create language selector class

android/engine/src/main/java/org/smartregister/fhircore/engine/configuration/app/ApplicationConfiguration.kt

@@ -31,6 +31,7 @@ data class ApplicationConfiguration(
   val appTitle: String = "",
   val remoteSyncPageSize: Int = ConfigurationRegistry.DEFAULT_COUNT,
   val languages: List<String> = listOf("en"),
+  val defaultLocale: String = "",
   val useDarkTheme: Boolean = false,
   val syncInterval: Long = 15,
   val syncStrategy: List<SyncStrategy> = listOf(),

android/engine/src/main/java/org/smartregister/fhircore/engine/ui/base/BaseMultiLanguageActivity.kt

@@ -21,10 +21,9 @@
 import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.app.AppCompatDelegate
 import java.lang.UnsupportedOperationException
-import java.util.Locale
 import javax.inject.Inject
-import org.smartregister.fhircore.engine.util.SharedPreferenceKey
-import org.smartregister.fhircore.engine.util.SharedPreferencesHelper
+import org.smartregister.fhircore.engine.configuration.ConfigurationRegistry
+import org.smartregister.fhircore.engine.util.DependenciesHolder
 import org.smartregister.fhircore.engine.util.extension.setAppLocale
 
 /**
@@ -33,7 +32,9 @@
  */
 abstract class BaseMultiLanguageActivity : AppCompatActivity() {
 
-  @Inject lateinit var sharedPreferencesHelper: SharedPreferencesHelper
+  @Inject lateinit var languageSelector: LanguageSelector
+
+  @Inject lateinit var configurationRegistry: ConfigurationRegistry
 
   override fun onCreate(savedInstanceState: Bundle?) {
     inject()
@@ -43,14 +44,12 @@
   }
 
   override fun attachBaseContext(baseContext: Context) {
-    val lang =
-      baseContext
-        .getSharedPreferences(SharedPreferencesHelper.PREFS_NAME, Context.MODE_PRIVATE)
-        .getString(SharedPreferenceKey.LANG.name, Locale.ENGLISH.toLanguageTag())
-        ?: Locale.ENGLISH.toLanguageTag()
-    baseContext.setAppLocale(lang).run {
-      super.attachBaseContext(baseContext)
-      applyOverrideConfiguration(this)
+    val lang = DependenciesHolder.languageSelector?.getDefaultLocale(baseContext)
+    if (lang != null) {
+      baseContext.setAppLocale(lang).run {
+        super.attachBaseContext(baseContext)
+        applyOverrideConfiguration(this)
+      }
     }
   }
 

android/engine/src/main/java/org/smartregister/fhircore/engine/ui/base/LanguageSelector.kt

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2021-2024 Ona Systems, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.smartregister.fhircore.engine.ui.base
+
+import android.content.Context
+import java.util.Locale
+import javax.inject.Inject
+import org.smartregister.fhircore.engine.configuration.ConfigType
+import org.smartregister.fhircore.engine.configuration.ConfigurationRegistry
+import org.smartregister.fhircore.engine.configuration.app.ApplicationConfiguration
+import org.smartregister.fhircore.engine.domain.model.Language
+import org.smartregister.fhircore.engine.util.SharedPreferenceKey
+import org.smartregister.fhircore.engine.util.SharedPreferencesHelper
+import org.smartregister.fhircore.engine.util.extension.fetchLanguages
+
+class LanguageSelector
+@Inject
+constructor(
+  val configurationRegistry: ConfigurationRegistry,
+  val sharedPreferencesHelper: SharedPreferencesHelper
+) {
+  fun getDefaultLocale(baseContext: Context): String {
+    val sharedPrefLocale =
+      baseContext
+        .getSharedPreferences(SharedPreferencesHelper.PREFS_NAME, Context.MODE_PRIVATE)
+        .getString(SharedPreferenceKey.LANG.name, null)
+    val deviceDefaultLocale = Locale.getDefault()
+    val applicationConfiguration =
+      configurationRegistry.retrieveConfiguration<ApplicationConfiguration>(ConfigType.Application)
+    val appConfigDefaultLocale = applicationConfiguration.defaultLocale
+    val firstLocaleInLanguagesList = applicationConfiguration.languages.first()
+
+    val selectedLocale =  when {
+      !sharedPrefLocale.isNullOrBlank() && isLanguageSupported(sharedPrefLocale) -> sharedPrefLocale
+      isLanguageSupported(deviceDefaultLocale.toLanguageTag()) ->
+        deviceDefaultLocale.toLanguageTag()
+      appConfigDefaultLocale.isNotBlank() && isLanguageSupported(appConfigDefaultLocale) ->
+        appConfigDefaultLocale
+      else -> firstLocaleInLanguagesList
+    }
+    sharedPreferencesHelper.write(SharedPreferenceKey.LANG.name, selectedLocale)
+    return selectedLocale
+  }
+
+  private fun isLanguageSupported(lang: String): Boolean {
+    val locale = Locale.forLanguageTag(lang)
+    val language = Language(lang, locale.displayName)
+    return configurationRegistry.fetchLanguages().any { it == language }
+  }
+}

