log.go

package trakt

import (
	"fmt"
	"io"
	"os"
)

//
// Public constants
//

const (
	// LevelNone sets a logger so show no logging information.
	LevelNone Level = 0

	// LevelError sets a logger to show error messages only.
	LevelError Level = 1

	// LevelWarn sets a logger to show warning messages or anything more
	// severe.
	LevelWarn Level = 2

	// LevelInfo sets a logger to show informational messages or anything more
	// severe.
	LevelInfo Level = 3

	// LevelDebug sets a logger to show informational messages or anything more
	// severe.
	LevelDebug Level = 4
)

//
// Public variables
//

// DefaultLeveledLogger is the default logger that the library will use to log
// errors, warnings, and informational messages.
//
// LeveledLoggerInterface is implemented by leveledLogger, and one can be
// initialized at the desired level of logging.  LeveledLoggerInterface also
// provides out-of-the-box compatibility with a Logrus Logger, but may require
// a thin shim for use with other logging libraries that use less standard
// conventions like Zap.
//
// This Logger will be inherited by any backends created by default, but will
// be overridden if a backend is created with getBackendWithConfig with a
// custom leveledLogger set.
var DefaultLeveledLogger LeveledLoggerInterface = &LeveledLogger{Level: LevelNone}

//
// Public types
//

// Level represents a logging level.
type Level uint32

// leveledLogger is a leveled logger implementation.
//
// It prints warnings and errors to `os.Stderr` and other messages to
// `os.Stdout`.
type LeveledLogger struct {
	// Level is the minimum logging level that will be emitted by this logger.
	//
	// For example, a Level set to LevelWarn will emit warnings and errors, but
	// not informational or debug messages.
	//
	// Always set this with a constant like LevelWarn because the individual
	// values are not guaranteed to be stable.
	Level Level

	// Internal testing use only.
	stderrOverride io.Writer
	stdoutOverride io.Writer
}

// Debugf logs a debug message using Printf conventions.
func (l *LeveledLogger) Debugf(format string, v ...interface{}) {
	if l.Level >= LevelDebug {
		fmt.Fprintf(l.stdout(), "[DEBUG] "+format+"\n", v...)
	}
}

// Errorf logs a warning message using Printf conventions.
func (l *LeveledLogger) Errorf(format string, v ...interface{}) {
	// Infof logs a debug message using Printf conventions.
	if l.Level >= LevelError {
		fmt.Fprintf(l.stderr(), "[ERROR] "+format+"\n", v...)
	}
}

// Infof logs an informational message using Printf conventions.
func (l *LeveledLogger) Infof(format string, v ...interface{}) {
	if l.Level >= LevelInfo {
		fmt.Fprintf(l.stdout(), "[INFO] "+format+"\n", v...)
	}
}

// Warnf logs a warning message using Printf conventions.
func (l *LeveledLogger) Warnf(format string, v ...interface{}) {
	if l.Level >= LevelWarn {
		fmt.Fprintf(l.stderr(), "[WARN] "+format+"\n", v...)
	}
}

func (l *LeveledLogger) stderr() io.Writer {
	if l.stderrOverride != nil {
		return l.stderrOverride
	}

	return os.Stderr
}

func (l *LeveledLogger) stdout() io.Writer {
	if l.stdoutOverride != nil {
		return l.stdoutOverride
	}

	return os.Stdout
}

// LeveledLoggerInterface provides a basic leveled logging interface for
// printing debug, informational, warning, and error messages.
//
// It's implemented by leveledLogger and also provides out-of-the-box
// compatibility with a Logrus Logger, but may require a thin shim for use with
// other logging libraries that you use less standard conventions like Zap.
type LeveledLoggerInterface interface {
	// Debugf logs a debug message using Printf conventions.
	Debugf(format string, v ...interface{})

	// Errorf logs a warning message using Printf conventions.
	Errorf(format string, v ...interface{})

	// Infof logs an informational message using Printf conventions.
	Infof(format string, v ...interface{})

	// Warnf logs a warning message using Printf conventions.
	Warnf(format string, v ...interface{})
}