A facade which provides an implementation of a billing manager depending on whether in-app billing via PlayStore is available

BillingManagerProvider.kt

import android.content.Context
import android.util.Log
import com.android.billingclient.api.BillingClient
import com.android.billingclient.api.BillingClientStateListener
import com.android.billingclient.api.Purchase
import com.wacom.cloud.billing.manager.BillingManagerAliPay
import com.wacom.cloud.billing.manager.BillingManagerPlayStore
import kotlinx.coroutines.experimental.Dispatchers
import kotlinx.coroutines.experimental.withContext
import kotlin.coroutines.experimental.suspendCoroutine

object BillingManagerProvider {
    private val TAG by lazy { BillingManagerProvider::class.java.simpleName }
    private const val DEBUG = false

    /**
     * Returns PlayStore billing manager (if available) or falls back to
     * the AliPay implementation
     */
    suspend fun get(context: Context): BillingManagerInterface {
        return withContext(Dispatchers.Main) {
            return@withContext if (!isPlayStoreAvailable(context)) {
                BillingManagerAliPay(context)
            } else {
                BillingManagerPlayStore(context)
            }
        }
    }

    /**
     * Possible responses (also tested in China):
     * 0 - [com.android.billingclient.api.BillingClient.BillingResponse.OK]
     * 3 - [com.android.billingclient.api.BillingClient.BillingResponse.BILLING_UNAVAILABLE]
     */
    private suspend fun isPlayStoreAvailable(context: Context): Boolean =
            suspendCoroutine { cont ->
                if (DEBUG) {
                    Log.d(TAG, "suspendCoroutine: startConnection")
                }
                val billingClient: BillingClient = BillingClient.newBuilder(context)
                        .setListener { _: Int, _: MutableList<Purchase>? -> }.build()
                billingClient.startConnection(
                        object : BillingClientStateListener {
                            override fun onBillingSetupFinished(responseCode: Int) {
                                if (DEBUG) {
                                    Log.d(TAG, "onBillingSetupFinished = $responseCode")
                                }
                                cont.resume(responseCode == BillingClient.BillingResponse.OK)
                                billingClient.endConnection()
                            }

                            override fun onBillingServiceDisconnected() {
                                if (DEBUG) {
                                    Log.d(TAG, "onBillingServiceDisconnected")
                                }
                                cont.resume(false)
                                billingClient.endConnection()
                            }
                        })
            }
}