1 files changed, 98 insertions, 0 deletions
diff --git a/asl/logging/logging.hpp b/asl/logging/logging.hpp
new file mode 100644
index 0000000..81f10e7
--- /dev/null
+++ b/asl/logging/logging.hpp
@@ -0,0 +1,98 @@
+#pragma once
+
+#include "asl/format.hpp"
+#include "asl/utility.hpp"
+#include "asl/box.hpp"
+
+namespace asl::log
+{
+
+enum level : uint8_t
+{
+    kDebug = 0,
+    kInfo,
+    kWarning,
+    kError,
+};
+
+struct message
+{
+    level level;
+    string_view message;
+    source_location location;
+};
+
+// @Todo Write and use an intrusive doubly-linked list
+class Logger
+{
+    Logger* m_next{};
+
+public:
+    Logger() = default;
+    ASL_DEFAULT_COPY_MOVE(Logger);
+    virtual ~Logger() = default;
+
+    virtual void log(const message&) = 0;
+
+    friend void register_logger(box<Logger>);
+
+    constexpr Logger* next_logger() const { return m_next; }
+};
+
+class DefaultLoggerBase : public Logger
+{
+protected:
+    static void log_inner(Writer&, const message&);
+};
+
+template<derefs_as<Writer> W>
+class DefaultLogger : public DefaultLoggerBase
+{
+    W m_writer;
+
+public:
+    explicit constexpr DefaultLogger(W&& writer) : m_writer{ASL_FWD(writer)} {}
+
+    constexpr void log(const message& m) override
+    {
+        log_inner(deref<Writer>(m_writer), m);
+    }
+};
+
+void register_logger(box<Logger>);
+
+// @Todo Add a way to remove loggers (including all)
+
+template<typename T, typename... Args>
+requires constructible_from<T, Args&&...> && convertible_from<Logger*, T*>
+void register_logger(Args&&... args)
+{
+    register_logger(make_box<T>(ASL_FWD(args)...));
+}
+
+void log_inner(level l, string_view fmt, span<const format_internals::type_erased_arg> args, const source_location& sl);
+
+template<formattable... Args>
+void log(level l, const source_location& sl, string_view fmt, const Args&... args)
+{
+    if constexpr (sizeof...(Args) == 0)
+    {
+        log_inner(l, fmt, {}, sl);
+    }
+    else
+    {
+        format_internals::type_erased_arg type_erased_args[] = {
+            format_internals::type_erased_arg(args)...
+        };
+        log_inner(l, fmt, type_erased_args, sl);
+    }
+}
+
+} // namespace asl::log
+
+// @Todo Compile-time configuration of logging
+
+#define ASL_LOG_DEBUG(...) ::asl::log::log(::asl::log::kDebug, ::asl::source_location{}, __VA_ARGS__)
+#define ASL_LOG_INFO(...) ::asl::log::log(::asl::log::kInfo, ::asl::source_location{}, __VA_ARGS__)
+#define ASL_LOG_WARNING(...) ::asl::log::log(::asl::log::kWarning, ::asl::source_location{}, __VA_ARGS__)
+#define ASL_LOG_ERROR(...) ::asl::log::log(::asl::log::kError, ::asl::source_location{}, __VA_ARGS__)