {
        let label = UILabel()
        let color = Asset.Colors.danger.color
        let font = UIFont.preferredFont(forTextStyle: .caption1)
        return label
    }()
    
    let passwordTextField: UITextField = {
        let textField = UITextField()
        textField.autocapitalizationType = .none
        textField.autocorrectionType = .no
        textField.keyboardType = .asciiCapable
        textField.isSecureTextEntry = true
        textField.backgroundColor = Asset.Colors.Background.secondaryGroupedSystemBackground.color
        textField.textColor = Asset.Colors.Label.primary.color
        textField.attributedPlaceholder = NSAttributedString(string: L10n.Scene.Register.Input.Password.placeholder,
                                                             attributes: [NSAttributedString.Key.foregroundColor: Asset.Colors.Label.secondary.color,
                                                                          NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .headline)])
        textField.borderStyle = UITextField.BorderStyle.roundedRect
        let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: 5, height: textField.frame.height))
        textField.leftView = paddingView
        textField.leftViewMode = .always
        return textField
    }()
    
    let passwordCheckLabel: UILabel = {
        let label = UILabel()
        label.numberOfLines = 0
        return label
    }()
    
    let passwordErrorPromptLabel: UILabel = {
        let label = UILabel()
        let color = Asset.Colors.danger.color
        let font = UIFont.preferredFont(forTextStyle: .caption1)
        return label
    }()
    
    
    lazy var reasonTextField: UITextField = {
        let textField = UITextField()
        textField.autocapitalizationType = .none
        textField.autocorrectionType = .no
        textField.backgroundColor = Asset.Colors.Background.secondaryGroupedSystemBackground.color
        textField.textColor = Asset.Colors.Label.primary.color
        textField.attributedPlaceholder = NSAttributedString(string: L10n.Scene.Register.Input.Invite.registrationUserInviteRequest,
                                                             attributes: [NSAttributedString.Key.foregroundColor: Asset.Colors.Label.secondary.color,
                                                                          NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .headline)])
        textField.borderStyle = UITextField.BorderStyle.roundedRect
        let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: 5, height: textField.frame.height))
        textField.leftView = paddingView
        textField.leftViewMode = .always
        return textField
    }()
    
    let reasonErrorPromptLabel: UILabel = {
        let label = UILabel()
        let color = Asset.Colors.danger.color
        let font = UIFont.preferredFont(forTextStyle: .caption1)
        return label
    }()
    
    let buttonContainer = UIView()
    let signUpButton: PrimaryActionButton = {
        let button = PrimaryActionButton()
        button.isEnabled = false
        button.setTitle(L10n.Common.Controls.Actions.continue, for: .normal)
        return button
    }()
    
    deinit {
        os_log(.info, log: .debug, "%{public}s[%{public}ld], %{public}s", (#file as NSString).lastPathComponent, #line, #function)
    }
}

extension MastodonRegisterViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setupOnboardingAppearance()
        defer { setupNavigationBarBackgroundView() }
        
        avatarButton.menu = createMediaContextMenu()
        avatarButton.showsMenuAsPrimaryAction = true
        
        domainLabel.text = "@" + viewModel.domain + "  "
        domainLabel.sizeToFit()
        passwordCheckLabel.attributedText = MastodonRegisterViewModel.attributeStringForPassword(validateState: .empty)
        usernameTextField.rightView = domainLabel
        usernameTextField.rightViewMode = .always
        usernameTextField.delegate = self
        displayNameTextField.delegate = self
        emailTextField.delegate = self
        passwordTextField.delegate = self
        
        // gesture
        view.addGestureRecognizer(tapGestureRecognizer)
        tapGestureRecognizer.addTarget(self, action: #selector(tapGestureRecognizerHandler))
        