android/engine/src/main/java/org/smartregister/fhircore/engine/util/DependenciesHolder.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2021-2024 Ona Systems, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.smartregister.fhircore.engine.util
+
+import org.smartregister.fhircore.engine.ui.base.LanguageSelector
+
+// A holder for dependencies that are not yet available in the activity lifecycle
+// before inject() is called (e.g., during attachBaseContext).
+// Ideally, dependencies should be set in QuestApplication's onCreate() method.
+
+object DependenciesHolder {
+  var languageSelector: LanguageSelector? = null
+}

android/engine/src/test/java/org/smartregister/fhircore/engine/ui/base/LanguageSelectorTest.kt

@@ -0,0 +1,165 @@
+package org.smartregister.fhircore.engine.ui.base
+
+import android.content.Context
+import android.content.SharedPreferences
+import androidx.test.core.app.ApplicationProvider
+import ca.uhn.fhir.context.FhirContext
+import com.google.android.fhir.FhirEngine
+import dagger.hilt.android.testing.HiltAndroidRule
+import dagger.hilt.android.testing.HiltAndroidTest
+import dagger.hilt.android.testing.HiltTestApplication
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.spyk
+import io.mockk.verify
+import kotlinx.serialization.json.Json
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.smartregister.fhircore.engine.configuration.ConfigType
+import org.smartregister.fhircore.engine.configuration.Configuration
+import org.smartregister.fhircore.engine.configuration.ConfigurationRegistry
+import org.smartregister.fhircore.engine.configuration.app.ApplicationConfiguration
+import org.smartregister.fhircore.engine.configuration.app.ConfigService
+import org.smartregister.fhircore.engine.data.remote.fhir.resource.FhirResourceDataSource
+import org.smartregister.fhircore.engine.data.remote.fhir.resource.FhirResourceService
+import org.smartregister.fhircore.engine.domain.model.Language
+import org.smartregister.fhircore.engine.robolectric.RobolectricTest
+import org.smartregister.fhircore.engine.rule.CoroutineTestRule
+import org.smartregister.fhircore.engine.util.DispatcherProvider
+import org.smartregister.fhircore.engine.util.SharedPreferenceKey
+import org.smartregister.fhircore.engine.util.SharedPreferencesHelper
+import org.smartregister.fhircore.engine.util.extension.fetchLanguages
+import java.util.Locale
+import javax.inject.Inject
+
+@HiltAndroidTest
+class LanguageSelectorTest : RobolectricTest() {
+
+    @get:Rule(order = 0) val hiltRule = HiltAndroidRule(this)
+
+
+    @Inject
+    lateinit var fhirEngine: FhirEngine
+
+    @Inject
+    lateinit var dispatcherProvider: DispatcherProvider
+
+    @Inject
+    lateinit var sharedPreferencesHelper: SharedPreferencesHelper
+
+    @Inject
+    lateinit var configService: ConfigService
+
+    @Inject
+    lateinit var json: Json
+
+    @Inject
+    lateinit var fhirContext: FhirContext
+
+    private val context: Context = ApplicationProvider.getApplicationContext()
+    private val fhirResourceService = mockk<FhirResourceService>()
+    private lateinit var fhirResourceDataSource: FhirResourceDataSource
+    private lateinit var configRegistry: ConfigurationRegistry
+
+    // System under test
+    private lateinit var languageSelector: LanguageSelector
+
+    @Before
+    fun setUp() {
+        hiltRule.inject()
+        fhirResourceDataSource = spyk(FhirResourceDataSource(fhirResourceService))
+        configRegistry =
+            ConfigurationRegistry(
+                fhirEngine = fhirEngine,
+                fhirResourceDataSource = fhirResourceDataSource,
+                sharedPreferencesHelper = sharedPreferencesHelper,
+                dispatcherProvider = dispatcherProvider,
+                configService = configService,
+                json = json,
+                context = ApplicationProvider.getApplicationContext<HiltTestApplication>(),
+            )
+        languageSelector = LanguageSelector(configRegistry, sharedPreferencesHelper)
+
+    }
+
+    @Test
+    fun `getDefaultLocale should return shared preference locale if it is supported`() {
+        // Arrange
+        val sharedPrefLocale = "es"
+        sharedPreferencesHelper.write(SharedPreferenceKey.LANG.name, sharedPrefLocale)
+        configRegistry.configsJsonMap["application"] =
+            """
+              {
+                "appId": "testAppId",
+                "configType": "application",
+                "theme": "DEFAULT",
+                "appTitle": "testAppId",
+                "remoteSyncPageSize": 250,
+                "languages": [
+                    "en",
+                    "es"
+                  ]
+              }
+                 """
+                .trimIndent()
+
+        // Act
+        val result = languageSelector.getDefaultLocale(context)
+
+        // Assert
+        assertEquals(sharedPrefLocale, result)
+    }
+
+    @Test
+    fun `getDefaultLocale should return device default locale if shared preference locale is not supported`() {
+        // Arrange
+        val deviceDefaultLocale = Locale("en", "US")
+//        every { mockSharedPreferences.getString(any(), any()) } returns null
+        every { configRegistry.fetchLanguages() } returns
+                listOf(Language("en", "English"),
+                    Language("es", "Espanyol"),
+                    Language("fr", "French")
+                )
+        // Act
+        val result = languageSelector.getDefaultLocale(context)
+
+        // Assert
+        assertEquals(deviceDefaultLocale.toLanguageTag(), result)
+    }
+
+    @Test
+    fun `getDefaultLocale should return app config default locale if device default locale is not supported`() {
+        // Arrange
+        val appConfigDefaultLocale = "fr"
+//        every { mockSharedPreferences.getString(any(), any()) } returns null
+        every { configRegistry.fetchLanguages() } returns listOf(Language("en", "English"),
+            Language("es", "Espanyol"),
+            Language("fr", "French")) as List<Language>
+
+        // Act
+        val result = languageSelector.getDefaultLocale(context)
+
+        // Assert
+        assertEquals(appConfigDefaultLocale, result)
+        verify { sharedPreferencesHelper.write(SharedPreferenceKey.LANG.name, appConfigDefaultLocale) }
+    }
+
+    @Test
+    fun `getDefaultLocale should return first locale in languages list if no other locale is supported`() {
+        // Arrange
+        val firstLocaleInLanguagesList = "en"
+//        every { mockSharedPreferences.getString(any(), any()) } returns null
+        every { configRegistry.fetchLanguages() } returns listOf(Language("en", "English"),
+            Language("es", "Espanyol"),
+            Language("fr", "French"))
+
+        // Act
+        val result = languageSelector.getDefaultLocale(context)
+
+        // Assert
+        assertEquals(firstLocaleInLanguagesList, result)
+        verify { sharedPreferencesHelper.write(SharedPreferenceKey.LANG.name, firstLocaleInLanguagesList) }
+    }
+}

