refactor syslog formatting

the goal is making circolog-tail apply formatting "locally", receiving
structured messages instead

cmd/circologd/http_log.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"git.lattuga.net/boyska/circolog"
+	"git.lattuga.net/boyska/circolog/formatter"
 	"github.com/gorilla/websocket"
 	"gopkg.in/mcuadros/go-syslog.v2/format"
 )
@@ -56,7 +57,7 @@ func parseParameters(r *http.Request) (circolog.ClientOptions, error) {
 }
 
 type renderOptions struct { // those are options relevant to the rendered (that is, the HTTP side of circologd)
-	Format renderFormat
+	Format formatter.Format
 }
 
 func parseRenderParameters(r *http.Request) (renderOptions, error) {
@@ -70,11 +71,10 @@ func parseRenderParameters(r *http.Request) (renderOptions, error) {
 		if len(val) != 1 {
 			return opts, errors.New("Format repeated multiple times")
 		}
-		format, err := parseRenderFormat(val[0])
+		err := opts.Format.Set(val[0])
 		if err != nil {
 			return opts, err
 		}
-		opts.Format = format
 	}
 	return opts, nil
 }
@@ -106,9 +106,10 @@ func getHTTPHandler(hub circolog.Hub) http.HandlerFunc {
 		hub.Register <- client
 
 		for x := range client.Messages {
-			writeFormatted(w, render_opts.Format, x)
-			if render_opts.Format != formatJSON { // bleah
-				w.Write([]byte("\n"))
+			if err := render_opts.Format.WriteFormatted(w, x); err == nil {
+				if render_opts.Format != formatter.FormatJSON { // bleah
+					w.Write([]byte("\n"))
+				}
 			}
 		}
 	}
@@ -166,7 +167,7 @@ func getWSHandler(hub circolog.Hub) http.HandlerFunc {
 					if err != nil {
 						return
 					}
-					writeFormatted(w, render_opts.Format, message)
+					render_opts.Format.WriteFormatted(w, message)
 
 					if err := w.Close(); err != nil {
 						return

formatter/format.go

@@ -1,4 +1,4 @@
-package main
+package formatter
 
 import (
 	"encoding/json"
@@ -33,29 +33,52 @@ func init() {
 	))
 }
 
-type renderFormat int
+type Format int
 
-func parseRenderFormat(s string) (renderFormat, error) {
+func (rf *Format) Set(v string) error {
+	newvalue, err := parseFormat(v)
+	if err != nil {
+		return err
+	}
+	*rf = newvalue
+	return nil
+}
+
+func (rf Format) String() string {
+	switch rf {
+	case FormatJSON:
+		return "json"
+	case FormatSyslog:
+		return "syslog"
+	}
+	return ""
+}
+
+func (rf Format) WriteFormatted(w io.Writer, msg format.LogParts) error {
+	return WriteFormatted(w, rf, msg)
+}
+
+func parseFormat(s string) (Format, error) {
 	switch s {
 	case "json":
-		return formatJSON, nil
+		return FormatJSON, nil
 	case "syslog":
-		return formatSyslog, nil
+		return FormatSyslog, nil
 	default:
 		return 0, fmt.Errorf("Undefined format `%s`", s)
 	}
 }
 
 const (
-	formatSyslog = iota // 0
-	formatJSON   = iota
+	FormatSyslog = iota // 0
+	FormatJSON   = iota
 )
 
-func writeFormatted(w io.Writer, f renderFormat, msg format.LogParts) error {
+func WriteFormatted(w io.Writer, f Format, msg format.LogParts) error {
 	switch f {
-	case formatSyslog:
+	case FormatSyslog:
 		return syslogTmpl.Execute(w, msg)
-	case formatJSON:
+	case FormatJSON:
 		enc := json.NewEncoder(w)
 		enc.SetIndent("", "  ")
 		return enc.Encode(msg)