Example of a local-version request code for Stripe.confirmSetupIntent

AddCardUseCase.kt

// AddCardUseCase designed to be injected into any view-layer presenter, 
// regardless of whether it is an activity or fragemnt. In our case, we are
// injecting this AddCardUseCase into two fragments, possibly contained in the same Activity
class AddCardUseCase(
    private val accountRepo: accountRepository,
    private val setupIntentRelay: SetupIntentRelay,
    private val stripeManager: StripeManager,
    private val containingActivity: Activity // <- injected here just for demonstration
) {
  
  fun addCard(params: PaymentMethodCreateParams): Flow<AddCardState> {
    val confirmSetupIntentId = UUID.randomUUID().toString()    
    
    accountRepository.createSetupIntentFromOurBackend(accountRepo.userId)
      .flatmapLatest { setupIntent ->
    
        val confirmParams = ConfirmSetupIntentParams.create(params, setupIntent.clientSecret)
                      
        stripe.confirmSetupIntent(
          containingActivity = Activity,
          confirmSetupIntentParams = confirmParams, 
          clientRequestCode = confirmSetupIntentId // <- I wish I could have a local-version request code
        )
                      
        return@flatMapLatest setupIntentRelay.setupIntentResultFlow()
          .filter{ codeToPaymentIntentState: Pair<String, SetupIntentState> ->
             codeToSetupIntentState.first == confirmSetupIntentId
          }.take(1)
      }.flatMapLatest { codeToSetupIntentState: Pair<String, SetupIntentState> ->
         when (val state = codeToSetupIntentState.second) {
           PaymentIntentState.Success -> {
             accountRepository.addCreditCardToUserInOurBackend(
               state.second.setupIntent,
             )
           }
           else -> throw IllegalStateException()
         }
      }
     .catch { t ->
         emit(AddCreditCartState.Error(t))
     }
  }
}

class ContainingActivity: Activity {
  
  @Inject lateinit var setupIntentRelay: SetupIntentRelay

  override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    val weakActivity = WeakReference<Activity>(this)

    // Handle the result of stripe.confirmSetup
    stripe.onSetupResult(requestCode, data, object : ApiResultCallback<SetupIntentResult> {
        override fun onSuccess(result: SetupIntentResult) {
            val setupIntent = result.intent
            val clientRequestCode = result.clientRequestCode // <- Having this returned by the result means that I can completly decouple stripe from my UI logic
            val status = paymentIntent.status
            if (status == StripeIntent.Status.Succeeded) {
                setupIntentRelay.postToSetupIntentResultFlow(
                  clientRequestCode to SetupIntentState.Success(paymentIntent)
                )
            } else if (status == StripeIntent.Status.RequiresPaymentMethod) {
                setupIntentRelay.postToSetupIntentResultFlow(
                  clientRequestCode to SetupIntentState.Error(IllegalStateException(
                    "Payment failed", paymentIntent.lastPaymentError?.message ?: ""
                  )
                )
            }
        }

        override fun onError(e: Exception) {
            setupIntentRelay.postToSetupIntentResultFlow(
                  clientRequestCode to SetupIntentState.Error(e)
            )
        }
    })
}

}

sealed class SetupIntentState {
  data class Error(val t: Throwable): SetupIntentState()
  data class Success(val paymentIntent: PaymentIntent): SetupIntentState()
}

data class SetupIntent(
    val stripeSetupIntentId: String,
    val clientSecret: String
)