        // stackview
        let stackView = UIStackView()
        stackView.axis = .vertical
        stackView.distribution = .fill
        stackView.spacing = 40
        stackView.layoutMargins = UIEdgeInsets(top: 20, left: 0, bottom: 26, right: 0)
        stackView.isLayoutMarginsRelativeArrangement = true
        stackView.addArrangedSubview(largeTitleLabel)
        stackView.addArrangedSubview(avatarView)
        stackView.addArrangedSubview(usernameTextField)
        stackView.addArrangedSubview(displayNameTextField)
        stackView.addArrangedSubview(emailTextField)
        stackView.addArrangedSubview(passwordTextField)
        stackView.addArrangedSubview(passwordCheckLabel)
        if viewModel.approvalRequired {
            stackView.addArrangedSubview(reasonTextField)
        }
        
        usernameErrorPromptLabel.translatesAutoresizingMaskIntoConstraints = false
        stackView.addSubview(usernameErrorPromptLabel)
        NSLayoutConstraint.activate([
            usernameErrorPromptLabel.topAnchor.constraint(equalTo: usernameTextField.bottomAnchor, constant: 6),
            usernameErrorPromptLabel.leadingAnchor.constraint(equalTo: usernameTextField.leadingAnchor),
            usernameErrorPromptLabel.trailingAnchor.constraint(equalTo: usernameTextField.trailingAnchor),
        ])
        
        emailErrorPromptLabel.translatesAutoresizingMaskIntoConstraints = false
        stackView.addSubview(emailErrorPromptLabel)
        NSLayoutConstraint.activate([
            emailErrorPromptLabel.topAnchor.constraint(equalTo: emailTextField.bottomAnchor, constant: 6),
            emailErrorPromptLabel.leadingAnchor.constraint(equalTo: emailTextField.leadingAnchor),
            emailErrorPromptLabel.trailingAnchor.constraint(equalTo: emailTextField.trailingAnchor),
        ])
        
        passwordErrorPromptLabel.translatesAutoresizingMaskIntoConstraints = false
        stackView.addSubview(passwordErrorPromptLabel)
        NSLayoutConstraint.activate([
            passwordErrorPromptLabel.topAnchor.constraint(equalTo: passwordCheckLabel.bottomAnchor, constant: 2),
            passwordErrorPromptLabel.leadingAnchor.constraint(equalTo: passwordTextField.leadingAnchor),
            passwordErrorPromptLabel.trailingAnchor.constraint(equalTo: passwordTextField.trailingAnchor),
        ])

        // scrollView
        view.addSubview(scrollView)
        NSLayoutConstraint.activate([
            scrollView.frameLayoutGuide.topAnchor.constraint(equalTo: view.layoutMarginsGuide.topAnchor),
            scrollView.frameLayoutGuide.leadingAnchor.constraint(equalTo: view.readableContentGuide.leadingAnchor),
            view.readableContentGuide.trailingAnchor.constraint(equalTo: scrollView.frameLayoutGuide.trailingAnchor),
            scrollView.frameLayoutGuide.bottomAnchor.constraint(equalTo: view.layoutMarginsGuide.bottomAnchor),
            scrollView.frameLayoutGuide.widthAnchor.constraint(equalTo: scrollView.contentLayoutGuide.widthAnchor),
        ])

        // stackview
        scrollView.addSubview(stackView)
        stackView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            stackView.topAnchor.constraint(equalTo: scrollView.contentLayoutGuide.topAnchor),
            stackView.leadingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.leadingAnchor),
            stackView.trailingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.trailingAnchor),
            stackView.widthAnchor.constraint(equalTo: scrollView.contentLayoutGuide.widthAnchor),
            scrollView.contentLayoutGuide.bottomAnchor.constraint(equalTo: stackView.bottomAnchor),
        ])

