TabPanelParallaxEffect

//
//  ContentView.swift
//
//  Carousel with Parallax Effect SwiftUI
//  Created by Igor Shelopaev on 10.08.2022.
//

import SwiftUI
import Combine

struct ContentView: View {
    
    @State private var selected = 0
    
    @State private var current: Int = 0
    
    @State private  var opacity: CGFloat = 1
    
    private let pass: PassthroughSubject<Void, Never>
    
    private let publisher: AnyPublisher<Void, Never>
    
    private let lenght : CGFloat = 0.5
    
    // MARK: - Life circle
    
    init() {
        
        let pass = PassthroughSubject<Void, Never>()
        publisher = pass.delay(for: .seconds(lenght), scheduler: RunLoop.main, options: .none)
            .eraseToAnyPublisher()
        
        self.pass = pass
    }
    
    var body: some View {
        ZStack { tabTpl }
        .background(blurBg)
        .onChange(of: selected, perform: onChange)
        .onReceive(publisher, perform: onReceive)
        .preferredColorScheme(.dark)
    }
    
    // MARK: - Private
    
    private var blurBg : some View{
        GeometryReader { _ in
            Image("w\(selected + 1)")
                .resizable()
                .scaledToFill()
                .blur(radius: 25)
                .scaleEffect(1.1)
            Image("w\(current + 1)")
                .resizable()
                .scaledToFill()
                .blur(radius: 25)
                .scaleEffect(1.1)
                .opacity(opacity)
        }
    }
    
    private var tabTpl : some View{
        TabView(selection: $selected) {
            ForEach(1..<6) { index in
                GeometryReader { proxy in
                    let minX = proxy.frame(in: .global).minX
                    ZStack { Color.clear }
                        .background(
                            Image("w\(index)")
                                .resizable()
                                .scaledToFill()
                                .offset(x: -minX / 2)
                                .opacity(0.9)
                        )
                        .mask(RoundedRectangle(cornerRadius: 32, style: .continuous))
                    
                }.padding(.horizontal)
            }
        }
        .tabViewStyle(.page(indexDisplayMode: .always))
        .shadow(color: .black.opacity(0.25), radius: 5, x: 5, y: 50)
        .shadow(color: .black.opacity(0.15), radius: 5, x: 5, y: -5)
    }
    
    private func onChange(selected : Int) {
        withAnimation(.linear(duration: lenght)) {
            opacity = 0
        }
        pass.send()
    }
    
   private func onReceive(){
        withAnimation(.linear(duration: lenght)) {
            current = selected
            opacity = 1
        }
    }
    
}