From 96cc182a8c0734fb5c82067f11971e7eac8c1712 Mon Sep 17 00:00:00 2001
From: Huang Xin <chrox.huang@gmail.com>
Date: Tue, 14 Oct 2025 19:09:23 +0800
Subject: [PATCH] feat: support overriding html language code with language
 code in metadata, closes #2222 (#2227)

---
 .../app/reader/components/FoliateViewer.tsx   |  9 +++++---
 .../src/services/transformers/index.ts        |  2 ++
 .../src/services/transformers/language.ts     |  8 ++++---
 .../src/services/transformers/types.ts        |  1 +
 .../src/services/transformers/whitespace.ts   | 21 +++++++++++++++++++
 5 files changed, 35 insertions(+), 6 deletions(-)
 create mode 100644 apps/readest-app/src/services/transformers/whitespace.ts

diff --git a/apps/readest-app/src/app/reader/components/FoliateViewer.tsx b/apps/readest-app/src/app/reader/components/FoliateViewer.tsx
index 59989549..bc19a631 100644
--- a/apps/readest-app/src/app/reader/components/FoliateViewer.tsx
+++ b/apps/readest-app/src/app/reader/components/FoliateViewer.tsx
@@ -43,6 +43,7 @@ import { getMaxInlineSize } from '@/utils/config';
 import { getDirFromUILanguage } from '@/utils/rtl';
 import { isCJKLang } from '@/utils/lang';
 import { isTauriAppPlatform } from '@/services/environment';
+import { TransformContext } from '@/services/transformers/types';
 import { transformContent } from '@/services/transformService';
 import { lockScreenOrientation } from '@/utils/bridge';
 import { useTextTranslation } from '../hooks/useTextTranslation';
@@ -118,15 +119,17 @@ const FoliateViewer: React.FC<{
       detail.data = Promise.resolve(detail.data)
         .then((data) => {
           const viewSettings = getViewSettings(bookKey);
+          const bookData = getBookData(bookKey);
           if (viewSettings && detail.type === 'text/css')
             return transformStylesheet(width, height, data);
-          if (viewSettings && detail.type === 'application/xhtml+xml') {
+          if (viewSettings && bookData && detail.type === 'application/xhtml+xml') {
             const ctx = {
               bookKey,
               viewSettings,
+              primaryLanguage: bookData.book?.primaryLanguage,
               content: data,
-              transformers: ['punctuation', 'footnote', 'language'],
-            };
+              transformers: ['punctuation', 'footnote', 'whitespace', 'language'],
+            } as TransformContext;
             return Promise.resolve(transformContent(ctx));
           }
           return data;
diff --git a/apps/readest-app/src/services/transformers/index.ts b/apps/readest-app/src/services/transformers/index.ts
index 71eba61d..a4a6bf91 100644
--- a/apps/readest-app/src/services/transformers/index.ts
+++ b/apps/readest-app/src/services/transformers/index.ts
@@ -2,10 +2,12 @@ import type { Transformer } from './types';
 import { footnoteTransformer } from './footnote';
 import { languageTransformer } from './language';
 import { punctuationTransformer } from './punctuation';
+import { whitespaceTransformer } from './whitespace';
 
 export const availableTransformers: Transformer[] = [
   punctuationTransformer,
   footnoteTransformer,
   languageTransformer,
+  whitespaceTransformer,
   // Add more transformers here
 ];
diff --git a/apps/readest-app/src/services/transformers/language.ts b/apps/readest-app/src/services/transformers/language.ts
index dc0c1ee7..f3b578da 100644
--- a/apps/readest-app/src/services/transformers/language.ts
+++ b/apps/readest-app/src/services/transformers/language.ts
@@ -1,10 +1,11 @@
-import { detectLanguage, isValidLang } from '@/utils/lang';
+import { detectLanguage, isSameLang, isValidLang } from '@/utils/lang';
 import type { Transformer } from './types';
 
 export const languageTransformer: Transformer = {
   name: 'language',
 
   transform: async (ctx) => {
+    const primaryLanguage = ctx.primaryLanguage;
     let result = ctx.content;
     const attrsMatch = result.match(/<html\b([^>]*)>/i);
     if (attrsMatch) {
@@ -13,9 +14,10 @@ export const languageTransformer: Transformer = {
       const xmlLangRegex = / xml:lang="([^"]*)"/i;
       const xmlLangMatch = attrs.match(xmlLangRegex);
       const langMatch = attrs.match(langRegex);
-      if (!isValidLang(langMatch?.[1] || xmlLangMatch?.[1])) {
+      const docLang = langMatch?.[1] || xmlLangMatch?.[1];
+      if (!isValidLang(docLang) || !isSameLang(docLang, primaryLanguage)) {
         const mainContent = result.replace(/<[^>]+>/g, ' ');
-        const lang = detectLanguage(mainContent);
+        const lang = isValidLang(primaryLanguage) ? primaryLanguage : detectLanguage(mainContent);
         const newLangAttr = ` lang="${lang}"`;
         const newXmlLangAttr = ` xml:lang="${lang}"`;
         attrs = langMatch ? attrs.replace(langRegex, newLangAttr) : attrs + newLangAttr;
diff --git a/apps/readest-app/src/services/transformers/types.ts b/apps/readest-app/src/services/transformers/types.ts
index 16473e08..c48109ef 100644
--- a/apps/readest-app/src/services/transformers/types.ts
+++ b/apps/readest-app/src/services/transformers/types.ts
@@ -3,6 +3,7 @@ import { ViewSettings } from '@/types/book';
 export type TransformContext = {
   bookKey: string;
   viewSettings: ViewSettings;
+  primaryLanguage?: string;
   content: string;
   transformers: string[];
   reversePunctuationTransform?: boolean;
diff --git a/apps/readest-app/src/services/transformers/whitespace.ts b/apps/readest-app/src/services/transformers/whitespace.ts
new file mode 100644
index 00000000..62eb3789
--- /dev/null
+++ b/apps/readest-app/src/services/transformers/whitespace.ts
@@ -0,0 +1,21 @@
+import type { Transformer } from './types';
+
+export const whitespaceTransformer: Transformer = {
+  name: 'whitespace',
+
+  transform: async (ctx) => {
+    const viewSettings = ctx.viewSettings;
+    if (viewSettings.overrideLayout) {
+      const cleaned = ctx.content
+        // Replace &nbsp; but skip literal "&amp;nbsp;"
+        .replace(/(?<!&amp;)&nbsp;/g, ' ')
+        // Replace literal non-breaking space characters (U+00A0) with normal spaces
+        .replace(/\u00A0/g, ' ')
+        // Collapse consecutive spaces into one
+        .replace(/ {2,}/g, ' ');
+      return cleaned;
+    } else {
+      return ctx.content;
+    }
+  },
+};