import Combine
import SwiftUI

struct RoundedBackground: ViewModifier {
    private let color: Color

    init(color: Color = Color("CapsuleColor")) {
        self.color = color
    }

    func body(content: Content) -> some View {
        content
            .padding()
            .background(
                RoundedRectangle(cornerRadius: 8, style: .continuous)
                    .fill()
                    .foregroundColor(color)
            )
    }
}

struct CapsulaBackground: ViewModifier {
    private let color: Color

    init(color: Color = Color("CapsuleColor")) {
        self.color = color
    }

    func body(content: Content) -> some View {
        content
            .padding()
            .background(
                Capsule()
                    .fill()
                    .foregroundColor(color)
            )
    }
}

struct Link<T>: ViewModifier where T: View {
    private let destination: T
    init(destination: T) {
        self.destination = destination
    }

    func body(content: Content) -> some View {
        ZStack {
            NavigationLink(destination: destination) {
                EmptyView()
            }.hidden()
            content
        }
    }
}

struct AdaptsToSoftwareKeyboard: ViewModifier {
    @State var currentHeight: CGFloat = 0

    func body(content: Content) -> some View {
        content
            .padding(.bottom, currentHeight).animation(.easeOut(duration: 0.25))
            .edgesIgnoringSafeArea(currentHeight == 0 ? Edge.Set() : .bottom)
            .onAppear(perform: subscribeToKeyboardChanges)
    }

    private let keyboardHeightOnOpening = NotificationCenter.default
        .publisher(for: UIResponder.keyboardWillShowNotification)
        .map { $0.userInfo![UIResponder.keyboardFrameEndUserInfoKey] as! CGRect }
        .map(\.height)

    private let keyboardHeightOnHiding = NotificationCenter.default
        .publisher(for: UIResponder.keyboardWillHideNotification)
        .map { _ in CGFloat(0) }

    private func subscribeToKeyboardChanges() {
        _ = Publishers.Merge(keyboardHeightOnOpening, keyboardHeightOnHiding)
            .subscribe(on: DispatchQueue.main)
            .sink { height in
                if self.currentHeight == 0 || height == 0 {
                    self.currentHeight = height
                }
            }
    }
}

extension View {
    func roundedBackground() -> some View {
        modifier(RoundedBackground())
    }

    func buttonBackground() -> some View {
        modifier(RoundedBackground(color: .accentColor))
    }

    func navigationLink<V: BaseView>(to screen: Screen, from view: V) -> some View {
        modifier(Link(destination: view.viewModel.view(for: screen)))
    }

    func adaptsToSoftwareKeyboard() -> some View {
        modifier(AdaptsToSoftwareKeyboard())
    }

    func modal<V: BaseView>(for screen: Screen?, from view: V) -> some View {
        onTapGesture {
            view.viewModel.showModal(for: screen)
        }
    }

    func asAny() -> AnyView { .init(self) }
}