Props: Add encoding func for DOM's container

Signed-off-by: Richard Kosegi <richard.kosegi@gmail.com>

props/codec.go

@@ -19,13 +19,29 @@ package props
 import (
 	"fmt"
 	"github.com/magiconair/properties"
+	"github.com/rkosegi/yaml-toolkit/dom"
 	"github.com/rkosegi/yaml-toolkit/utils"
 	"io"
 )
 
+func encodeKv(k string, v interface{}, w io.Writer) error {
+	_, err := w.Write([]byte(fmt.Sprintf("%s=%v\n", k, v)))
+	return err
+}
+
 func EncoderFn(w io.Writer, x interface{}) error {
 	for k, v := range x.(map[string]interface{}) {
-		_, err := w.Write([]byte(fmt.Sprintf("%s=%v\n", k, v)))
+		err := encodeKv(k, v, w)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func DomEncoderFn(w io.Writer, x interface{}) error {
+	for k, v := range x.(dom.Container).Children() {
+		err := encodeKv(k, v.(dom.Leaf).Value(), w)
 		if err != nil {
 			return err
 		}

props/codec_test.go

@@ -18,6 +18,7 @@ package props
 
 import (
 	"bytes"
+	"github.com/rkosegi/yaml-toolkit/dom"
 	"github.com/rkosegi/yaml-toolkit/utils"
 	"github.com/stretchr/testify/assert"
 	"strings"
@@ -38,6 +39,20 @@ func TestEncoderFn(t *testing.T) {
 	assert.Error(t, EncoderFn(utils.FailingWriter(), m))
 }
 
+func TestDomEncoderFn(t *testing.T) {
+	m := map[string]interface{}{
+		"a.b.c": 1,
+		"x.y.z": "Hi!",
+	}
+	var buff bytes.Buffer
+	c := dom.Builder().FromMap(m)
+	err := DomEncoderFn(&buff, c)
+	assert.NoError(t, err)
+	assert.Contains(t, buff.String(), "a.b.c=1\n")
+	assert.Contains(t, buff.String(), "x.y.z=Hi!\n")
+	assert.Error(t, DomEncoderFn(utils.FailingWriter(), c))
+}
+
 func TestDecoderFn(t *testing.T) {
 	m := make(map[string]interface{})
 	err := DecoderFn(strings.NewReader("a.b=1\nx.y=Hi!\n"), &m)