From 4523437e34dd9f0d04430a61b2fefc6e7d2d9f23 Mon Sep 17 00:00:00 2001
From: Huang Xin <chrox.huang@gmail.com>
Date: Sun, 18 May 2025 23:16:44 +0800
Subject: [PATCH] refactor: add kv cache for translation backend (#1184)

---
 .../components/annotator/DeepLPopup.tsx       |   7 +-
 apps/readest-app/src/components/Popup.tsx     |  16 +-
 .../src/pages/api/deepl/translate.ts          | 157 +++++++++++++-----
 .../src/services/transformers/index.ts        |   2 -
 .../src/services/transformers/translate.ts    |   9 -
 apps/readest-app/src/utils/sel.ts             |   5 +
 apps/readest-app/wrangler.json                |  12 --
 apps/readest-app/wrangler.toml                |  12 ++
 8 files changed, 150 insertions(+), 70 deletions(-)
 delete mode 100644 apps/readest-app/src/services/transformers/translate.ts
 delete mode 100644 apps/readest-app/wrangler.json
 create mode 100644 apps/readest-app/wrangler.toml

diff --git a/apps/readest-app/src/app/reader/components/annotator/DeepLPopup.tsx b/apps/readest-app/src/app/reader/components/annotator/DeepLPopup.tsx
index 6537457b..d42415a4 100644
--- a/apps/readest-app/src/app/reader/components/annotator/DeepLPopup.tsx
+++ b/apps/readest-app/src/app/reader/components/annotator/DeepLPopup.tsx
@@ -4,7 +4,6 @@ import { Position } from '@/utils/sel';
 import { useAuth } from '@/context/AuthContext';
 import { useSettingsStore } from '@/store/settingsStore';
 import { useTranslation } from '@/hooks/useTranslation';
-import { useResponsiveSize } from '@/hooks/useResponsiveSize';
 import { getAPIBaseUrl } from '@/services/environment';
 import { TRANSLATED_LANGS } from '@/services/constants';
 
@@ -119,17 +118,13 @@ const DeepLPopup: React.FC<DeepLPopupProps> = ({
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [text, token, sourceLang, targetLang]);
 
-  const popupPadding = useResponsiveSize(10);
-  const maxHeight = window.innerHeight - 2 * popupPadding;
-  const popupMaxHeight = Math.min(360, maxHeight);
-
   return (
     <div>
       <Popup
         trianglePosition={trianglePosition}
         width={popupWidth}
         minHeight={popupHeight}
-        maxHeight={popupMaxHeight}
+        maxHeight={720}
         position={position}
         className='grid h-full select-text grid-rows-[1fr,auto,1fr] bg-gray-600 text-white'
         triangleClassName='text-gray-600'
diff --git a/apps/readest-app/src/components/Popup.tsx b/apps/readest-app/src/components/Popup.tsx
index 247af118..d44be8f9 100644
--- a/apps/readest-app/src/components/Popup.tsx
+++ b/apps/readest-app/src/components/Popup.tsx
@@ -1,5 +1,7 @@
+import clsx from 'clsx';
 import { Position } from '@/utils/sel';
 import { useEffect, useRef, useState } from 'react';
+import { useResponsiveSize } from '@/hooks/useResponsiveSize';
 
 const Popup = ({
   width,
@@ -28,6 +30,18 @@ const Popup = ({
   const [adjustedPosition, setAdjustedPosition] = useState(position);
   const [childrenHeight, setChildrenHeight] = useState(height || minHeight || 0);
 
