//
//  DragView.swift
//  SwiftUIDemo
//
//  Created by shiyanjun on 2023/2/12.
//

import SwiftUI

struct DragView: View {
    @State private var location: CGPoint = CGPoint(x: 50, y: 50)
    @GestureState private var fingerLocation: CGPoint? = nil
    @GestureState private var startLocation: CGPoint? = nil // 1
    
    var simpleDrag: some Gesture {
        DragGesture()
            .onChanged { value in
                var newLocation = startLocation ?? location // 3
                newLocation.x += value.translation.width
                newLocation.y += value.translation.height
                self.location = newLocation
            }.updating($startLocation) { (value, startLocation, transaction) in
                startLocation = startLocation ?? location // 2
            }
    }
    
    var fingerDrag: some Gesture {
        DragGesture()
            .updating($fingerLocation) { (value, fingerLocation, transaction) in
                fingerLocation = value.location
            }
    }
    
    var body: some View {
        VStack {
            ZStack {
                RoundedRectangle(cornerRadius: 10)
                    .foregroundColor(.pink)
                    .frame(width: 100, height: 100)
                    .position(location)
                    .gesture(
                        simpleDrag.simultaneously(with: fingerDrag)
                    )
                if let fingerLocation = fingerLocation {
                    Circle()
                        .stroke(Color.green, lineWidth: 2)
                        .frame(width: 44, height: 44)
                        .position(fingerLocation)
                }
            }
            HStack {
                Text("X:\(String(format: "%0.f", location.x))")
                    .foregroundColor(.indigo)
                    .font(.system(.largeTitle, design: .rounded))
                Text("Y:\(String(format: "%0.f", location.y))")
                    .foregroundColor(.indigo)
                    .font(.system(.largeTitle, design: .rounded))
            }
        }
    }
}

struct DragView_Previews: PreviewProvider {
    static var previews: some View {
        DragView()
    }
}