//  Created by Marlon Monroy on 5/19/18.
//  Copyright © 2018 Monroy.io All rights reserved.
//

import Foundation
import UIKit
import Dispatch

protocol Shimmerable {
	func start(count: Int) -> Void
	func stop() -> Void
	var lightColor: UIColor {get set}
	var darkColor: UIColor {get set}
	var isShimmering: Bool {get}
}

extension UIView: Shimmerable {

	private struct ShimmerProperties {
		static let shimmerKey:String = "io.monroy.shimmer.key"
		static var lightColor:CGColor = UIColor.white.withAlphaComponent(0.1).cgColor
		static var darkColor:CGColor = UIColor.black.withAlphaComponent(1).cgColor
		static var isShimmering:Bool = false
		static var gradient:CAGradientLayer = CAGradientLayer()
		static var animation:CABasicAnimation = CABasicAnimation(keyPath: "locations")
	}
	var lightColor: UIColor {
		get {
			return UIColor(cgColor: ShimmerProperties.lightColor)
		}
		set {
			ShimmerProperties.lightColor = newValue.cgColor
		}
	}
	var darkColor: UIColor {
		get {
			return UIColor(cgColor: ShimmerProperties.darkColor)
		}
		set {
			ShimmerProperties.darkColor = newValue.cgColor
		}
	}

	var isShimmering: Bool {
		get {
			return ShimmerProperties.isShimmering
		}
	}

	func stop() {
		guard ShimmerProperties.isShimmering else {return}
		self.layer.mask?.removeAnimation(forKey: ShimmerProperties.shimmerKey)
		self.layer.mask = nil
		ShimmerProperties.isShimmering = false
		self.layer.setNeedsDisplay()
	}

	func start(count: Int = 3) {
		guard !ShimmerProperties.isShimmering else {return}

		CATransaction.begin()
		CATransaction.setCompletionBlock({
			self.stop()
		})

		ShimmerProperties.isShimmering = true

		ShimmerProperties.gradient.colors = [ShimmerProperties.darkColor, ShimmerProperties.lightColor, ShimmerProperties.darkColor];
		ShimmerProperties.gradient.frame = CGRect(x: CGFloat(-2*self.bounds.size.width), y: CGFloat(0.0), width: CGFloat(4*self.bounds.size.width), height: CGFloat(self.bounds.size.height))
		ShimmerProperties.gradient.startPoint = CGPoint(x: Double(0.0), y: Double(0.5));
		ShimmerProperties.gradient.endPoint = CGPoint(x: Double(1.0), y: Double(0.5));
		ShimmerProperties.gradient.locations = [0.4, 0.5, 0.6];

		ShimmerProperties.animation.duration = 1.0
		ShimmerProperties.animation.repeatCount = (count > 0) ? Float(count) : .infinity
		ShimmerProperties.animation.fromValue = [0.0, 0.12, 0.3]
		ShimmerProperties.animation.toValue = [0.6, 0.86, 1.0]

		ShimmerProperties.gradient.add(ShimmerProperties.animation, forKey: ShimmerProperties.shimmerKey)
		self.layer.mask = ShimmerProperties.gradient;

		CATransaction.commit()
	}
}