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/fs.go

@@ -45,6 +45,9 @@ type Ops interface {
 	Root(host *check.Absolute, flags int) Ops
 	// Etc appends an op that expands host /etc into a toplevel symlink mirror with /etc semantics.
 	Etc(host *check.Absolute, prefix string) Ops
+
+	// Daemon appends an op that starts a daemon in the container and blocks until target appears.
+	Daemon(target, path *check.Absolute, args ...string) Ops
 }
 
 // ApplyState holds the address of [Ops] and any relevant application state.
@@ -124,6 +127,12 @@ func (f *FilesystemConfigJSON) MarshalJSON() ([]byte, error) {
 			*FSLink
 		}{fsType{FilesystemLink}, cv}
 
+	case *FSDaemon:
+		v = &struct {
+			fsType
+			*FSDaemon
+		}{fsType{FilesystemDaemon}, cv}
+
 	default:
 		return nil, FSImplError{f.FilesystemConfig}
 	}
@@ -152,6 +161,9 @@ func (f *FilesystemConfigJSON) UnmarshalJSON(data []byte) error {
 	case FilesystemLink:
 		*f = FilesystemConfigJSON{new(FSLink)}
 
+	case FilesystemDaemon:
+		*f = FilesystemConfigJSON{new(FSDaemon)}
+
 	default:
 		return FSTypeError(t.Type)
 	}

hst/fs_test.go

@@ -84,6 +84,16 @@ func TestFilesystemConfigJSON(t *testing.T) {
 		}, nil,
 			`{"type":"link","dst":"/run/current-system","linkname":"/run/current-system","dereference":true}`,
 			`{"fs":{"type":"link","dst":"/run/current-system","linkname":"/run/current-system","dereference":true},"magic":3236757504}`},
+
+		{"daemon", hst.FilesystemConfigJSON{
+			FilesystemConfig: &hst.FSDaemon{
+				Target: m("/run/user/1971/pulse/native"),
+				Exec:   m("/run/current-system/sw/bin/pipewire-pulse"),
+				Args:   []string{"-v"},
+			},
+		}, nil,
+			`{"type":"daemon","dst":"/run/user/1971/pulse/native","path":"/run/current-system/sw/bin/pipewire-pulse","args":["-v"]}`,
+			`{"fs":{"type":"daemon","dst":"/run/user/1971/pulse/native","path":"/run/current-system/sw/bin/pipewire-pulse","args":["-v"]},"magic":3236757504}`},
 	}
 
 	for _, tc := range testCases {
@@ -345,6 +355,10 @@ func (p opsAdapter) Etc(host *check.Absolute, prefix string) hst.Ops {
 	return opsAdapter{p.Ops.Etc(host, prefix)}
 }
 
+func (p opsAdapter) Daemon(target, path *check.Absolute, args ...string) hst.Ops {
+	return opsAdapter{p.Ops.Daemon(target, path, args...)}
+}
+
 func m(pathname string) *check.Absolute { return check.MustAbs(pathname) }
 func ms(pathnames ...string) []*check.Absolute {
 	as := make([]*check.Absolute, len(pathnames))

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()
+}

hst/fsdaemon_test.go

@@ -0,0 +1,29 @@
+package hst_test
+
+import (
+	"testing"
+
+	"hakurei.app/container"
+	"hakurei.app/hst"
+)
+
+func TestFSDaemon(t *testing.T) {
+	t.Parallel()
+
+	checkFs(t, []fsTestCase{
+		{"nil", (*hst.FSDaemon)(nil), false, nil, nil, nil, "<invalid>"},
+		{"zero", new(hst.FSDaemon), false, nil, nil, nil, "<invalid>"},
+
+		{"pipewire-pulse", &hst.FSDaemon{
+			Target: m("/run/user/1971/pulse/native"),
+			Exec:   m("/run/current-system/sw/bin/pipewire-pulse"),
+			Args:   []string{"-v"},
+		}, true, container.Ops{
+			&container.DaemonOp{
+				Target: m("/run/user/1971/pulse/native"),
+				Path:   m("/run/current-system/sw/bin/pipewire-pulse"),
+				Args:   []string{"-v"},
+			},
+		}, m("/run/user/1971/pulse/native"), nil, `daemon:/run/user/1971/pulse/native`},
+	})
+}

internal/outcome/spcontainer.go

@@ -382,6 +382,10 @@ func (p opsAdapter) Link(target *check.Absolute, linkName string, dereference bo
 	return opsAdapter{p.Ops.Link(target, linkName, dereference)}
 }
 
+func (p opsAdapter) Daemon(target, path *check.Absolute, args ...string) hst.Ops {
+	return opsAdapter{p.Ops.Daemon(target, path, args...)}
+}
+
 func (p opsAdapter) Root(host *check.Absolute, flags int) hst.Ops {
 	return opsAdapter{p.Ops.Root(host, flags)}
 }