Only offer translation for supported languages (#23879)

1 files changed, 27 insertions, 11 deletions

diff --git a/app/lib/translation_service/libre_translate.rb b/app/lib/translation_service/libre_translate.rb
index 4ebe21e45..743e4d77f 100644
--- a/app/lib/translation_service/libre_translate.rb
+++ b/app/lib/translation_service/libre_translate.rb
@@ -9,29 +9,45 @@ class TranslationService::LibreTranslate < TranslationService
   end
 
   def translate(text, source_language, target_language)
-    request(text, source_language, target_language).perform do |res|
+    body = Oj.dump(q: text, source: source_language.presence || 'auto', target: target_language, format: 'html', api_key: @api_key)
+    request(:post, '/translate', body: body) do |res|
+      transform_response(res.body_with_limit, source_language)
+    end
+  end
+
+  def supported?(source_language, target_language)
+    languages.key?(source_language) && languages[source_language].include?(target_language)
+  end
+
+  private
+
+  def languages
+    Rails.cache.fetch('translation_service/libre_translate/languages', expires_in: 7.days, race_condition_ttl: 1.minute) do
+      request(:get, '/languages') do |res|
+        languages = Oj.load(res.body_with_limit).to_h { |language| [language['code'], language['targets']] }
+        languages[nil] = languages.values.flatten.uniq
+        languages
+      end
+    end
+  end
+
+  def request(verb, path, **options)
+    req = Request.new(verb, "#{@base_url}#{path}", allow_local: true, **options)
+    req.add_headers('Content-Type': 'application/json')
+    req.perform do |res|
       case res.code
       when 429
         raise TooManyRequestsError
       when 403
         raise QuotaExceededError
       when 200...300
-        transform_response(res.body_with_limit, source_language)
+        yield res
       else
         raise UnexpectedResponseError
       end
     end
   end
 
-  private
-
-  def request(text, source_language, target_language)
-    body = Oj.dump(q: text, source: source_language.presence || 'auto', target: target_language, format: 'html', api_key: @api_key)
-    req = Request.new(:post, "#{@base_url}/translate", body: body, allow_local: true)
-    req.add_headers('Content-Type': 'application/json')
-    req
-  end
-
   def transform_response(str, source_language)
     json = Oj.load(str, mode: :strict)