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/acl.go

@@ -0,0 +1,69 @@
+package system
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"slices"
+
+	"hakurei.app/container/check"
+	"hakurei.app/hst"
+	"hakurei.app/internal/system/acl"
+)
+
+// UpdatePerm calls UpdatePermType with the [Process] criteria.
+func (sys *I) UpdatePerm(path *check.Absolute, perms ...acl.Perm) *I {
+	sys.UpdatePermType(Process, path, perms...)
+	return sys
+}
+
+// UpdatePermType maintains [acl.Perms] on a file until its [Enablement] is no longer satisfied.
+func (sys *I) UpdatePermType(et hst.Enablement, path *check.Absolute, perms ...acl.Perm) *I {
+	sys.ops = append(sys.ops, &aclUpdateOp{et, path.String(), perms})
+	return sys
+}
+
+// aclUpdateOp implements [I.UpdatePermType].
+type aclUpdateOp struct {
+	et    hst.Enablement
+	path  string
+	perms acl.Perms
+}
+
+func (a *aclUpdateOp) Type() hst.Enablement { return a.et }
+
+func (a *aclUpdateOp) apply(sys *I) error {
+	sys.msg.Verbose("applying ACL", a)
+	return newOpError("acl", sys.aclUpdate(a.path, sys.uid, a.perms...), false)
+}
+
+func (a *aclUpdateOp) revert(sys *I, ec *Criteria) error {
+	if ec.hasType(a.Type()) {
+		sys.msg.Verbose("stripping ACL", a)
+		err := sys.aclUpdate(a.path, sys.uid)
+		if errors.Is(err, os.ErrNotExist) {
+			// the ACL is effectively stripped if the file no longer exists
+			sys.msg.Verbosef("target of ACL %s no longer exists", a)
+			err = nil
+		}
+		return newOpError("acl", err, true)
+	} else {
+		sys.msg.Verbose("skipping ACL", a)
+		return nil
+	}
+}
+
+func (a *aclUpdateOp) Is(o Op) bool {
+	target, ok := o.(*aclUpdateOp)
+	return ok && a != nil && target != nil &&
+		a.et == target.et &&
+		a.path == target.path &&
+		slices.Equal(a.perms, target.perms)
+}
+
+func (a *aclUpdateOp) Path() string { return a.path }
+
+func (a *aclUpdateOp) String() string {
+	return fmt.Sprintf("%s type: %s path: %q",
+		a.perms, TypeString(a.et), a.path)
+}