FeatherMC/src/logging/Logger.h

#pragma once

#include <fmt/core.h>
#include <fmt/color.h>
#include <ostream>
#include <fmt/ostream.h>
#include <vector>
#include <array>

//#define FEATHER_LOG_COLUMNS

#ifdef _DEBUG

// Prints an error if 'expr' is not false. Message is optional.
#define Assert(expr,/* fmt, */...) \
do { \
    if (!(expr)) { \
        Feather::Log::Logger::Instance().LogAssert(Feather::Log::Channels::General, __FILE__, __LINE__, #expr, ##__VA_ARGS__); \
    } \
} while (0)

// Asserts an expression once only.
#define AssertOnce(expr,/* fmt, */...) \
do { \
    static bool asserted = false; \
    if (!(expr) && !asserted) { \
        asserted = true; \
        Feather::Log::Logger::Instance().LogAssert(Feather::Log::Channels::General, __FILE__, __LINE__, #expr, ##__VA_ARGS__); \
    } \
} while (0)

#else // !defined(_DEBUG)

#define Assert(expr,...)        ((void)0)
#define AssertOnce(expr,...)    ((void)0)

#endif

namespace Feather::Log
{
    enum class Level
    {
        // Failed assertions
        Assert = -3,

        // Serious problems
        Error = -2,

        // Potential problems of note
        Warning = -1,

        // General messages for end-users
        Info = 0,

        // More advanced information for problem-solving
        Debug = 1,

        // Fine grained spew
        Trace = 2,
    };

    constexpr std::string_view GetLevelStringView(Level level)
    {
        switch (level)
        {
            case Level::Assert:  return "Assert";
            case Level::Error:   return "Error";
            case Level::Warning: return "Warning";
            case Level::Info:    return "Info";
            case Level::Debug:   return "Debug";
            case Level::Trace:   return "Trace";
            default:             return "Unknown";
        }
    }

    constexpr size_t MaxLevelLength   = 7;
    constexpr size_t MaxChannelLength = 15;

    inline std::ostream& operator << (std::ostream& os, Level level)
    {
        os << GetLevelStringView(level);
        return os;
    }

    constexpr fmt::text_style GetLevelTextStyle(Level level)
    {
        switch (level)
        {
            default:
            case Level::Assert:  return fmt::fg(fmt::color::orange_red);
            case Level::Error:   return fmt::fg(fmt::color::crimson);
            case Level::Warning: return fmt::fg(fmt::color::yellow);
            case Level::Info:    return fmt::fg(fmt::color::white);
            case Level::Debug:   return fmt::fg(fmt::color::rebecca_purple);
            case Level::Trace:   return fmt::fg(fmt::color::aquamarine);
        }
    }

    using ChannelID = size_t;

    class Channel
    {        
    public:
        Channel(std::string_view name) : m_name(name) {}

        inline std::string_view GetName() { return m_name; }

    private:
        std::string_view m_name;
    };

    namespace Channels
    {
        extern ChannelID General;
    }

    class Logger
    {
    public:
        template <class S, typename... Args>
        void LogRaw(const fmt::text_style& style, const S& fmt, Args... args)
        {
            fmt::print(style, fmt, args...);
        }

        template <class S, typename... Args>
        void LogRaw(const S& fmt, Args... args)
        {
            constexpr fmt::text_style white = fmt::fg(fmt::color::white);
            LogRaw(white, fmt, args...);
        }

        template <class S, typename... Args>
        void Log(ChannelID channel, Level level, const S& fmt, Args... args)
        {
            std::string_view levelString   = GetLevelStringView(level);
            std::string_view channelString = m_channels[channel].GetName();
#ifdef FEATHER_LOG_COLUMNS
            std::array<char, MaxLevelLength + 1> levelSpaces = {};
            std::fill_n(levelSpaces.data(), MaxLevelLength - levelString.size(), ' ');

            std::array<char, MaxChannelLength> channelSpaces = {};
            std::fill_n(channelSpaces.data(), MaxChannelLength - channelString.size(), ' ');

            LogRaw(GetLevelTextStyle(level), levelString);
            LogRaw("{}|", levelSpaces.data());
            LogRaw(channelString);
            LogRaw("{}|", channelSpaces.data());
            LogRaw(fmt, args...);
            LogRaw("\n");
#else
            if (level < Level::Info)
            {
                fmt::text_style style = GetLevelTextStyle(level);
                if (channel != Channels::General)
                    LogRaw(style, "[{}] ", channelString);

                LogRaw(style, "[");
                LogRaw(style, levelString);
                LogRaw(style, "] ");
                LogRaw(style, fmt, args...);
            }
            else
            {
                if (channel != Channels::General)
                    LogRaw("[{}] ", channelString);

                LogRaw("[");
                LogRaw(GetLevelTextStyle(level), levelString);
                LogRaw("] ");
                LogRaw(fmt, args...);
            }
            LogRaw("\n");
#endif
        }

        // Prints message for a failed assertion. Use the Assert or AssertOnce macros instead of calling this directly.
        template <class S, typename... Args>
        inline void LogAssert(ChannelID channel, const char* file, uint64_t lineNum, const char* expr, const S& fmt, Args... args)
        {
            std::string msg = fmt::format("{} ({}): {}", file, lineNum, fmt);
            Log(channel, Level::Assert, msg, args...);
        }

        // Prints message for a failed assertion. Use the Assert or AssertOnce macros instead of calling this directly.
        inline void LogAssert(ChannelID channel, const char* file, uint64_t lineNum, const char* expr)
        {
            // When no message is provided we print the asserted expression instead
            Log(channel, Level::Assert, "{} ({}): Assertion failed: {}", file, lineNum, expr);
        }

        ChannelID RegisterChannel(const char* name);

        static Logger& Instance();

    private:
        std::vector<Channel> m_channels;
    };

    // Logs a message, specifying a channel and log level
    template <class S, typename... Args>
    void Msg(ChannelID channel, Level level, const S& fmt, Args... args)
    {
        Logger::Instance().Log(channel, level, fmt, args...);
    }

    // Logs a general message for end-users
    template <class S, typename... Args>
    void Info(const S& fmt, Args... args) { Msg(Channels::General, Level::Info, fmt, args...); }

    // Logs a potential problem of note
    template <class S, typename... Args>
    void Warn(const S& fmt, Args... args) { Msg(Channels::General, Level::Warning, fmt, args...); }

    // Logs a serious problem
    template <class S, typename... Args>
    void Error(const S& fmt, Args... args) { Msg(Channels::General, Level::Error, fmt, args...); }

    // Logs debug information for developers
    template <class S, typename... Args>
    void Debug(const S& fmt, Args... args) { Msg(Channels::General, Level::Debug, fmt, args...); }

    // Logs fine grained debug information
    template <class S, typename... Args>
    void Trace(const S& fmt, Args... args) { Msg(Channels::General, Level::Trace, fmt, args...); }
}