logging_policy.h

// Logging-related utilities for configuring spdlog the way we like it
// (see github.com/gabime/spdlog).

#pragma once

#include <stdexcept>
#include <string>

#include <fmt/core.h>
#include <spdlog/cfg/helpers.h>
#include <spdlog/spdlog.h>

namespace pivid {

// Convenience aliases
namespace log = ::spdlog;
using log_level = ::spdlog::level::level_enum;

// Logs a trace message; does not evaluate args if trace logging is not enabled
#define TRACE(l, ...) \
    [&]{ if (l->should_log(log_level::trace)) l->trace(__VA_ARGS__); }()

// Logs a debug message; does not evaluate args if debug logging is not enabled
#define DEBUG(l, ...) \
    [&]{ if (l->should_log(log_level::debug)) l->debug(__VA_ARGS__); }()

// Throws std::logic_error if the condition is false
#define ASSERT(f) \
    [&]{ if (!(f)) throw std::logic_error("ASSERT fail (" FILELINE ") " #f); }()

// Throws std::invalid_argument if the condition is false, using fmt args
#define CHECK_ARG(f, ...) \
    [&]{ if (!(f)) throw std::invalid_argument(fmt::format(__VA_ARGS__)); }()

// Throws std::runtime_error if the condition is false, using fmt args
#define CHECK_RUNTIME(f, ...) \
    [&]{ if (!(f)) throw std::runtime_error(fmt::format(__VA_ARGS__)); }()

// File and line number used by ASSERT
#define FILELINE __FILE__ ":" STRINGIFY(__LINE__)
#define STRINGIFY(x) STRINGIFY2(x)
#define STRINGIFY2(x) #x

// Configures the logger output format with our preferred pattern.
// Sets log levels based on a string, typically a command line --log arg,
// to allow "--log=info,display=trace,media=debug" type parameters.
inline void configure_logging(std::string config) {
    auto const utc = spdlog::pattern_time_type::utc;
    spdlog::set_pattern("%H:%M:%S.%e %6iu %^%L [%n] %v%$", utc);
    spdlog::cfg::helpers::load_levels(config);
}

// Creates a new logger that shares the same "sinks" as the default logger.
// Used to create named loggers for subcomponents that can have their
// log levels adjusted separately but all write in the same output stream.
inline std::shared_ptr<spdlog::logger> make_logger(char const* name) {
    auto const& s = spdlog::default_logger()->sinks();
    auto logger = std::make_shared<spdlog::logger>(name, s.begin(), s.end());
    spdlog::initialize_logger(logger);
    return logger;
}

}