+  const popupPadding = useResponsiveSize(10);
+  let availableHeight = window.innerHeight - 2 * popupPadding;
+  if (trianglePosition?.dir === 'up') {
+    availableHeight = trianglePosition.point.y - popupPadding;
+  } else if (trianglePosition?.dir === 'down') {
+    availableHeight = window.innerHeight - trianglePosition.point.y - popupPadding;
+  }
+  maxHeight = Math.min(maxHeight || availableHeight, availableHeight);
+  if (minHeight) {
+    minHeight = Math.min(minHeight, availableHeight);
+  }
+
   useEffect(() => {
     if (!containerRef.current) return;
     const resizeObserver = new ResizeObserver((entries) => {
@@ -69,7 +83,7 @@ const Popup = ({
       <div
         id='popup-container'
         ref={containerRef}
-        className={`bg-base-300 absolute rounded-lg font-sans shadow-xl ${className}`}
+        className={clsx('bg-base-300 absolute rounded-lg font-sans shadow-xl', className)}
         style={{
           width: `${width}px`,
           height: height ? `${height}px` : 'auto',
diff --git a/apps/readest-app/src/pages/api/deepl/translate.ts b/apps/readest-app/src/pages/api/deepl/translate.ts
index e3a095de..eebb8ed6 100644
--- a/apps/readest-app/src/pages/api/deepl/translate.ts
+++ b/apps/readest-app/src/pages/api/deepl/translate.ts
@@ -1,12 +1,22 @@
+import crypto from 'crypto';
 import { NextApiRequest, NextApiResponse } from 'next';
 import { corsAllMethods, runMiddleware } from '@/utils/cors';
 import { supabase } from '@/utils/supabase';
 import { getUserPlan } from '@/utils/access';
-import { query as deeplQuery } from '@/utils/deepl';
 
 const DEFAULT_DEEPL_FREE_API = 'https://api-free.deepl.com/v2/translate';
 const DEFAULT_DEEPL_PRO_API = 'https://api.deepl.com/v2/translate';
 
+interface KVNamespace {
+  get(key: string): Promise<string | null>;
+  put(key: string, value: string, options?: { expirationTtl?: number }): Promise<void>;
+  delete(key: string): Promise<void>;
+}
+
+interface CloudflareEnv {
+  TRANSLATIONS_KV?: KVNamespace;
+}
+
 const getUserAndToken = async (authHeader: string | undefined) => {
   if (!authHeader) return {};
 
@@ -27,7 +37,13 @@ const LANG_V2_V1_MAP: Record<string, string> = {
 
 const getDeepLAPIKey = (keys: string | undefined) => {
   const keyArray = keys?.split(',') ?? [];
-  return keyArray.length ? keyArray[Math.floor(Math.random() * keyArray.length)] : '';
+  return keyArray.length ? keyArray[Math.floor(Math.random() * keyArray.length)]! : '';
+};
+
+const generateCacheKey = (text: string, sourceLang: string, targetLang: string): string => {
+  const inputString = `${sourceLang}:${targetLang}:${text}`;
+  const hash = crypto.createHash('sha1').update(inputString).digest('hex');
+  return `tr:${hash}`;
 };
 
 const handler = async (req: NextApiRequest, res: NextApiResponse) => {
@@ -37,6 +53,9 @@ const handler = async (req: NextApiRequest, res: NextApiResponse) => {
     return res.status(405).json({ error: 'Method not allowed' });
   }
 
