Preset: Add presetMap variable

It remove some of the duplication we are having with switch case
and also allow us to use it for another helper which can provide
us list of all preset ( next commit)

Author: praveenkumar

pkg/crc/preset/preset.go

@@ -15,18 +15,19 @@ const (
 	Microshift Preset = "microshift"
 )
 
+var presetMap = map[Preset]string{
+	Podman:     string(Podman),
+	OpenShift:  string(OpenShift),
+	OKD:        string(OKD),
+	Microshift: string(Microshift),
+}
+
 func (preset Preset) String() string {
-	switch preset {
-	case Podman:
-		return string(Podman)
-	case OpenShift:
-		return string(OpenShift)
-	case OKD:
-		return string(OKD)
-	case Microshift:
-		return string(Microshift)
+	presetStr, presetExists := presetMap[preset]
+	if !presetExists {
+		return "invalid"
 	}
-	return "invalid"
+	return presetStr
 }
 
 func (preset Preset) ForDisplay() string {
@@ -44,18 +45,13 @@ func (preset Preset) ForDisplay() string {
 }
 
 func ParsePresetE(input string) (Preset, error) {
-	switch input {
-	case Podman.String():
-		return Podman, nil
-	case OpenShift.String():
-		return OpenShift, nil
-	case OKD.String():
-		return OKD, nil
-	case Microshift.String():
-		return Microshift, nil
-	default:
-		return OpenShift, fmt.Errorf("Cannot parse preset '%s'", input)
+	for pSet, pString := range presetMap {
+		if pString == input {
+			return pSet, nil
+		}
 	}
+	return OpenShift, fmt.Errorf("Cannot parse preset '%s'", input)
+
 }
 func ParsePreset(input string) Preset {
 	preset, err := ParsePresetE(input)