Logging: add log levels to mirror Core's

For now, all messages are reported at Log::Info.

Author: theuni

include/mp/proxy-io.h

@@ -98,12 +98,35 @@ class LoggingErrorHandler : public kj::TaskSet::ErrorHandler
     EventLoop& m_loop;
 };
 
+enum class Log {
+    Trace = 0,
+    Debug,
+    Info,
+    Warning,
+    Error,
+    Raise,
+};
+
 using LogFn = std::function<void(bool raise, std::string message)>;
 
+struct LogOptions {
+
+    //! External logging callback.
+    LogFn log_fn;
+
+    //! Maximum number of characters to use when representing
+    //! request and response structs as strings.
+    size_t max_chars{200};
+
+    //! Messages with a severity level less than log_level will not be
+    //! reported.
+    Log log_level{Log::Trace};
+};
+
 class Logger
 {
 public:
-    Logger(bool raise, LogFn& fn) : m_raise(raise), m_fn(fn) {}
+    Logger(const LogOptions& options, Log log_level) : m_options(options), m_log_level(log_level) {}
 
     Logger(Logger&&) = delete;
     Logger& operator=(Logger&&) = delete;
@@ -112,13 +135,13 @@ class Logger
 
     ~Logger() noexcept(false)
     {
-        if (m_fn) m_fn(m_raise, m_buffer.str());
+        if (m_options.log_fn) m_options.log_fn(m_log_level == Log::Raise, m_buffer.str());
     }
 
     template <typename T>
     friend Logger& operator<<(Logger& logger, T&& value)
     {
-        if (logger.m_fn) logger.m_buffer << std::forward<T>(value);
+        if (logger.m_options.log_fn) logger.m_buffer << std::forward<T>(value);
         return logger;
     }
 
@@ -128,21 +151,11 @@ class Logger
         return logger << std::forward<T>(value);
     }
 
-    bool m_raise;
-    LogFn& m_fn;
+    const LogOptions& m_options;
+    Log m_log_level;
     std::ostringstream m_buffer;
 };
 
-struct LogOptions {
-
-    //! External logging callback.
-    LogFn log_fn;
-
-    //! Maximum number of characters to use when representing
-    //! request and response structs as strings.
-    size_t max_chars{200};
-};
-
 std::string LongThreadName(const char* exe_name);
 
 //! Event loop implementation.
@@ -222,12 +235,12 @@ class EventLoop
 
     Logger log()
     {
-        Logger logger(false, m_log_opts.log_fn);
+        Logger logger(m_log_opts, Log::Info);
         logger << "{" << LongThreadName(m_exe_name) << "} ";
         return logger;
     }
-    Logger logPlain() { return {false, m_log_opts.log_fn}; }
-    Logger raise() { return {true, m_log_opts.log_fn}; }
+    Logger logPlain() { return {m_log_opts, Log::Info}; }
+    Logger raise() { return {m_log_opts, Log::Raise}; }
 
     //! Process name included in thread names so combined debug output from
     //! multiple processes is easier to understand.