CardDeck.swift

struct Card : Identifiable {
    var id = UUID()
    var imageName: String
}

struct CardView: View {
    
    var card: Card
    
    var body: some View {
        return ZStack(alignment: .top) {
            Image(card.imageName)
                .resizable()
                .renderingMode(.original)
        }
        .cornerRadius(20)
    }
}

struct CardDeckView: View {
    
    @State var cards: [Card] = []
    
    @State var dragOffset: CGSize = .zero
    @State var isMoving = false
    
    var body: some View {
        ZStack(alignment: .center) {
            ForEach(cards) { card in
                CardView(card: card)
                    // General Appearance
                    .zIndex(Double(self.cards.count - 1) - Double(self.order(for: card)))
                    .scaleEffect((self.isMoving && self.order(for: card) != 0) ? 0.92 - CGFloat(self.order(for: card)-1) * 0.1:0.92 - CGFloat(self.order(for: card)) * 0.1)
                    .offset(x: 0, y: (self.isMoving && self.order(for: card) != 0) ? -CGFloat(self.order(for: card)-1) * 30.0:-CGFloat(self.order(for: card)) * 30.0)
                    .opacity((self.isMoving && self.order(for: card) != 0) ? 1 - Double(self.order(for: card)-1) * 0.3:1 - Double(self.order(for: card)) * 0.3)
                    
                    // Animations
                    .offset(x: self.order(for: card) == 0 ? self.dragOffset.width : 0, y: self.order(for: card) == 0 ? self.dragOffset.height: 0)
                    .animation(.fluidSpring(stiffness: 90, dampingFraction: 0.5))
                    
                    // Gesture
                    .gesture(DragGesture()
                        .onChanged({ value in
                            self.dragOffset = value.translation
                            self.isMoving = true
                        })
                        .onEnded({ _ in
                            if self.dragOffset.width < -200 {
                                self.sendToBack(self.cards[0])
                            } else if self.dragOffset.width > 200 {
                                self.sendToBack(self.cards[0])
                            } else {
                                self.dragOffset = .zero
                            }
                            self.isMoving = false
                        })
                )
            }
        }
        .offset(x: 0, y: 10)
    }
    
    private func order(for card: Card) -> Int {
        return cards.firstIndex(where: { $0.id == card.id })!
    }
    
    private func sendToBack(_ card: Card) {
        guard let idx = cards.firstIndex(where: { $0.id == card.id }) else { return }
        
        var mutablecards = cards
        let mutablecard = card
        
        mutablecards.remove(at: idx)
        mutablecards.append(mutablecard)
        
        cards = mutablecards
        self.dragOffset = .zero
    }
}