feat: Enhance AddEntries and RemoveByHostname functions with subdomain and alias handling

hostfile/managed_test.go

@@ -201,6 +201,52 @@ func TestAddEntries_ReplacesExistingHostname(t *testing.T) {
 	}
 }
 
+func TestAddEntries_DoesNotClobberSubdomains(t *testing.T) {
+	// Regression: substring matching would cause adding "example.com" to
+	// incorrectly remove "sub.example.com" entries.
+	existing := []string{
+		"1.1.1.1\tsub.example.com",
+		"2.2.2.2\tother.example.com",
+	}
+	entries := []hostfile.DNSEntry{{IP: "9.9.9.9", Hostname: "example.com"}}
+	result := hostfile.AddEntries(existing, entries)
+	if len(result) != 3 {
+		t.Fatalf("expected 3 entries (2 existing + 1 new), got %d: %v", len(result), result)
+	}
+	for _, line := range result {
+		if line == "1.1.1.1\tsub.example.com" || line == "2.2.2.2\tother.example.com" || line == "9.9.9.9\texample.com" {
+			continue
+		}
+		t.Errorf("unexpected line: %q", line)
+	}
+}
+
+func TestAddEntries_MatchesAliasColumn(t *testing.T) {
+	// A hosts-file line can have aliases: "IP primary alias1 alias2"
+	// Replacing "alias1" should remove the entire line.
+	existing := []string{"1.1.1.1\tprimary\talias1"}
+	entries := []hostfile.DNSEntry{{IP: "9.9.9.9", Hostname: "alias1"}}
+	result := hostfile.AddEntries(existing, entries)
+	for _, line := range result {
+		if strings.Contains(line, "primary") {
+			t.Errorf("line with alias1 should have been removed, but found: %q", line)
+		}
+	}
+}
+
+func TestAddEntries_CaseInsensitive(t *testing.T) {
+	// RFC 4343: hostnames are case-insensitive.
+	existing := []string{"1.1.1.1\tHost1.Example.COM"}
+	entries := []hostfile.DNSEntry{{IP: "9.9.9.9", Hostname: "host1.example.com"}}
+	result := hostfile.AddEntries(existing, entries)
+	if len(result) != 1 {
+		t.Fatalf("expected 1 entry (old replaced), got %d: %v", len(result), result)
+	}
+	if result[0] != "9.9.9.9\thost1.example.com" {
+		t.Errorf("expected new entry, got %q", result[0])
+	}
+}
+
 func TestAddEntries_Deduplicates(t *testing.T) {
 	existing := []string{"1.1.1.1\thost1"}
 	entries := []hostfile.DNSEntry{
@@ -332,6 +378,54 @@ func TestRemoveByHostname_RegressionNoDuplicates(t *testing.T) {
 	}
 }
 
+func TestRemoveByHostname_DoesNotClobberSubdomains(t *testing.T) {
+	// Regression: substring matching would remove "sub.example.com" when
+	// only "example.com" was requested for removal.
+	existing := []string{
+		"1.1.1.1\texample.com",
+		"2.2.2.2\tsub.example.com",
+		"3.3.3.3\tmy-example.com",
+	}
+	result := hostfile.RemoveByHostname(existing, []string{"example.com"})
+	if len(result) != 2 {
+		t.Fatalf("expected 2 remaining entries, got %d: %v", len(result), result)
+	}
+	if result[0] != "2.2.2.2\tsub.example.com" {
+		t.Errorf("expected sub.example.com to remain, got %q", result[0])
+	}
+	if result[1] != "3.3.3.3\tmy-example.com" {
+		t.Errorf("expected my-example.com to remain, got %q", result[1])
+	}
+}
+
+func TestRemoveByHostname_MatchesAliasColumn(t *testing.T) {
+	existing := []string{
+		"1.1.1.1\tprimary\talias1",
+		"2.2.2.2\thost2",
+	}
+	result := hostfile.RemoveByHostname(existing, []string{"alias1"})
+	if len(result) != 1 {
+		t.Fatalf("expected 1 remaining entry, got %d: %v", len(result), result)
+	}
+	if result[0] != "2.2.2.2\thost2" {
+		t.Errorf("expected host2 to remain, got %q", result[0])
+	}
+}
+
+func TestRemoveByHostname_CaseInsensitive(t *testing.T) {
+	existing := []string{
+		"1.1.1.1\tHost1.Example.COM",
+		"2.2.2.2\thost2",
+	}
+	result := hostfile.RemoveByHostname(existing, []string{"host1.example.com"})
+	if len(result) != 1 {
+		t.Fatalf("expected 1 remaining entry, got %d: %v", len(result), result)
+	}
+	if result[0] != "2.2.2.2\thost2" {
+		t.Errorf("expected host2 to remain, got %q", result[0])
+	}
+}
+
 // ---------------------------------------------------------------------------
 // RemoveAll tests (T018)
 // ---------------------------------------------------------------------------