reading list: Set device by flag instead of arg

cmd/reading/list/list.go

@@ -30,6 +30,7 @@ import (
 )
 
 var limit int32
+var device string
 
 const readingTemplate = "Reading ID\tName\tDevice\tOrigin\tValue\tCreated\tModified\tPushed\n" +
 	"{{range .}}" +
@@ -40,31 +41,26 @@ const readingTemplate = "Reading ID\tName\tDevice\tOrigin\tValue\tCreated\tModif
 func NewCommand() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "list",
-		Short: "A list of all device readings",
-		Long:  `Return all device readings.`,
+		Short: "A list of readings across devices or pertaining to a specified device",
+		Long:  `Return list of readings across devices or pertaining to a specified device.`,
 		Args:  cobra.MaximumNArgs(1),
-		RunE: listHandler,
+		RunE:  listHandler,
 	}
-	cmd.Flags().Int32VarP(&limit, "limit", "l", 0, "Limit number of results")
+	cmd.Flags().StringVarP(&device, "device", "d", "", "Readings generated by specific device with given name.")
+	cmd.Flags().Int32VarP(&limit, "limit", "l", 50, "Limit number of results")
 	return cmd
 }
 
 func listHandler(cmd *cobra.Command, args []string) (err error) {
 	var url string
-	if len(args) > 0 {
-		var limitUrl string
-		device := args[0]
-		if limit > 0 {
-			limitUrl = strconv.FormatInt(int64(limit), 10)
-		} else {
-			limitUrl = strconv.FormatInt(int64(50), 10)
-		}
+	if device != "" {
+		limitUrl := strconv.FormatInt(int64(limit), 10)
 		url = config.Conf.Clients["CoreData"].Url() + clients.ApiReadingRoute + "/device/" + device + "/" + limitUrl
 	} else {
 		url = config.Conf.Clients["CoreData"].Url() + clients.ApiReadingRoute
 	}
-	var readings []models.Reading
 
+	var readings []models.Reading
 	err = request.Get(url, &readings)
 	if err != nil {
 		return