import UIKit
import Spinnable

class ViewController: UIViewController, Spinnable {
    
    typealias SpinnerType = SpinnerView  // Spinnable requirement: in this typealias, a type substitution takes place that satisfies
                                         // the requirements of the Spinner protocol (an example implementation is given below)
    
    var isLoaded: Bool = false           // Spinnable requirement: this property is an indicator
                                         // of whether data is being loaded at this moment.
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        self.getDataFromNetwork()
    }
    
    private func getDataFromNetwork() {
        self.showSpinner()    // Set a spinner for the duration of a network request
        
        let url = ...
        let task = URLSession.shared.dataTask(with: url) { data, response, error in
            DispatchQueue.main.async {
                // ... Your code for processing data and responce from the server
                self.hideSpinner()  // Hide the spinner when a response is received from the server. We do it ON THE MAIN THREAD
            }
        }
        
        task.resume()
    }
}

public class SpinnerView: Spinner {
    
    public static func preparedSpinner() -> UIView {
        let bg = UIView(frame: .init(x: 0, y: 0, width: 100, height: 100))
        bg.backgroundColor = .clear
        let plate = UIView(frame: .init(x: 0, y: 0, width: 100, height: 100))
        plate.backgroundColor = .systemGray6
        plate.idp_cornerRadius = 10
        let indicator = UIActivityIndicatorView(style: .large)
        
        bg.addSubview(plate)
        plate.addSubview(indicator)
        
        self.addCenteredConstraint(view: plate, superview: bg, heightOffset: -40)
        self.addCenteredConstraint(view: indicator, superview: plate)
        
        indicator.startAnimating()
        
        return bg
    }
    
    private static func addCenteredConstraint(
        view: UIView,
        superview: UIView,
        heightOffset: CGFloat = 0
    ) {
        view.translatesAutoresizingMaskIntoConstraints = false
        let horizontalConstraint = view.centerXAnchor.constraint(equalTo: superview.centerXAnchor)
        let verticalConstraint = view.centerYAnchor.constraint(equalTo: superview.centerYAnchor, constant: heightOffset)
        let widthConstraint = view.widthAnchor.constraint(equalToConstant: 100)
        let heightConstraint = view.heightAnchor.constraint(equalToConstant: 100)
        
        NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint, widthConstraint, heightConstraint])
    }
}