deltachat-ios/deltachat-ios/Controller/HelpViewController.swift

import UIKit
import WebKit

class HelpViewController: WebViewViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        self.title = String.localized("menu_help")
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        loadHtmlContent { [weak self] url in
            // return to main thread
            DispatchQueue.main.async {
                self?.webView.loadFileURL(url, allowingReadAccessTo: url)
            }
        }
    }

    private func loadHtmlContent(completionHandler: ((URL) -> Void)?) {
        // execute in background thread because file loading would blockui for a few milliseconds
        DispatchQueue.global(qos: .background).async {
            let lang = Utils.getDeviceLanguage() ?? "en" // en is backup
            var fileURL: URL?

            fileURL = Bundle.main.url(forResource: "help", withExtension: "html", subdirectory: "Assets/Help/\(lang)") ??
                Bundle.main.url(forResource: "help", withExtension: "html", subdirectory: "Assets/Help/en")

            guard let url = fileURL else {
                safe_fatalError("could not find help asset")
                return
            }
            completionHandler?(url)
        }
    }
}