circolog/cmd/circologd/format.go

package main

import (
	"encoding/json"
	"fmt"
	"io"
	"text/template"
	"time"

	"gopkg.in/mcuadros/go-syslog.v2/format"
)

// Formatter is an interface, so that multiple implementations can exist
type Formatter func(format.LogParts) string

var tmplFuncs template.FuncMap
var syslogTmpl *template.Template

func init() {
	tmplFuncs := template.FuncMap{
		"dateFormat": func(dt time.Time, fmt string) string {
			return dt.Format(fmt)
		},
		"rfc822": func(dt time.Time) string {
			return dt.Format(time.RFC822)
		},
	}
	syslogTmpl = template.Must(template.New("syslog").Funcs(tmplFuncs).Parse(
		"{{rfc822 (index . \"timestamp\")}} {{index . \"hostname\"}} " +
			"{{index . \"app_name\"}}" +
			"{{ if (ne (index . \"proc_id\") \"-\")}}[{{index . \"proc_id\"}}]{{end}}: " +
			"{{index . \"message\"}}",
	))
}

type renderFormat int

func parseRenderFormat(s string) (renderFormat, error) {
	switch s {
	case "json":
		return formatJSON, nil
	case "syslog":
		return formatSyslog, nil
	default:
		return 0, fmt.Errorf("Undefined format `%s`", s)
	}
}

const (
	formatSyslog = iota // 0
	formatJSON   = iota
)

func writeFormatted(w io.Writer, f renderFormat, msg format.LogParts) error {
	switch f {
	case formatSyslog:
		return syslogTmpl.Execute(w, msg)
	case formatJSON:
		enc := json.NewEncoder(w)
		enc.SetIndent("", "  ")
		return enc.Encode(msg)
	}
	return nil
}