tercul-backend/internal/platform/log/logger.go

package log

import (
	"context"
	"fmt"
	"tercul/internal/observability"

	"github.com/rs/zerolog"
)

// LogLevel represents the severity level of a log message.
type LogLevel int

const (
	// DebugLevel for detailed troubleshooting.
	DebugLevel LogLevel = iota
	// InfoLevel for general operational information.
	InfoLevel
	// WarnLevel for potentially harmful situations.
	WarnLevel
	// ErrorLevel for error events that might still allow the application to continue.
	ErrorLevel
	// FatalLevel for severe error events that will lead the application to abort.
	FatalLevel
)

// Field represents a key-value pair for structured logging.
type Field struct {
	Key   string
	Value interface{}
}

// F creates a new Field.
func F(key string, value interface{}) Field {
	return Field{Key: key, Value: value}
}

// Logger provides structured logging capabilities.
type Logger struct {
	*observability.Logger
}

var defaultLogger = &Logger{observability.NewLogger("tercul", "development")}

// Init re-initializes the default logger. This is useful for applications
// that need to configure the logger with dynamic values.
func Init(serviceName, environment string) {
	defaultLogger = &Logger{observability.NewLogger(serviceName, environment)}
}

// SetDefaultLevel sets the log level for the default logger.
func SetDefaultLevel(level LogLevel) {
	var zlevel zerolog.Level
	switch level {
	case DebugLevel:
		zlevel = zerolog.DebugLevel
	case InfoLevel:
		zlevel = zerolog.InfoLevel
	case WarnLevel:
		zlevel = zerolog.WarnLevel
	case ErrorLevel:
		zlevel = zerolog.ErrorLevel
	case FatalLevel:
		zlevel = zerolog.FatalLevel
	default:
		zlevel = zerolog.InfoLevel
	}
	zerolog.SetGlobalLevel(zlevel)
}

func log(level LogLevel, msg string, fields ...Field) {
	var event *zerolog.Event
	// Access the embedded observability.Logger to get to zerolog's methods.
	zlog := defaultLogger.Logger
	switch level {
	case DebugLevel:
		event = zlog.Debug()
	case InfoLevel:
		event = zlog.Info()
	case WarnLevel:
		event = zlog.Warn()
	case ErrorLevel:
		event = zlog.Error()
	case FatalLevel:
		event = zlog.Fatal()
	default:
		event = zlog.Info()
	}

	for _, f := range fields {
		event.Interface(f.Key, f.Value)
	}
	event.Msg(msg)
}

// LogDebug logs a message at debug level using the default logger.
func LogDebug(msg string, fields ...Field) {
	log(DebugLevel, msg, fields...)
}

// LogInfo logs a message at info level using the default logger.
func LogInfo(msg string, fields ...Field) {
	log(InfoLevel, msg, fields...)
}

// LogWarn logs a message at warn level using the default logger.
func LogWarn(msg string, fields ...Field) {
	log(WarnLevel, msg, fields...)
}

// LogError logs a message at error level using the default logger.
func LogError(msg string, fields ...Field) {
	log(ErrorLevel, msg, fields...)
}

// LogFatal logs a message at fatal level using the default logger and then calls os.Exit(1).
func LogFatal(msg string, fields ...Field) {
	log(FatalLevel, msg, fields...)
}

// WithFields returns a new logger with the given fields added using the default logger.
func WithFields(fields ...Field) *Logger {
	sublogger := defaultLogger.With().Logger()
	for _, f := range fields {
		sublogger = sublogger.With().Interface(f.Key, f.Value).Logger()
	}
	return &Logger{&observability.Logger{&sublogger}}
}

// WithContext returns a new logger with the given context added using the default logger.
func WithContext(ctx context.Context) *Logger {
	return &Logger{defaultLogger.Ctx(ctx)}
}

// The following functions are kept for compatibility but are now simplified or deprecated.

// SetDefaultLogger is deprecated. Use Init.
func SetDefaultLogger(logger *Logger) {
	// Deprecated: Logger is now initialized via Init.
}

// String returns the string representation of the log level.
func (l LogLevel) String() string {
	switch l {
	case DebugLevel:
		return "DEBUG"
	case InfoLevel:
		return "INFO"
	case WarnLevel:
		return "WARN"
	case ErrorLevel:
		return "ERROR"
	case FatalLevel:
		return "FATAL"
	default:
		return "UNKNOWN"
	}
}

// Debug logs a message at debug level.
func (l *Logger) Debug(msg string, fields ...Field) {
	l.log(DebugLevel, msg, fields...)
}

// Info logs a message at info level.
func (l *Logger) Info(msg string, fields ...Field) {
	l.log(InfoLevel, msg, fields...)
}

// Warn logs a message at warn level.
func (l *Logger) Warn(msg string, fields ...Field) {
	l.log(WarnLevel, msg, fields...)
}

// Error logs a message at error level.
func (l *Logger) Error(msg string, fields ...Field) {
	l.log(ErrorLevel, msg, fields...)
}

// Fatal logs a message at fatal level and then calls os.Exit(1).
func (l *Logger) Fatal(msg string, fields ...Field) {
	l.log(FatalLevel, msg, fields...)
}

func (l *Logger) log(level LogLevel, msg string, fields ...Field) {
	var event *zerolog.Event
	switch level {
	case DebugLevel:
		event = l.Logger.Debug()
	case InfoLevel:
		event = l.Logger.Info()
	case WarnLevel:
		event = l.Logger.Warn()
	case ErrorLevel:
		event = l.Logger.Error()
	case FatalLevel:
		event = l.Logger.Fatal()
	default:
		event = l.Logger.Info()
	}

	for _, f := range fields {
		event.Interface(f.Key, f.Value)
	}
	event.Msg(msg)
}

// WithFields returns a new logger with the given fields added.
func (l *Logger) WithFields(fields ...Field) *Logger {
	sublogger := l.With().Logger()
	for _, f := range fields {
		sublogger = sublogger.With().Interface(f.Key, f.Value).Logger()
	}
	return &Logger{&observability.Logger{&sublogger}}
}

func (l *Logger) WithContext(ctx map[string]interface{}) *Logger {
    // To maintain compatibility with the old API, we will convert the map to a context.
    // This is not ideal and should be refactored in the future.
    zlog := l.Logger.With().Logger()
    for k, v := range ctx {
        zlog = zlog.With().Interface(k, v).Logger()
    }
    return &Logger{&observability.Logger{&zlog}}
}

func (l *Logger) SetLevel(level LogLevel) {
    // This now controls the global log level.
    SetDefaultLevel(level)
}

// Fmt versions for simple string formatting
func LogInfof(format string, v ...interface{}) {
    log(InfoLevel, fmt.Sprintf(format, v...))
}

func LogErrorf(format string, v ...interface{}) {
    log(ErrorLevel, fmt.Sprintf(format, v...))
}