Introduce the server functionality in the kiwix-lib.

This code is mainly copied from kiwix-tools.

But :
- Move all the response thing in a new class Response.
- This Response class is responsible to handle all the MHD_response
  configuration. This way the server handle a global object and do
  no call to MHD_response*
- Server uses a lot more the templating system with mustache.
  There are still few regex operations (because we need to
  change a content already existing).
- By default, the server serves the content using the id as name.
- Server creates a new Searcher per request. This way, we don't have
  to protect the search for multi-thread and we can do several search
  in the same time.
- search results are not cached, this will allow future improvement in the
  search algorithm.
- the home page is not cached.
- Few more verbose information (number of request served, time spend to
  respond to a request).

TOOD:
 - Readd interface selection.
 - Do Android wrapper.
 - Remove KiwixServer (who use a external process).
 -

include/entry.h

@@ -25,6 +25,8 @@
 #include <exception>
 #include <string>
 
+#include "common.h"
+
 using namespace std;
 
 namespace kiwix

include/meson.build

@@ -11,6 +11,7 @@ headers = [
   'entry.h',
   'searcher.h',
   'search_renderer.h',
+  'server.h',
   'kiwixserve.h',
   'name_mapper.h'
 ]

include/server.h

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2019 Matthieu Gautier <mgautier@kymeria.fr>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU  General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+
+#ifndef KIWIX_SERVER_H
+#define KIWIX_SERVER_H
+
+#include <string>
+#include <memory>
+
+namespace kiwix
+{
+  class Library;
+  class NameMapper;
+  class InternalServer;
+
+  class Server {
+     public:
+       /**
+        * The default constructor.
+        *
+        * @param library The library to serve.
+        */
+       Server(Library& library, NameMapper* nameMapper=nullptr);
+
+       virtual ~Server();
+
+       /**
+        * Serve the content.
+        */
+       bool start();
+
+       /**
+        * Stop the daemon.
+        */
+       void stop();
+
+       void set_root(const std::string& root) { m_root = root; }
+       void set_port(int port) { m_port = port; }
+       void set_nbThreads(int threads) { m_nbThreads = threads; }
+       void set_verbose(bool verbose) { m_verbose = verbose; }
+       void set_taskbar(bool withTaskbar, bool withLibraryButton)
+         { m_withTaskbar = withTaskbar; m_withLibraryButton = withLibraryButton; }
+
+     protected:
+       Library& m_library;
+       NameMapper* mp_nameMapper;
+       std::string m_root = "";
+       int m_port = 80;
+       int m_nbThreads = 1;
+       bool m_verbose = false;
+       bool m_withTaskbar = true;
+       bool m_withLibraryButton = true;
+       std::unique_ptr<InternalServer> mp_server;
+  };
+}
+
+#endif