Swift remastered minimal snap carousel View

SnapCarousel.swift

//
//  SnapCarousel.swift
//  Spontanea
//
//  Created by  Alex Dremov on 10.08.2021.
//

import Foundation
import SwiftUI

struct Card: Decodable, Hashable, Identifiable {
    var id: Int
    var name: String = ""
}

struct SnapCarousel: View {
    @State var state = CarouselState()
    
    var body: some View {
        let items = [
            Card(id: 0, name: "Hey"),
            Card(id: 1, name: "Ho"),
            Card(id: 2, name: "Lets"),
            Card(id: 3, name: "Go")
        ]
        let width = UIConfig.screenWidth
        state.cardsNum = items.count
        return Carousel(cardWidth: width,
                        state: $state){
            ForEach(items, id:\.id) { item in
                Text(item.name)
                    .padding()
                    .background(Color.black)
                    .foregroundColor(Color.white)
                    .cornerRadius(8)
                    .shadow(color: Color.black, radius: 4, x: 0, y: 4)
                    .frame(width: width, height: 100, alignment: .center)
                    .transition(AnyTransition.slide)
                    .animation(.spring())
            }
        }
    }
}


public class CarouselState: ObservableObject {
    @Published var cardsNum: Int = 0
    @Published var activeCard: Int = 0
}

struct Carousel<Content : View>: View {
    @State var offset: CGFloat = 0
    @Binding var state: CarouselState
    @State var screenDrag: Float = 0.0
    var onSnap: ()->() = {}
    
    let cardWidth: CGFloat
    let items: Content
    
    @inline(__always) func updateOffset() {
        self.offset = self.cardWidth * CGFloat(self.state.activeCard) + CGFloat(self.screenDrag)
    }
    
    @inline(__always) func updateOffset(_ loc: Int) {
        self.offset = self.cardWidth * CGFloat(loc) + CGFloat(self.screenDrag)
    }
    
    @inlinable public init(
        cardWidth: CGFloat,
        state: Binding<CarouselState>,
        onSnap: @escaping ()->() = {},
        @ViewBuilder items: () -> Content) {
        self.items = items()
        self.cardWidth = cardWidth
        self._state = state
        self.onSnap = onSnap
    }
    
    var body: some View {
        return Group{
            HStack(alignment: .center, spacing: 0) {
                items
                    .frame(minWidth: 0,
                           maxWidth: .infinity,
                           alignment: .leading)
            }
            .frame(width: cardWidth * CGFloat(state.cardsNum), alignment: .leading)
        }
        .offset(x: -offset + CGFloat(screenDrag), y: 0)
        .frame(width: cardWidth, alignment: .leading)
        .contentShape(Rectangle())
        .simultaneousGesture(DragGesture(minimumDistance: 0)
                    .onChanged { currentState in
                        self.screenDrag = Float(currentState.translation.width)
                    }.onEnded { value in
                        self.screenDrag = 0
                        if self.state.cardsNum != 0 {
                            if (value.translation.width < -50) {
                                self.state.activeCard = (self.state.activeCard + 1)  % self.state.cardsNum
                                onSnap()
                            }
                            
                            if (value.translation.width > 50) {
                                self.state.activeCard = (self.state.cardsNum +  self.state.activeCard - 1) % self.state.cardsNum
                                onSnap()
                            }
                        }
                    })
        .onReceive(state.$activeCard, perform: { activeCard in
            updateOffset(activeCard)
        })
        .onReceive(state.$cardsNum, perform: { activeCard in
            updateOffset(activeCard)
        })
        
    }
}

struct SnapCarousel_Previews: PreviewProvider {
    static var previews: some View {
        SnapCarousel()
        
    }
}