Demo of error page translation

This commit demonstrates front-end-side translation of an error page
for a URL like /viewer#INVALIDBOOK/whatever (where INVALIDBOOK should
be a book name not present in the library)

Known issues:

- Tests are broken (not counting that in the CI they are broken due
  the missing patch to mustache.hpp)

- Changing the UI language while an error page is displayed in the
  viewer doesn't retranslate it.

src/server/internalServer.cpp

@@ -1133,7 +1133,7 @@ std::unique_ptr<Response> InternalServer::handle_content(const RequestContext& r
 
   if (archive == nullptr) {
     const std::string searchURL = m_root + "/search?pattern=" + kiwix::urlEncode(pattern);
-    return UrlNotFoundResponse(request)
+    return UrlNotFoundResponse(request, true)
            + suggestSearchMsg(searchURL, kiwix::urlDecode(pattern));
   }
 

src/server/response.cpp

@@ -269,16 +269,20 @@ HTTPErrorResponse::HTTPErrorResponse(const RequestContext& request,
   };
 }
 
-HTTP404Response::HTTP404Response(const RequestContext& request)
+HTTP404Response::HTTP404Response(const RequestContext& request,
+                                 bool includeKiwixResponseData)
   : HTTPErrorResponse(request,
                       MHD_HTTP_NOT_FOUND,
                       "404-page-title",
-                      "404-page-heading")
+                      "404-page-heading",
+                      std::string(),
+                      includeKiwixResponseData)
 {
 }
 
-UrlNotFoundResponse::UrlNotFoundResponse(const RequestContext& request)
-    : HTTP404Response(request)
+UrlNotFoundResponse::UrlNotFoundResponse(const RequestContext& request,
+                                         bool includeKiwixResponseData)
+    : HTTP404Response(request, includeKiwixResponseData)
 {
   const std::string requestUrl = urlDecode(m_request.get_full_url(), false);
   *this += ParameterizedMessage("url-not-found", {{"url", requestUrl}});

src/server/response.h

@@ -161,12 +161,14 @@ struct HTTPErrorResponse : ContentResponseBlueprint
 
 struct HTTP404Response : HTTPErrorResponse
 {
-  explicit HTTP404Response(const RequestContext& request);
+  explicit HTTP404Response(const RequestContext& request,
+                           bool includeKiwixResponseData = false);
 };
 
 struct UrlNotFoundResponse : HTTP404Response
 {
-  explicit UrlNotFoundResponse(const RequestContext& request);
+  explicit UrlNotFoundResponse(const RequestContext& request,
+                               bool includeKiwixResponseData = false);
 };
 
 struct HTTP400Response : HTTPErrorResponse

static/skin/i18n.js

@@ -69,6 +69,43 @@ function $t(msgId, params={}) {
   }
 }
 
+const I18n = {
+  instantiateParameterizedMessages: function(data) {
+    //console.log('I18n.instantiateParameterizedMessages: data = ' + JSON.stringify(data));
+    if ( data.__proto__ == Array.prototype ) {
+      //console.log('I18n.instantiateParameterizedMessages: data is an array');
+      const result = [];
+      for ( const x of data ) {
+        result.push(this.instantiateParameterizedMessages(x));
+      }
+      return result;
+    } else if ( data.__proto__ == Object.prototype ) {
+      //console.log('I18n.instantiateParameterizedMessages: data is an object');
+      const msgId = data.msgid;
+      const msgParams = data.params;
+      if ( msgId && msgId.__proto__ == String.prototype && msgParams && msgParams.__proto__ == Object.prototype ) {
+        return $t(msgId, msgParams);
+      } else {
+        const result = {};
+        for ( const p in data ) {
+          result[p] = this.instantiateParameterizedMessages(data[p]);
+        }
+        return result;
+      }
+    } else {
+      //console.log('I18n.instantiateParameterizedMessages: data is something else');
+      return data;
+    }
+  },
+
+  render: function (template, params) {
+    console.log('I18n.render: params = ' + JSON.stringify(params));
+    params = this.instantiateParameterizedMessages(params);
+    console.log('I18n.render: instantiated params = ' + JSON.stringify(params));
+    return mustache.render(template, params);
+  }
+}
+
 const DEFAULT_UI_LANGUAGE = 'en';
 
 Translations.load(DEFAULT_UI_LANGUAGE, /*asDefault=*/true);
@@ -145,3 +182,4 @@ window.$t = $t;
 window.getUserLanguage = getUserLanguage;
 window.setUserLanguage = setUserLanguage;
 window.initUILanguageSelector = initUILanguageSelector;
+window.I18n = I18n;

static/skin/viewer.js

@@ -249,6 +249,18 @@ function handle_location_hash_change() {
   history.replaceState(viewerState, null);
 }
 
+function translateErrorPageIfNeeded() {
+  const cw = contentIframe.contentWindow;
+  if ( cw.KIWIX_RESPONSE_TEMPLATE && cw.KIWIX_RESPONSE_DATA ) {
+    const template = htmlDecode(cw.KIWIX_RESPONSE_TEMPLATE);
+    const params = JSON.parse(JSON.stringify(cw.KIWIX_RESPONSE_DATA));
+    const html = I18n.render(template, params);
+    setTimeout(function() {
+      cw.document.documentElement.innerHTML = new DOMParser().parseFromString(html, "text/html").documentElement.innerHTML;
+    }, 0);
+  }
+}
+
 function handle_content_url_change() {
   const iframeLocation = contentIframe.contentWindow.location;
   console.log('handle_content_url_change: ' + iframeLocation.href);
@@ -258,6 +270,7 @@ function handle_content_url_change() {
   const newHash = iframeUrl2UserUrl(iframeContentUrl, iframeContentQuery);
   history.replaceState(viewerState, null, makeURL(location.search, newHash));
   updateCurrentBookIfNeeded(newHash);
+  translateErrorPageIfNeeded();
 };
 
 ////////////////////////////////////////////////////////////////////////////////