feat(release): newrelic#45 WIP add support for command chaining

This PR adds utility methods and logic to read stdin
for details needed in commands, allowing each command
ouput to be piped to the next command

newrelic#45

go.mod

@@ -22,6 +22,7 @@ require (
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.7.1
 	github.com/stretchr/testify v1.6.1
+	github.com/tidwall/gjson v1.6.1
 	golang.org/x/crypto v0.0.0-20200709230013-948cd5f35899
 	golang.org/x/tools v0.0.0-20200724022722-7017fd6b1305
 	gopkg.in/yaml.v2 v2.3.0

go.sum

@@ -769,6 +769,12 @@ github.com/tdakkota/asciicheck v0.0.0-20200416190851-d7f85be797a2 h1:Xr9gkxfOP0K
 github.com/tdakkota/asciicheck v0.0.0-20200416190851-d7f85be797a2/go.mod h1:yHp0ai0Z9gUljN3o0xMhYJnH/IcvkdTBOX2fmJ93JEM=
 github.com/tetafro/godot v0.4.8 h1:h61+hQraWhdI6WYqMwAwZYCE5yxL6a9/Orw4REbabSU=
 github.com/tetafro/godot v0.4.8/go.mod h1:/7NLHhv08H1+8DNj0MElpAACw1ajsCuf3TKNQxA5S+0=
+github.com/tidwall/gjson v1.6.1 h1:LRbvNuNuvAiISWg6gxLEFuCe72UKy5hDqhxW/8183ws=
+github.com/tidwall/gjson v1.6.1/go.mod h1:BaHyNc5bjzYkPqgLq7mdVzeiRtULKULXLgZFKsxEHI0=
+github.com/tidwall/match v1.0.1 h1:PnKP62LPNxHKTwvHHZZzdOAOCtsJTjo6dZLCwpKm5xc=
+github.com/tidwall/match v1.0.1/go.mod h1:LujAq0jyVjBy028G1WhWfIzbpQfMO8bBZ6Tyb0+pL9E=
+github.com/tidwall/pretty v1.0.2 h1:Z7S3cePv9Jwm1KwS0513MRaoUe3S01WPbLNV40pwWZU=
+github.com/tidwall/pretty v1.0.2/go.mod h1:XNkn88O1ChpSDQmQeStsy+sBenx6DDtFZJxhVysOjyk=
 github.com/timakin/bodyclose v0.0.0-20190930140734-f7f2e9bca95e h1:RumXZ56IrCj4CL+g1b9OL/oH0QnsF976bC8xQFYUD5Q=
 github.com/timakin/bodyclose v0.0.0-20190930140734-f7f2e9bca95e/go.mod h1:Qimiffbc6q9tBWlVV6x0P9sat/ao1xEkREYPPj9hphk=
 github.com/tj/assert v0.0.0-20171129193455-018094318fb0 h1:Rw8kxzWo1mr6FSaYXjQELRe88y2KdfynXdnK72rdjtA=

internal/entities/command_tags.go

@@ -2,6 +2,7 @@ package entities
 
 import (
 	"errors"
+	"os"
 	"strings"
 
 	log "github.com/sirupsen/logrus"
@@ -17,6 +18,8 @@ import (
 var (
 	entityTag  string
 	entityTags []string
+	guid       string
+	inPipe     bool
 )
 
 var cmdTags = &cobra.Command{
@@ -40,7 +43,11 @@ The get command returns JSON output of the tags for the requested entity.
 	Example: "newrelic entity tags get --guid <entityGUID>",
 	Run: func(cmd *cobra.Command, args []string) {
 		client.WithClient(func(nrClient *newrelic.NewRelic) {
+			if inPipe {
+				entityGUID = guid
+			}
 			tags, err := nrClient.Entities.ListTags(entityGUID)
+
 			utils.LogIfFatal(err)
 
 			utils.LogIfError(output.Print(tags))
@@ -200,8 +207,24 @@ func init() {
 	Command.AddCommand(cmdTags)
 
 	cmdTags.AddCommand(cmdTagsGet)
-	cmdTagsGet.Flags().StringVarP(&entityGUID, "guid", "g", "", "the entity GUID to retrieve tags for")
-	utils.LogIfError(cmdTagsGet.MarkFlagRequired("guid"))
+
+	fi, err := os.Stdin.Stat()
+	if err != nil {
+		panic(err)
+	}
+
+	inPipe = (fi.Mode() & os.ModeCharDevice) == 0
+
+	if inPipe {
+		guidArray, err := utils.ReadStdin(os.Stdin, []string{"guid"})
+		if err != nil {
+			panic(err)
+		}
+		guid = guidArray[0]["guid"]
+	} else {
+		cmdTagsGet.Flags().StringVarP(&entityGUID, "guid", "g", "", "the entity GUID to retrieve tags for")
+		utils.LogIfError(cmdTagsGet.MarkFlagRequired("guid"))
+	}
 
 	cmdTags.AddCommand(cmdTagsDelete)
 	cmdTagsDelete.Flags().StringVarP(&entityGUID, "guid", "g", "", "the entity GUID to delete tags on")

internal/utils/utils.go

@@ -1,10 +1,14 @@
 package utils
 
 import (
+	"bufio"
+	"fmt"
+	"io"
 	"reflect"
 	"strings"
 
 	log "github.com/sirupsen/logrus"
+	"github.com/tidwall/gjson"
 )
 
 type StructToMapCallback func(item interface{}, fields []string) map[string]interface{}
@@ -39,6 +43,69 @@ func StructToMap(item interface{}, fields []string) map[string]interface{} {
 	return mapped
 }
 
+type PipeReader interface {
+	ReadPipe(r io.Reader) (string, error)
+}
+
+type StdinPipeReader struct{}
+
+func (spr StdinPipeReader) ReadPipe(r io.Reader) (string, error) {
+	text := ""
+	var err error = nil
+	scanner := bufio.NewScanner(r)
+
+	for scanner.Scan() {
+		text = fmt.Sprintf("%s%s ", text, strings.TrimSpace(scanner.Text()))
+	}
+
+	if scanErr := scanner.Err(); scanErr != nil {
+		err = scanErr
+	}
+
+	return strings.TrimSpace(text), err
+}
+
+func JSONToFilteredMap(r string, selectors []string) ([]map[string]string, error) {
+	text := r
+
+	// always start with an array of values
+	if strings.HasPrefix(text, "{") {
+		text = fmt.Sprintf("[ %s ]", text)
+	}
+
+	// returns []gjson.Result
+	jsonArray := gjson.Parse(text).Array()
+
+	resultsArray := make([]map[string]string, len(jsonArray))
+
+	for index, resultObj := range jsonArray {
+		resultMap := make(map[string]string)
+		for _, selector := range selectors {
+			// Convert every value to a string
+			resultMap[selector] = resultObj.Get(selector).String()
+		}
+		resultsArray[index] = resultMap
+	}
+
+	return resultsArray, nil
+}
+
+func ReadStdin(reader io.Reader, selectorList []string) ([]map[string]string, error) {
+	pipe := StdinPipeReader{}
+
+	jsonString, pipeErr := pipe.ReadPipe(reader)
+	if pipeErr != nil {
+		return nil, pipeErr
+	}
+
+	filteredMap, mapErr := JSONToFilteredMap(jsonString, selectorList)
+	if mapErr != nil {
+		return nil, mapErr
+	}
+
+	return filteredMap, nil
+}
+
 // LogIfError wraps the err nil check to cleanup the code.
 // Logs at Error level
 func LogIfError(err error) {