facade1.swift

import UIKit

class MarkdownPreviewViewController: UIViewController {
    @IBOutlet weak var markdownTextView: UITextView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        Task {
            await prepareMarkdown(from: "https://www.awesomemarkdownsource.com")
        }
    }
}

extension MarkdownPreviewViewController {
    func prepareMarkdown(from url: String) async {
        do {
            let markdownFromWebService = try await fetchMarkdownData(url: url)
            let parsedMarkdown = parseMarkdownData(rawMarkdown: markdownFromWebService)
            let cachedMarkdown = cacheMarkdownData(parsedMarkdown: parsedMarkdown)
            showMarkdownData(in: markdownTextView, markdown: cachedMarkdown)
        } catch {
            print(error.localizedDescription)
        }
        
    }
}

private extension MarkdownPreviewViewController {
    struct MarkdownParser {
        static func parse(markdown: String) -> String { markdown }
    }
    
    struct MarkdownCacher {
        @discardableResult static func cache(markdown: String) -> String { markdown }
    }
    
    func fetchMarkdownData(url urlString: String) async throws -> String {
        let url = URL(string: urlString)!
        let (data, _) = try await URLSession.shared.data(from: url)
        let downloadedMarkdownData = String(data: data, encoding: .utf8) ?? ""
        return downloadedMarkdownData
    }
    
    func parseMarkdownData(rawMarkdown markdown: String) -> String {
        print(".......parsed")
        return MarkdownParser.parse(markdown: markdown)
    }
    
    func cacheMarkdownData(parsedMarkdown markdown: String) -> String {
        print(".......cached")
        return MarkdownCacher.cache(markdown: markdown)
    }
    
    func showMarkdownData(in uiElement: UITextView, markdown markdownToShow: String) {
        uiElement.text = markdownToShow
    }
}