+  const env = (req.env || {}) as CloudflareEnv;
+  const hasKVCache = !!env['TRANSLATIONS_KV'];
+
   const { user, token } = await getUserAndToken(req.headers['authorization']);
   const { DEEPL_PRO_API, DEEPL_FREE_API } = process.env;
   const deepFreeApiUrl = DEEPL_FREE_API || DEFAULT_DEEPL_FREE_API;
@@ -47,8 +66,6 @@ const handler = async (req: NextApiRequest, res: NextApiResponse) => {
   if (user && token) {
     userPlan = getUserPlan(token);
     if (userPlan === 'pro') deeplApiUrl = deeplProApiUrl;
-  } else {
-    res.status(403).json({ error: 'Not authenticated' });
   }
   const deeplAuthKey =
     deeplApiUrl === deeplProApiUrl
@@ -59,46 +76,106 @@ const handler = async (req: NextApiRequest, res: NextApiResponse) => {
     text,
     source_lang: sourceLang = 'AUTO',
     target_lang: targetLang = 'EN',
-  }: { text: string[]; source_lang: string; target_lang: string } = req.body;
+    use_cache: useCache = false,
+  }: { text: string[]; source_lang: string; target_lang: string; use_cache: boolean } = req.body;
+
   try {
-    if (user && token) {
-      const isV2Api = deeplApiUrl.endsWith('/v2/translate');
-      const requestBody = {
-        text: isV2Api ? text : (text[0] ?? ''),
-        source_lang: isV2Api ? sourceLang : (LANG_V2_V1_MAP[sourceLang] ?? sourceLang),
-        target_lang: isV2Api ? targetLang : (LANG_V2_V1_MAP[targetLang] ?? targetLang),
-      };
-      const response = await fetch(deeplApiUrl, {
-        method: 'POST',
-        headers: {
-          Authorization: `DeepL-Auth-Key ${deeplAuthKey}`,
-          'x-fingerprint': process.env['DEEPL_X_FINGERPRINT'] || '',
-          'Content-Type': 'application/json',
-        },
-        body: JSON.stringify(requestBody),
-      });
-      const data = await response.json();
-      const result = {
-        ...data,
-        translations: data.translations || [
-          {
-            text: data.data,
-          },
-        ],
-      };
-      res.status(response.status).json(result);
-    } else {
-      const result = await deeplQuery({
-        text: text[0] ?? '',
-        sourceLang,
-        targetLang,
-      });
-      res.status(200).json(result);
-    }
+    const translations = await Promise.all(
+      text.map(async (singleText) => {
+        if (!singleText?.trim()) {
+          return { text: '' };
+        }
+        if (useCache && hasKVCache) {
+          try {
+            const cacheKey = generateCacheKey(singleText, sourceLang, targetLang);
+            const cachedTranslation = await env['TRANSLATIONS_KV']!.get(cacheKey);
+
+            if (cachedTranslation) {
+              return {
+                text: cachedTranslation,
+                detected_source_language: sourceLang,
+              };
+            }
+          } catch (cacheError) {
+            console.error('Cache retrieval error:', cacheError);
+          }
+        }
+
+        return await callDeepLAPI(
+          singleText,
+          sourceLang,
+          targetLang,
+          deeplApiUrl,
+          deeplAuthKey,
+          env['TRANSLATIONS_KV'],
+          useCache,
+        );
+      }),
+    );
+    return res.status(200).json({ translations });
   } catch (error) {
     console.error('Error proxying DeepL request:', error);
-    res.status(500).json({ error: 'Internal Server Error' });
+    return res.status(500).json({ error: 'Internal Server Error' });
   }
 };
 
