custom formatter api

include/journal.hpp

@@ -2,6 +2,8 @@
 
 #include <format>
 #include <ios>
+#include <memory>
+#include <string>
 #include <string_view>
 
 namespace journal {
@@ -48,8 +50,30 @@ enum LogVerbosity {
   Error,
 };
 
+struct Verbosity {
+  journal::detail::LogVerbosity inner;
+
+  Verbosity(journal::detail::LogVerbosity &&value) : inner(value) {}
+  Verbosity(const journal::detail::LogVerbosity &value) : inner(value) {}
+
+  auto operator<=>(const Verbosity &rhs) const -> std::strong_ordering {
+    return static_cast<std::underlying_type_t<decltype(inner)>>(inner) <=>
+           static_cast<std::underlying_type_t<decltype(rhs.inner)>>(rhs.inner);
+  }
+};
+
 constexpr auto to_string(const LogVerbosity& verbosity) -> std::string;
 
+namespace formatter {
+
+struct Formatter {
+  virtual auto operator()(const Verbosity &verbosity,
+                          const source_location &source) -> std::string = 0;
+  virtual ~Formatter() {}
+};
+
+} // namespace formatter
+
 template <typename... Args>
 inline constexpr auto log(const LogVerbosity &verbosity, std::string_view fmt,
                           Args... args, const detail::source_location source)
@@ -61,6 +85,7 @@ inline constexpr auto log(const LogVerbosity &verbosity, std::string_view fmt,
 auto log_internal(const LogVerbosity &verbosity,
                   const detail::source_location source, const std::string &msg)
     -> void;
+
 } // namespace detail
 
 using detail::LogVerbosity;
@@ -69,6 +94,8 @@ auto init_std_out(const LogVerbosity &min = LogVerbosity::Info) -> void;
 auto init_std_out_err(const LogVerbosity &min = LogVerbosity::Info) -> void;
 auto init() -> void;
 auto init_no_threads() -> void;
+auto set_formatter(std::unique_ptr<detail::formatter::Formatter> &&formatter)
+    -> void;
 auto add_std_out() -> void;
 auto add_std_err() -> void;
 auto add_file(std::string_view file_path,

src/journal.cc

@@ -11,6 +11,7 @@
 #include <optional>
 #include <ostream>
 #include <stop_token>
+#include <string>
 #include <string_view>
 #include <thread>
 
@@ -166,17 +167,30 @@ constexpr auto to_string(const LogVerbosity& verbosity) -> std::string {
         }
 }
 
-struct Verbosity {
+namespace formatter {
-  journal::detail::LogVerbosity inner;
 
-  Verbosity(journal::detail::LogVerbosity &&value) : inner(value) {}
+struct DefaultFormatter : public Formatter {
-  Verbosity(const journal::detail::LogVerbosity &value) : inner(value) {}
+  virtual auto operator()(const Verbosity &verbosity,
+                          const source_location &source) -> std::string {
+    return std::format("[{}] [{: <5}] [{}]", get_current_time_string(),
+                       to_string(verbosity.inner),
+                       get_source_location_string(source));
+  }
 
-  auto operator<=>(const Verbosity &rhs) const -> std::strong_ordering {
+  auto get_source_location_string(const source_location &source)
-    return static_cast<std::underlying_type_t<decltype(inner)>>(inner) <=>
+      -> std::string {
-           static_cast<std::underlying_type_t<decltype(rhs.inner)>>(rhs.inner);
+    const auto file =
+        std::filesystem::path(source.file_name()).filename().string();
+    return std::format("{}::{}", file, source.line());
+  }
+
+  auto get_current_time_string() -> std::string {
+    const auto now = std::chrono::utc_clock::now();
+
+    return std::format("{:%Y-%m-%d %H:%M:%OS} UTC", now);
   }
 };
+} // namespace formatter
 
 using namespace std::chrono_literals;
 
@@ -251,11 +265,14 @@ static auto try_flush_all_loop(std::stop_token) -> void;
 
 class Journal {
   std::vector<std::unique_ptr<sinks::BaseSink>> sinks;
+  std::unique_ptr<formatter::Formatter> formatter;
   std::optional<std::jthread> flush_thread;
   std::chrono::system_clock::duration flush_interval;
 
 public:
-  Journal() : flush_interval(250ms) {}
+  Journal()
+      : flush_interval(250ms),
+        formatter(std::make_unique<formatter::DefaultFormatter>()) {}
   ~Journal() {
     if (flush_thread) {
       log(LogVerbosity::Trace, source_location::current(),
@@ -270,6 +287,15 @@ public:
     flush_all();
   }
 
+  auto reset_formatter() -> void {
+    formatter = std::make_unique<formatter::DefaultFormatter>();
+  }
+
+  auto set_formatter(std::unique_ptr<formatter::Formatter> &&formatter)
+      -> void {
+    formatter = std::move(formatter);
+  }
+
   auto
   set_flush_interval(const std::chrono::system_clock::duration &new_interval)
       -> void {
@@ -311,20 +337,7 @@ public:
 
 auto format(std::string_view str, const Verbosity &verbosity,
             const source_location &source) -> std::string {
-  return std::format("[{}] [{: <5}] [{}] {}\n", get_current_time_string(),
+  return std::format("{} {}\n", (*formatter)(verbosity, source), str);
-                     to_string(verbosity.inner),
-                     get_source_location_string(source), str);
-}
-
-auto get_source_location_string(const source_location& source) -> std::string {
-  const auto file = std::filesystem::path(source.file_name()).filename().string();
-  return std::format("{}::{}", file, source.line());
-}
-
-auto get_current_time_string() -> std::string {
-  const auto now = std::chrono::utc_clock::now();
-
-  return std::format("{:%Y-%m-%d %H:%M:%OS} UTC", now);
 }
 
 auto add_file(const std::string &file_name,
@@ -392,6 +405,12 @@ auto init_std_out_err(const LogVerbosity &min) -> void {
   ref->add_std_err();
 }
 
+auto set_formatter(std::unique_ptr<detail::formatter::Formatter> &&formatter)
+    -> void {
+  auto &&[lock, ref] = detail::global_journal.mut();
+  ref->set_formatter(std::move(formatter));
+}
+
 auto add_std_out() -> void {
   auto &&[lock, ref] = detail::global_journal.mut();
   ref->add_std_out();