From 8cd379c814c0218e77f359476cb4ac491a3e4dc0 Mon Sep 17 00:00:00 2001
From: Mathieu Acthernoene <zoontek@gmail.com>
Date: Mon, 28 Jan 2019 19:15:30 +0100
Subject: [PATCH] Add findBestAvailableLanguage function

---
 index.d.ts |  4 ++++
 index.js   | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/index.d.ts b/index.d.ts
index 0418590..dff179e 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -30,4 +30,8 @@ declare module "react-native-localize" {
     type: LocalizationEvent,
     handler: Function,
   ): void;
+
+  export function findBestAvailableLanguage<T extends string>(
+    languageTags: T[],
+  ): { languageTag: T; isRTL: boolean } | void;
 }
diff --git a/index.js b/index.js
index 1266bb0..1fab904 100644
--- a/index.js
+++ b/index.js
@@ -79,3 +79,38 @@ export function removeEventListener(
     handlers.delete(handler);
   }
 }
+
+export function findBestAvailableLanguage(
+  languageTags: string[],
+): {|
+  languageTag: string,
+  isRTL: boolean,
+|} | void {
+  const locales = getLocales();
+
+  for (let index = 0; index < locales.length; index++) {
+    const currentLocale = locales[index];
+    const { languageTag, languageCode, isRTL } = currentLocale;
+
+    if (languageTags.includes(languageTag)) {
+      return { languageTag, isRTL };
+    }
+
+    const partialTag = getPartialTag(currentLocale);
+    const nextLocale = locales[index + 1];
+
+    if (
+      (!nextLocale || partialTag !== getPartialTag(nextLocale)) &&
+      languageTags.includes(partialTag)
+    ) {
+      return { languageTag: partialTag, isRTL };
+    }
+
+    if (
+      (!nextLocale || languageCode !== nextLocale.languageCode) &&
+      languageTags.includes(languageCode)
+    ) {
+      return { languageTag: languageCode, isRTL };
+    }
+  }
+}