        // photoview
        avatarView.translatesAutoresizingMaskIntoConstraints = false
        avatarView.addSubview(avatarButton)
        NSLayoutConstraint.activate([
            avatarView.heightAnchor.constraint(equalToConstant: 90).priority(.defaultHigh),
        ])
        avatarButton.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            avatarButton.heightAnchor.constraint(equalToConstant: 92).priority(.defaultHigh),
            avatarButton.widthAnchor.constraint(equalToConstant: 92).priority(.defaultHigh),
            avatarButton.centerXAnchor.constraint(equalTo: avatarView.centerXAnchor),
            avatarButton.centerYAnchor.constraint(equalTo: avatarView.centerYAnchor),
        ])

        plusIconImageView.translatesAutoresizingMaskIntoConstraints = false
        avatarView.addSubview(plusIconImageView)
        NSLayoutConstraint.activate([
            plusIconImageView.centerXAnchor.constraint(equalTo: avatarButton.trailingAnchor),
            plusIconImageView.centerYAnchor.constraint(equalTo: avatarButton.bottomAnchor),
        ])

        // textfield
        NSLayoutConstraint.activate([
            usernameTextField.heightAnchor.constraint(equalToConstant: 50).priority(.defaultHigh),
            displayNameTextField.heightAnchor.constraint(equalToConstant: 50).priority(.defaultHigh),
            emailTextField.heightAnchor.constraint(equalToConstant: 50).priority(.defaultHigh),
            passwordTextField.heightAnchor.constraint(equalToConstant: 50).priority(.defaultHigh),
        ])

        // password
        stackView.setCustomSpacing(6, after: passwordTextField)
        stackView.setCustomSpacing(32, after: passwordCheckLabel)
        
        //return
        if viewModel.approvalRequired {
            passwordTextField.returnKeyType = .continue
        } else {
            passwordTextField.returnKeyType = .done
        }
        reasonTextField.returnKeyType = .done

        // button
        stackView.addArrangedSubview(buttonContainer)
        signUpButton.translatesAutoresizingMaskIntoConstraints = false
        buttonContainer.addSubview(signUpButton)
        NSLayoutConstraint.activate([
            signUpButton.topAnchor.constraint(equalTo: buttonContainer.topAnchor),
            signUpButton.leadingAnchor.constraint(equalTo: buttonContainer.leadingAnchor, constant: MastodonRegisterViewController.actionButtonMargin),
            buttonContainer.trailingAnchor.constraint(equalTo: signUpButton.trailingAnchor, constant: MastodonRegisterViewController.actionButtonMargin),
            buttonContainer.bottomAnchor.constraint(equalTo: signUpButton.bottomAnchor),
            signUpButton.heightAnchor.constraint(equalToConstant: MastodonRegisterViewController.actionButtonHeight).priority(.defaultHigh),
        ])
        
        Publishers.CombineLatest(
            KeyboardResponderService.shared.state.eraseToAnyPublisher(),
            KeyboardResponderService.shared.endFrame.eraseToAnyPublisher()
        )
        .sink(receiveValue: { [weak self] state, endFrame in
            guard let self = self else { return }
            
            guard state == .dock else {
                self.scrollView.contentInset.bottom = 0.0
                self.scrollView.verticalScrollIndicatorInsets.bottom = 0.0
                return
            }

            let contentFrame = self.view.convert(self.scrollView.frame, to: nil)
            let padding = contentFrame.maxY - endFrame.minY
            guard padding > 0 else {
                self.scrollView.contentInset.bottom = 0.0
                self.scrollView.verticalScrollIndicatorInsets.bottom = 0.0
                return
            }
            
            self.scrollView.contentInset.bottom = padding + 16
            self.scrollView.verticalScrollIndicatorInsets.bottom = padding + 16
            
            if self.passwordTextField.isFirstResponder {
                let contentFrame = self.buttonContainer.convert(self.signUpButton.frame, to: nil)
                let labelPadding = contentFrame.maxY - endFrame.minY
                let contentOffsetY = self.scrollView.contentOffset.y
                DispatchQueue.main.async {
                    self.scrollView.setContentOffset(CGPoint(x: 0, y: contentOffsetY + labelPadding + 16.0), animated: true)
                }
            }
        })
        .store(in: &disposeBag)
        
        avatarButton.publisher(for: \.isHighlighted, options: .new)
            .receive(on: DispatchQueue.main)
            .sink { [weak self] isHighlighted in
                guard let self = self else { return }
                let alpha: CGFloat = isHighlighted ? 0.6 : 1
                self.plusIconImageView.alpha = alpha
            }
            .store(in: &disposeBag)

