fun launchBillingFlow()

in TrivialDriveKotlin/app/src/main/java/com/sample/android/trivialdrivesample/billing/BillingDataSource.kt [628:666]
39 lines of code
3 McCabe index (conditional complexity)

    fun launchBillingFlow(activity: Activity?, sku: String, vararg upgradeSkusVarargs: String) {
        val skuDetails = skuDetailsMap[sku]?.value
        if (null != skuDetails) {
            val billingFlowParamsBuilder = BillingFlowParams.newBuilder()
            billingFlowParamsBuilder.setSkuDetails(skuDetails)
            val upgradeSkus = arrayOf(*upgradeSkusVarargs)
            defaultScope.launch {
                val heldSubscriptions = getPurchases(upgradeSkus, BillingClient.SkuType.SUBS)
                when (heldSubscriptions.size) {
                    1 -> {
                        val purchase = heldSubscriptions[0]
                        billingFlowParamsBuilder.setSubscriptionUpdateParams(
                                BillingFlowParams.SubscriptionUpdateParams.newBuilder()
                                        .setOldSkuPurchaseToken(purchase.purchaseToken)
                                        .build()
                        )
                    }
                    0 -> {
                    }
                    else -> Log.e(
                            TAG,
                            heldSubscriptions.size.toString() +
                                    " subscriptions subscribed to. Upgrade not possible."
                    )
                }
                val br = billingClient.launchBillingFlow(
                        activity!!,
                        billingFlowParamsBuilder.build()
                )
                if (br.responseCode == BillingClient.BillingResponseCode.OK) {
                    billingFlowInProcess.emit(true)
                } else {
                    Log.e(TAG, "Billing failed: + " + br.debugMessage)
                }
            }
        } else {
            Log.e(TAG, "SkuDetails not found for: $sku")
        }
    }