android/quest/src/main/java/org/smartregister/fhircore/quest/QuestApplication.kt

@@ -34,6 +34,8 @@ import io.sentry.android.fragment.FragmentLifecycleIntegration
 import java.net.URL
 import javax.inject.Inject
 import org.smartregister.fhircore.engine.data.remote.fhir.resource.ReferenceUrlResolver
+import org.smartregister.fhircore.engine.ui.base.LanguageSelector
+import org.smartregister.fhircore.engine.util.DependenciesHolder
 import org.smartregister.fhircore.engine.util.extension.getSubDomain
 import org.smartregister.fhircore.quest.data.QuestXFhirQueryResolver
 import org.smartregister.fhircore.quest.ui.questionnaire.QuestionnaireItemViewHolderFactoryMatchersProviderFactoryImpl
@@ -53,6 +55,8 @@ class QuestApplication : Application(), DataCaptureConfig.Provider, Configuratio
 
   private var configuration: DataCaptureConfig? = null
 
+  @Inject lateinit var languageSelector: LanguageSelector
+
   override fun onCreate() {
     super.onCreate()
     if (BuildConfig.DEBUG) {
@@ -75,6 +79,7 @@ class QuestApplication : Application(), DataCaptureConfig.Provider, Configuratio
     } catch (e: Exception) {
       Timber.e(e)
     }
+    DependenciesHolder.languageSelector = languageSelector
   }
 
   @VisibleForTesting

android/quest/src/test/java/org/smartregister/fhircore/quest/ui/main/AppMainViewModelTest.kt

@@ -139,7 +139,7 @@ class AppMainViewModelTest : RobolectricTest() {
   fun testOnEventSwitchLanguage() {
     val appMainEvent =
       AppMainEvent.SwitchLanguage(
-        Language("en", "English"),
+        Language("fr", "English"),
         mockkClass(Activity::class, relaxed = true),
       )