Migrate active selection language script

Author: jonathanKingston

injected/src/features/page-context.js

@@ -1,6 +1,7 @@
 import ContentFeature from '../content-feature.js';
 import { getFaviconList } from './favicon.js';
 import { isDuckAi, isBeingFramed, getTabUrl } from '../utils.js';
+import { getActiveSelectionLanguage } from './page-context/utils.js';
 const MSG_PAGE_CONTEXT_RESPONSE = 'collectionResult';
 
 function collapseWhitespace(str) {
@@ -76,12 +77,21 @@ export default class PageContext extends ContentFeature {
     listenForUrlChanges = true;
 
     init() {
+        this.setupActiveSelectionLanguageListener();
         if (!this.shouldActivate()) {
             return;
         }
         this.setupListeners();
     }
 
+    setupActiveSelectionLanguageListener() {
+        this.messaging.subscribe('getActiveSelectionLanguage', () => {
+            const activeSelectionLanguage = getActiveSelectionLanguage();
+            this.log.info('Active selection language', activeSelectionLanguage);
+            this.messaging.notify('getActiveSelectionLanguageResult', { activeSelectionLanguage });
+        });
+    }
+
     setupListeners() {
         this.observeContentChanges();
         if (this.getFeatureSettingEnabled('subscribeToCollect', 'enabled')) {

injected/src/features/page-context/utils.js

@@ -0,0 +1,40 @@
+export function getActiveSelectionLanguage() {
+    // BCP 47 language tag regex
+    const bcp47 = /^(?:en-GB-oed|i-ami|i-bnn|i-default|i-enochian|i-hak|i-klingon|i-lux|i-mingo|i-navajo|i-pwn|i-tao|i-tay|i-tsu|sgn-BE-FR|sgn-BE-NL|sgn-CH-DE|art-lojban|cel-gaulish|no-bok|no-nyn|zh-guoyu|zh-hakka|zh-min|zh-min-nan|zh-xiang|(?<langtag>(?<language>[A-Za-z]{2,3}(?<extlang>-[A-Za-z]{3}(-[A-Za-z]{3}){0,2})?|[A-Za-z]{4,8})(?:-(?<script>[A-Za-z]{4}))?(?:-(?<region>[A-Za-z]{2}|[0-9]{3}))?(?<variants>(?:-(?:[0-9A-Za-z]{5,8}|[0-9][0-9A-Za-z]{3}))*)(?<extensions>(?:-(?:[0-9A-WY-Za-wy-z](?:-[0-9A-Za-z]{2,8})+))*)(?:-(?<privateuse>x(?:-[0-9A-Za-z]{1,8})+))?)|(?<privateuse>x(?:-[0-9A-Za-z]{1,8})+))$/mgi
+    
+    // Get the Selection from the currently focused document (top or same-origin iframe)
+    function getActiveSelection() {
+        const activeElement = document.activeElement;
+        if (activeElement && activeElement.tagName === 'IFRAME') {
+            try {
+                return activeElement.contentWindow?.getSelection() || null;
+            } catch {
+                // Cross-origin iframe: cannot access its selection
+            }
+        }
+        return window.getSelection?.() || null;
+    }
+    
+    const selection = getActiveSelection();
+    const startContainer = selection?.rangeCount ? selection.getRangeAt(0).startContainer : null;
+
+    // If no selection, use the document's lang (or null if absent)
+    if (!startContainer) {
+        return document.documentElement.getAttribute('lang') || null;
+    }
+
+    // If the start is a text node, step up to its parent element
+    const startElement =
+        startContainer.nodeType === Node.ELEMENT_NODE
+            ? startContainer
+            : startContainer.parentElement;
+
+    // Look up the DOM tree for a lang attribute; fallback to the document's lang
+    const lang = startElement?.closest('[lang]')?.getAttribute('lang') ||
+        document.documentElement.getAttribute('lang');
+    
+    // Validate the lang attribute against the BCP 47 regex
+    if (lang && bcp47.test(lang)) return lang;
+    
+    return null;
+}