Toast.swift

//
//  Toast.swift
//  IOS17-Swift
//
//  Created by xqsadness on 18/12/2023.
//

import SwiftUI

// Root view for creating overlay window
struct RootView<Content: View>: View {
    @ViewBuilder var content: Content
    // View Properties
    @State private var overlayWindow: UIWindow?
    
    var body: some View {
        content
            .onAppear {
                if let windowScene = UIApplication.shared.connectedScenes.first as? UIWindowScene, overlayWindow == nil {
                    let window = PassthroughWindow (windowScene: windowScene)
                    window.backgroundColor = .clear
                    // View Controller
                    let rootController = UIHostingController(rootView: ToastGroup())
                    rootController.view.frame = windowScene.keyWindow?.frame ?? .zero
                    rootController.view.backgroundColor = .clear
                    window.rootViewController = rootController
                    
                    window.isHidden = false
                    window.isUserInteractionEnabled = true
                    window.tag = 1009
                    
                    overlayWindow = window
                }
            }
    }
}

fileprivate class PassthroughWindow: UIWindow {
    override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        guard let view = super.hitTest (point, with: event) else { return nil}
        
        return rootViewController?.view == view ? nil : view
    }
}

@Observable
class Toast {
    static let shared = Toast()
    fileprivate var toasts: [ToastItem] = []
    var position: Position = .bottom
    
    func present(title: String, symbol: String?, tint: Color = .primary, isUserInteractionEnabled: Bool = false, timing: ToastTime = .medium, position: Position){
        self.position = position
        withAnimation(.snappy) {
            toasts.append(ToastItem(title: title, symbol: symbol, tint: tint, isUserInteractionEnabled: isUserInteractionEnabled, timing: timing))
        }
    }
}

struct ToastItem: Identifiable {
    let id: UUID = .init()
    /// Custom Properties
    var title: String
    var symbol: String?
    var tint: Color
    var isUserInteractionEnabled: Bool
    /// Timing
    var timing: ToastTime = .medium
}

enum ToastTime: CGFloat {
    case short = 1.0
    case medium = 2.0
    case long = 3.5
}

fileprivate struct ToastGroup: View {
    var model = Toast.shared
    
    var body: some View {
        GeometryReader{
            let size = $0.size
            let safeArea = $0.safeAreaInsets
            
            ZStack{
                ForEach(model.toasts){ toast in
                    ToastView(size: size, item: toast)
                        .scaleEffect(scale(toast))
                        .offset(y: offsetY(toast))
                        .zIndex(Double(model.toasts.firstIndex(where: { $0.id == toast.id }) ?? 0))
                }
            }
            .padding(model.position == .bottom ? .bottom : .top, safeArea.top == .zero ? 15 : 10)
            .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: model.position == .bottom ? .bottom : .top)
        }
    }
    
    func offsetY(_ item: ToastItem) -> CGFloat{
        let index = CGFloat(model.toasts.firstIndex(where: { $0.id == item.id }) ?? 0)
        let totalCount = CGFloat(model.toasts.count) - 1
        return (totalCount - index) >= 2 ? -20 : ((totalCount - index) * -10)
    }
    
    func scale(_ item: ToastItem) -> CGFloat{
        let index = CGFloat(model.toasts.firstIndex(where: { $0.id == item.id }) ?? 0)
        let totalCount = CGFloat(model.toasts.count) - 1
        return 1.0 - ((totalCount - index) >= 2 ? 0.2 : ((totalCount - index) * 0.1))
    }
}

fileprivate struct ToastView: View {
    var size: CGSize
    var item: ToastItem
    var model = Toast.shared
    //View props
    @State private var delayTask: DispatchWorkItem?
    
    var body: some View {
        HStack(spacing: 0){
            if let symbol = item.symbol{
                Image(systemName: symbol)
                    .font(.title3)
                    .padding(.trailing, 10)
            }
            
            Text(item.title)
                .lineLimit(1)
        }
        .foregroundStyle(item.tint)
        .padding(.horizontal, 15)
        .padding(.vertical, 8)
        .background(
            .background
                .shadow(.drop(color: .primary.opacity(0.06), radius: 5,x: 5, y: 5))
                .shadow(.drop(color: .primary.opacity(0.06), radius: 5,x: -5, y: -5)), in: .capsule
        )
        .contentShape(Capsule())
        .gesture(
            DragGesture(minimumDistance: 0)
                .onEnded({ value in
                    guard item.isUserInteractionEnabled else { return }
                    let endY = value.translation.height
                    let velocityY = value.velocity.height
                    
                    if model.position == .bottom{
                        if (endY + velocityY) > 100{
                            // Removing toast
                            removeToast()
                        }
                    }else{
                        if (endY + velocityY) < 100{
                            // Removing toast
                            removeToast()
                        }
                    }
                    
                })
        )
        .onAppear{
            guard delayTask == nil else { return }
            
            delayTask = .init(block: {
                removeToast()
            })
            
            if let delayTask{
                DispatchQueue.main.asyncAfter(deadline: .now() + item.timing.rawValue, execute: delayTask)
            }
        }
        //Limiting size
        .frame(maxWidth: size.width * 0.7)
        .transition(.offset(y: model.position == .bottom ? 150 : -150))
    }
    
    func removeToast(){
        if let delayTask{
            delayTask.cancel()
        }
        print("dismiss")
        withAnimation(.snappy){
            Toast.shared.toasts.removeAll(where: { $0.id == item.id })
        }
    }
}

#Preview{
    RootView{
        ContentView()
    }
}

enum Position{
    case top
    case bottom
}