klog.go

package goklog

import (
	"fmt"
	"github.com/go-errors/errors"
	"os"
	"strconv"
	"sync"
	"time"
)

type ListenerFunc func(string)

func emptyListener(message string) {

}

type KLog struct {
	listener      ListenerFunc
	inspectOpened bool
	formatter     string
	printLevel    int
}

var instance *KLog

var once sync.Once

const (
	NORMAL_LEVEL = iota
	ERROR_LEVEL
	VITAL
)

// copied from: https://stackoverflow.com/questions/40326540/how-to-assign-default-value-if-env-var-is-empty
func getenv(key, fallback string) string {
	value := os.Getenv(key)
	if len(value) == 0 {
		return fallback
	}
	return value
}

func getErrorCallStack(e error) string {
	if e == nil {
		return ""
	}

	e0, ok := e.(*errors.Error)
	if !ok {
		return e.Error()
	}
	callStack := string(e0.ErrorStack())
	return callStack
}

func GetInstance() *KLog {
	once.Do(func() {
		level, err := strconv.ParseInt(getenv("KLOG_PRINT_LEVEL", "0"), 0, 8)
		if err != nil {
			fmt.Println("System environment KLOG_PRINT_LEVEL is polluted")
			level = NORMAL_LEVEL
		}
		instance = &KLog{
			listener:      emptyListener,
			inspectOpened: false,
			formatter:     "2006-01-02-15.04.05.999",
			printLevel:    int(level),
		}
	})
	return instance
}

func (klog *KLog) SetListener(listener ListenerFunc) {
	klog.listener = listener
}

func (klog *KLog) ToggleInspector() {
	klog.inspectOpened = !klog.inspectOpened
}

func (klog *KLog) LogIn(title string, text string) {
	if klog.inspectOpened {
		klog.Info(title, text, NORMAL_LEVEL)
	}
}

func (klog *KLog) Info(title string, text string, level int) {
	today := time.Now()
	logText := fmt.Sprintf("[klog:%s] (%s) %s", today.Format(klog.formatter), title, text)

	if level >= klog.printLevel {
		fmt.Println(logText)
	}

	klog.listener(logText)
}

func (klog *KLog) LogVital(title string, text string) {
	klog.Info(title, text, VITAL)
}

func (klog *KLog) LogError(title string, err error) {
	errorText := getErrorCallStack(err)
	klog.Info(fmt.Sprintf("error-response-%s", title), errorText, ERROR_LEVEL)
}

func (klog *KLog) LogNormal(title string, text string) {
	klog.Info(title, text, NORMAL_LEVEL)
}