element-ios/Tools/Templates/buildable/ScreenTemplate/TemplateScreenViewController.swift

/*
Copyright 2021-2024 New Vector Ltd.

SPDX-License-Identifier: AGPL-3.0-only
Please see LICENSE in the repository root for full details.
 */

import UIKit

final class TemplateScreenViewController: UIViewController {
    
    // MARK: - Constants
    
    private enum Constants {
        static let aConstant: Int = 666
    }
    
    // MARK: - Properties
    
    // MARK: Outlets

    @IBOutlet private weak var scrollView: UIScrollView!
    
    @IBOutlet private weak var informationLabel: UILabel!
    @IBOutlet private weak var doneButton: UIButton!
    
    // MARK: Private

    private var viewModel: TemplateScreenViewModelProtocol!
    private var theme: Theme!
    private var keyboardAvoider: KeyboardAvoider?
    private var errorPresenter: MXKErrorPresentation!
    private var activityPresenter: ActivityIndicatorPresenter!

    // MARK: - Setup
    
    class func instantiate(with viewModel: TemplateScreenViewModelProtocol) -> TemplateScreenViewController {
        let viewController = StoryboardScene.TemplateScreenViewController.initialScene.instantiate()
        viewController.viewModel = viewModel
        viewController.theme = ThemeService.shared().theme
        return viewController
    }
    
    // MARK: - Life cycle
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Do any additional setup after loading the view.
        
        self.setupViews()
        self.keyboardAvoider = KeyboardAvoider(scrollViewContainerView: self.view, scrollView: self.scrollView)
        self.activityPresenter = ActivityIndicatorPresenter()
        self.errorPresenter = MXKErrorAlertPresentation()
        
        self.registerThemeServiceDidChangeThemeNotification()
        self.update(theme: self.theme)
        
        self.viewModel.viewDelegate = self

        self.viewModel.process(viewAction: .loadData)
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        self.keyboardAvoider?.startAvoiding()
    }
    
    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        
        self.keyboardAvoider?.stopAvoiding()
    }
    
    override var preferredStatusBarStyle: UIStatusBarStyle {
        return self.theme.statusBarStyle
    }
    
    // MARK: - Private
    
    private func update(theme: Theme) {
        self.theme = theme
        
        self.view.backgroundColor = theme.headerBackgroundColor
        
        if let navigationBar = self.navigationController?.navigationBar {
            theme.applyStyle(onNavigationBar: navigationBar)
        }


        // TODO: Set view colors here
        self.informationLabel.textColor = theme.textPrimaryColor

        self.doneButton.backgroundColor = theme.backgroundColor
        theme.applyStyle(onButton: self.doneButton)
    }
    
    private func registerThemeServiceDidChangeThemeNotification() {
        NotificationCenter.default.addObserver(self, selector: #selector(themeDidChange), name: .themeServiceDidChangeTheme, object: nil)
    }
    
    @objc private func themeDidChange() {
        self.update(theme: ThemeService.shared().theme)
    }
    
    private func setupViews() {
        let cancelBarButtonItem = MXKBarButtonItem(title: VectorL10n.cancel, style: .plain) { [weak self] in
            self?.cancelButtonAction()
        }
        
        self.navigationItem.rightBarButtonItem = cancelBarButtonItem
        
        self.title = "Template"
        
        self.scrollView.keyboardDismissMode = .interactive
        
        self.informationLabel.text = "VectorL10n.templateScreenTitle"
    }

    private func render(viewState: TemplateScreenViewState) {
        switch viewState {
        case .idle:
            break
        case .loading:
            self.renderLoading()
        case .loaded(let displayName):
            self.renderLoaded(displayName: displayName)
        case .error(let error):
            self.render(error: error)
        }
    }
    
    private func renderLoading() {
        self.activityPresenter.presentActivityIndicator(on: self.view, animated: true)
        self.informationLabel.text = "Fetch display name"
    }
    
    private func renderLoaded(displayName: String) {
        self.activityPresenter.removeCurrentActivityIndicator(animated: true)

        self.informationLabel.text = "You display name: \(displayName)"
    }
    
    private func render(error: Error) {
        self.activityPresenter.removeCurrentActivityIndicator(animated: true)
        self.errorPresenter.presentError(from: self, forError: error, animated: true, handler: nil)
    }

    
    // MARK: - Actions

    @IBAction private func doneButtonAction(_ sender: Any) {
        self.viewModel.process(viewAction: .complete)
    }

    private func cancelButtonAction() {
        self.viewModel.process(viewAction: .cancel)
    }
}


// MARK: - TemplateScreenViewModelViewDelegate
extension TemplateScreenViewController: TemplateScreenViewModelViewDelegate {

    func templateScreenViewModel(_ viewModel: TemplateScreenViewModelProtocol, didUpdateViewState viewSate: TemplateScreenViewState) {
        self.render(viewState: viewSate)
    }
}