pekoe/internal/logger/logger.go

// @tag logging
// @tag core
package logger

import (
	"fmt"
	"log"
	"os"
	"sync"
	"time"
)

// Level represents the minimum severity for log messages.
type Level int

// Log severity levels from most verbose to most critical.
const (
	LevelDebug Level = iota // Debug logs everything including diagnostic messages
	LevelInfo               // Info logs informational messages and above (default)
	LevelWarn               // Warn logs warnings, errors, and critical messages
	LevelError              // LevelError logs only errors and critical messages
)

var (
	currentLevel = LevelInfo
	logger       = log.New(os.Stdout, "", 0)
	logFile      *os.File
	logPath      string
	pid          int
	mu           sync.Once
	loggerMu     sync.Mutex // Protects logger and logFile
)

// initPID gets the process ID for log messages
func initPID() {
	pid = os.Getpid()
}

// formatLog formats a message with timestamp, log level, and pid.
// Format: timestamp level pekoe[pid]: message
func formatLog(level string, message string) string {
	mu.Do(initPID)

	// Timestamp format: "YYYY Mmm dd hh:mm:ss"
	// e.g., "2024 Apr  2 14:30:15"
	now := time.Now()
	timestamp := now.Format("2006 Jan _2 15:04:05")

	// Format: timestamp level pekoe[pid]: message
	// e.g., "2024 Apr  2 14:30:15 INFO pekoe[12345]: event=startup"
	return fmt.Sprintf("%s %s pekoe[%d]: %s", timestamp, level, pid, message)
}

// SetOutput configures the logger to write to the specified file.
// An empty path resets to stdout.
// Returns an error if the file cannot be opened/created.
// nolint: gosec
func SetOutput(path string) error {
	loggerMu.Lock()
	defer loggerMu.Unlock()

	// Close existing log file if any
	if logFile != nil {
		_ = logFile.Close()
		logFile = nil
	}

	if path == "" {
		logPath = ""
		logger = log.New(os.Stdout, "", 0)
		return nil
	}

	file, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return err
	}

	logPath = path
	logFile = file
	logger = log.New(file, "", 0)
	return nil
}

// Reopen reopens the log file.
// This is useful for log rotation - after the log file is moved/renamed,
// sending SIGUSR1 will cause the server to reopen the log file.
// Returns an error if the log file cannot be opened.
func Reopen() error {
	loggerMu.Lock()
	defer loggerMu.Unlock()

	// If logging to stdout, nothing to reopen
	if logPath == "" {
		return nil
	}

	// Close existing file
	if logFile != nil {
		_ = logFile.Close()
		logFile = nil
	}

	// Open the file again (create if doesn't exist)
	//nolint: gosec // logPath is configured by admin, not user input
	file, err := os.OpenFile(logPath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		// Fall back to stdout if we can't reopen
		logger = log.New(os.Stdout, "", 0)
		return fmt.Errorf("failed to reopen log file %s: %w", logPath, err)
	}

	logFile = file
	logger = log.New(file, "", 0)
	return nil
}

// SetLevel configures the minimum log level from a string name.
// Accepted values: "debug", "info", "warn", "error".
func SetLevel(level string) {
	switch level {
	case "debug":
		currentLevel = LevelDebug
	case "info":
		currentLevel = LevelInfo
	case "warn":
		currentLevel = LevelWarn
	case "error":
		currentLevel = LevelError
	}
}

// Debug logs a message at debug level. Uses fmt.Sprintf formatting.
func Debug(format string, v ...any) {
	if currentLevel <= LevelDebug {
		msg := fmt.Sprintf(format, v...)
		logger.Println(formatLog("DEBUG", msg))
	}
}

// Info logs a message at info level. Uses fmt.Sprintf formatting.
func Info(format string, v ...any) {
	if currentLevel <= LevelInfo {
		msg := fmt.Sprintf(format, v...)
		logger.Println(formatLog("INFO", msg))
	}
}

// Warn logs a message at warning level. Uses fmt.Sprintf formatting.
func Warn(format string, v ...any) {
	if currentLevel <= LevelWarn {
		msg := fmt.Sprintf(format, v...)
		logger.Println(formatLog("WARN", msg))
	}
}

// Error logs a message at error level. Uses fmt.Sprintf formatting.
func Error(format string, v ...any) {
	if currentLevel <= LevelError {
		msg := fmt.Sprintf(format, v...)
		logger.Println(formatLog("ERROR", msg))
	}
}

// Fatal logs a message at critical level and terminates the process with exit code 1.
func Fatal(format string, v ...any) {
	msg := fmt.Sprintf(format, v...)
	logger.Println(formatLog("CRITICAL", msg))
	os.Exit(1)
}