Move backend name to config file

Still, only one backend is available at this point.

orotool.conf

@@ -1,6 +1,7 @@
 [system]
 db_path=originsro.db3
 worker_threads=3
+backend=sqlite
 
 [rules]
 fetch_extra_delay=30

src/app_config.cpp

@@ -34,6 +34,9 @@ namespace {
 	constexpr const char g_worker_threads_sect[] = "system";
 	constexpr const char g_worker_threads[] = "worker_threads";
 
+	constexpr const char g_backend_sect[] = "system";
+	constexpr const char g_backend[] = "backend";
+
 	constexpr const char g_fetch_extra_delay_sect[] = "rules";
 	constexpr const char g_fetch_extra_delay[] = "fetch_extra_delay";
 	constexpr const char g_fetch_extra_delay_def[] = "30";
@@ -125,4 +128,8 @@ std::size_t AppConfig::fetch_extra_delay() const {
 	}
 }
 
+std::string_view AppConfig::backend() const {
+	return value_ifp(m_ini, g_backend_sect, g_backend, g_def_backend_name, false);
+}
+
 } //namespace duck

src/app_config.hpp

@@ -32,6 +32,7 @@ public:
 	std::string_view api_key() const;
 	std::size_t worker_threads() const;
 	std::size_t fetch_extra_delay() const;
+	std::string_view backend() const;
 
 private:
 	kamokan::IniFile m_ini;

src/config.hpp.in

@@ -31,4 +31,12 @@ constexpr const unsigned short int g_version_patch = @PROJECT_VERSION_PATCH@;
 
 #mesondefine OROTOOL_WITH_SQLITE
 
+#if defined(OROTOOL_WITH_SQLITE)
+constexpr const char g_sqlite_backend_name[] = "sqlite";
+#endif
+
+#if defined(OROTOOL_WITH_SQLITE)
+inline constexpr const auto& g_def_backend_name = g_sqlite_backend_name;
+#endif
+
 } //namespace duck

src/main.cpp

@@ -74,7 +74,7 @@ int main(int argc, char* argv[]) {
 
 		print_ping(oro_api);
 
-		std::unique_ptr<oro::OriginsDB> db(oro::OriginsDB::make("sqlite", app_conf.db_path()));
+		std::unique_ptr<oro::OriginsDB> db(oro::OriginsDB::make(app_conf.backend(), app_conf.db_path()));
 
 		duck::test(
 			&oro_api,

src/oro/originsdb.cpp

@@ -29,7 +29,7 @@ namespace oro {
 			return {};
 		}
 #if defined(OROTOOL_WITH_SQLITE)
-		else if (name == "sqlite") {
+		else if (name == duck::g_sqlite_backend_name) {
 			return std::make_unique<OriginsDBSQLite>(param);
 		}
 #endif