Support multiple template formats (#30)

Thing templates are now supported in both json and yaml formats.
This means that, during the thing creation, the thing template can be passed either as json or yaml file.
On the other hand, during the template extraction, the user can specify his preferred format with an appropriate flag. The default value for the format is yaml.
$ ./iot-cloud-cli thing extract --format json

* Thing template - Support both yaml and json formats

* Update docs

* Extract template supports multiple formats

* thing extract - set yaml as default format

* Update readme

Author: polldo

README.md

@@ -45,9 +45,9 @@ Devices currently present on Arduino IoT Cloud can be retrieved by using this co
 
 Things can be created starting from a template or by cloning another thing.
 
-Create a thing from a thing template. The name parameter is optional. If it is provided then it overrides the name retrieved from the template:
+Create a thing from a thing template. Supported template formats are JSON and YAML. The name parameter is optional. If it is provided then it overrides the name retrieved from the template:
 
-`$ iot-cloud-cli thing create --name <thingName> --template <template.json>`
+`$ iot-cloud-cli thing create --name <thingName> --template <template.(json|yaml)>`
 
 Create a thing by cloning another thing, here the *name is mandatory*:
 
@@ -72,9 +72,9 @@ Delete a thing with the following command:
 
 `$ iot-cloud-cli thing delete --device-id <deviceID>`
 
-Extract a template from an existing thing:
+Extract a template from an existing thing. The template can be saved in two formats: json or yaml. The default format is yaml:
 
-`$ iot-cloud-cli thing extract --id <thingID> --outfile <templateFile.json>`
+`$ iot-cloud-cli thing extract --id <thingID> --outfile <templateFile> --format <yaml|json>`
 
 Bind a thing to an existing device:
 

cli/thing/create.go

@@ -20,7 +20,13 @@ func initCreateCommand() *cobra.Command {
 		RunE:  runCreateCommand,
 	}
 	createCommand.Flags().StringVarP(&createFlags.name, "name", "n", "", "Thing name")
-	createCommand.Flags().StringVarP(&createFlags.template, "template", "t", "", "File containing a thing template")
+	createCommand.Flags().StringVarP(
+		&createFlags.template,
+		"template",
+		"t",
+		"",
+		"File containing a thing template, JSON and YAML format are supported",
+	)
 	createCommand.MarkFlagRequired("template")
 	return createCommand
 }

cli/thing/extract.go

@@ -10,6 +10,7 @@ import (
 var extractFlags struct {
 	id      string
 	outfile string
+	format  string
 }
 
 func initExtractCommand() *cobra.Command {
@@ -21,6 +22,13 @@ func initExtractCommand() *cobra.Command {
 	}
 	extractCommand.Flags().StringVarP(&extractFlags.id, "id", "i", "", "Thing ID")
 	extractCommand.Flags().StringVarP(&extractFlags.outfile, "outfile", "o", "", "Template file destination path")
+	extractCommand.Flags().StringVar(
+		&extractFlags.format,
+		"format",
+		"yaml",
+		"Format of template file, can be {json|yaml}. Default is 'yaml'",
+	)
+
 	extractCommand.MarkFlagRequired("id")
 	return extractCommand
 }
@@ -29,7 +37,8 @@ func runExtractCommand(cmd *cobra.Command, args []string) error {
 	fmt.Printf("Extracting template from thing %s\n", extractFlags.id)
 
 	params := &thing.ExtractParams{
-		ID: extractFlags.id,
+		ID:     extractFlags.id,
+		Format: extractFlags.format,
 	}
 	if extractFlags.outfile != "" {
 		params.Outfile = &extractFlags.outfile

command/thing/create.go

@@ -10,6 +10,7 @@ import (
 	iotclient "github.com/arduino/iot-client-go"
 	"github.com/arduino/iot-cloud-cli/internal/config"
 	"github.com/arduino/iot-cloud-cli/internal/iot"
+	"gopkg.in/yaml.v3"
 )
 
