zones: introduce Machine.ReadFile()

Signed-off-by: Alejandro Mery <amery@jpi.io>

pkg/zones/machine.go

@@ -1,7 +1,10 @@
 package zones
 
 import (
+	"fmt"
+	"io/fs"
 	"net/netip"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"sync"
@@ -56,3 +59,25 @@ func (m *Machine) FullName() string {
 
 	return m.Name
 }
+
+// ReadFile reads a file from the machine's config directory
+func (m *Machine) ReadFile(name string, args ...any) ([]byte, error) {
+	base := m.zone.zones.dir
+	fullName := m.getFilename(name, args...)
+
+	return fs.ReadFile(base, fullName)
+}
+
+func (m *Machine) getFilename(name string, args ...any) string {
+	if len(args) > 0 {
+		name = fmt.Sprintf(name, args...)
+	}
+
+	s := []string{
+		m.zone.Name,
+		m.Name,
+		name,
+	}
+
+	return filepath.Join(s...)
+}