import SwiftUI
#if canImport(UIKit)
  import UIKit
#endif

public extension View {
  func applyTheme(_ theme: Theme) -> some View {
    modifier(ThemeApplier(theme: theme))
  }
}

struct ThemeApplier: ViewModifier {
  @ObservedObject var theme: Theme

  func body(content: Content) -> some View {
    content
      .tint(theme.tintColor)
      .preferredColorScheme(theme.selectedScheme == ColorScheme.dark ? .dark : .light)
    #if canImport(UIKit)
      .onAppear {
        setWindowTint(theme.tintColor)
        setWindowUserInterfaceStyle(theme.selectedScheme)
        setBarsColor(theme.primaryBackgroundColor)
      }
      .onChange(of: theme.tintColor) { newValue in
        setWindowTint(newValue)
      }
      .onChange(of: theme.selectedScheme) { newValue in
        setWindowUserInterfaceStyle(newValue)
      }
      .onChange(of: theme.primaryBackgroundColor) { newValue in
        setBarsColor(newValue)
      }
    #endif
  }

  #if canImport(UIKit)
    private func setWindowUserInterfaceStyle(_ colorScheme: ColorScheme) {
      allWindows()
        .forEach {
          switch colorScheme {
          case .dark:
            $0.overrideUserInterfaceStyle = .dark
          case .light:
            $0.overrideUserInterfaceStyle = .light
          }
        }
    }

    private func setWindowTint(_ color: Color) {
      allWindows()
        .forEach {
          $0.tintColor = UIColor(color)
        }
    }

    private func setBarsColor(_ color: Color) {
      UINavigationBar.appearance().isTranslucent = true
      UINavigationBar.appearance().barTintColor = UIColor(color)
    }

    private func allWindows() -> [UIWindow] {
      UIApplication.shared.connectedScenes
        .compactMap { $0 as? UIWindowScene }
        .flatMap { $0.windows }
    }
  #endif
}