journal/src/journal.cc

#include "journal.hpp"

#include <chrono>
#include <compare>
#include <concepts>
#include <cstdio>
#include <iostream>
#include <memory>
#include <mutex>
#include <optional>
#include <string_view>
#include <type_traits>
#include <filesystem>

namespace journal {
namespace mutex {
class Lock {
  std::mutex &mutex;
  bool moved = false;

public:
  Lock(Lock &rhs) = delete;
  Lock(std::mutex &mutex) : mutex(mutex) { mutex.lock(); 
  };
  Lock(Lock &&rhs) : mutex(rhs.mutex) { rhs.moved = true; 
  };
  auto operator=(Lock &rhs) = delete;
  ~Lock() {
    if (!moved) {
      mutex.unlock();
    }
  }
};

template <typename T> class Mutex {
  std::mutex mutex;
  T inner;

public:
  template <typename U>
  Mutex(U &&value) requires(std::assignable_from<U, T>)
      : inner(std::move(value)) {}
  Mutex() requires(std::default_initializable<T>) : inner(T{}) {}

  auto ref() -> std::pair<Lock, const T &> {
    return {std::move(scoped_lock()), inner};
  }
  auto mut() -> std::pair<Lock, T &> {
    return {std::move(scoped_lock()), inner};
  }

  auto operator->() -> T& {
    return inner;
  }

  auto scoped_lock() -> Lock { return Lock(mutex); }

  auto unique_lock() -> std::unique_lock<std::mutex> {
    return std::unique_lock(mutex);
  }

  auto lock() -> void { mutex.lock(); }

  auto try_lock() -> bool { return mutex.try_lock(); }

  auto unlock() -> void { mutex.unlock(); }
};
} // namespace mutex

namespace detail {

constexpr auto to_string(const LogVerbosity& verbosity) -> std::string {
    switch (verbosity) {
        case LogVerbosity::Trace:
        return "Trace";
        case LogVerbosity::Debug:
        return "Debug";
        case LogVerbosity::Info:
        return "Info";
        case LogVerbosity::Warn:
        return "Warn";
        case LogVerbosity::Error:
        return "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) -> std::strong_ordering {
    return static_cast<std::underlying_type_t<decltype(inner)>>(inner) <=>
           static_cast<std::underlying_type_t<decltype(rhs.inner)>>(rhs.inner);
  }
};

struct Sink {
  std::shared_ptr<std::ostream> stream;
  Verbosity min_verbosity;
  Verbosity max_verbosity;

  Sink(std::shared_ptr<std::ostream> &&stream)
      : stream(std::move(stream)),
        min_verbosity(journal::detail::LogVerbosity::Trace),
        max_verbosity(journal::detail::LogVerbosity::Error) {}
  Sink(std::shared_ptr<std::ostream>&& stream, const Verbosity &min,
       const Verbosity &max)
      : stream(std::move(stream)),min_verbosity(min), max_verbosity(max) {}
  Sink(std::shared_ptr<std::ostream> &&stream, const Verbosity &min)
      : stream(std::move(stream)), min_verbosity(min),
        max_verbosity(journal::detail::Error) {}

  auto operator<<(std::string_view msg) { (*stream) << msg; }
};

class Journal {
  std::vector<Sink> sinks;

public:
Journal() {}
auto log(const Verbosity &verbosity, source_location source,
         std::string_view msg) {
  for (auto &&sink : sinks) {
    if (verbosity >= sink.min_verbosity && verbosity <= sink.max_verbosity) {
      sink << std::format("[{}] [{: <5}] [{}] {}\n",
                          get_current_time_string(), to_string(verbosity.inner),
                          get_source_location_string(source), msg);
    }
  }
}

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_std_out(const Verbosity &min = journal::detail::LogVerbosity::Info) {
  auto out = std::shared_ptr<std::ostream>(&std::cout, [](auto &&_) {});
  sinks.emplace_back(std::move(out));
}
};

static mutex::Mutex<std::unique_ptr<Journal>> global_journal;

auto log_internal(const LogVerbosity &verbosity, detail::source_location source,
                  const std::string &msg) -> void {
  auto &&[lock, ref] = global_journal.ref();

  ref->log(verbosity, source, msg);
}
} // namespace detail

auto init() {
  auto &&[lock, ref] = detail::global_journal.mut();
  if (!ref.get()) {
    ref = std::make_unique<detail::Journal>();
  }
}

auto init_stdout(const LogVerbosity &min) -> void {
    init();
    auto &&[lock, ref] = detail::global_journal.mut();
    ref->add_std_out();
}
} // namespace journal