Simplify presence stringification (should help with vector-im/element-android#5712)

syncapi/types/presence.go

@@ -21,25 +21,41 @@ import (
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
-//go:generate stringer -type=Presence -linecomment
 type Presence uint8
 
 const (
-	PresenceUnavailable Presence = iota + 1 // unavailable
-	PresenceOnline                          // online
-	PresenceOffline                         // offline
+	PresenceUnknown     Presence = iota
+	PresenceUnavailable          // unavailable
+	PresenceOnline               // online
+	PresenceOffline              // offline
 )
 
+func (p Presence) String() string {
+	switch p {
+	case PresenceUnavailable:
+		return "unavailable"
+	case PresenceOnline:
+		return "online"
+	case PresenceOffline:
+		return "offline"
+	default:
+		return "unknown"
+	}
+}
+
 // PresenceFromString returns the integer representation of the given input presence.
 // Returns false for ok, if input is not a valid presence value.
-func PresenceFromString(input string) (p Presence, ok bool) {
-	for i := 0; i < len(_Presence_index)-1; i++ {
-		l, r := _Presence_index[i], _Presence_index[i+1]
-		if strings.EqualFold(input, _Presence_name[l:r]) {
-			return Presence(i + 1), true
-		}
+func PresenceFromString(input string) (Presence, bool) {
+	switch strings.ToLower(input) {
+	case "unavailable":
+		return PresenceUnavailable, true
+	case "online":
+		return PresenceOnline, true
+	case "offline":
+		return PresenceOffline, true
+	default:
+		return PresenceUnknown, false
 	}
-	return 0, false
 }
 
 type PresenceInternal struct {