//
//  LoginViewController.swift
//  MullvadVPN
//
//  Created by pronebird on 19/03/2019.
//  Copyright © 2025 Mullvad VPN AB. All rights reserved.
//

import MullvadLogging
import MullvadTypes
import Operations
import UIKit

enum LoginState {
    case `default`
    case authenticating(LoginAction)
    case failure(LoginAction, Error)
    case success(LoginAction)
}

enum LoginAction {
    case useExistingAccount(String)
    case createAccount
}

enum EndLoginAction {
    /// Do nothing.
    case nothing

    /// Set focus on account text field.
    case activateTextField

    /// Wait for promise before showing login error.
    case wait(Promise<Void, Error>)
}

class LoginViewController: UIViewController, RootContainment {
    private lazy var contentView: LoginContentView = {
        let view = LoginContentView(frame: self.view.bounds)
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()

    private lazy var accountInputAccessoryCancelButton = UIBarButtonItem(
        barButtonSystemItem: .cancel,
        target: self,
        action: #selector(cancelLogin)
    )

    private lazy var accountInputAccessoryLoginButton: UIBarButtonItem = {
        let barButtonItem = UIBarButtonItem(
            title: NSLocalizedString("Login", comment: ""),
            style: .done,
            target: self,
            action: #selector(doLogin)
        )
        barButtonItem.setAccessibilityIdentifier(.loginBarButton)

        return barButtonItem
    }()

    private lazy var accountInputAccessoryToolbar: UIToolbar = {
        let toolbar = UIToolbar(frame: CGRect(x: 0, y: 0, width: 320, height: 44))
        toolbar.items = [
            self.accountInputAccessoryCancelButton,
            UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil),
            self.accountInputAccessoryLoginButton,
        ]
        toolbar.sizeToFit()
        return toolbar
    }()

    private let logger = Logger(label: "LoginViewController")

    private var loginState = LoginState.default {
        didSet {
            loginStateDidChange()
        }
    }

    private var canBeginLogin: Bool {
        contentView.accountInputGroup.satisfiesMinimumTokenLengthRequirement
    }

    var prefersDeviceInfoBarHidden: Bool {
        true
    }

    private let interactor: LoginInteractor

    var didFinishLogin: ((LoginAction, Error?) -> EndLoginAction)?

    override var preferredStatusBarStyle: UIStatusBarStyle {
        .lightContent
    }

    var preferredHeaderBarPresentation: HeaderBarPresentation {
        HeaderBarPresentation(style: .transparent, showsDivider: false)
    }

    var prefersHeaderBarHidden: Bool {
        false
    }

    private let alertPresenter: AlertPresenter

    init(interactor: LoginInteractor, alertPresenter: AlertPresenter) {
        self.interactor = interactor
        self.alertPresenter = alertPresenter
        super.init(nibName: nil, bundle: nil)
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(contentView)
        NSLayoutConstraint.activate([
            contentView.topAnchor.constraint(equalTo: view.topAnchor),
            contentView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            contentView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            contentView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        ])
        updateLastUsedAccount()

        contentView.accountInputGroup.didRemoveLastUsedAccount = { [weak self] in
            self?.showLastUsedAccountRemovalWarning()
        }

        contentView.accountInputGroup.didEnterAccount = { [weak self] in
            self?.attemptLogin()
        }

        interactor.suggestPreferredAccountNumber = { [weak self] value in
            Task { @MainActor in
                self?.contentView.accountInputGroup.setAccount(value)
            }
        }

        contentView.accountInputGroup.setOnReturnKey { [weak self] _ in
            guard let self else { return true }

            return attemptLogin()
        }

        // There is no need to set the input accessory toolbar on iPad since it has a dedicated
        // button to dismiss the keyboard.
        if case .phone = UIDevice.current.userInterfaceIdiom {
            contentView.accountInputGroup.textField.inputAccessoryView = accountInputAccessoryToolbar
        } else {
            contentView.accountInputGroup.textField.inputAccessoryView = nil
        }

        updateDisplayedMessage()
        updateStatusIcon()
        updateKeyboardToolbar()

        let notificationCenter = NotificationCenter.default

        contentView.createAccountButton.addTarget(
            self,
            action: #selector(createNewAccount),
            for: .touchUpInside
        )

        notificationCenter.addObserver(
            self,
            selector: #selector(textDidChange(_:)),
            name: UITextField.textDidChangeNotification,
            object: contentView.accountInputGroup.textField
        )
    }

    // MARK: - Public

    func start(action: LoginAction) {
        beginLogin(action)
        Task { [weak self] in
            guard let self else { return }
            do {
                switch action {
                case .createAccount:
                    self.contentView.accountInputGroup.setAccount(try await interactor.createAccount())

                case let .useExistingAccount(accountNumber):
                    try await interactor.setAccount(accountNumber: accountNumber)
                }
                self.endLogin(action: action, error: nil)
            } catch {
                self.endLogin(action: action, error: error)
            }
        }
    }

    func reset() {
        contentView.accountInputGroup.clearAccount()
        loginState = .default
        updateKeyboardToolbar()
        updateLastUsedAccount()
    }

    // MARK: - UITextField notifications

    @objc func textDidChange(_ notification: Notification) {
        // Reset the text style as user start typing
        if case .failure = loginState {
            loginState = .default
        }

        // Enable the log in button in the keyboard toolbar.
        updateKeyboardToolbar()

        // Update "create account" button state.
        updateCreateButtonEnabled()
    }

