From 08fb61ce36384ff90a704faffe4761eccfb76da1 Mon Sep 17 00:00:00 2001
From: Tom Moor <tom.moor@gmail.com>
Date: Mon, 23 Nov 2020 21:54:14 -0800
Subject: [PATCH] cache translations in client

---
 package.json                |  2 ++
 shared/translations/i18n.js | 24 +++++++++++++++++++-----
 yarn.lock                   | 16 +++++++++++++++-
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/package.json b/package.json
index ffc94c6a93..004cdf0aa8 100644
--- a/package.json
+++ b/package.json
@@ -94,7 +94,9 @@
     "google-auth-library": "^5.5.1",
     "http-errors": "1.4.0",
     "i18next": "^19.8.3",
+    "i18next-chained-backend": "^2.0.1",
     "i18next-http-backend": "^1.0.21",
+    "i18next-localstorage-backend": "^3.1.2",
     "immutable": "^3.8.2",
     "imports-loader": "0.6.5",
     "invariant": "^2.2.2",
diff --git a/shared/translations/i18n.js b/shared/translations/i18n.js
index b77f86e17a..40207c4a0b 100644
--- a/shared/translations/i18n.js
+++ b/shared/translations/i18n.js
@@ -1,6 +1,8 @@
 // @flow
 import i18n from "i18next";
-import backend from "i18next-http-backend";
+import Backend from "i18next-chained-backend";
+import HttpApi from "i18next-http-backend";
+import LocalStorageBackend from "i18next-localstorage-backend";
 import { initReactI18next } from "react-i18next";
 
 const initI18n = () => {
@@ -8,12 +10,24 @@ const initI18n = () => {
     "DEFAULT_LANGUAGE" in process.env ? process.env.DEFAULT_LANGUAGE : "en_US";
 
   i18n
-    .use(backend)
+    .use(Backend)
     .use(initReactI18next)
     .init({
-      backend: {
-        loadPath: "/locales/{{lng}}.json",
-      },
+      backend:
+        process.env.NODE_ENV === "test"
+          ? {}
+          : {
+              backends: [LocalStorageBackend, HttpApi],
+              backendOptions: [
+                {
+                  prefix: "translations-",
+                  expirationTime: 7 * 24 * 60 * 60 * 1000,
+                },
+                {
+                  loadPath: "/locales/{{lng}}.json",
+                },
+              ],
+            },
       interpolation: {
         escapeValue: false,
       },
diff --git a/yarn.lock b/yarn.lock
index 729461fdbd..ffbacd4c67 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -955,7 +955,7 @@
     core-js-pure "^3.0.0"
     regenerator-runtime "^0.13.4"
 
-"@babel/runtime@^7.0.0", "@babel/runtime@^7.1.2", "@babel/runtime@^7.10.2", "@babel/runtime@^7.11.2", "@babel/runtime@^7.12.0", "@babel/runtime@^7.12.1", "@babel/runtime@^7.3.1", "@babel/runtime@^7.8.4", "@babel/runtime@^7.9.2":
+"@babel/runtime@^7.0.0", "@babel/runtime@^7.1.2", "@babel/runtime@^7.10.2", "@babel/runtime@^7.11.2", "@babel/runtime@^7.12.0", "@babel/runtime@^7.12.1", "@babel/runtime@^7.3.1", "@babel/runtime@^7.4.5", "@babel/runtime@^7.8.4", "@babel/runtime@^7.9.2":
   version "7.12.5"
   resolved "https://registry.yarnpkg.com/@babel/runtime/-/runtime-7.12.5.tgz#410e7e487441e1b360c29be715d870d9b985882e"
   integrity sha512-plcc+hbExy3McchJCEQG3knOsuh3HH+Prx1P6cLIkET/0dLuQDEnrT+s27Axgc9bqfsmNUNHfscgMUdBpC9xfg==
@@ -5926,6 +5926,13 @@ humanize-number@0.0.2:
   resolved "https://registry.yarnpkg.com/humanize-number/-/humanize-number-0.0.2.tgz#11c0af6a471643633588588048f1799541489c18"
   integrity sha1-EcCvakcWQ2M1iFiASPF5lUFInBg=
 
+i18next-chained-backend@^2.0.1:
+  version "2.0.1"
+  resolved "https://registry.yarnpkg.com/i18next-chained-backend/-/i18next-chained-backend-2.0.1.tgz#762f78b30aafc5cab9f85f520f8281172380d1a1"
+  integrity sha512-IKLRCJ767tPWd3nKQMbcqbjd/tHcv+DjFIkaNd1yJSdnS6PME4lvCRYx+gl3gMMMbCL0r+l1bvRVBkTkRRXGVQ==
+  dependencies:
+    "@babel/runtime" "^7.4.5"
+
 i18next-http-backend@^1.0.21:
   version "1.0.21"
   resolved "https://registry.yarnpkg.com/i18next-http-backend/-/i18next-http-backend-1.0.21.tgz#cee901b3527dad5165fa91de973b6aa6404c1c37"
@@ -5933,6 +5940,13 @@ i18next-http-backend@^1.0.21:
   dependencies:
     node-fetch "2.6.1"
 
+i18next-localstorage-backend@^3.1.2:
+  version "3.1.2"
+  resolved "https://registry.yarnpkg.com/i18next-localstorage-backend/-/i18next-localstorage-backend-3.1.2.tgz#415fcac42d6d66ff8bc878d269c5b5719fdedc2c"
+  integrity sha512-J81qf9atTAc9iMdHUNKJeAWgUsFvqbxfHIIztmF62tOaINA2AJk0kewJjm8LQDuArkiuW9RhQPbhqbyeZut35g==
+  dependencies:
+    "@babel/runtime" "^7.4.5"
+
 i18next-parser@^3.3.0:
   version "3.3.0"
   resolved "https://registry.yarnpkg.com/i18next-parser/-/i18next-parser-3.3.0.tgz#5cd907aff5e791c043137a4902ab42631cde9656"