import SwiftUI

@propertyWrapper public final class Store<Value, Action>: DynamicViewProperty, BindingConvertible {

  public let update: (inout Value, Action) -> Void
  public private(set) var value: Value

  public var binding: Binding<Value> {
    Binding<Value>(
      getValue: { self.value },
      setValue: { self.value = $0 }
    )
  }

  public init(_ initialValue: Value, _ update: @escaping (inout Value, Action) -> Void) {
    self.update = update
    self.value = initialValue
  }
}

enum Action {
  case increment
  case decrement
}

func update(_ state: inout Int, _ action: Action) {
  switch action {
  case .increment:
    state += 1
  case .decrement:
    state -= 1
  }
}

struct ContentView : View {
  @Store(0, update) var store

  var body: some View {
    Text("Hello World")
  }
}

#if DEBUG
struct ContentView_Previews : PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}
#endif