logfmt for Ardanlabs Service5 course

main.go

package main

import (
	"bufio"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"os"
	"strings"
	"time"
)

const (
	pref    = "\033["
	end     = pref + "0m"
	red     = "31m"
	green   = "32m"
	yellow  = "33m"
	blue    = "34;3;1m"
	magenta = "35m"
	cyan    = "36m"
	gray    = "37;1m"
	white   = "97;1m"
)

func happy(color, s any) string {
	return fmt.Sprint(pref, color, s, end)
}

func serviceFlag(service *string) {
	flag.StringVar(service, "service", "", "filter which service to see")
	flag.Parse()
}

const (
	OK = "✅"
	KO = "❌"
	OH = "😯"
)

func levelIcon(level any) string {
	switch level {
	case "INFO":
		return OK

	case "ERROR":
		return KO

	default:
		return OH
	}

}

type LogLine struct {
	Service    string        `json:"service"`
	Level      string        `json:"level,omitempty"`
	Time       time.Time     `json:"time,omitempty"`
	File       string        `json:"file,omitempty"`
	TraceID    string        `json:"trace_id"`
	Msg        string        `json:"msg,omitempty"`
	Method     string        `json:"method,omitempty"`
	StatusCode int           `json:"statuscode,omitempty"`
	Path       string        `json:"path,omitempty"`
	RemoteAddr string        `json:"remoteaddr,omitempty"`
	Duration   time.Duration `json:"since,omitempty"`
}

func (l LogLine) String() string {
	var line = []string{
		happy(blue, "%s"), // service
		"%s",
		happy(gray, "%s"),      // time
		happy(cyan, "%-12s"),   // file:line
		happy(gray, "%-.8s"),   // uuid
		happy(green, "%-25s"),  // msg
		happy(magenta, "%4s"),  // -----
		happy(yellow, "%3v"),   //
		happy(green, "%-.20s"), //
		happy(white, "%-18s"),  //
		happy(red, "%7d"),      //
	}

	return fmt.Sprintf(strings.Join(line, " "),
		l.Service,
		levelIcon(l.Level),
		l.Time.Format(time.StampNano),
		l.File,
		l.TraceID,
		l.Msg,
		l.Method,
		l.StatusCode,
		l.Path,
		l.RemoteAddr,
		l.Duration.Nanoseconds())

}

func main() {
	var (
		service string
		b       strings.Builder
	)

	serviceFlag(&service)

	service = strings.ToLower(service)

	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		s := scanner.Text()

		m := new(LogLine)
		err := json.Unmarshal([]byte(s), m)
		if err != nil {
			fmt.Println(s)
			continue
		}
		// If a service filter was provided, check.
		if service != "" && strings.ToLower(m.Service) != service {
			continue
		}

		b.Reset()
		b.WriteString(m.String())

		// Write the new log format, removing the last :
		fmt.Println(b.String())
	}

	if err := scanner.Err(); err != nil {
		log.Println(err)
	}

}