logging/logger.go

package logging

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

const exitCodeFatal = 100

// Logger is a facility that writes logs to one or more backands (files,
// stdout/stderr, syslog, etc.) which can be configured independently
//
// Loggers are concurrent-safe.
type Logger struct {
	mutex    sync.Mutex
	name     string
	backends []Backend
}

// NewLogger initializes a new Logger with no backend and with the default log level.
func NewLogger(name string) *Logger {
	l := &Logger{
		name: name,
	}

	return l
}

// AddBackend add a new Backend to the logger. All set backends are kept.
func (l *Logger) AddBackend(b Backend) {
	l.mutex.Lock()
	defer l.mutex.Unlock()

	l.backends = append(l.backends, b)
}

// SetBackend sets the backend list to the logger. Any existing backend will be lost.
func (l *Logger) SetBackend(b ...Backend) {
	l.mutex.Lock()
	defer l.mutex.Unlock()

	l.backends = b
}

// SetLevel changes the log level of all regisered backends to the given level.
func (l *Logger) SetLevel(level Level) {
	for _, backend := range l.backends {
		backend.SetLevel(level)
	}
}

type buffer struct {
	logger *Logger
	level  Level
}

func (b *buffer) Write(p []byte) (int, error) {
	b.logger.Log(b.level, string(p))
	return len(p), nil
}

// AsStdLog encapsulate the logger in an instance of lof.Logger from the
// standard library and returns it.
//
// It is there for interoperability reasons.
func (l *Logger) AsStdLog(level Level) *log.Logger {
	stdLogger := log.New(&buffer{logger: l, level: level}, "", 0)

	return stdLogger
}

// Log sends a record containing the message `m` to the registered backends
// whose level is at least `level`.
func (l *Logger) Log(level Level, m string) {
	l.mutex.Lock()
	defer l.mutex.Unlock()

	r := NewRecord(l.name, level, m)
	for _, backend := range l.backends {
		if r.Level >= backend.Level() {
			if err := backend.Write(r); err != nil {
				//revive:disable-next-line:unhandled-error stop error handling recursion!
				fmt.Fprintf(os.Stderr, "Cannot write logs: %v", err)
			}
		}
	}
}

// Trace logs a message with the Trace level.
func (l *Logger) Trace(text string) {
	l.Log(Trace, text)
}

// Tracef formats the message with given args and logs the result with the
// Trace level.
func (l *Logger) Tracef(text string, args ...interface{}) {
	l.Trace(fmt.Sprintf(text, args...))
}

// Debug logs a message with the Debug level.
func (l *Logger) Debug(text string) {
	l.Log(Debug, text)
}

// Debugf formats the message with given args and logs the result with the
// Debug level.
func (l *Logger) Debugf(text string, args ...interface{}) {
	l.Debug(fmt.Sprintf(text, args...))
}

// Info logs a message with the Info level.
func (l *Logger) Info(text string) {
	l.Log(Info, text)
}

// Infof formats the message with given args and logs the result with the
// Info level.
func (l *Logger) Infof(text string, args ...interface{}) {
	l.Info(fmt.Sprintf(text, args...))
}

// Notice logs a message with the Notice level.
func (l *Logger) Notice(text string) {
	l.Log(Notice, text)
}

// Noticef formats the message with given args and logs the result with the
// Notice level.
func (l *Logger) Noticef(text string, args ...interface{}) {
	l.Notice(fmt.Sprintf(text, args...))
}

// Warning logs a message with the Warning level.
func (l *Logger) Warning(text string) {
	l.Log(Warning, text)
}

// Warningf formats the message with given args and logs the result with the
// Warning level.
func (l *Logger) Warningf(text string, args ...interface{}) {
	l.Warning(fmt.Sprintf(text, args...))
}

// Error logs a message with the Error level.
func (l *Logger) Error(text string) {
	l.Log(Error, text)
}

// Errorf formats the message with given args and logs the result with the
// Error level.
func (l *Logger) Errorf(text string, args ...interface{}) {
	l.Error(fmt.Sprintf(text, args...))
}

// Critical logs a message with the Critical level.
func (l *Logger) Critical(text string) {
	l.Log(Critical, text)
}

// Criticalf formats the message with given args and logs the result with the.
// Critical level.
func (l *Logger) Criticalf(text string, args ...interface{}) {
	l.Critical(fmt.Sprintf(text, args...))
}

// Alert logs a message with the Alert level.
func (l *Logger) Alert(text string) {
	l.Log(Alert, text)
}

// Alertf formats the message with given args and logs the result with the.
// Alert level.
func (l *Logger) Alertf(text string, args ...interface{}) {
	l.Alert(fmt.Sprintf(text, args...))
}

// Fatal logs a message with the Fatal level.
func (l *Logger) Fatal(text string) {
	l.Log(Debug, text)

	os.Exit(exitCodeFatal) //nolint:revive // This is wanted if fatal is called
}

// Fatalf formats the message with given args and logs the result with the
// Fatal level.
func (l *Logger) Fatalf(text string, args ...interface{}) {
	l.Fatal(fmt.Sprintf(text, args...))
}