// Start a new project
//	Add a UILabel and UIButton to the default view controller
//	connect the label to countLabel @IBOutlet
//	connect the button to doFetch @IBAction
//
// each tap of the button will call fetch() in LoginManager.shared
//	and use a 1-second delay to simulate fetching data from an API

class ViewController: UIViewController {
	
	@IBOutlet var countLabel: UILabel!
	
	override func viewDidLoad() {
		super.viewDidLoad()
		
		// set the "callback" closure in LoginManager
		LoginManager.shared.callback = { [weak self] str in
			// safely unwrap self
			guard let self = self else { return }
			// we have to update UI elements on the main thread
			DispatchQueue.main.async {
				// set the returned str to countLabel's text
				self.countLabel.text = str
			}
		}
	}
	@IBAction func doFetch(_ sender: Any) {
		countLabel.text = "Calling API..."
		LoginManager.shared.fetch()
	}
	
}

class LoginManager {
	
	static let shared = LoginManager()
	
	// counter var
	var myCounter: Int = 0
	
	// closure for communication
	var callback: ((String) -> ())?
	
	func fetch() -> Void {
		// increment the counter
		myCounter += 1
		// 1-second delay to simulate getting data from API
		DispatchQueue.global(qos: .userInitiated).asyncAfter(deadline: .now() + 1, execute: {
			// get a random number from 1 to 9999
			let n = Int.random(in: 1...9999)
			// use the closure to send it back as a string
			self.callback?("API Count: \(self.myCounter) Random: \(n)")
		})
	}
	
}