Rework billing client integration.

billing/src/main/java/org/signal/billing/BillingApiImpl.kt

@@ -22,20 +22,14 @@ import com.android.billingclient.api.QueryProductDetailsParams
 import com.android.billingclient.api.QueryPurchasesParams
 import com.android.billingclient.api.queryProductDetails
 import com.android.billingclient.api.queryPurchasesAsync
-import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.asCoroutineDispatcher
-import kotlinx.coroutines.cancel
-import kotlinx.coroutines.channels.awaitClose
-import kotlinx.coroutines.channels.trySendBlocking
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.callbackFlow
 import kotlinx.coroutines.flow.filter
 import kotlinx.coroutines.flow.first
-import kotlinx.coroutines.flow.retry
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
@@ -75,6 +69,7 @@ internal class BillingApiImpl(
 
   private val connectionState = MutableStateFlow<State>(State.Init)
   private val coroutineScope = CoroutineScope(Dispatchers.Default)
+  private val connectionStateDispatcher = Executors.newSingleThreadExecutor().asCoroutineDispatcher()
 
   private val internalResults = MutableSharedFlow<BillingPurchaseResult>()
 
@@ -102,49 +97,61 @@ internal class BillingApiImpl(
           }
         }
       }
+
       BillingResponseCode.BILLING_UNAVAILABLE -> {
         Log.d(TAG, "purchasesUpdatedListener: Billing unavailable.")
         BillingPurchaseResult.BillingUnavailable
       }
+
       BillingResponseCode.USER_CANCELED -> {
         Log.d(TAG, "purchasesUpdatedListener: User cancelled.")
         BillingPurchaseResult.UserCancelled
       }
+
       BillingResponseCode.ERROR -> {
         Log.d(TAG, "purchasesUpdatedListener: error.")
         BillingPurchaseResult.GenericError
       }
+
       BillingResponseCode.NETWORK_ERROR -> {
         Log.d(TAG, "purchasesUpdatedListener: Network error.")
         BillingPurchaseResult.NetworkError
       }
+
       BillingResponseCode.DEVELOPER_ERROR -> {
         Log.d(TAG, "purchasesUpdatedListener: Developer error.")
         BillingPurchaseResult.GenericError
       }
+
       BillingResponseCode.FEATURE_NOT_SUPPORTED -> {
         Log.d(TAG, "purchasesUpdatedListener: Feature not supported.")
         BillingPurchaseResult.FeatureNotSupported
       }
+
       BillingResponseCode.ITEM_ALREADY_OWNED -> {
         Log.d(TAG, "purchasesUpdatedListener: Already owned.")
         BillingPurchaseResult.AlreadySubscribed
       }
+
       BillingResponseCode.ITEM_NOT_OWNED -> {
         error("This shouldn't happen during the purchase process")
       }
+
       BillingResponseCode.ITEM_UNAVAILABLE -> {
         Log.d(TAG, "purchasesUpdatedListener: Item is unavailable")
         BillingPurchaseResult.TryAgainLater
       }
+
       BillingResponseCode.SERVICE_UNAVAILABLE -> {
         Log.d(TAG, "purchasesUpdatedListener: Service is unavailable.")
         BillingPurchaseResult.TryAgainLater
       }
+
       BillingResponseCode.SERVICE_DISCONNECTED -> {
         Log.d(TAG, "purchasesUpdatedListener: Service is disconnected.")
         BillingPurchaseResult.TryAgainLater
       }
+
       else -> {
         Log.d(TAG, "purchasesUpdatedListener: No purchases.")
         BillingPurchaseResult.None
@@ -163,19 +170,6 @@ internal class BillingApiImpl(
     )
     .build()
 