    // MARK: - Actions

    @objc private func cancelLogin() {
        view.endEditing(true)
    }

    @objc private func doLogin() {
        let accountNumber = contentView.accountInputGroup.parsedToken

        start(action: .useExistingAccount(accountNumber))
    }

    @objc private func createNewAccount() {
        if interactor.hasLastAccountNumber {
            let message = NSMutableAttributedString(
                markdownString: [
                    NSLocalizedString(
                        "You already have a saved account number, by creating a new account the "
                            + "saved account number will be removed from this device. This cannot be undone.",
                        comment: ""
                    ),
                    NSLocalizedString("Do you want to create a new account?", comment: ""),
                ].joinedParagraphs(lineBreaks: 1),
                options: MarkdownStylingOptions(font: .preferredFont(forTextStyle: .body))
            )
            let presentation = AlertPresentation(
                id: "create-account-confirmation-dialog",
                icon: .info,
                attributedMessage: message,
                buttons: [
                    AlertAction(
                        title: NSLocalizedString("Create new account", comment: ""),
                        style: .default,
                        accessibilityId: .createAccountConfirmationButton,
                        handler: {
                            self.start(action: .createAccount)
                        }
                    ),
                    AlertAction(
                        title: NSLocalizedString("Cancel", comment: ""),
                        style: .default,
                        accessibilityId: .createAccountCancelButton
                    ),
                ]
            )
            alertPresenter.showAlert(presentation: presentation, animated: true)
        } else {
            start(action: .createAccount)
        }
    }

    // MARK: - Private

    private func showLastUsedAccountRemovalWarning() {
        let message = NSMutableAttributedString(
            markdownString: NSLocalizedString(
                """
                Removing the saved account number from this device cannot be undone.
                Do you want to remove the saved account number?
                """,
                comment: ""
            ),
            options: MarkdownStylingOptions(font: .preferredFont(forTextStyle: .body))
        )

        let presentation = AlertPresentation(
            id: "remove-saved-account-number-dialog",
            icon: .info,
            attributedMessage: message,
            buttons: [
                AlertAction(
                    title: NSLocalizedString("Remove", comment: ""),
                    style: .destructive,
                    accessibilityId: .removeLastUsedAccountButton,
                    handler: {
                        self.interactor.removeLastUsedAccount()
                        self.contentView.accountInputGroup.setLastUsedAccount(
                            nil,
                            animated: true
                        )
                    }
                ),
                AlertAction(
                    title: NSLocalizedString("Cancel", comment: ""),
                    style: .default,
                    accessibilityId: .cancelRemoveLastUsedAccountButton
                ),
            ]
        )
        self.alertPresenter.showAlert(presentation: presentation, animated: true)
    }

    private func updateLastUsedAccount() {
        contentView.accountInputGroup.setLastUsedAccount(
            interactor.getLastUsedAccount(),
            animated: false
        )
    }

    private func loginStateDidChange() {
        contentView.accountInputGroup.setLoginState(loginState, animated: true)

        updateDisplayedMessage()
        updateStatusIcon()
        updateCreateButtonEnabled()
    }

    private func updateStatusIcon() {
        contentView.statusActivityView.state = loginState.statusActivityState
    }

    private func beginLogin(_ action: LoginAction) {
        loginState = .authenticating(action)

        view.endEditing(true)
    }

    private func endLogin(action: LoginAction, error: Error?) {
        let nextLoginState: LoginState = error.map { .failure(action, $0) } ?? .success(action)

        let endAction = didFinishLogin?(action, error) ?? .nothing

        switch endAction {
        case .activateTextField:
            contentView.accountInputGroup.textField.becomeFirstResponder()
            loginState = nextLoginState

        case .nothing:
            loginState = nextLoginState

        case let .wait(promise):
            promise.observe { result in
                self.loginState = result.error.map { .failure(action, $0) } ?? nextLoginState
            }
        }
    }

    private func updateDisplayedMessage() {
        contentView.titleLabel.text = loginState.localizedTitle
        contentView.messageLabel.text = loginState.localizedMessage
    }

    private func updateKeyboardToolbar() {
        accountInputAccessoryLoginButton.isEnabled = canBeginLogin
    }

    private func updateCreateButtonEnabled() {
        let isEnabled: Bool

        switch loginState {
        case .failure, .default:
            isEnabled = true

        case .success, .authenticating:
            isEnabled = false
        }

        contentView.createAccountButton.isEnabled = isEnabled
    }

    @discardableResult private func attemptLogin() -> Bool {
        if canBeginLogin {
            doLogin()
            return true
        } else {
            return false
        }
    }
}

/// Private extension that brings localizable messages displayed in the Login view controller
private extension LoginState {
    var localizedTitle: String {
        switch self {
        case .default:
            return NSLocalizedString("Login", comment: "")

        case .authenticating:
            return NSLocalizedString("Logging in...", comment: "")

        case .failure:
            return NSLocalizedString("Login failed", comment: "")

        case .success:
            return NSLocalizedString("Logged in", comment: "")
        }
    }

    var localizedMessage: String {
        switch self {
        case .default:
            return NSLocalizedString("Enter your account number", comment: "")

        case let .authenticating(method):
            switch method {
            case .useExistingAccount:
                return NSLocalizedString("Checking account number", comment: "")
            case .createAccount:
                return NSLocalizedString("Creating account...", comment: "")
            }

        case let .failure(_, error):
            return (error as? DisplayError)?.displayErrorDescription ?? error.localizedDescription

        case let .success(method):
            switch method {
            case .useExistingAccount:
                return NSLocalizedString("Valid account number", comment: "")
            case .createAccount:
                return NSLocalizedString("Account created", comment: "")
            }
        }
    }

    var statusActivityState: StatusActivityView.State {
        switch self {
        case .failure:
            return .failure
        case .success:
            return .success
        case .authenticating:
            return .activity
        case .default:
            return .hidden
        }
    }
}  // swiftlint:disable:this file_length