1 files changed, 92 insertions, 0 deletions
diff --git a/include/cru/common/Logger.hpp b/include/cru/common/Logger.hpp
new file mode 100644
index 00000000..bd16678b
--- /dev/null
+++ b/include/cru/common/Logger.hpp
@@ -0,0 +1,92 @@
+#pragma once
+#include "cru/common/Base.hpp"
+
+#include <fmt/format.h>
+#include <fmt/ostream.h>
+#include <iostream>
+#include <list>
+#include <memory>
+#include <string_view>
+
+namespace cru::log {
+
+enum class LogLevel { Debug, Info, Warn, Error };
+
+struct ILogSource : virtual Interface {
+  // Write the string s. LogLevel is just a helper. It has no effect on the
+  // content to write.
+  virtual void Write(LogLevel level, const std::string_view& s) = 0;
+};
+
+class StdioLogSource : public virtual ILogSource {
+ public:
+  StdioLogSource() = default;
+
+  CRU_DELETE_COPY(StdioLogSource)
+  CRU_DELETE_MOVE(StdioLogSource)
+
+  ~StdioLogSource() override = default;
+
+  void Write(LogLevel level, const std::string_view& s) override {
+    // TODO: Emmm... Since it is buggy to use narrow char in UTF-8 on Windows. I
+    // think this implementation might be broken. (However, I didn't test it.)
+    // Maybe, I should detect Windows and use wide char (And I didn't test this
+    // either) or other more complicated implementation. Currently, I settled
+    // with this.
+    if (level == LogLevel::Error) {
+      std::cerr << s;
+    } else {
+      std::cout << s;
+    }
+  }
+};
+
+class Logger : public Object {
+ public:
+  static Logger* GetInstance();
+
+ public:
+  Logger() = default;
+
+  CRU_DELETE_COPY(Logger)
+  CRU_DELETE_MOVE(Logger)
+
+  ~Logger() override = default;
+
+ public:
+  void AddSource(std::unique_ptr<ILogSource> source);
+  void RemoveSource(ILogSource* source);
+
+ public:
+  void Log(LogLevel level, const std::string_view& s);
+
+ public:
+  std::list<std::unique_ptr<ILogSource>> sources_;
+};
+
+template <typename... TArgs>
+void Debug([[maybe_unused]] TArgs&&... args) {
+#ifdef CRU_DEBUG
+  Logger::GetInstance()->Log(LogLevel::Debug,
+                             fmt::format(std::forward<TArgs>(args)...));
+#endif
+}
+
+template <typename... TArgs>
+void Info(TArgs&&... args) {
+  Logger::GetInstance()->Log(LogLevel::Info,
+                             fmt::format(std::forward<TArgs>(args)...));
+}
+
+template <typename... TArgs>
+void Warn(TArgs&&... args) {
+  Logger::GetInstance()->Log(LogLevel::Warn,
+                             fmt::format(std::forward<TArgs>(args)...));
+}
+
+template <typename... TArgs>
+void Error(TArgs&&... args) {
+  Logger::GetInstance()->Log(LogLevel::Error,
+                             fmt::format(std::forward<TArgs>(args)...));
+}
+}  // namespace cru::log