//
//  ContentView.swift
//  Shared
//
//  Created by Costantino Pistagna on 25/03/21.
//

import SwiftUI

struct ContentView: View {
    var body: some View {
        GeometryReader { geometry in
            ScrollView(.horizontal) {
                TabView {
                    SplashPageView(iconName: "paperplane.circle.fill",
                                   title: "Welcome to",
                                   subtitle: "Super SplashScreen")
                    SplashPageView(iconName: "leaf.fill",
                                   title: "We will make",
                                   subtitle: "Great things")
                    SplashPageView(iconName: "link.badge.plus",
                                   title: "Let's start",
                                   subtitle: "With a touch")
                }.tabViewStyle(PageTabViewStyle())
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

struct SplashPageView: View {
    var iconName: String
    var title: String
    var subtitle: String
    @State private var currentOffset:CGFloat = 0.0
    var body: some View {
        VStack {
            Spacer()
            Image(systemName: iconName)
                .renderingMode(.original)
                .resizable()
                .frame(width: 100, height: 100, alignment: .center)
                .padding(.vertical, 20)
                .offset(x: currentOffset)
                .animation(currentOffset == 0 ? .none : .easeInOut)
            Text(title)
                .font(.title2)
                .padding(10)
                .offset(x: currentOffset * 0.9)
                .animation(currentOffset == 0 ? .none : .easeInOut)
            Text(subtitle)
                .font(.title)
                .offset(x: currentOffset * 0.8)
                .animation(currentOffset == 0 ? .none : .easeInOut)
            Spacer()
        }
        .frame(width: UIScreen.main.bounds.size.width, alignment: .center)
        .readFrame(onChange: { (newFrame) in
            print(currentOffset)
            currentOffset = newFrame.origin.x
        })
    }
}

//Based on Sharing layout information in SwiftUI
//https://fivestars.blog/swiftui/swiftui-share-layout-information.html
extension View {
    func readSize(onChange: @escaping (CGSize) -> Void) -> some View {
        background(
            GeometryReader { geometryProxy in
                Color.clear
                    .preference(key: SizePreferenceKey.self, value: geometryProxy.size)
            }
        )
        .onPreferenceChange(SizePreferenceKey.self, perform: onChange)
    }
    
    func readFrame(onChange: @escaping (CGRect) -> Void) -> some View {
        background(
            GeometryReader { geometryProxy in
                Color.clear
                    .preference(key: RectPreferenceKey.self, value: geometryProxy.frame(in: CoordinateSpace.global))
            }
        )
        .onPreferenceChange(RectPreferenceKey.self, perform: onChange)
    }
}
private struct SizePreferenceKey: PreferenceKey {
    static var defaultValue: CGSize = .zero
    static func reduce(value: inout CGSize, nextValue: () -> CGSize) {}
}
private struct RectPreferenceKey: PreferenceKey {
    static var defaultValue: CGRect = .zero
    static func reduce(value: inout CGRect, nextValue: () -> CGRect) {}
}