hst: expose daemon as fs entry

This is slightly counterintuitive, but it turned out well under this framework since the daemon backs its target file.

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

hst/fsdaemon.go

@@ -0,0 +1,48 @@
+package hst
+
+import (
+	"encoding/gob"
+
+	"hakurei.app/container/check"
+)
+
+func init() { gob.Register(new(FSDaemon)) }
+
+// FilesystemDaemon is the type string of a daemon.
+const FilesystemDaemon = "daemon"
+
+// FSDaemon represents a daemon to be started in the container.
+type FSDaemon struct {
+	// Pathname indicating readiness of daemon.
+	Target *check.Absolute `json:"dst"`
+	// Absolute pathname to daemon executable file.
+	Exec *check.Absolute `json:"path"`
+	// Arguments (excl. first) passed to daemon.
+	Args []string `json:"args"`
+}
+
+func (d *FSDaemon) Valid() bool { return d != nil && d.Target != nil && d.Exec != nil }
+
+func (d *FSDaemon) Path() *check.Absolute {
+	if !d.Valid() {
+		return nil
+	}
+	return d.Target
+}
+
+func (d *FSDaemon) Host() []*check.Absolute { return nil }
+
+func (d *FSDaemon) Apply(z *ApplyState) {
+	if !d.Valid() {
+		return
+	}
+	z.Daemon(d.Target, d.Exec, d.Args...)
+}
+
+func (d *FSDaemon) String() string {
+	if !d.Valid() {
+		return "<invalid>"
+	}
+
+	return "daemon:" + d.Target.String()
+}