Fix for translator not initializing in time on ScanBarcodeScreen for …

…when the scanned barcode arrives hence leading to an incorrect state:

When we start the ScanBarcodeScreen we immediately launch the Google ML Lib’s camera app. Which moves focus away from our app and also this camera app consumes a lot of the CPU. Because of that the ‘init translators’ code that happens in parallel, which involves a bunch of back-n-forth with WebView where translator JS is running sometimes doesn’t have enough time to finish hence the translator is not actually ready when you scan barcode.
It happens intermittently because some devices are fast enough to init the translators and some are too slow, also it depends on how quick you are at pointing the camera at the barcode.
So the fix is to queue up all of the scanned barcodes until the translators are initialized and then pass them to the translator.

Upping versionCode to 69.

app/src/main/java/org/zotero/android/architecture/core/StateEventStream.kt

@@ -3,16 +3,23 @@ package org.zotero.android.architecture.core
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
 import org.zotero.android.architecture.coroutines.ApplicationScope
 
 open class StateEventStream<T>(private val applicationScope: ApplicationScope, initValue: T?) {
 
-    private val sharedFlow = MutableStateFlow<T?>(initValue)
+    private val sharedFlow = MutableStateFlow(initValue)
 
     fun emit(update: T?) {
         sharedFlow.tryEmit(update)
     }
 
+    fun emitAsync(update: T) {
+        applicationScope.launch {
+            sharedFlow.emit(update)
+        }
+    }
+
     fun flow(): StateFlow<T?> = sharedFlow.asStateFlow()
 
     fun currentValue(): T? {

app/src/main/java/org/zotero/android/screens/scanbarcode/ScanBarcodeViewModel.kt

@@ -4,6 +4,7 @@ import android.content.Context
 import androidx.lifecycle.viewModelScope
 import com.google.mlkit.vision.codescanner.GmsBarcodeScanning
 import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.filter
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
@@ -22,22 +23,28 @@ import org.zotero.android.sync.LibraryIdentifier
 import org.zotero.android.sync.SchemaController
 import org.zotero.android.uicomponents.Strings
 import org.zotero.android.uicomponents.addbyidentifier.IdentifierLookupController
+import org.zotero.android.uicomponents.addbyidentifier.TranslatorLoadedEventStream
 import org.zotero.android.uicomponents.addbyidentifier.data.LookupRow
 import org.zotero.android.uicomponents.addbyidentifier.data.LookupRowItem
 import timber.log.Timber
+import java.util.LinkedList
 import javax.inject.Inject
 
 @HiltViewModel
 internal class ScanBarcodeViewModel @Inject constructor(
     private val fileStore: FileStore,
     private val identifierLookupController: IdentifierLookupController,
     private val attachmentDownloaderEventStream: RemoteAttachmentDownloaderEventStream,
+    private val translatorLoadedEventStream: TranslatorLoadedEventStream,
     private val schemaController: SchemaController,
     private val remoteFileDownloader: RemoteAttachmentDownloader,
     private val context: Context,
 ) : BaseViewModel2<ScanBarcodeViewState, ScanBarcodeViewEffect>(ScanBarcodeViewState()) {
 
+    private val queueOfScannedBarcodes = LinkedList<String>()
+
     fun init() = initOnce {
+        setupTranslatorLoadedObserving()
         setupAttachmentObserving()
         val collectionKeys =
             fileStore.getSelectedCollectionId().keyGet?.let { setOf(it) } ?: emptySet()
@@ -58,7 +65,11 @@ internal class ScanBarcodeViewModel @Inject constructor(
         scanner.startScan()
             .addOnSuccessListener { barcode ->
                 val scannedString = barcode.rawValue ?: ""
-                onLookup(scannedString)
+                if (translatorLoadedEventStream.currentValue() == true) {
+                    onLookup(scannedString)
+                } else {
+                   queueOfScannedBarcodes.add(scannedString)
+                }
             }
             .addOnCanceledListener {
                 triggerEffect(NavigateBack)
@@ -186,6 +197,16 @@ internal class ScanBarcodeViewModel @Inject constructor(
             }.launchIn(viewModelScope)
     }
 
