feat: create and expose android API to react-native thread

Author: jakex7

android/build.gradle

@@ -87,6 +87,9 @@ dependencies {
   //noinspection GradleDynamicVersion
   implementation "com.facebook.react:react-native:+"
   implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
+  
+  implementation "androidx.appcompat:appcompat:1.6.0-rc01"
+  implementation "androidx.appcompat:appcompat-resources:1.6.0-rc01"
 }
 
 if (isNewArchitectureEnabled()) {

android/src/main/java/com/localizationsettings/LocalizationSettingsModule.kt

@@ -1,8 +1,15 @@
 package com.localizationsettings
 
+import android.content.Context
+import android.content.SharedPreferences
+import android.os.Build
+import androidx.appcompat.app.AppCompatDelegate
+import androidx.core.os.LocaleListCompat
+import com.facebook.react.bridge.Promise
 import com.facebook.react.bridge.ReactApplicationContext
 import com.facebook.react.bridge.ReactMethod
-import com.facebook.react.bridge.Promise
+import java.util.*
+
 
 class LocalizationSettingsModule internal constructor(context: ReactApplicationContext) :
   LocalizationSettingsSpec(context) {
@@ -11,11 +18,99 @@ class LocalizationSettingsModule internal constructor(context: ReactApplicationC
     return NAME
   }
 
-  // Example method
-  // See https://reactnative.dev/docs/native-modules-android
+  /**
+   * Get IETF BCP 47 (language-COUNTRY "pl-PL")
+   * if country is not available in locale, then use system defaults (even if it's not 100% correct, like "pl-US")
+   **/
+  private fun getLanguageTag(language: String): String {
+    // if language have format language_COUNTRY, then return it
+    if (Locale(language).country != "") return Locale(language).toLanguageTag()
+    // fallback for system country
+    return "$language-${Locale.getDefault().country}"
+  }
+
+
+  /**
+   * Get current language
+   * returns string in IETF BCP 47 (language-COUNTRY "pl-PL")
+   *  If API version >= 33, use native per-app language feature
+   *  else, fallback to SharedPreferences
+   **/
+  private fun getCurrentLanguage(): String? {
+    // If API version is >= 33, then use per-app language settings
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+      val currentLocaleName = if (!AppCompatDelegate.getApplicationLocales().isEmpty) {
+        // get per-app language
+        AppCompatDelegate.getApplicationLocales()[0]?.toLanguageTag()
+      } else {
+        // Fallback to the default System Locale
+        Locale.getDefault().toLanguageTag()
+      }
+      return currentLocaleName
+    }
+    // if API is < 33, then use SharedPreferences with fallback to default System Locale
+    if (getPreferences().getString("languageFrom", null) == Locale.getDefault().language) {
+      return getPreferences().getString("language", Locale.getDefault().toLanguageTag())
+    }
+    return Locale.getDefault().toLanguageTag()
+  }
+
+
+  /**
+   * Set current language
+   * passed language can be in ISO 639-1 (language "pl")
+   * or IETF BCP 47 (language-COUNTRY "pl-PL")
+   *  If API version >= 33, use native per-app language feature
+   *  else, fallback to SharedPreferences
+   **/
+  private fun setCurrentLanguage(language: String) {
+    // If API version is >= 33, then use per-app language settings
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+      val localeList = LocaleListCompat.forLanguageTags(getLanguageTag(language))
+      AppCompatDelegate.setApplicationLocales(localeList)
+    } else {
+      // if API is < 33, then set SharedPreferences language
+      val editor = getEditor();
+      editor.putString("languageFrom", Locale.getDefault().language)
+      editor.putString("language", getLanguageTag(language))
+      editor.apply()
+    }
+  }
+
+
+  /**
+   * Expose functions to react-native
+   **/
   @ReactMethod
-  override fun multiply(a: Double, b: Double, promise: Promise) {
-    promise.resolve(a * b)
+  override fun getLanguage(promise: Promise) {
+    promise.resolve(getCurrentLanguage())
+  }
+
+  @ReactMethod
+  override fun setLanguage(language: String) {
+    setCurrentLanguage(language)
+  }
+
+  /**
+   * Expose constants to react-native
+   **/
+  override fun getConstants(): MutableMap<String, String?>? {
+    val constants: MutableMap<String, String?> = HashMap()
+    constants["language"] = getCurrentLanguage()
+    return constants
+  }
+
+  /**
+   * SharedPreferences (only used when API version is below 33)
+   **/
+  private fun getPreferences(): SharedPreferences {
+    return reactApplicationContext.getSharedPreferences(
+      "LocalizationSettings", Context.MODE_PRIVATE
+    )
+  }
+
+  private fun getEditor(): SharedPreferences.Editor {
+    return getPreferences().edit()
   }
 
   companion object {

android/src/oldarch/LocalizationSettingsSpec.kt

@@ -7,5 +7,6 @@ import com.facebook.react.bridge.Promise
 abstract class LocalizationSettingsSpec internal constructor(context: ReactApplicationContext) :
   ReactContextBaseJavaModule(context) {
 
-  abstract fun multiply(a: Double, b: Double, promise: Promise)
+  abstract fun getLanguage(promise: Promise)
+  abstract fun setLanguage(language: String)
 }