Sunset.swift

import SwiftUI
import UIKit

struct Sunset: View {
	@State var backgroundColor = Color.blue
	@State var sunSetted = false
	
	let skyGradientDay = [Color(#colorLiteral(red: 0.2196078449, green: 0.007843137719, blue: 0.8549019694, alpha: 1)), Color(#colorLiteral(red: 0.2392156869, green: 0.6745098233, blue: 0.9686274529, alpha: 1)), Color(#colorLiteral(red: 0.6254054655, green: 0.9221722869, blue: 0.9686274529, alpha: 1)), Color(#colorLiteral(red: 0.8345658875, green: 0.9221722869, blue: 0.9686274529, alpha: 1))]
	let skyGradientNight = [Color(#colorLiteral(red: 0.2196078449, green: 0.007843137719, blue: 0.4246178452, alpha: 1)), Color(#colorLiteral(red: 0.8078431487, green: 0.02745098062, blue: 0.7072513187, alpha: 1)), Color(#colorLiteral(red: 0.8078431487, green: 0.02745098062, blue: 0.3333333433, alpha: 1)), Color(#colorLiteral(red: 0.8078431487, green: 0.2959635248, blue: 0.6193262317, alpha: 1))]
	
	let sunGradient = [Color.yellow, Color.orange]
	let moonGradient = [Color(#colorLiteral(red: 0.5463274121, green: 0.04594885558, blue: 0.2291798294, alpha: 1)), Color(#colorLiteral(red: 0.5668596029, green: 0.1581864655, blue: 0.4246562719, alpha: 1))]
	@State var alignment = Alignment.top
	
	var body: some View {
		ZStack(alignment: alignment) {
			ZStack {
				Sun(gradient: sunGradient)
				Sun(gradient: moonGradient)
					.opacity(self.sunSetted ? 1 : 0)
			}
			
			GeometryReader { geometry in
				VStack {
					Spacer()
					Blur(style: .systemUltraThinMaterial)
						.frame(height: geometry.size.height / 2)
				}
			}
		}
		.background (
			ZStack {
				Sky(gradient: skyGradientDay)
				Sky(gradient: skyGradientNight)
					.opacity(self.sunSetted ? 1 : 0)
		   }
		)
		.onAppear {
			withAnimation(Animation.linear(duration: 12).repeatForever(autoreverses: true)) {
				self.sunset()
			}
		}
	}
	
	func sunset() {
		backgroundColor = .black
		sunSetted = true
		alignment = .bottom
	}
}

struct Sky: View {
	@State var gradient: [Color]
	
	var body: some View {
	LinearGradient(gradient: Gradient(colors: gradient), startPoint: .top, endPoint: .bottom)
	}
	
}

struct Sun: View {
	@State var gradient: [Color]
	
	var body: some View {
		Circle()
			.fill(
				LinearGradient(gradient: Gradient(colors: gradient), startPoint: .top, endPoint: .bottom)
			)
			.frame(width: 192, height: 192)
			.padding()
	}
}

struct Blur: UIViewRepresentable {
	var style: UIBlurEffect.Style
	
	func makeUIView(context: Context) -> UIVisualEffectView {
		return UIVisualEffectView(effect: UIBlurEffect(style: style))
	}
	
	func updateUIView(_ uiView: UIVisualEffectView, context: Context) {
		uiView.effect = UIBlurEffect(style: style)
	}
}

struct Sunset_Previews: PreviewProvider {
	static var previews: some View {
		Sunset()
			.previewLayout(PreviewLayout.sizeThatFits)
	}
}