 // CreateParams contains the parameters needed to create a new thing.
@@ -67,9 +68,12 @@ func loadTemplate(file string) (*iotclient.Thing, error) {
 	}
 
 	template := make(map[string]interface{})
-	err = json.Unmarshal([]byte(templateBytes), &template)
-	if err != nil {
-		return nil, fmt.Errorf("%s: %w", "reading template file: template not valid: ", err)
+
+	// Extract template trying all the supported formats: json and yaml
+	if err = json.Unmarshal([]byte(templateBytes), &template); err != nil {
+		if err = yaml.Unmarshal([]byte(templateBytes), &template); err != nil {
+			return nil, errors.New("reading template file: template format is not valid")
+		}
 	}
 
 	// Adapt thing template to thing structure

command/thing/extract.go

@@ -2,26 +2,36 @@ package thing
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
+	"strings"
 
 	iotclient "github.com/arduino/iot-client-go"
 	"github.com/arduino/iot-cloud-cli/internal/config"
 	"github.com/arduino/iot-cloud-cli/internal/iot"
+	"gopkg.in/yaml.v3"
 )
 
 // ExtractParams contains the parameters needed to
 // extract a thing from Arduino IoT Cloud and save it on local storage.
+// Format determines the file format of the template ("json" or "yaml")
 // Output indicates the destination path of the extraction.
 type ExtractParams struct {
 	ID      string
+	Format  string
 	Outfile *string
 }
 
 // Extract command is used to extract a thing template
 // from a thing on Arduino IoT Cloud.
 func Extract(params *ExtractParams) error {
+	params.Format = strings.ToLower(params.Format)
+	if params.Format != "json" && params.Format != "yaml" {
+		return errors.New("format is not valid: only 'json' and 'yaml' are supported")
+	}
+
 	conf, err := config.Retrieve()
 	if err != nil {
 		return err
@@ -42,23 +52,19 @@ func Extract(params *ExtractParams) error {
 		return err
 	}
 
-	if params.Outfile == nil {
-		outfile := thing.Name + "-template.json"
-		params.Outfile = &outfile
-	}
-	err = ioutil.WriteFile(*params.Outfile, template, os.FileMode(0644))
+	err = templateToFile(template, params)
 	if err != nil {
-		err = fmt.Errorf("%s: %w", "cannot write outfile: ", err)
 		return err
 	}
 
 	return nil
 }
 
-func templateFromThing(thing *iotclient.ArduinoThing) ([]byte, error) {
+func templateFromThing(thing *iotclient.ArduinoThing) (map[string]interface{}, error) {
 	template := make(map[string]interface{})
 	template["name"] = thing.Name
 
+	// Extract template from thing structure
 	var props []map[string]interface{}
 	for _, p := range thing.Properties {
 		prop := make(map[string]interface{})
@@ -72,11 +78,42 @@ func templateFromThing(thing *iotclient.ArduinoThing) ([]byte, error) {
 	}
 	template["variables"] = props
 
-	// Extract json template from thing structure
-	file, err := json.MarshalIndent(template, "", "    ")
+	return template, nil
+}
+
+func templateToFile(template map[string]interface{}, params *ExtractParams) error {
+	var file []byte
+	var err error
+
+	if params.Format == "json" {
+		file, err = json.MarshalIndent(template, "", "    ")
+		if err != nil {
+			return fmt.Errorf("%s: %w", "thing marshal failure: ", err)
+		}
+
+	} else if params.Format == "yaml" {
+		file, err = yaml.Marshal(template)
+		if err != nil {
+			return fmt.Errorf("%s: %w", "thing marshal failure: ", err)
+		}
+
+	} else {
+		return errors.New("format is not valid: only 'json' and 'yaml' are supported")
+	}
+
+	if params.Outfile == nil {
+		name, ok := template["name"].(string)
+		if name == "" || !ok {
+			return errors.New("thing template does not have a valid name")
+		}
+		outfile := name + "." + params.Format
+		params.Outfile = &outfile
+	}
+
+	err = ioutil.WriteFile(*params.Outfile, file, os.FileMode(0644))
 	if err != nil {
-		err = fmt.Errorf("%s: %w", "thing marshal failure: ", err)
-		return nil, err
+		return fmt.Errorf("%s: %w", "cannot write outfile: ", err)
 	}
-	return file, nil
+
+	return nil
 }

go.mod

@@ -21,4 +21,5 @@ require (
 	google.golang.org/genproto v0.0.0-20210504143626-3b2ad6ccc450 // indirect
 	google.golang.org/grpc v1.39.0
 	google.golang.org/protobuf v1.27.1 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c
 )