Give download hints to relevant file extensions

#920
The Swift macOS app somehow needs those hints to download certain files that Safari would download from itself.

index/listing.cpp

@@ -17,6 +17,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
 
+#include <forward_list>
 #include <index/listing.h>
 #include <assets/view.h>
 #include <assets/page.h>
@@ -36,26 +37,29 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 #include <pugixml.hpp>
 #endif
 #pragma GCC diagnostic pop
-using namespace std;
-using namespace pugi;
 
 
-bool index_listing_match (string url)
+static bool index_listing_match (const std::string& url)
 {
-  if (url.length () >= 9) if (url.substr (0, 9) == "revisions") return true;
-  if (url.length () >= 7) if (url.substr (0, 7) == "exports") return true;
+  if (url.length () >= 9) 
+    if (url.substr (0, 9) == "revisions")
+      return true;
+  if (url.length () >= 7) 
+    if (url.substr (0, 7) == "exports")
+      return true;
   return false;
 }
 
 
-string index_listing_url (string url)
+std::string index_listing_url (const std::string& url)
 {
-  if (index_listing_match (url)) return url;
+  if (index_listing_match (url)) 
+    return url;
   return "\\";
 }
 
 
-bool index_listing_acl (Webserver_Request& webserver_request, string url)
+bool index_listing_acl (Webserver_Request& webserver_request, std::string url)
 {
   // Bible exports are public.
   if (url.find ("exports") == 0) {
@@ -66,64 +70,66 @@ bool index_listing_acl (Webserver_Request& webserver_request, string url)
 }
 
 
-string index_listing (Webserver_Request& webserver_request, string url)
+std::string index_listing (Webserver_Request& webserver_request, std::string url)
 {
-  string page;
-  page = assets_page::header (translate ("Bibledit"), webserver_request);
+  std::string page = assets_page::header (translate ("Bibledit"), webserver_request);
   // No breadcrumbs because the user can arrive here from more than one place.
   Assets_View view;
   url = filter_url_urldecode (url);
-  url = filter_url_create_path ({string(), url});
+  url = filter_url_create_path ({std::string(), url});
   url = filter::strings::replace (R"(\)", "/", url);
   view.set_variable ("url", url);
-  string parent = filter_url_dirname_web (url);
+  const std::string parent = filter_url_dirname_web (url);
   if (parent.length () > 1) {
     view.enable_zone ("parent");
     view.set_variable ("parent", parent);
   }
-  string directory = filter_url_create_root_path ({url});
+  const std::string directory = filter_url_create_root_path ({url});
   if (!file_or_dir_exists (directory) || filter_url_is_dir (directory)) {
     // The document that contains the listing.
-    xml_document listing_document;
-    string listing;
+    pugi::xml_document listing_document;
+    std::string listing;
     // Check the files in this folder.
-    vector <string> files = filter_url_scandir (directory);
+    std::vector <std::string> files = filter_url_scandir (directory);
     // Handle empty folder.
     if (files.empty()) {
-      xml_node span_node = listing_document.append_child("span");
+      pugi::xml_node span_node = listing_document.append_child("span");
       span_node.text().set(translate ("No files in this folder").c_str());
     }
     // Handle file / folder listing.
     else {
-      xml_node table_node = listing_document.append_child("table");
-      for (auto & file : files) {
+      pugi::xml_node table_node = listing_document.append_child("table");
+      for (const auto& file : files) {
         // Open a new row.
-        xml_node tr_node = table_node.append_child("tr");
+        pugi::xml_node tr_node = table_node.append_child("tr");
         // Add the link to the file in the first column.
-        xml_node td_node = tr_node.append_child("td");
-        xml_node a_node = td_node.append_child("a");
-        string href = filter_url_create_path ({url, file});
+        pugi::xml_node td_node = tr_node.append_child("td");
+        pugi::xml_node a_node = td_node.append_child("a");
+        const std::string href = filter_url_create_path ({url, file});
         a_node.append_attribute("href") = href.c_str();
         a_node.text().set(file.c_str());
-        // Implement force download for USFM files.
+        // Implement force download for USFM files and other files.
         // https://github.com/bibledit/cloud/issues/771
-        string suffix = filter_url_get_extension (file);
-        if (suffix == "usfm") {
+        constexpr std::array<std::string_view, 5> downloadable_suffixes {
+          "bblx", "exp", "odt", "zip", "usfm"
+        };
+        const std::string suffix = filter_url_get_extension (file);
+        if (std::find (downloadable_suffixes.begin(), downloadable_suffixes.end(), suffix) != downloadable_suffixes.end()) {
           a_node.append_attribute("download") = file.c_str();
         }
         // Optionally add the file size.
-        string path = filter_url_create_path ({directory, file});
+        const std::string path = filter_url_create_path ({directory, file});
         if (!filter_url_is_dir (path)) {
           td_node = tr_node.append_child("td");
           td_node.text().set(filter::strings::convert_to_string (filter_url_filesize (path)).c_str());
         }
       }
     }
-    stringstream ss;
-    listing_document.print (ss, "", format_raw);
+    std::stringstream ss {};
+    listing_document.print (ss, "", pugi::format_raw);
     view.set_variable ("listing", ss.str());
   } else {
-    string filename = filter_url_create_root_path ({url});
+    const std::string filename = filter_url_create_root_path ({url});
     return filter_url_file_get_contents (filename);
   }
   page += view.render ("index", "listing");

index/listing.h

@@ -23,6 +23,6 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 class Webserver_Request;
 
-std::string index_listing_url (std::string url);
+std::string index_listing_url (const std::string& url);
 bool index_listing_acl (Webserver_Request& webserver_request, std::string url);
 std::string index_listing (Webserver_Request& webserver_request, std::string url);