+    private fun setupTranslatorLoadedObserving() {
+        translatorLoadedEventStream.flow()
+            .filter { it == true }
+            .onEach { _ ->
+                queueOfScannedBarcodes.forEach {
+                    onLookup(it)
+                }
+            }.launchIn(viewModelScope)
+    }
+
     private fun updateLookupState(lookupState: State) {
         updateState {
             copy(lookupState = lookupState)

app/src/main/java/org/zotero/android/screens/scanbarcode/ui/ScanBarcodeScreen.kt

@@ -69,13 +69,30 @@ internal fun ScanBarcodeScreen(
                     .background(color = CustomTheme.colors.zoteroItemDetailSectionBackground)
                     .padding(horizontal = 16.dp)
             ) {
-                scanBarcodeTable(rows = viewState.lookupRows)
-                if (viewState.lookupState == State.loadingIdentifiers ) {
+                if (viewState.lookupState == State.waitingInput) {
                     scanBarcodeLoadingIndicator()
+                    item {
+                        Spacer(modifier = Modifier.height(20.dp))
+                        Row(
+                            modifier = Modifier.fillMaxWidth(),
+                            horizontalArrangement = Arrangement.Center
+                        ) {
+                            Text(
+                                text = stringResource(id = Strings.loading_translators),
+                                style = CustomTheme.typography.newBody,
+                                color = CustomTheme.colors.primaryContent,
+                            )
+                        }
+                    }
+                } else {
+                    scanBarcodeTable(rows = viewState.lookupRows)
+                    if (viewState.lookupState == State.loadingIdentifiers ) {
+                        scanBarcodeLoadingIndicator()
+                    }
+                    scanBarcodeError(
+                        failedState = viewState.lookupState as? State.failed
+                    )
                 }
-                scanBarcodeError(
-                    failedState = viewState.lookupState as? State.failed
-                )
             }
         }
     }

app/src/main/java/org/zotero/android/uicomponents/addbyidentifier/IdentifierLookupController.kt

@@ -54,6 +54,7 @@ class IdentifierLookupController @Inject constructor(
     private val schemaController: SchemaController,
     private val dbWrapper: DbWrapper,
     private val defaults: Defaults,
+    private val translatorLoadedEventStream: TranslatorLoadedEventStream,
     private val attachmentDownloaderEventStream: RemoteAttachmentDownloaderEventStream,
 ) {
 
@@ -109,6 +110,7 @@ class IdentifierLookupController @Inject constructor(
             translatorsLoader = translatorsLoader,
             fileStore = fileStore,
             noAuthenticationApi = noAuthenticationApi,
+            translatorLoadedEventStream = translatorLoadedEventStream,
         )
         lookupWebViewHandlersByLookupSettings[lookupSettings] = lookupWebViewHandler
         setupObserver(lookupWebViewHandler)

app/src/main/java/org/zotero/android/uicomponents/addbyidentifier/LookupWebCallChainExecutor.kt

@@ -31,7 +31,8 @@ class LookupWebCallChainExecutor(
     private val gson: Gson,
     private val translatorsLoader: TranslatorsLoader,
     private val fileStore: FileStore,
-    private val noAuthenticationApi: NoAuthenticationApi
+    private val noAuthenticationApi: NoAuthenticationApi,
+    private val translatorLoadedEventStream: TranslatorLoadedEventStream,
 ) {
 
     private lateinit var lookupWebViewHandler: LookupWebViewHandler
@@ -166,6 +167,7 @@ class LookupWebCallChainExecutor(
             val translatorsResult =
                 translatorsLoader.translators(null)
             sendInitTranslatorsMessage(translatorsResult)
+            translatorLoadedEventStream.emitAsync(true)
         }
     }
 

app/src/main/java/org/zotero/android/uicomponents/addbyidentifier/TranslatorLoadedEventStream.kt

@@ -0,0 +1,10 @@
+package org.zotero.android.uicomponents.addbyidentifier
+
+import org.zotero.android.architecture.core.StateEventStream
+import org.zotero.android.architecture.coroutines.ApplicationScope
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class TranslatorLoadedEventStream @Inject constructor(applicationScope: ApplicationScope) :
+    StateEventStream<Boolean>(applicationScope = applicationScope, initValue = false)

app/src/main/res/values/strings.xml

@@ -24,4 +24,5 @@
     <string name="queued">Queued…</string>
     <string name="failed">Failed</string>
     <string name="scan_another">Scan Another</string>
+    <string name="loading_translators">Loading translators… Please wait.</string>
 </resources>

buildSrc/src/main/kotlin/BuildConfig.kt

@@ -4,7 +4,7 @@ object BuildConfig {
     const val compileSdkVersion = 34
     const val targetSdk = 33
 
-    val versionCode = 68 // Must be updated on every build
+    val versionCode = 69 // Must be updated on every build
     val version = Version(
         major = 1,
         minor = 0,