From 64632fa6407c310467ec0581c813c2e1a011aed4 Mon Sep 17 00:00:00 2001
From: Cuong Manh Le <cuong@windscribe.com>
Date: Tue, 17 Jun 2025 19:33:45 +0700
Subject: [PATCH] cmd/cli: use resolvconffile lib for parsing

---
 cmd/cli/resolvconf.go          | 24 +++---------------
 cmd/cli/resolvconf_test.go     | 46 ++++++++++++++++++++++++++++++++++
 internal/resolvconffile/dns.go | 13 ++++++----
 3 files changed, 57 insertions(+), 26 deletions(-)
 create mode 100644 cmd/cli/resolvconf_test.go

diff --git a/cmd/cli/resolvconf.go b/cmd/cli/resolvconf.go
index 587841d..496bd9b 100644
--- a/cmd/cli/resolvconf.go
+++ b/cmd/cli/resolvconf.go
@@ -3,36 +3,18 @@ package cli
 import (
 	"net"
 	"net/netip"
-	"os"
 	"path/filepath"
-	"strings"
 	"time"
 
 	"github.com/fsnotify/fsnotify"
+
+	"github.com/Control-D-Inc/ctrld/internal/resolvconffile"
 )
 
 // parseResolvConfNameservers reads the resolv.conf file and returns the nameservers found.
 // Returns nil if no nameservers are found.
 func (p *prog) parseResolvConfNameservers(path string) ([]string, error) {
-	content, err := os.ReadFile(path)
-	if err != nil {
-		return nil, err
-	}
-
-	// Parse the file for "nameserver" lines
-	var currentNS []string
-	lines := strings.Split(string(content), "\n")
-	for _, line := range lines {
-		trimmed := strings.TrimSpace(line)
-		if strings.HasPrefix(trimmed, "nameserver") {
-			parts := strings.Fields(trimmed)
-			if len(parts) >= 2 {
-				currentNS = append(currentNS, parts[1])
-			}
-		}
-	}
-
-	return currentNS, nil
+	return resolvconffile.NameserversFromFile(path)
 }
 
 // watchResolvConf watches any changes to /etc/resolv.conf file,
diff --git a/cmd/cli/resolvconf_test.go b/cmd/cli/resolvconf_test.go
new file mode 100644
index 0000000..9ee7e3b
--- /dev/null
+++ b/cmd/cli/resolvconf_test.go
@@ -0,0 +1,46 @@
+//go:build unix
+
+package cli
+
+import (
+	"os"
+	"slices"
+	"strings"
+	"testing"
+
+	"github.com/Control-D-Inc/ctrld/internal/dns/resolvconffile"
+)
+
+func oldParseResolvConfNameservers(path string) ([]string, error) {
+	content, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	// Parse the file for "nameserver" lines
+	var currentNS []string
+	lines := strings.Split(string(content), "\n")
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if strings.HasPrefix(trimmed, "nameserver") {
+			parts := strings.Fields(trimmed)
+			if len(parts) >= 2 {
+				currentNS = append(currentNS, parts[1])
+			}
+		}
+	}
+
+	return currentNS, nil
+}
+
+func Test_prog_parseResolvConfNameservers(t *testing.T) {
+	oldNss, _ := oldParseResolvConfNameservers(resolvconffile.Path)
+	p := &prog{}
+	nss, _ := p.parseResolvConfNameservers(resolvconffile.Path)
+	slices.Sort(oldNss)
+	slices.Sort(nss)
+	if !slices.Equal(oldNss, nss) {
+		t.Errorf("result mismatched, old: %v, new: %v", oldNss, nss)
+	}
+	t.Logf("result: %v", nss)
+}
diff --git a/internal/resolvconffile/dns.go b/internal/resolvconffile/dns.go
index 0d532eb..386e9a8 100644
--- a/internal/resolvconffile/dns.go
+++ b/internal/resolvconffile/dns.go
@@ -1,5 +1,3 @@
-//go:build !js && !windows
-
 package resolvconffile
 
 import (
@@ -24,15 +22,20 @@ func NameServersWithPort() []string {
 }
 
 func NameServers() []string {
-	c, err := resolvconffile.ParseFile(resolvconfPath)
+	nss, _ := NameserversFromFile(resolvconfPath)
+	return nss
+}
+
+func NameserversFromFile(path string) ([]string, error) {
+	c, err := resolvconffile.ParseFile(path)
 	if err != nil {
-		return nil
+		return nil, err
 	}
 	ns := make([]string, 0, len(c.Nameservers))
 	for _, nameserver := range c.Nameservers {
 		ns = append(ns, nameserver.String())
 	}
-	return ns
+	return ns, nil
 }
 
 // SearchDomains returns the current search domains config in /etc/resolv.conf file.