internal/system: relocate from system

These packages are highly specific to hakurei and are difficult to use safely from other pieces of code.

Their exported symbols are made available until v0.4.0 where they will be removed for #24.

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

internal/system/xhost.go

@@ -0,0 +1,38 @@
+package system
+
+import (
+	"hakurei.app/hst"
+	"hakurei.app/internal/system/xcb"
+)
+
+// ChangeHosts inserts the target user into X11 hosts and deletes it once its [Enablement] is no longer satisfied.
+func (sys *I) ChangeHosts(username string) *I {
+	sys.ops = append(sys.ops, xhostOp(username))
+	return sys
+}
+
+// xhostOp implements [I.ChangeHosts].
+type xhostOp string
+
+func (x xhostOp) Type() hst.Enablement { return hst.EX11 }
+
+func (x xhostOp) apply(sys *I) error {
+	sys.msg.Verbosef("inserting entry %s to X11", x)
+	return newOpError("xhost",
+		sys.xcbChangeHosts(xcb.HostModeInsert, xcb.FamilyServerInterpreted, "localuser\x00"+string(x)), false)
+}
+
+func (x xhostOp) revert(sys *I, ec *Criteria) error {
+	if ec.hasType(x.Type()) {
+		sys.msg.Verbosef("deleting entry %s from X11", x)
+		return newOpError("xhost",
+			sys.xcbChangeHosts(xcb.HostModeDelete, xcb.FamilyServerInterpreted, "localuser\x00"+string(x)), true)
+	} else {
+		sys.msg.Verbosef("skipping entry %s in X11", x)
+		return nil
+	}
+}
+
+func (x xhostOp) Is(o Op) bool   { target, ok := o.(xhostOp); return ok && x == target }
+func (x xhostOp) Path() string   { return "/tmp/.X11-unix" }
+func (x xhostOp) String() string { return string("SI:localuser:" + x) }