        viewModel.isRegistering
            .receive(on: DispatchQueue.main)
            .sink { [weak self] isRegistering in
                guard let self = self else { return }
                isRegistering ? self.signUpButton.showLoading() : self.signUpButton.stopLoading()
            }
            .store(in: &disposeBag)

        viewModel.usernameValidateState
            .receive(on: DispatchQueue.main)
            .sink { [weak self] validateState in
                guard let self = self else { return }
                self.setTextFieldValidAppearance(self.usernameTextField, validateState: validateState)
            }
            .store(in: &disposeBag)
        viewModel.usernameErrorPrompt
            .receive(on: DispatchQueue.main)
            .sink { [weak self] prompt in
                guard let self = self else { return }
                self.usernameErrorPromptLabel.attributedText = prompt
            }
            .store(in: &disposeBag)
        viewModel.displayNameValidateState
            .receive(on: DispatchQueue.main)
            .sink { [weak self] validateState in
                guard let self = self else { return }
                self.setTextFieldValidAppearance(self.displayNameTextField, validateState: validateState)
            }
            .store(in: &disposeBag)
        viewModel.emailValidateState
            .receive(on: DispatchQueue.main)
            .sink { [weak self] validateState in
                guard let self = self else { return }
                self.setTextFieldValidAppearance(self.emailTextField, validateState: validateState)
            }
            .store(in: &disposeBag)
        viewModel.emailErrorPrompt
            .receive(on: DispatchQueue.main)
            .sink { [weak self] prompt in
                guard let self = self else { return }
                self.emailErrorPromptLabel.attributedText = prompt
            }
            .store(in: &disposeBag)
        viewModel.passwordValidateState
            .receive(on: DispatchQueue.main)
            .sink { [weak self] validateState in
                guard let self = self else { return }
                self.setTextFieldValidAppearance(self.passwordTextField, validateState: validateState)
                self.passwordCheckLabel.attributedText = MastodonRegisterViewModel.attributeStringForPassword(validateState: validateState)
            }
            .store(in: &disposeBag)
        viewModel.passwordErrorPrompt
            .receive(on: DispatchQueue.main)
            .sink { [weak self] prompt in
                guard let self = self else { return }
                self.passwordErrorPromptLabel.attributedText = prompt
            }
            .store(in: &disposeBag)
        viewModel.reasonErrorPrompt
            .receive(on: DispatchQueue.main)
            .sink { [weak self] prompt in
                guard let self = self else { return }
                self.reasonErrorPromptLabel.attributedText = prompt
            }
            .store(in: &disposeBag)
        
        viewModel.isAllValid
            .receive(on: DispatchQueue.main)
            .sink { [weak self] isAllValid in
                guard let self = self else { return }
                self.signUpButton.isEnabled = isAllValid
            }
            .store(in: &disposeBag)

        viewModel.error
            .receive(on: DispatchQueue.main)
            .sink { [weak self] error in
                guard let self = self else { return }
                guard let error = error as? Mastodon.API.Error else { return }
                let alertController = UIAlertController(for: error, title: "Sign Up Failure", preferredStyle: .alert)
                let okAction = UIAlertAction(title: L10n.Common.Controls.Actions.ok, style: .default, handler: nil)
                alertController.addAction(okAction)
                self.coordinator.present(
                    scene: .alertController(alertController: alertController),
                    from: nil,
                    transition: .alertController(animated: true, completion: nil)
                )
            }
            .store(in: &disposeBag)

