✨ Add AddFormatter function to allow custom builds to register new formatters

formatters/new.go

@@ -2,18 +2,22 @@ package formatters
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"sync"
 
 	"codeberg.org/danjones000/my-log/config"
 	"github.com/spf13/viper"
 )
 
-type formatMaker func(config *viper.Viper) (Formatter, error)
+var mut sync.RWMutex
 
-var formatterMap = map[string]formatMaker{
-	"plain": newPlain,
-	"json":  newJson,
-	"zero":  newNull,
+type FormatInit func(config *viper.Viper) (Formatter, error)
+
+var formatterMap = map[string]FormatInit{
+	FormatPlain: newPlain,
+	FormatJSON:  newJson,
+	FormatNull:  newNull,
 }
 
 func Preferred(ctx context.Context) (f Formatter, err error) {
@@ -25,6 +29,8 @@ func New(ctx context.Context, kind string) (f Formatter, err error) {
 	v, _ := config.RetrieveFromContext(ctx)
 	formatterConf := v.Sub("formatters." + kind)
 
+	mut.RLock()
+	defer mut.RUnlock()
 	if maker, ok := formatterMap[kind]; ok {
 		return maker(formatterConf)
 	}
@@ -34,8 +40,24 @@ func New(ctx context.Context, kind string) (f Formatter, err error) {
 
 func Kinds() []string {
 	r := []string{}
+
+	mut.RLock()
+	defer mut.RUnlock()
 	for kind, _ := range formatterMap {
 		r = append(r, kind)
 	}
 	return r
 }
+
+var ErrAlreadyAdded = errors.New("formatter already present")
+
+func AddFormatter(key string, f FormatInit) error {
+	mut.Lock()
+	defer mut.Unlock()
+	if _, present := formatterMap[key]; present {
+		return fmt.Errorf("%w: %s", ErrAlreadyAdded, key)
+	}
+
+	formatterMap[key] = f
+	return nil
+}