websocket: Make StatusConnectionListener generic

Only the call to get the status is status-specific, the rest of the code
marshalling the data, fetching it every few seconds, ... is applicable
to anything we want to send through websocket. This commit extracts the
'status' bit from the generic code, this will be useful if we add other
similar websocket calls.

pkg/crc/api/websocket/status.go

@@ -6,24 +6,35 @@ import (
 	"time"
 
 	"github.com/crc-org/crc/pkg/crc/logging"
-	"github.com/crc-org/crc/pkg/crc/machine"
+	crcMachine "github.com/crc-org/crc/pkg/crc/machine"
 )
 
-type StatusConnectionListener struct {
-	machine machine.Client
-	done    chan bool
+type genData func() (interface{}, error)
+
+type TickListener struct {
+	done       chan bool
+	generator  genData
+	tickPeriod time.Duration
 }
 
-func NewStatusListener(machine machine.Client) ConnectionListener {
-	return &StatusConnectionListener{
-		machine: machine,
-		done:    make(chan bool),
+func NewStatusListener(machine crcMachine.Client) ConnectionListener {
+	getStatus := func() (interface{}, error) {
+		return machine.GetClusterLoad()
 	}
+	return NewTickListener(getStatus)
 }
 
-func (s StatusConnectionListener) start(dataSender io.Writer) {
+func NewTickListener(generator genData) ConnectionListener {
+	return &TickListener{
+		done:       make(chan bool),
+		generator:  generator,
+		tickPeriod: 2000 * time.Millisecond,
+	}
+}
 
-	ticker := time.NewTicker(2000 * time.Millisecond)
+func (s *TickListener) start(dataSender io.Writer) {
+
+	ticker := time.NewTicker(s.tickPeriod)
 	go func() {
 		for {
 			select {
@@ -32,12 +43,13 @@ func (s StatusConnectionListener) start(dataSender io.Writer) {
 				logging.Debug("stop fetching machine info")
 				return
 			case <-ticker.C:
-				status, err := s.machine.GetClusterLoad()
+				data, err := s.generator()
 				if err != nil {
 					logging.Errorf("unexpected error during getting machine status: %v", err)
+					continue
 				}
 
-				bytes, marshallError := json.Marshal(status)
+				bytes, marshallError := json.Marshal(data)
 				if marshallError != nil {
 					logging.Errorf("unexpected error during status object to JSON conversion: %v", err)
 					continue
@@ -52,6 +64,6 @@ func (s StatusConnectionListener) start(dataSender io.Writer) {
 
 }
 
-func (s StatusConnectionListener) stop() {
+func (s *TickListener) stop() {
 	s.done <- true
 }