add config

config/reader/json/json.go

@@ -0,0 +1,83 @@
+package json
+
+import (
+	"errors"
+	"time"
+
+	"github.com/imdario/mergo"
+	"github.com/micro/go-micro/config/encoder"
+	"github.com/micro/go-micro/config/encoder/json"
+	"github.com/micro/go-micro/config/reader"
+	"github.com/micro/go-micro/config/source"
+)
+
+type jsonReader struct {
+	opts reader.Options
+	json encoder.Encoder
+}
+
+func (j *jsonReader) Merge(changes ...*source.ChangeSet) (*source.ChangeSet, error) {
+	var merged map[string]interface{}
+
+	for _, m := range changes {
+		if m == nil {
+			continue
+		}
+
+		if len(m.Data) == 0 {
+			continue
+		}
+
+		codec, ok := j.opts.Encoding[m.Format]
+		if !ok {
+			// fallback
+			codec = j.json
+		}
+
+		var data map[string]interface{}
+		if err := codec.Decode(m.Data, &data); err != nil {
+			return nil, err
+		}
+		if err := mergo.Map(&merged, data, mergo.WithOverride); err != nil {
+			return nil, err
+		}
+	}
+
+	b, err := j.json.Encode(merged)
+	if err != nil {
+		return nil, err
+	}
+
+	cs := &source.ChangeSet{
+		Timestamp: time.Now(),
+		Data:      b,
+		Source:    "json",
+		Format:    j.json.String(),
+	}
+	cs.Checksum = cs.Sum()
+
+	return cs, nil
+}
+
+func (j *jsonReader) Values(ch *source.ChangeSet) (reader.Values, error) {
+	if ch == nil {
+		return nil, errors.New("changeset is nil")
+	}
+	if ch.Format != "json" {
+		return nil, errors.New("unsupported format")
+	}
+	return newValues(ch)
+}
+
+func (j *jsonReader) String() string {
+	return "json"
+}
+
+// NewReader creates a json reader
+func NewReader(opts ...reader.Option) reader.Reader {
+	options := reader.NewOptions(opts...)
+	return &jsonReader{
+		json: json.NewEncoder(),
+		opts: options,
+	}
+}