Add language-aware filtering to random book feature

openlibrary/plugins/openlibrary/home.py

@@ -11,7 +11,11 @@
 from infogami.utils.view import public, render_template
 from openlibrary.core import admin, cache, ia, lending
 from openlibrary.i18n import gettext as _
-from openlibrary.plugins.upstream.utils import get_blog_feeds
+from openlibrary.plugins.upstream.utils import (
+    convert_iso_to_marc,
+    get_blog_feeds,
+    get_populated_languages,
+)
 from openlibrary.plugins.worksearch import search, subjects
 from openlibrary.utils import dateutil
 from openlibrary.utils.async_utils import set_context_from_legacy_web_py
@@ -112,12 +116,19 @@ def GET(self):
 
 
 @cache.memoize(
-    engine="memcache", key="home.random_book", expires=dateutil.HALF_HOUR_SECS
+    engine="memcache",
+    key=lambda count, language=None: f"home.random_book.{language or 'all'}",
+    expires=dateutil.HALF_HOUR_SECS,
 )
-def get_random_borrowable_ebook_keys(count: int) -> list[str]:
+def get_random_borrowable_ebook_keys(
+    count: int, language: str | None = None
+) -> list[str]:
     solr = search.get_solr()
+    query = 'type:edition AND ebook_access:[borrowable TO *]'
+    if language:
+        query += f' AND language:{language}'
     docs = solr.select(
-        'type:edition AND ebook_access:[borrowable TO *]',
+        query,
         fields=['key'],
         rows=count,
         sort=f'random_{random.random()} desc',
@@ -129,7 +140,16 @@ class random_book(delegate.page):
     path = "/random"
 
     def GET(self):
-        keys = get_random_borrowable_ebook_keys(1000)
+        # Get user's language preference
+        user_lang = None
+        web_lang = web.ctx.lang or 'en'
+        marc_lang = convert_iso_to_marc(web_lang)
+
+        # Only filter by language if it's a populated language
+        if marc_lang and marc_lang in get_populated_languages():
+            user_lang = marc_lang
+
+        keys = get_random_borrowable_ebook_keys(1000, language=user_lang)
         raise web.seeother(random.choice(keys))