//
//  ContentView.swift
//  StackOverflowSwitUI
//
//  Created by V15a1 on 2021-07-08.
//

import SwiftUI

struct ContentView: View {

    @State var didScrollUp: Bool = false
    var body: some View {
        NavigationView {
            ScrollView {
                ZStack {
                    VStack(alignment:.leading) {
                        VStack {
                            TagLineView(isHStacked: $didScrollUp.animation())
                        }
                        .padding()
                        ZStack(alignment:.leading) {
                            Color(#colorLiteral(red: 0.937254902, green: 0.937254902, blue: 0.937254902, alpha: 1))
                                .edgesIgnoringSafeArea(.all)
                                .cornerRadius(30.0)
                            VStack(alignment: .leading) {
                                Text("Popular")
                                    .font(.custom("PlayfairDisplay-Bold", size: 24))
                                    .padding(.leading,27)
                                    .padding(.top,20)

                                ScrollView (.horizontal, showsIndicators: false) {
                                    LazyVStack {
                                        ForEach(0..<100) { x in
                                            Text("\(x): Cell")
                                                .frame(width: 200)
                                        }
                                    }
                                }
                                .padding(.bottom)

                            }


                        }

                    }.background(GeometryReader {
                        Color.clear.preference(key: ViewOffsetKey.self,
                                               value: -$0.frame(in: .named("scroll")).origin.y)
                    })
                    .onPreferenceChange(ViewOffsetKey.self) { didScrollUp = $0 > 5 ? true : false }
                }

            }
            .coordinateSpace(name: "scroll")
        }

    }
}

struct ViewOffsetKey: PreferenceKey {
    typealias Value = CGFloat
    static var defaultValue = CGFloat.zero
    static func reduce(value: inout Value, nextValue: () -> Value) {
        value += nextValue()
    }
}


struct TagLineView: View {

    @Binding var isHStacked: Bool

    var body: some View {
        Text("Hello")
            .font(.title)
            .fontWeight(.bold) + Text(isHStacked ? " " : "\n") +  // Adding a newline or adding a space based on the orientation of the stack
            Text("Welcome!")
            .font(.title)
    }
}