From e96782baab087cccc86a125f219a7da5b7ef54ef Mon Sep 17 00:00:00 2001
From: Huang Xin <chrox.huang@gmail.com>
Date: Sat, 22 Feb 2025 09:09:25 +0100
Subject: [PATCH] api: load balance of the API keys for deepl translate, closes
 #429 (#431)

---
 apps/readest-app/.env.local.example              |  4 ++--
 .../readest-app/src/pages/api/deepl/translate.ts | 16 ++++++++++++++--
 apps/readest-app/src/utils/access.ts             |  5 +++++
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/apps/readest-app/.env.local.example b/apps/readest-app/.env.local.example
index 3ada9deb..9f4102f2 100644
--- a/apps/readest-app/.env.local.example
+++ b/apps/readest-app/.env.local.example
@@ -4,8 +4,8 @@ NEXT_PUBLIC_POSTHOG_HOST=YOUR_POSTHOG_HOST
 NEXT_PUBLIC_SUPABASE_URL=YOUR_SUPABASE_URL
 NEXT_PUBLIC_SUPABASE_ANON_KEY=YOUR_SUPABASE_ANON_KEY
 
-DEEPL_PRO_API_KEY=YOUR_DEEPL_PRO_API_KEY
-DEEPL_FREE_API_KEY=YOUR_DEEPL_FREE_API_KEY
+DEEPL_PRO_API_KEYS=YOUR_DEEPL_PRO_API_KEYS
+DEEPL_FREE_API_KEYS=YOUR_DEEPL_FREE_API_KEYS
 
 R2_TOKEN_VALUE=YOUR_R2_TOKEN_VALUE
 R2_ACCESS_KEY_ID=YOUR_R2_ACCESS_KEY_ID
diff --git a/apps/readest-app/src/pages/api/deepl/translate.ts b/apps/readest-app/src/pages/api/deepl/translate.ts
index d3f8a5ed..2445355d 100644
--- a/apps/readest-app/src/pages/api/deepl/translate.ts
+++ b/apps/readest-app/src/pages/api/deepl/translate.ts
@@ -1,6 +1,7 @@
 import { NextApiRequest, NextApiResponse } from 'next';
 import { corsAllMethods, runMiddleware } from '@/utils/cors';
 import { supabase } from '@/utils/supabase';
+import { getUserPlan } from '@/utils/access';
 
 const DEEPL_FREE_API = 'https://api-free.deepl.com/v2/translate';
 const DEEPL_PRO_API = 'https://api.deepl.com/v2/translate';
@@ -18,11 +19,22 @@ const getUserAndToken = async (authHeader: string | undefined) => {
   return { user, token };
 };
 
+const getDeepLAPIKey = (keys: string | undefined) => {
+  const keyArray = keys?.split(',') ?? [];
+  return keyArray[Math.floor(Math.random() * keyArray.length)];
+};
+
 const handler = async (req: NextApiRequest, res: NextApiResponse) => {
   const { user, token } = await getUserAndToken(req.headers['authorization']);
-  const deeplApiUrl = user && token ? DEEPL_PRO_API : DEEPL_FREE_API;
+  let deeplApiUrl = DEEPL_FREE_API;
+  if (user && token) {
+    const userPlan = await getUserPlan(token);
+    if (userPlan !== 'free') deeplApiUrl = DEEPL_PRO_API;
+  }
   const deeplAuthKey =
-    user && token ? process.env['DEEPL_PRO_API_KEY'] : process.env['DEEPL_FREE_API_KEY'];
+    deeplApiUrl === DEEPL_PRO_API
+      ? getDeepLAPIKey(process.env['DEEPL_PRO_API_KEYS'])
+      : getDeepLAPIKey(process.env['DEEPL_FREE_API_KEYS']);
 
   await runMiddleware(req, res, corsAllMethods);
 
diff --git a/apps/readest-app/src/utils/access.ts b/apps/readest-app/src/utils/access.ts
index fe46ff1d..8f2df135 100644
--- a/apps/readest-app/src/utils/access.ts
+++ b/apps/readest-app/src/utils/access.ts
@@ -10,6 +10,11 @@ interface Token {
   [key: string]: string | number;
 }
 
+export const getUserPlan = async (token: string): Promise<UserPlan> => {
+  const data = jwtDecode<Token>(token) || {};
+  return data['plan'] || 'free';
+};
+
 export const getStoragePlanData = (token: string) => {
   const data = jwtDecode<Token>(token) || {};
   const plan = data['plan'] || 'free';