        viewModel.avatarImage
            .receive(on: DispatchQueue.main)
            .sink{ [weak self] image in
                guard let self = self else { return }
                self.avatarButton.menu = self.createMediaContextMenu()
                if let avatar = image {
                    self.avatarButton.setImage(avatar, for: .normal)
                } else {
                    let boldFont = UIFont.systemFont(ofSize: 42)
                    let configuration = UIImage.SymbolConfiguration(font: boldFont)
                    let image = UIImage(systemName: "person.fill.viewfinder", withConfiguration: configuration)
                    self.avatarButton.setImage(image?.withRenderingMode(UIImage.RenderingMode.alwaysTemplate), for: UIControl.State.normal)
                }
            }
            .store(in: &disposeBag)
        NotificationCenter.default
            .publisher(for: UITextField.textDidChangeNotification, object: usernameTextField)
            .receive(on: DispatchQueue.main)
            .sink { [weak self] _ in
                guard let self = self else { return }
                self.viewModel.username.value = self.usernameTextField.text?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
            }
            .store(in: &disposeBag)
        
        NotificationCenter.default
            .publisher(for: UITextField.textDidChangeNotification, object: displayNameTextField)
            .receive(on: DispatchQueue.main)
            .sink { [weak self] _ in
                guard let self = self else { return }
                self.viewModel.displayName.value = self.displayNameTextField.text?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
            }
            .store(in: &disposeBag)
        
        NotificationCenter.default
            .publisher(for: UITextField.textDidChangeNotification, object: emailTextField)
            .receive(on: DispatchQueue.main)
            .sink { [weak self] _ in
                guard let self = self else { return }
                self.viewModel.email.value = self.emailTextField.text?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
            }
            .store(in: &disposeBag)
        
        NotificationCenter.default
            .publisher(for: UITextField.textDidChangeNotification, object: passwordTextField)
            .receive(on: DispatchQueue.main)
            .sink { [weak self] _ in
                guard let self = self else { return }
                self.viewModel.password.value = self.passwordTextField.text?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
            }
            .store(in: &disposeBag)

        if viewModel.approvalRequired {
            reasonTextField.delegate = self
            NSLayoutConstraint.activate([
                reasonTextField.heightAnchor.constraint(equalToConstant: 50).priority(.defaultHigh),
            ])
            reasonErrorPromptLabel.translatesAutoresizingMaskIntoConstraints = false
            stackView.addSubview(reasonErrorPromptLabel)
            NSLayoutConstraint.activate([
                reasonErrorPromptLabel.topAnchor.constraint(equalTo: reasonTextField.bottomAnchor, constant: 6),
                reasonErrorPromptLabel.leadingAnchor.constraint(equalTo: reasonTextField.leadingAnchor),
                reasonErrorPromptLabel.trailingAnchor.constraint(equalTo: reasonTextField.trailingAnchor),
            ])
            
            viewModel.reasonValidateState
                .receive(on: DispatchQueue.main)
                .sink { [weak self] validateState in
                    guard let self = self else { return }
                    self.setTextFieldValidAppearance(self.reasonTextField, validateState: validateState)
                }
                .store(in: &disposeBag)
            NotificationCenter.default
                .publisher(for: UITextField.textDidChangeNotification, object: reasonTextField)
                .receive(on: DispatchQueue.main)
                .sink { [weak self] _ in
                    guard let self = self else { return }
                    self.viewModel.reason.value = self.reasonTextField.text?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
                }
                .store(in: &disposeBag)
        }
        
        signUpButton.addTarget(self, action: #selector(MastodonRegisterViewController.signUpButtonPressed(_:)), for: .touchUpInside)
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        plusIconImageView.layer.cornerRadius = plusIconImageView.frame.width / 2
        plusIconImageView.layer.masksToBounds = true
    }
    
}

extension MastodonRegisterViewController: UITextFieldDelegate {
    func textFieldDidBeginEditing(_ textField: UITextField) {
        let text = textField.text?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
        
        switch textField {
        case usernameTextField:
            viewModel.username.value = text
        case displayNameTextField:
            viewModel.displayName.value = text
        case emailTextField:
            viewModel.email.value = text
        case passwordTextField:
            viewModel.password.value = text
        case reasonTextField:
            viewModel.reason.value = text
        default:
            break
        }
    }

