import SwiftUI
import FirebaseAuth

/// A class conforming to `ObservableObject` used to represent a user's authentication status.
final class AuthenticationViewModel: ObservableObject {
  /// The user's log in status.
  /// - note: This will publish updates when its value changes.
  @Published var state: State
  private var authenticator: GoogleSignInAuthenticator {
    return GoogleSignInAuthenticator(authViewModel: self)
  }

  /// Creates an instance of this view model.
  init() {
    if let user = Auth.auth().currentUser {
      self.state = .signedIn(user)
    } else {
      self.state = .signedOut
    }
  }

  /// Signs the user in.
  @MainActor func signIn() {
    authenticator.signIn()
  }

  /// Signs the user out.
  func signOut() {
    authenticator.signOut()
  }

}

extension AuthenticationViewModel {
  /// An enumeration representing logged in status.
  enum State {
    /// The user is logged in and is the associated value of this case.
    case signedIn(User)
    /// The user is logged out.
    case signedOut
  }
}