Supabase "Native Apple Sign In" Workaround for Compose Multiplatform

iOSApp.swift

@main
struct iOSApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var delegate
    
    init() {
        // [...]
        SupabaseHelper.shared.setSignInWithApple(factory: { () -> UIViewController in
            let swiftUIView = SignInView()
            return UIHostingController(rootView: swiftUIView)
        })
    }
}

iosMain-SignInOptions.ios.kt

@OptIn(ExperimentalForeignApi::class)
@Composable
actual fun SignInOptions(eventSink: (AuthScreenEvent) -> Unit) {
    UIKitViewController(
        factory = SupabaseHelper.signInWithApple,
        modifier = Modifier.fillMaxWidth().height(40.dp)
    )
}

iosMain-SupabaseHelper.kt

@Suppress("unused") // Called from Swift
object SupabaseHelper : KoinComponent {

    var signInWithApple: () -> UIViewController = { throw NotImplementedError() }


    fun setSignInWithApple(factory: () -> UIViewController) {
        signInWithApple = factory
    }

    fun importSession(
        accessToken: String,
        refreshToken: String,
        providerRefreshToken: String? = null,
        providerToken: String? = null,
        expiresIn: Long,
        tokenType: String,
        type: String = "",
        aud: String,
        id: String
    ) {
        val supabase = getKoin().get<SupabaseClient>()
        val session = UserSession(
            accessToken = accessToken,
            refreshToken = refreshToken,
            providerRefreshToken = providerRefreshToken,
            providerToken = providerToken,
            expiresIn = expiresIn,
            tokenType = tokenType,
            user = UserInfo(aud = aud, id = id),
            type = type,
        )
        CoroutineScope(Dispatchers.IO).launch {
            supabase.auth.importSession(session = session)
        }
    }
}

SignInOptions.kt

@Composable
expect fun SignInOptions(eventSink: (AuthScreenEvent) -> Unit)

SignInView.swift

import Foundation
import SwiftUI
import Supabase
import AuthenticationServices
import ComposeApp

struct SignInView: View {
    let client = SupabaseClient(supabaseURL: URL(string: "url")!, supabaseKey: "key")

    var body: some View {
      SignInWithAppleButton { request in
        request.requestedScopes = [.email, .fullName]
      } onCompletion: { result in
        Task {
          do {
            guard let credential = try result.get().credential as? ASAuthorizationAppleIDCredential
            else {
              return
            }

            guard let idToken = credential.identityToken
              .flatMap({ String(data: $0, encoding: .utf8) })
            else {
              return
            }
              let session = try await client.auth.signInWithIdToken(
                credentials: .init(
                    provider: .apple,
                    idToken: idToken
                )
              )
              
              Dependencies.shared.importSession(accessToken: session.accessToken,
                                                refreshToken: session.refreshToken,
                                                providerRefreshToken: session.providerRefreshToken,
                                                providerToken: session.providerToken,
                                                expiresIn: Int64(session.expiresIn),
                                                tokenType: session.tokenType,
                                                type: session.tokenType,
                                                aud: session.user.aud,
                                                id: session.user.id.uuidString
                                            )
              dump(session)
          } catch {
            dump(error)
          }
        }
      }
    }
}