RefreshableScrollView.swift

import SwiftUI

public struct RefreshableScrollView<Content, Value>: View where Content: View {
    private let content: () -> Content
    private let action: () async -> Value

    init(@ViewBuilder content:  @escaping () -> Content, action: @escaping () async -> Value) {
        self.content = content
        self.action = action
    }

    @State var startY: Double = Double.greatestFiniteMagnitude
    @State var isLoading = false

    @State var value: Value?

    public var body: some View {
        ScrollView {
            GeometryReader { geometry in
                HStack {
                    Spacer()
                    ProgressView()
                        .opacity(calculate(offset: geometry.frame(in: .global).minY))
                        .padding(.top, -30)
                        .transition(.move(edge: .top))
                        .onChange(of: geometry.frame(in: .global), perform: { frame in
                            if !hasReachedThreshold(frame.minY) && isLoading && value != nil {
                                isLoading = false
                                return
                            }
                            guard hasReachedThreshold(frame.minY), !isLoading else { return }
                            self.isLoading = true
                            let feedback = UIImpactFeedbackGenerator(style: .light)
                            feedback.prepare()
                            feedback.impactOccurred()
                            Task.init(priority: .userInitiated, operation: {
                                self.value = await action()
                            })
                        })
                    Spacer()
                }
                .onAppear {
                    startY = geometry.frame(in: .global).minY
                }
            }
            content()
        }
    }

    private func hasReachedThreshold(_ offset: CGFloat) -> Bool {
        calculate(offset: offset) == 1
    }

    private func calculate(offset: CGFloat) -> CGFloat {
        min((offset - startY) / 30 + 1, 1.0)
    }
}