system: move out of internal

Signed-off-by: Ophestra <cat@gensokyo.uk>

system/enablement.go

@@ -0,0 +1,68 @@
+package system
+
+import (
+	"strings"
+)
+
+type (
+	// Enablement represents an optional system resource
+	Enablement uint8
+	// Enablements represents optional system resources to share
+	Enablements uint64
+)
+
+const (
+	EWayland Enablement = iota
+	EX11
+	EDBus
+	EPulse
+)
+
+var enablementString = [...]string{
+	EWayland: "Wayland",
+	EX11:     "X11",
+	EDBus:    "D-Bus",
+	EPulse:   "PulseAudio",
+}
+
+const ELen = len(enablementString)
+
+func (e Enablement) String() string {
+	if int(e) >= ELen {
+		return "<invalid enablement>"
+	}
+	return enablementString[e]
+}
+
+func (e Enablement) Mask() Enablements {
+	return 1 << e
+}
+
+// Has returns whether a feature is enabled
+func (es *Enablements) Has(e Enablement) bool {
+	return *es&e.Mask() != 0
+}
+
+// Set enables a feature
+func (es *Enablements) Set(e Enablement) {
+	if es.Has(e) {
+		panic("enablement " + e.String() + " set twice")
+	}
+
+	*es |= e.Mask()
+}
+
+func (es *Enablements) String() string {
+	buf := new(strings.Builder)
+	for i := Enablement(0); i < Enablement(ELen); i++ {
+		if es.Has(i) {
+			buf.WriteString(", " + i.String())
+		}
+	}
+
+	if buf.Len() == 0 {
+		buf.WriteString("(No enablements)")
+	}
+
+	return strings.TrimPrefix(buf.String(), ", ")
+}