logger.go

package main

import (
	"errors"
	"io"
	"log"
	"os"
)

// Logger struct defines the path to the log file
type Logger struct {
	fileHandle  *os.File
	infoLogger  *log.Logger
	errorLogger *log.Logger
}

// Info prints and logs a specified info message
func (l *Logger) Info(format string, v ...interface{}) {
	l.infoLogger.Printf(format, v...)
}

// Error prints and logs a specified error message
func (l *Logger) Error(format string, v ...interface{}) {
	l.errorLogger.Printf(format, v...)
}

// CloseFile closes the file handle
func (l *Logger) CloseFile() error {
	return l.fileHandle.Close()
}

// NewFileLogger opens the logging file specified and redirects log output to
// both the file and stdout. It returns pointer to Logger object.
func NewFileLogger(path string) (*Logger, error) {
	// check if log file exists, if not then create it and continue
	_, err := os.Stat(path)
	if errors.Is(err, os.ErrNotExist) {
		_, err = os.Create(path)
		if err != nil {
			return nil, err
		}
	}

	// Open log file
	f, e := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
	if e != nil {
		return nil, e
	}

	infoMultiWriter := io.MultiWriter(os.Stdout, f)
	errMultiWriter := io.MultiWriter(os.Stderr, f)

	return &Logger{
		fileHandle: f,
		infoLogger: log.New(
			infoMultiWriter,
			"INFO: ",
			log.Ldate|log.Ltime|log.Lmsgprefix,
		),
		errorLogger: log.New(
			errMultiWriter,
			"ERROR: ",
			log.Ldate|log.Ltime|log.Lmsgprefix,
		),
	}, nil
}