WelcomeViewController.swift

import UIKit


class WelcomeViewController: UIViewController {

  override func loadView() {
    let view = UIView(frame: .zero)
    view.backgroundColor = .systemBackground

    let title = makeTitleLabel()
    let subtitle = makeSubtitleLabel()

    let buttonHeight: CGFloat = 48
    let buttonSpacing: CGFloat = 4

    let createDefaultCatalog = makeCreateDefaultCatalogButton()
    createDefaultCatalog.addTarget(
      self,
      action: #selector(didTapCreateDefaultAction(_:)),
      for: .touchUpInside
    )

    let restoreCatalog = makeRestoreCatalogButton()
    restoreCatalog.addTarget(
      self,
      action: #selector(didTapRestoreCatalog),
      for: .touchUpInside
    )

    let skipCatalogConfiguration = makeSkipCatalogConfigurationButton()
    skipCatalogConfiguration.addTarget(
      self,
      action: #selector(didTapSkipCatalogConfiguration(_:)),
      for: .touchUpInside
    )

    let actionsStack =
      UIStackView(
        arrangedSubviews: [
          skipCatalogConfiguration,
          restoreCatalog,
          createDefaultCatalog
        ]
      )

    actionsStack.axis = .vertical
    actionsStack.spacing = buttonSpacing
    actionsStack.distribution = .fillEqually

    view.addSubview(title)
    title.translatesAutoresizingMaskIntoConstraints = false

    view.addSubview(subtitle)
    subtitle.translatesAutoresizingMaskIntoConstraints = false

    view.addSubview(actionsStack)
    actionsStack.translatesAutoresizingMaskIntoConstraints = false

    let actionsCount = actionsStack.arrangedSubviews.count
    let actionsStackHeight =
      CGFloat(actionsCount) * buttonHeight +
        CGFloat(actionsCount - 1) * buttonSpacing

    NSLayoutConstraint.activate([
      title.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 24),
      title.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 16),
      title.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -16),

      subtitle.topAnchor.constraint(equalTo: title.lastBaselineAnchor, constant: 12),
      subtitle.leadingAnchor.constraint(equalTo: title.leadingAnchor),
      subtitle.trailingAnchor.constraint(equalTo: title.trailingAnchor),

      actionsStack.leadingAnchor.constraint(equalTo: title.leadingAnchor),
      actionsStack.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -16),
      actionsStack.trailingAnchor.constraint(equalTo: title.trailingAnchor),
      actionsStack.heightAnchor.constraint(equalToConstant: actionsStackHeight)
    ])

    self.view = view
  }

  @objc private func didTapCreateDefaultAction(_ sender: Any) {
    state.didTapCreateDefaultCatalog(self)
  }

  @objc private func didTapRestoreCatalog(_ sender: Any) {
    state.didTapRestoreCatalog(self)
  }

  @objc private func didTapSkipCatalogConfiguration(_ sender: Any) {

  }

  fileprivate var state: WelcomeViewControllerState =
    IdleWelcomeViewControllerState()

  fileprivate enum Action {
    case createDefaultCatalog
    case restoreCatalog
  }

  fileprivate func disableActionsAnimating(action: Action) {

  }

  fileprivate func createDefaultCatalog() {
    // defaultCatalogCreator.createDefaultCatalog(completion: {
    //   self.state.didCreateDefaultCatalog()
    // })

    state.didCreateDefaultCatalog(self)
  }

  fileprivate func restoreCatalog() {
    // catalogRestorer.restoreCatalog(completion: {
    //   self.state.didRestoreCatalog()
    // })

    state.didRestoreCatalog(self)
  }

  fileprivate func enableActionsStoppingAnimation(action: Action) {

  }

  fileprivate func finish() {
    // delegate?.fooViewControllerDidFinish(self)
  }
}

// MARK: - State Management

class WelcomeViewControllerState {
  func didTapCreateDefaultCatalog(_ controller: StateBasedWelcomeViewController) { }
  func didTapRestoreCatalog(      _ controller: StateBasedWelcomeViewController) { }
  func didCreateDefaultCatalog(   _ controller: StateBasedWelcomeViewController) { }
  func didRestoreCatalog(         _ controller: StateBasedWelcomeViewController) { }
}


class IdleWelcomeViewControllerState: WelcomeViewControllerState {

  override func didTapCreateDefaultCatalog(
    _ controller: StateBasedWelcomeViewController
  ) {
    controller.disableActionsAnimating(action: .createDefaultCatalog)
    controller.state = CreatingDefaultCatalogWelcomeViewControllerState()
    controller.createDefaultCatalog()
  }

  override func didTapRestoreCatalog(
    _ controller: StateBasedWelcomeViewController
  ) {
    controller.disableActionsAnimating(action: .restoreCatalog)
    controller.state = CreatingDefaultCatalogWelcomeViewControllerState()
    controller.restoreCatalog()
  }

}


class CreatingDefaultCatalogWelcomeViewControllerState: WelcomeViewControllerState {

  override func didTapCreateDefaultCatalog(
    _ controller: StateBasedWelcomeViewController
  ) {
    controller.state = IdleWelcomeViewControllerState()
    controller.enableActionsStoppingAnimation(action: .createDefaultCatalog)
    controller.finish()
  }

}


class RestoringCatalogWelcomeViewControllerState: WelcomeViewControllerState {

  override func didRestoreCatalog(
    _ controller: StateBasedWelcomeViewController
  ) {
    controller.state = IdleWelcomeViewControllerState()
    controller.enableActionsStoppingAnimation(action: .restoreCatalog)
    controller.finish()
  }

}

// MARK: - Views Making

private func makeTitleLabel() -> UILabel {
  let result = UILabel(frame: .zero)
  result.text = NSLocalizedString("Добро пожаловать!", comment: "")

  result.font =
    UIFont(
      descriptor: .preferredFontDescriptor(withTextStyle: .largeTitle),
      size: 24.0
    )

  result.numberOfLines = 1

  return result
}

private func makeSubtitleLabel() -> UILabel {
  let result = UILabel(frame: .zero)
  result.text =
    NSLocalizedString(
      "Хотите ли вы создать каталог товаров для покупки по-умолчанию? Это упрощает начало работы.\n\nОднако, если вы уже пользовались приложением и имеете резервную копию приложения, то можете восстановить её сейчас.\n\nЕсли же вы не готовы сейчас принять решение, то вы всегда можете создать дефолтный каталог или восстановить его из резервной копии в iCloud в настройках приложения.",
      comment: ""
    )

  result.font =
    UIFont(
      descriptor: .preferredFontDescriptor(withTextStyle: .body),
      size: 15.0
    )

  result.numberOfLines = 0

  return result
}

private func makeCreateDefaultCatalogButton() -> UIButton {
  let result =
    makeActionButton(
      title: NSLocalizedString("Создать по-умолчанию", comment: "")
    )

  return result
}

private func makeRestoreCatalogButton() -> UIButton {
  let result =
    makeActionButton(
      title: NSLocalizedString("Восстановить из резервной копии", comment: "")
    )

  return result
}

private func makeSkipCatalogConfigurationButton() -> UIButton {
  let result =
    makeActionButton(
      title: NSLocalizedString("Пропустить сейчас", comment: "")
    )

  return result
}

private func makeActionButton(title: String) -> UIButton {
  let result = UIButton(type: .system)

  result.layer.cornerRadius = 8
  result.setTitle(title, for: .normal)

  return result
}