Start in json mode if stdin contains json msg

cmd/service/main.go

@@ -9,7 +9,6 @@ import (
 
 	"git.kettek.net/accord/service/internal/cfg"
 	"git.kettek.net/accord/service/internal/version"
-	"git.kettek.net/accord/service/pkg/istty"
 )
 
 func main() {
@@ -20,10 +19,25 @@ func main() {
 	readChannel := make(chan AMessage)
 	quitChannel := make(chan error)
 
-	if istty.Is() {
-		fmt.Println("Running from TTY, starting as stand-alone service.")
+	var jsonEncoder *json.Encoder
+
+	stat, _ := os.Stdin.Stat()
+	var startMsg StartMessage
+	if (stat.Mode() & os.ModeCharDevice) == 0 {
+		dec := json.NewDecoder(os.Stdin)
+		dec.Decode(&startMsg)
+	}
+
+	if !startMsg.EnableJSON {
+		fmt.Println("No EnableJSON message received, starting as stand-alone service.")
 		fmt.Printf("  Git Id: %s\n", version.GitCommitId)
 	} else {
+		jsonEncoder = json.NewEncoder(os.Stdout)
+		jsonEncoder.Encode(VersionMessage{
+			GitCommitId: version.GitCommitId,
+		})
+		fmt.Fprintf(os.Stderr, "Starting in bi-directional JSON mode")
+
 		// Start our STDIN read loop
 		if cfg.UsePipes {
 			go readLoop(os.Stdin, quitChannel, readChannel)
@@ -34,12 +48,12 @@ func main() {
 	for {
 		select {
 		case msg := <-readChannel:
-			fmt.Printf("%+v\n", msg)
+			fmt.Fprintf(os.Stderr, "%+v\n", msg)
 		case err := <-quitChannel:
 			if err != nil {
 				log.Fatal(err)
 			}
-			fmt.Println("Quitting")
+			fmt.Fprintf(os.Stderr, "Quitting\n")
 			break
 		}
 	}
@@ -48,6 +62,16 @@ func main() {
 // AMessage is our base Accord message.
 type AMessage struct{}
 
+// StartMessage is a bogus message for enabling JSON mode
+type StartMessage struct {
+	EnableJSON bool `json:"enableJSON"`
+}
+
+// VersionMessage is a message sent to the frontend immediately after JSON mode has been initiated.
+type VersionMessage struct {
+	GitCommitId string
+}
+
 func readLoop(reader io.Reader, quitChannel chan error, readChannel chan AMessage) {
 	var msg AMessage