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        switch textField {
        case usernameTextField:
            displayNameTextField.becomeFirstResponder()
        case displayNameTextField:
            emailTextField.becomeFirstResponder()
        case emailTextField:
            passwordTextField.becomeFirstResponder()
        case passwordTextField:
            if viewModel.approvalRequired {
                reasonTextField.becomeFirstResponder()
            } else {
                passwordTextField.resignFirstResponder()
            }
        case reasonTextField:
            reasonTextField.resignFirstResponder()
        default:
            break
        }
        return true
    }
    
    func showShadowWithColor(color: UIColor, textField: UITextField) {
        // To apply Shadow
        textField.layer.shadowOpacity = 1
        textField.layer.shadowRadius = 2.0
        textField.layer.shadowOffset = CGSize.zero
        textField.layer.shadowColor = color.cgColor
        textField.layer.shadowPath = UIBezierPath(roundedRect: textField.bounds, byRoundingCorners: .allCorners, cornerRadii: CGSize(width: 2.0, height: 2.0)).cgPath
    }

    private func setTextFieldValidAppearance(_ textField: UITextField, validateState: MastodonRegisterViewModel.ValidateState) {
        switch validateState {
        case .empty:
            showShadowWithColor(color: textField.isFirstResponder ? Asset.Colors.TextField.highlight.color : .clear, textField: textField)
        case .valid:
            showShadowWithColor(color: Asset.Colors.TextField.valid.color, textField: textField)
        case .invalid:
            showShadowWithColor(color: Asset.Colors.TextField.invalid.color, textField: textField)
        }
    }
}

extension MastodonRegisterViewController {
    @objc private func tapGestureRecognizerHandler(_ sender: UITapGestureRecognizer) {
        view.endEditing(true)
    }
    
    @objc private func signUpButtonPressed(_ sender: UIButton) {
        os_log(.info, log: .debug, "%{public}s[%{public}ld], %{public}s", (#file as NSString).lastPathComponent, #line, #function)
        guard viewModel.isAllValid.value else { return }
        
        guard !viewModel.isRegistering.value else { return }
        viewModel.isRegistering.value = true
    
        let username = viewModel.username.value
        let email = viewModel.email.value
        let password = viewModel.password.value
        let query = Mastodon.API.Account.RegisterQuery(
            reason: viewModel.reason.value,
            username: username,
            email: email,
            password: password,
            agreement: true, // user confirmed in the server rules scene
            locale: Locale.current.languageCode ?? "en"
        )
 
        // register without show server rules
        context.apiService.accountRegister(
            domain: viewModel.domain,
            query: query,
            authorization: viewModel.applicationAuthorization
        )
        .receive(on: DispatchQueue.main)
        .sink { [weak self] completion in
            guard let self = self else { return }
            self.viewModel.isRegistering.value = false
            switch completion {
            case .failure(let error):
                self.viewModel.error.send(error)
            case .finished:
                break
            }
        } receiveValue: { [weak self] response in
            guard let self = self else { return }
            let userToken = response.value
            let updateCredentialQuery: Mastodon.API.Account.UpdateCredentialQuery = {
                let displayName: String? = self.viewModel.displayName.value.isEmpty ? nil : self.viewModel.displayName.value
                let avatar: Mastodon.Query.MediaAttachment? = {
                    guard let avatarImage = self.viewModel.avatarImage.value else { return nil }
                    guard avatarImage.size.width <= MastodonRegisterViewController.avatarImageMaxSizeInPixel.width else {
                        return .png(avatarImage.af.imageScaled(to: MastodonRegisterViewController.avatarImageMaxSizeInPixel).pngData())
                    }
                    return .png(avatarImage.pngData())
                }()
                return Mastodon.API.Account.UpdateCredentialQuery(
                    displayName: displayName,
                    avatar: avatar
                )
            }()
            let viewModel = MastodonConfirmEmailViewModel(context: self.context, email: email, authenticateInfo: self.viewModel.authenticateInfo, userToken: userToken, updateCredentialQuery: updateCredentialQuery)
            self.coordinator.present(scene: .mastodonConfirmEmail(viewModel: viewModel), from: self, transition: .show)
        }
        .store(in: &disposeBag)
    }
}