Suggestions now use xapian database when available.

If a embedded fulltext database is present, suggestion will search in it :
 - insensitive case search.
 - search for terms in the middle of the title.
 - xapian will try to complete the last word of the query (as if a '*'
   were added at the end)

include/searcher.h

@@ -61,6 +61,7 @@ class Searcher
               unsigned int resultStart,
               unsigned int resultEnd,
               const bool verbose = false);
+  void suggestions(std::string& search, const bool verbose = false);
   Result* getNextResult();
   void restart_search();
   unsigned int getEstimatedResultCount();

src/reader.cpp

@@ -20,6 +20,8 @@
 #include "reader.h"
 #include <time.h>
 
+#include <zim/search.h>
+
 inline char hi(char v)
 {
   char hex[] = "0123456789abcdef";
@@ -678,12 +680,30 @@ bool Reader::searchSuggestionsSmart(const string& prefix,
 
   this->suggestions.clear();
   this->suggestionsOffset = this->suggestions.begin();
+  /* Try to search in the title using fulltext search database */
+  const zim::Search* suggestionSearch
+      = this->getZimFileHandler()->suggestions(prefix, 0, suggestionsCount);
+
+  if (suggestionSearch->get_matches_estimated()) {
+    for (auto current = suggestionSearch->begin();
+         current != suggestionSearch->end();
+         current++) {
+      std::vector<std::string> suggestion;
+      suggestion.push_back(current->getTitle());
+      suggestion.push_back("/A/" + current->getUrl());
+      suggestion.push_back(kiwix::normalize(current->getTitle()));
+      this->suggestions.push_back(suggestion);
+    }
+    this->suggestionsOffset = this->suggestions.begin();
+    retVal = true;
+  } else {
     for (std::vector<std::string>::iterator variantsItr = variants.begin();
          variantsItr != variants.end();
          variantsItr++) {
       retVal = this->searchSuggestions(*variantsItr, suggestionsCount, false)
                || retVal;
     }
+  }
 
   return retVal;
 }

src/searcher.cpp

@@ -172,6 +172,31 @@ void Searcher::reset()
   return;
 }
 
+void Searcher::suggestions(std::string& search, const bool verbose)
+{
+  this->reset();
+
+  if (verbose == true) {
+    cout << "Performing suggestion query `" << search << "`" << endl;
+  }
+
+  this->searchPattern = search;
+  this->resultStart = 0;
+  this->resultEnd = 10;
+  string unaccentedSearch = removeAccents(search);
+
+  if (internal->_xapianSearcher) {
+    /* [TODO] Suggestion on a external database ?
+     * We do not support that. */
+    this->estimatedResultCount = 0;
+  } else {
+    internal->_search = this->reader->getZimFileHandler()->suggestions(
+          unaccentedSearch, resultStart, resultEnd);
+    internal->current_iterator = internal->_search->begin();
+    this->estimatedResultCount = internal->_search->get_matches_estimated();
+  }
+}
+
 /* Return the result count estimation */
 unsigned int Searcher::getEstimatedResultCount()
 {