Config: do not perform a copy after deserialization

alert_handler.go

@@ -21,8 +21,8 @@ type alertHandler struct {
 func NewAlertHandler(config *Config, sender Sender) http.Handler {
 	return &alertHandler{
 		sender:           sender,
-		firingTemplate:   config.Firing,
-		resolvedTemplate: config.Resolved,
+		firingTemplate:   config.Firing.ToTemplate(),
+		resolvedTemplate: config.Resolved.ToTemplate(),
 		format:           config.Format,
 	}
 }

config.go

@@ -2,47 +2,24 @@ package main
 
 import (
 	"encoding/json"
-	"fmt"
 	"log"
 	"os"
-	"sort"
-	"strings"
 	"text/template"
 )
 
 // Config is the internal configuration type
 type Config struct {
-	Listen         string
-	Debug          bool
-	StartupMessage string
-	Firing         *template.Template
-	Resolved       *template.Template
-	Format         Format
-	XMPP           ConfigXMPP
+	Debug          bool            `json:"debug"`
+	Listen         string          `json:"listen"`
+	StartupMessage string          `json:"startup_message"`
+	Firing         *ConfigTemplate `json:"firing"`
+	Resolved       *ConfigTemplate `json:"resolved"`
+	Format         Format          `json:"format"`
+	XMPP           ConfigXMPP      `json:"xmpp"`
 }
 
 // ConfigXMPP is the configuration for XMPP connection
 type ConfigXMPP struct {
-	OverrideServer string
-	User           string
-	Password       string
-	SendNotif      []string
-	Status         string
-	NoTLS          bool
-	TLSInsecure    bool
-}
-
-type internalConfig struct {
-	Debug          bool               `json:"debug"`
-	Listen         string             `json:"listen"`
-	StartupMessage string             `json:"startup_message"`
-	Firing         string             `json:"firing"`
-	Resolved       string             `json:"resolved"`
-	Format         string             `json:"format"`
-	XMPP           internalConfigXMPP `json:"xmpp"`
-}
-
-type internalConfigXMPP struct {
 	OverrideServer string   `json:"override_server"`
 	User           string   `json:"user"`
 	Password       string   `json:"password"`
@@ -60,59 +37,36 @@ func NewConfig(filename string) *Config {
 	}
 	defer fd.Close()
 
-	internalConfig := &internalConfig{
+	config := &Config{
 		Listen: ":9091",
-		XMPP: internalConfigXMPP{
+		XMPP: ConfigXMPP{
 			Status: "Monitoring",
 		},
 	}
-	if err := json.NewDecoder(fd).Decode(internalConfig); err != nil {
+	if err := json.NewDecoder(fd).Decode(config); err != nil {
 		log.Fatalln(err)
 	}
 
-	return internalConfig.parse()
+	return config
 }
 
-func (i *internalConfig) parse() *Config {
-	return &Config{
-		Debug:          i.Debug,
-		Listen:         i.Listen,
-		StartupMessage: i.StartupMessage,
-		Firing:         parseTemplate(i.Firing),
-		Resolved:       parseTemplate(i.Resolved),
-		Format:         parseFormat(i.Format),
-		XMPP:           i.XMPP.parse(),
-	}
-}
+// ConfigTemplate
 
-func (i *internalConfigXMPP) parse() ConfigXMPP {
-	result := ConfigXMPP{
-		OverrideServer: i.OverrideServer,
-		User:           i.User,
-		Password:       i.Password,
-		SendNotif:      i.SendNotif,
-		Status:         i.Status,
-		NoTLS:          i.NoTLS,
-		TLSInsecure:    i.TLSInsecure,
-	}
-	sort.Strings(result.SendNotif)
-	return result
-}
+type ConfigTemplate template.Template
 
-func parseTemplate(tmpl string) *template.Template {
-	if tmpl == "" {
-		return nil
+func (c *ConfigTemplate) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
 	}
 
-	return template.Must(template.New("").Parse(tmpl))
+	templ, err := template.New("").Parse(s)
+	if err == nil {
+		*c = ConfigTemplate(*templ)
+	}
+	return err
 }
 
-func parseFormat(format string) Format {
-	switch strings.ToLower(format) {
-	case "", "text":
-		return Format_Text
-	case "html":
-		return Format_HTML
-	}
-	panic(fmt.Sprintf("unknown format: %s", format))
+func (c *ConfigTemplate) ToTemplate() *template.Template {
+	return (*template.Template)(c)
 }

interfaces.go

@@ -1,5 +1,12 @@
 package main
 
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// Format
 type Format int
 
 const (
@@ -18,6 +25,23 @@ func (f Format) String() string {
 	}
 }
 
+func (f *Format) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
+	}
+
+	switch strings.ToLower(s) {
+	case "", "text":
+		*f = Format_Text
+	case "html":
+		*f = Format_HTML
+	default:
+		return fmt.Errorf("unknown format: %s", s)
+	}
+	return nil
+}
+
 // SendCloser is the interface to send messages
 type SendCloser interface {
 	Sender