Add a logger class

src/logger/logger.cpp

@@ -0,0 +1,41 @@
+#include <utils/make_unique.hpp>
+#include <logger/logger.hpp>
+#include <config/config.hpp>
+
+Logger::Logger(const int log_level):
+  log_level(log_level),
+  stream(std::cout.rdbuf())
+{
+  std::cout << "Logger(1)" << std::endl;
+}
+
+Logger::Logger(const int log_level, const std::string& log_file):
+  log_level(log_level),
+  ofstream(log_file.data(), std::ios_base::app),
+  stream(ofstream.rdbuf())
+{
+  std::cout << "Logger(" << this->log_level << ")" << std::endl;
+}
+
+std::unique_ptr<Logger>& Logger::instance()
+{
+  static std::unique_ptr<Logger> instance;
+
+  if (!instance)
+    {
+      const std::string log_file = Config::get("log_file", "");
+      const int log_level = Config::get_int("log_level", 0);
+      if (log_file.empty())
+        instance = std::make_unique<Logger>(log_level);
+      else
+        instance = std::make_unique<Logger>(log_level, log_file);
+    }
+  return instance;
+}
+
+std::ostream& Logger::get_stream(const int lvl)
+{
+  if (lvl >= this->log_level)
+    return this->stream;
+  return this->null_stream;
+}