milter-experiment/logger.go

package main

import (
	"io"
	"log"
)

// Loglevel is used to set the current loglevel of Logger.
type Loglevel int

const (
	// NONE is a loglevel for Logger.
	NONE Loglevel = 0
	// ERROR is a loglevel for Logger.
	ERROR Loglevel = 1
	// WARN is a loglevel for Logger.
	WARN Loglevel = 2
	// INFO is a loglevel for Logger.
	INFO Loglevel = 3
	// DEBUG is a loglevel for Logger.
	DEBUG Loglevel = 4
)

// Logger uses multiple instances of log.Logger to provide logging methods for multiple loglevels.
type Logger struct {
	debug    *log.Logger
	info     *log.Logger
	warn     *log.Logger
	error    *log.Logger
	logDebug bool
	logInfo  bool
	logWarn  bool
	logError bool
}

// NewLogger prepares a new instance of Logger for custom use.
func NewLogger(stdOut io.Writer, stdErr io.Writer, logLevel Loglevel) Logger {
	newLogger := Logger{}
	newLogger.debug = log.New(stdOut, "DEBUG ", 0)
	newLogger.info = log.New(stdOut, "INFO ", 0)
	newLogger.warn = log.New(stdErr, "WARN ", 0)
	newLogger.error = log.New(stdErr, "ERROR ", 0)
	newLogger.SetLogLevel(logLevel)
	return newLogger
}

// SetLogLevel can be used to change the loglevel of Logger on the fly.
func (l *Logger) SetLogLevel(logLevel Loglevel) {
	l.logDebug = (logLevel >= DEBUG)
	l.logInfo = (logLevel >= INFO)
	l.logWarn = (logLevel >= WARN)
	l.logError = (logLevel >= ERROR)
}

// Debug is an alias for log.Logger.Print() with severity DEBUG.
func (l *Logger) Debug(v ...interface{}) {
	if l.logDebug {
		l.debug.Print(v...)
	}
}

// Debugln is an alias for log.Logger.Println() with severity DEBUG.
func (l *Logger) Debugln(v ...interface{}) {
	if l.logDebug {
		l.debug.Println(v...)
	}
}

// Debugf is an alias for log.Logger.Printf() with severity DEBUG.
func (l *Logger) Debugf(format string, v ...interface{}) {
	if l.logDebug {
		l.debug.Printf(format, v...)
	}
}

// Info is an alias for log.Logger.Print() with severity INFO.
func (l *Logger) Info(v ...interface{}) {
	if l.logInfo {
		l.info.Print(v...)
	}
}

// Infoln is an alias for log.Logger.Println() with severity INFO.
func (l *Logger) Infoln(v ...interface{}) {
	if l.logInfo {
		l.info.Println(v...)
	}
}

// Infof is an alias for log.Logger.Printf() with severity INFO.
func (l *Logger) Infof(format string, v ...interface{}) {
	if l.logInfo {
		l.info.Printf(format, v...)
	}
}

// Warn is an alias for log.Logger.Print() with severity WARN.
func (l *Logger) Warn(v ...interface{}) {
	if l.logWarn {
		l.warn.Print(v...)
	}
}

// Warnln is an alias for log.Logger.Println() with severity WARN.
func (l *Logger) Warnln(v ...interface{}) {
	if l.logWarn {
		l.warn.Println(v...)
	}
}

// Warnf is an alias for log.Logger.Printf() with severity WARN.
func (l *Logger) Warnf(format string, v ...interface{}) {
	if l.logWarn {
		l.warn.Printf(format, v...)
	}
}

// Error is an alias for log.Logger.Print() with severity ERROR.
func (l *Logger) Error(v ...interface{}) {
	if l.logError {
		l.error.Print(v...)
	}
}

// Errorln is an alias for log.Logger.Println() with severity ERROR.
func (l *Logger) Errorln(v ...interface{}) {
	if l.logError {
		l.error.Println(v...)
	}
}

// Errorf is an alias for log.Logger.Printf() with severity ERROR.
func (l *Logger) Errorf(format string, v ...interface{}) {
	if l.logError {
		l.error.Printf(format, v...)
	}
}