Update the checkout amount

val originalAmount = 45.99
val tipPercent = 0.15
val totalAmount = originalAmount + (originalAmount * tipPercent)  // 52.89
val totalAmountString = "%.2f".format(totalAmount)               // "52.89"

// Get the execution ID from the active session
val executionId = session.query(PayrailsQuery.ExecutionId)

// Call your own backend endpoint, which in turn calls the Payrails lookup action
myApiClient.updateExecutionAmount(
    executionId = executionId,
    amount = totalAmountString,
    currency = "EUR"
)

POST /v1/merchant/executions/{executionId}/lookup
{
  "amount": {
    "value": "52.89",
    "currency": "EUR"
  }
}

session.update(
    PayrailsUpdate(
        amount = AmountUpdate(
            value = totalAmountString,
            currency = "EUR"
        )
    )
)

cardPaymentButton.pay()

@Composable
fun CheckoutScreen(session: Session, myApiClient: MyApiClient) {
    val scope = rememberCoroutineScope()
    var selectedTipPercent by remember { mutableStateOf(0.0) }
    var isUpdatingAmount by remember { mutableStateOf(false) }
    val baseAmount = 45.99
    val executionId = remember { session.query(PayrailsQuery.ExecutionId) }

    val cardPaymentButton = remember {
        Payrails.createCardPaymentButton(
            translations = CardPaymenButtonTranslations(label = "Pay")
        )
    }

    Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
        // Tip selector
        Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
            listOf(0.0, 0.10, 0.15, 0.20).forEach { tip ->
                Button(
                    enabled = !isUpdatingAmount,
                    onClick = {
                        scope.launch {
                            isUpdatingAmount = true
                            val total = baseAmount + (baseAmount * tip)
                            val totalString = "%.2f".format(total)

                            // Step 1: update the execution on your backend first
                            myApiClient.updateExecutionAmount(
                                executionId = executionId,
                                amount = totalString,
                                currency = "EUR"
                            )

                            // Step 2: update the SDK with the same amount
                            session.update(
                                PayrailsUpdate(
                                    amount = AmountUpdate(
                                        value = totalString,
                                        currency = "EUR"
                                    )
                                )
                            )

                            selectedTipPercent = tip
                            isUpdatingAmount = false
                        }
                    }
                ) {
                    Text(if (tip == 0.0) "No tip" else "${(tip * 100).toInt()}%")
                }
            }
        }

        cardPaymentButton.Render()
    }
}