+async function callDeepLAPI(
+  text: string,
+  sourceLang: string,
+  targetLang: string,
+  apiUrl: string,
+  authKey: string,
+  translationsKV: KVNamespace | undefined,
+  useCache: boolean,
+) {
+  const isV2Api = apiUrl.endsWith('/v2/translate');
+
+  const requestBody = {
+    text: isV2Api ? [text] : text,
+    source_lang: isV2Api ? sourceLang : (LANG_V2_V1_MAP[sourceLang] ?? sourceLang),
+    target_lang: isV2Api ? targetLang : (LANG_V2_V1_MAP[targetLang] ?? targetLang),
+  };
+
+  const response = await fetch(apiUrl, {
+    method: 'POST',
+    headers: {
+      Authorization: `DeepL-Auth-Key ${authKey}`,
+      'x-fingerprint': process.env['DEEPL_X_FINGERPRINT'] || '',
+      'Content-Type': 'application/json',
+    },
+    body: JSON.stringify(requestBody),
+  });
+
+  if (!response.ok) {
+    const errorText = await response.text();
+    throw new Error(`DeepL API error (${response.status}): ${errorText}`);
+  }
+
+  const data = await response.json();
+
+  let translatedText = '';
+  let detectedSourceLanguage = '';
+
+  if (data.translations && data.translations.length > 0) {
+    translatedText = data.translations[0].text;
+    detectedSourceLanguage = data.translations[0].detected_source_language || '';
+  } else if (data.data) {
+    translatedText = data.data;
+  }
+
+  if (useCache && translationsKV && translatedText) {
+    try {
+      const cacheKey = generateCacheKey(text, sourceLang, targetLang);
+      await translationsKV.put(cacheKey, translatedText, { expirationTtl: 86400 * 90 });
+    } catch (cacheError) {
+      console.error('Cache storage error:', cacheError);
+    }
+  }
+
+  return {
+    text: translatedText,
+    detected_source_language: detectedSourceLanguage,
+  };
+}
+
 export default handler;
diff --git a/apps/readest-app/src/services/transformers/index.ts b/apps/readest-app/src/services/transformers/index.ts
index 4a8f68ed..b73d380c 100644
--- a/apps/readest-app/src/services/transformers/index.ts
+++ b/apps/readest-app/src/services/transformers/index.ts
@@ -1,11 +1,9 @@
 import type { Transformer } from './types';
 import { footnoteTransformer } from './footnote';
-import { translateTransformer } from './translate';
 import { punctuationTransformer } from './punctuation';
 
 export const availableTransformers: Transformer[] = [
   punctuationTransformer,
-  translateTransformer,
   footnoteTransformer,
   // Add more transformers here
 ];
diff --git a/apps/readest-app/src/services/transformers/translate.ts b/apps/readest-app/src/services/transformers/translate.ts
deleted file mode 100644
index abb2d9ad..00000000
--- a/apps/readest-app/src/services/transformers/translate.ts
+++ /dev/null
@@ -1,9 +0,0 @@
-import type { Transformer } from './types';
-
-export const translateTransformer: Transformer = {
-  name: 'translate',
-
-  transform: async (ctx) => {
-    return ctx.content;
-  },
-};
diff --git a/apps/readest-app/src/utils/sel.ts b/apps/readest-app/src/utils/sel.ts
index b90997ad..ed8ff2b6 100644
--- a/apps/readest-app/src/utils/sel.ts
+++ b/apps/readest-app/src/utils/sel.ts
@@ -122,6 +122,11 @@ export const getPosition = (
   return start.point.y > window.innerHeight - end.point.y ? start : end;
 };
 
+// The popup will be positioned based on the triangle position and the direction
+// up: above the triangle
+// down: below the triangle
+// left: to the left of the triangle
+// right: to the right of the triangle
 export const getPopupPosition = (
   position: Position,
   boundingReact: Rect,
diff --git a/apps/readest-app/wrangler.json b/apps/readest-app/wrangler.json
deleted file mode 100644
index 4759c3f6..00000000
--- a/apps/readest-app/wrangler.json
+++ /dev/null
@@ -1,12 +0,0 @@
-{
-  "$schema": "node_modules/wrangler/config-schema.json",
-  "main": ".open-next/worker.js",
-  "name": "readest-web",
-  "compatibility_date": "2025-02-04",
-  "compatibility_flags": ["nodejs_compat"],
-  "assets": {
-    "directory": ".open-next/assets",
-    "binding": "ASSETS"
-  },
-  "kv_namespaces": []
-}
diff --git a/apps/readest-app/wrangler.toml b/apps/readest-app/wrangler.toml
new file mode 100644
index 00000000..69c718ea
--- /dev/null
+++ b/apps/readest-app/wrangler.toml
@@ -0,0 +1,12 @@
+name = "readest-web"
+main = ".open-next/worker.js"
+compatibility_date = "2025-02-04"
+compatibility_flags = ["nodejs_compat"]
+
+[assets]
+directory = ".open-next/assets"
+binding = "ASSETS"
+
+[[kv_namespaces]]
+binding = "TRANSLATIONS_KV"
+id = "${TRANSLATIONS_KV_ID}"
\ No newline at end of file