Allow kiwix-serve to get suggestions of custom range

This will allow handle_suggest API to accept two arguments `start` and
`suggestionLength` that will allow handle_suggest to retrieve
suggestions in the given range rather than the default 0-10 range.

src/server/internalServer.cpp

@@ -334,15 +334,15 @@ std::unique_ptr<Response> InternalServer::build_homepage(const RequestContext& r
 
 // TODO: retrieve searcher from caching mechanism
 SuggestionsList_t getSuggestions(const zim::Archive* const archive,
-                  const std::string& queryString, int suggestionCount)
+                  const std::string& queryString, int start, int end)
 {
   SuggestionsList_t suggestions;
   if (archive->hasTitleIndex()) {
     auto searcher = zim::Searcher(*archive);
     zim::Query suggestionQuery;
     suggestionQuery.setQuery(queryString, true);
     auto suggestionSearch = searcher.search(suggestionQuery);
-    auto suggestionResult = suggestionSearch.getResults(0, suggestionCount);
+    auto suggestionResult = suggestionSearch.getResults(start, end);
 
     for (auto it = suggestionResult.begin(); it != suggestionResult.end(); it++) {
       SuggestionItem suggestion(it.getTitle(), kiwix::normalize(it.getTitle()),
@@ -353,6 +353,7 @@ SuggestionsList_t getSuggestions(const zim::Archive* const archive,
     // TODO: This case should be handled by libzim
     std::vector<std::string> variants = getTitleVariants(queryString);
     int currCount = 0;
+    int suggestionCount = end - start;
     for (auto it = variants.begin(); it != variants.end() && currCount < suggestionCount; it++) {
       for (auto& entry: archive->findByTitle(*it)) {
         SuggestionItem suggestion(entry.getTitle(), kiwix::normalize(entry.getTitle()),
@@ -426,8 +427,6 @@ std::unique_ptr<Response> InternalServer::handle_suggest(const RequestContext& r
 
   std::string content;
   std::string mimeType;
-  unsigned int maxSuggestionCount = 10;
-  unsigned int suggestionCount = 0;
 
   std::string bookName;
   std::string bookId;
@@ -442,6 +441,19 @@ std::unique_ptr<Response> InternalServer::handle_suggest(const RequestContext& r
     return Response::build_404(*this, request, bookName, "");
   }
 
+  auto start = 0;
+  try {
+    start = request.get_argument<unsigned int>("start");
+  } catch (const std::exception&) {}
+
+  unsigned int suggestionLength = 10;
+  try {
+    suggestionLength = request.get_argument<unsigned int>("suggestionLength");
+  } catch (const std::exception&) {}
+  if (suggestionLength == 0) suggestionLength = 10;
+
+  auto end = start + suggestionLength;
+
   if (archive == nullptr) {
     return Response::build_404(*this, request, bookName, "");
   }
@@ -455,7 +467,7 @@ std::unique_ptr<Response> InternalServer::handle_suggest(const RequestContext& r
   bool first = true;
 
   /* Get the suggestions */
-  SuggestionsList_t suggestions = getSuggestions(archive.get(), queryString, maxSuggestionCount);
+  SuggestionsList_t suggestions = getSuggestions(archive.get(), queryString, start, end);
   for(auto& suggestion:suggestions) {
     MustacheData result;
     result.set("label", suggestion.getTitle());
@@ -470,7 +482,6 @@ std::unique_ptr<Response> InternalServer::handle_suggest(const RequestContext& r
     result.set("first", first);
     first = false;
     results.push_back(result);
-    suggestionCount++;
   }