-  init {
-    coroutineScope.launch {
-      createConnectionFlow()
-        .retry { it is RetryException }
-        .collect { newState ->
-          Log.d(TAG, "Updating Google Play Billing connection state: $newState", true)
-          connectionState.update {
-            newState
-          }
-        }
-    }
-  }
-
   override fun getBillingPurchaseResults(): Flow<BillingPurchaseResult> {
     return internalResults
   }
@@ -318,6 +312,7 @@ internal class BillingApiImpl(
 
   private suspend fun <T> doOnConnectionReady(caller: String, block: suspend () -> T): T {
     Log.d(TAG, "Awaiting connection from $caller... (current state: ${connectionState.value})", true)
+    startBillingClientConnectionIfNecessary()
 
     val state = connectionState
       .filter { it == State.Connected || it is State.Failure }
@@ -331,37 +326,59 @@ internal class BillingApiImpl(
     }
   }
 
-  private fun createConnectionFlow(): Flow<State> {
-    return callbackFlow {
-      Log.d(TAG, "Starting Google Play Billing connection...", true)
-      send(State.Connecting)
-
-      billingClient.startConnection(object : BillingClientStateListener {
-        override fun onBillingServiceDisconnected() {
-          Log.d(TAG, "Google Play Billing became disconnected.", true)
-          trySendBlocking(State.Disconnected)
-          cancel(CancellationException("Google Play Billing became disconnected.", RetryException()))
-        }
-
-        override fun onBillingSetupFinished(billingResult: BillingResult) {
-          Log.d(TAG, "onBillingSetupFinished: ${billingResult.responseCode}", true)
-          if (billingResult.responseCode == BillingResponseCode.OK) {
-            Log.d(TAG, "Google Play Billing is ready.", true)
-            trySendBlocking(State.Connected)
-          } else {
-            Log.d(TAG, "Google Play Billing failed to connect.", true)
-            val billingError = BillingError(
-              billingResponseCode = billingResult.responseCode
+  private suspend fun startBillingClientConnectionIfNecessary() {
+    withContext(connectionStateDispatcher) {
+      val billingConnectionState = billingClient.connectionState
+      when (billingConnectionState) {
+        BillingClient.ConnectionState.DISCONNECTED -> {
+          Log.d(TAG, "BillingClient is disconnected. Starting connection attempt.", true)
+          connectionState.update { State.Connecting }
+          billingClient.startConnection(
+            BillingListener(
+              onStateUpdate = { new ->
+                connectionState.update { old ->
+                  Log.d(TAG, "Moving from state $old -> $new", true)
+                  new
+                }
+              }
             )
-            trySendBlocking(State.Failure(billingError))
-            channel.close()
-          }
+          )
         }
-      })
 
-      awaitClose {
-        Log.d(TAG, "Ending Google Play Billing connection.", true)
-        billingClient.endConnection()
+        BillingClient.ConnectionState.CONNECTING -> {
+          Log.d(TAG, "BillingClient is already connecting. Nothing to do.", true)
+        }
+
+        BillingClient.ConnectionState.CONNECTED -> {
+          Log.d(TAG, "BillingClient is already connected. Nothing to do.", true)
+        }
+
+        BillingClient.ConnectionState.CLOSED -> {
+          Log.w(TAG, "BillingClient was permanently closed. Cannot proceed.", true)
+        }
+      }
+    }
+  }
+
+  private class BillingListener(
+    private val onStateUpdate: (State) -> Unit
+  ) : BillingClientStateListener {
+    override fun onBillingServiceDisconnected() {
+      Log.d(TAG, "BillingListener#onBillingServiceDisconnected", true)
+      onStateUpdate(State.Disconnected)
+    }
+
+    override fun onBillingSetupFinished(billingResult: BillingResult) {
+      Log.d(TAG, "BillingListener#onBillingSetupFinished: ${billingResult.responseCode}", true)
+      if (billingResult.responseCode == BillingResponseCode.OK) {
+        Log.d(TAG, "BillingListener#onBillingSetupFinished: ready", true)
+        onStateUpdate(State.Connected)
+      } else {
+        Log.d(TAG, "BillingListener#onBillingSetupFinished: failure", true)
+        val billingError = BillingError(
+          billingResponseCode = billingResult.responseCode
+        )
+        onStateUpdate(State.Failure(billingError))
       }
     }
   }