all: refactor router code to use interface

So the code is more modular, easier to read/maintain.

internal/router/merlin/merlin.go

@@ -0,0 +1,133 @@
+package merlin
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"unicode"
+
+	"github.com/kardianos/service"
+
+	"github.com/Control-D-Inc/ctrld"
+	"github.com/Control-D-Inc/ctrld/internal/router/dnsmasq"
+	"github.com/Control-D-Inc/ctrld/internal/router/ntp"
+	"github.com/Control-D-Inc/ctrld/internal/router/nvram"
+)
+
+const Name = "merlin"
+
+var nvramKvMap = map[string]string{
+	"dnspriv_enable": "0", // Ensure Merlin native DoT disabled.
+}
+
+type Merlin struct {
+	cfg *ctrld.Config
+}
+
+// New returns a router.Router for configuring/setup/run ctrld on Merlin routers.
+func New(cfg *ctrld.Config) *Merlin {
+	return &Merlin{cfg: cfg}
+}
+
+func (m *Merlin) ConfigureService(config *service.Config) error {
+	return nil
+}
+
+func (m *Merlin) Install(_ *service.Config) error {
+	return nil
+}
+
+func (m *Merlin) Uninstall(_ *service.Config) error {
+	return nil
+}
+
+func (m *Merlin) PreRun() error {
+	_ = m.Cleanup()
+	return ntp.Wait()
+}
+
+func (m *Merlin) Configure() error {
+	m.cfg.Listener["0"].IP = "127.0.0.1"
+	m.cfg.Listener["0"].Port = 5354
+	return nil
+}
+
+func (m *Merlin) Setup() error {
+	buf, err := os.ReadFile(dnsmasq.MerlinPostConfPath)
+	// Already setup.
+	if bytes.Contains(buf, []byte(dnsmasq.MerlinPostConfMarker)) {
+		return nil
+	}
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+
+	data, err := dnsmasq.ConfTmpl(dnsmasq.MerlinPostConfTmpl, m.cfg)
+	if err != nil {
+		return err
+	}
+	data = strings.Join([]string{
+		data,
+		"\n",
+		dnsmasq.MerlinPostConfMarker,
+		"\n",
+		string(buf),
+	}, "\n")
+	// Write dnsmasq post conf file.
+	if err := os.WriteFile(dnsmasq.MerlinPostConfPath, []byte(data), 0750); err != nil {
+		return err
+	}
+	// Restart dnsmasq service.
+	if err := restartDNSMasq(); err != nil {
+		return err
+	}
+
+	if err := nvram.SetKV(nvramKvMap, nvram.CtrldSetupKey); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (m *Merlin) Cleanup() error {
+	if val, _ := nvram.Run("get", nvram.CtrldSetupKey); val == "1" {
+		// Restore old configs.
+		if err := nvram.Restore(nvramKvMap, nvram.CtrldSetupKey); err != nil {
+			return err
+		}
+	}
+
+	buf, err := os.ReadFile(dnsmasq.MerlinPostConfPath)
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	// Restore dnsmasq post conf file.
+	if err := os.WriteFile(dnsmasq.MerlinPostConfPath, merlinParsePostConf(buf), 0750); err != nil {
+		return err
+	}
+	// Restart dnsmasq service.
+	if err := restartDNSMasq(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func restartDNSMasq() error {
+	if out, err := exec.Command("service", "restart_dnsmasq").CombinedOutput(); err != nil {
+		return fmt.Errorf("restart_dnsmasq: %s, %w", string(out), err)
+	}
+	return nil
+}
+
+func merlinParsePostConf(buf []byte) []byte {
+	if len(buf) == 0 {
+		return nil
+	}
+	parts := bytes.Split(buf, []byte(dnsmasq.MerlinPostConfMarker))
+	if len(parts) != 1 {
+		return bytes.TrimLeftFunc(parts[1], unicode.IsSpace)
+	}
+	return buf
+}

internal/router/merlin/merlin_test.go

@@ -0,0 +1,40 @@
+package merlin
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/Control-D-Inc/ctrld/internal/router/dnsmasq"
+)
+
+func Test_merlinParsePostConf(t *testing.T) {
+	origContent := "# foo"
+	data := strings.Join([]string{
+		dnsmasq.MerlinPostConfTmpl,
+		"\n",
+		dnsmasq.MerlinPostConfMarker,
+		"\n",
+	}, "\n")
+
+	tests := []struct {
+		name     string
+		data     string
+		expected string
+	}{
+		{"empty", "", ""},
+		{"no ctrld", origContent, origContent},
+		{"ctrld with data", data + origContent, origContent},
+		{"ctrld without data", data, ""},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			//t.Parallel()
+			if got := merlinParsePostConf([]byte(tc.data)); !bytes.Equal(got, []byte(tc.expected)) {
+				t.Errorf("unexpected result, want: %q, got: %q", tc.expected, string(got))
+			}
+		})
+	}
+}