Add user content translations with configurable backends (#19218)

app/lib/translation_service/libre_translate.rb

@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+class TranslationService::LibreTranslate < TranslationService
+  def initialize(base_url, api_key)
+    super()
+
+    @base_url = base_url
+    @api_key  = api_key
+  end
+
+  def translate(text, source_language, target_language)
+    request(text, source_language, target_language).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)
+      else
+        raise UnexpectedResponseError
+      end
+    end
+  end
+
+  private
+
+  def request(text, source_language, target_language)
+    req = Request.new(:post, "#{@base_url}/translate", body: Oj.dump(q: text, source: source_language, target: target_language, format: 'html', api_key: @api_key))
+    req.add_headers('Content-Type': 'application/json')
+    req
+  end
+
+  def transform_response(str, source_language)
+    json = Oj.load(str, mode: :strict)
+
+    raise UnexpectedResponseError unless json.is_a?(Hash)
+
+    Translation.new(text: json['translatedText'], detected_source_language: source_language)
+  rescue Oj::ParseError
+    raise UnexpectedResponseError
+  end
+end