log.h

#pragma once
 
#include <cstdarg>
#include <cstdio>
 
namespace fz {
 
// ── Log levels ───────────────────────────────────────────────────────────────
 
enum class LogLevel : int {
    TRACE  = 0,  
    DEBUG  = 1,  
    INFO   = 2,  
    WARN   = 3,  
    SILENT = 255 
};
 
// ── Logger ───────────────────────────────────────────────────────────────────
 
class Logger {
public:
    using Callback = void(*)(LogLevel level, const char* msg);
 
    // ── Sink configuration ────────────────────────────────────────────────
 
    static void setCallback(Callback cb) { callback() = cb; }
 
    static void setMinLevel(LogLevel level) { minLevel() = level; }
    static LogLevel getMinLevel()           { return minLevel(); }
 
    static void enableStderr(LogLevel min_level = LogLevel::INFO) {
        minLevel() = min_level;
        setCallback([](LogLevel level, const char* msg) {
            if (level >= Logger::minLevel()) {
                fprintf(stderr, "[fzgmod:%s] %s\n", levelTag(level), msg);
            }
        });
    }
 
    // ── Logging ───────────────────────────────────────────────────────────
 
    static void log(LogLevel level, const char* fmt, ...) {
        if (!callback()) return;
        if (level < minLevel()) return;
        char buf[1024];
        va_list args;
        va_start(args, fmt);
        vsnprintf(buf, sizeof(buf), fmt, args);
        va_end(args);
        callback()(level, buf);
    }
 
    static void print(const char* fmt, ...) {
        char buf[1024];
        va_list args;
        va_start(args, fmt);
        vsnprintf(buf, sizeof(buf), fmt, args);
        va_end(args);
        if (callback()) {
            callback()(LogLevel::INFO, buf);
        } else {
            puts(buf);
        }
    }
 
    static const char* levelTag(LogLevel l) {
        switch (l) {
            case LogLevel::TRACE:  return "TRACE";
            case LogLevel::DEBUG:  return "DEBUG";
            case LogLevel::INFO:   return "INFO";
            case LogLevel::WARN:   return "WARN";
            default:               return "???";
        }
    }
 
private:
    static Callback& callback() {
        static Callback cb = nullptr;
        return cb;
    }
    static LogLevel& minLevel() {
        static LogLevel lvl = LogLevel::INFO;
        return lvl;
    }
};
 
} // namespace fz
 
// ── Compile-time level gating ─────────────────────────────────────────────────
//
// FZ_LOG_MIN_LEVEL is set by CMake (default 2 = INFO).  Log calls below this
// level expand to ((void)0) — the compiler eliminates them entirely and their
// arguments are never evaluated, giving true zero overhead.
//
// Override at the CMake level:
//   cmake -DFZ_LOG_MIN_LEVEL=0   # full TRACE logging (debug builds)
//   cmake -DFZ_LOG_MIN_LEVEL=255 # all logging compiled out (embedded)
 
#ifndef FZ_LOG_MIN_LEVEL
#  define FZ_LOG_MIN_LEVEL 2  // INFO
#endif
 
// FZ_LOG_DISABLE is kept for backward compatibility; equivalent to SILENT.
#ifdef FZ_LOG_DISABLE
#  undef  FZ_LOG_MIN_LEVEL
#  define FZ_LOG_MIN_LEVEL 255
#endif
 
#define FZ_LOG(level, ...)                                                      \
    do {                                                                        \
        if constexpr (static_cast<int>(::fz::LogLevel::level) >=               \
                      static_cast<int>(FZ_LOG_MIN_LEVEL)) {                     \
            ::fz::Logger::log(::fz::LogLevel::level, __VA_ARGS__);              \
        }                                                                       \
    } while (0)
 
#define FZ_PRINT(...) ::fz::Logger::print(__VA_ARGS__)