Add json-pretty as an output option (#214)

* Add json-pretty format option

Author: Xiol

README.md

@@ -152,6 +152,24 @@ Results can be output in JSON using the `json` format:
 [{"id":3337874,"template_id":0,"name":"test.example.co.uk","type":"A","content":"1.2.3.4","updated_at":"2019-03-19T16:33:55+00:00","ttl":0,"priority":0}]
 ```
 
+You can also the use the `json-pretty` format to output pretty-printed JSON:
+
+```
+> ans safedns zone record show example.co.uk 3337874 --output json-pretty
+[
+  {
+    "id": 3337874,
+    "template_id": 0,
+    "name": "test.example.co.uk",
+    "type": "A",
+    "content": "1.2.3.4",
+    "updated_at": "2019-03-19T16:33:55+00:00",
+    "ttl": 0,
+    "priority": 0
+  }
+]
+```
+
 ### YAML
 
 Results can be output in YAML using the `yaml` format:

internal/pkg/output/output_handler.go

@@ -73,7 +73,9 @@ func (o *OutputHandler) Output(cmd *cobra.Command, d interface{}) error {
 
 	switch format {
 	case "json":
-		return o.JSON(d)
+		return o.JSON(d, false)
+	case "json-pretty":
+		return o.JSON(d, true)
 	case "list":
 		return o.List(cmd, d)
 	case "value":
@@ -94,8 +96,14 @@ func (o *OutputHandler) Output(cmd *cobra.Command, d interface{}) error {
 	}
 }
 
-func (o *OutputHandler) JSON(d interface{}) error {
-	out, err := json.Marshal(d)
+func (o *OutputHandler) JSON(d interface{}, pretty bool) error {
+	var out []byte
+	var err error
+	if pretty {
+		out, err = json.MarshalIndent(d, "", "  ")
+	} else {
+		out, err = json.Marshal(d)
+	}
 	if err != nil {
 		return fmt.Errorf("failed to marshal json: %s", err)
 	}