Loader

import Foundation
import UIKit

class Loader {
 
    static var instance: Loader?
    static var isLoading: Bool = false
    var activityIndicator: UIActivityIndicatorView?
    var loaderView: UIView?
    weak var destinationView: UIView?

    init(destinationView: UIView) {
        self.destinationView = destinationView
        Loader.instance = self
    }
    
    static func configureDestinationView(destinationView: UIView) {
        _ = Loader.init(destinationView: destinationView)
    }
    
    static func show() {
        guard let self = Loader.instance, let destinationView = self.destinationView, self.loaderView == nil else { return }
        Loader.show(destinationView: destinationView)
    }
    
    static func show(destinationView: UIView, backgroundColor: UIColor = UIColor.black.withAlphaComponent(0.1), withCenterPercentualOffset centerOffset: Float = 0) {
        guard let self = Loader.instance else { return }
        // Create the main loader view
        if self.loaderView == nil {
            self.loaderView = UIView.init(frame: destinationView.frame)
            guard let loaderView = self.loaderView else { return }
            loaderView.backgroundColor = backgroundColor
        }
        guard let loaderView = self.loaderView else { return }
        
        self.activityIndicator = UIActivityIndicatorView(style: .large)
        
        if let activityIndicator = self.activityIndicator {
            activityIndicator.color = UIColor.lightGray

            let offsetPercent = ((loaderView.frame.size.height/2) * CGFloat(centerOffset)) / 100

            let center = CGPoint.init(x: loaderView.center.x , y: loaderView.center.y + offsetPercent)
            activityIndicator.center = center
            loaderView.addSubview(activityIndicator)
            activityIndicator.startAnimating()
        }
        
        isLoading = true
        destinationView.addSubview(loaderView)
    }

    static func hide() {
        // Remove the loadView to free up memory
        guard Thread.isMainThread else {
            DispatchQueue.main.async {
                self.hide()
            }
            return
        }
        
        guard let self = Loader.instance else { return }

        DispatchQueue.main.async {
            self.activityIndicator?.stopAnimating()
            self.activityIndicator?.removeFromSuperview()
            self.loaderView?.removeFromSuperview()
            self.loaderView = nil
            isLoading = false
        }
    }
    
}