WIP

peer/hosts_test.go

@@ -0,0 +1,167 @@
+package peer
+
+import (
+	"net/netip"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"testing"
+)
+
+// writeTempHosts creates a temp hosts file with the given content and returns
+// its path.
+func writeTempHosts(t *testing.T, content string) string {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "hosts")
+	if err := os.WriteFile(path, []byte(content), 0600); err != nil {
+		t.Fatal(err)
+	}
+	return path
+}
+
+// readManagedSection returns the lines between the begin/end markers for the
+// given localDomain, plus everything outside the section ("outside").
+func readManagedSection(t *testing.T, path, localDomain string) (inside, outside []string) {
+	t.Helper()
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	begin := hostsBegin + localDomain
+	end := hostsEnd + localDomain
+
+	inSection := false
+	for _, line := range strings.Split(string(raw), "\n") {
+		switch {
+		case strings.HasPrefix(line, begin):
+			inSection = true
+		case strings.HasPrefix(line, end):
+			inSection = false
+		case inSection:
+			if f := strings.Join(strings.Fields(line), " "); f != "" {
+				inside = append(inside, f)
+			}
+		default:
+			if f := strings.Join(strings.Fields(line), " "); f != "" {
+				outside = append(outside, f)
+			}
+		}
+	}
+	return inside, outside
+}
+
+func peer(name string) *Peer {
+	return &Peer{Name: name}
+}
+
+func TestUpdateHosts_AddsSection(t *testing.T) {
+	path := writeTempHosts(t, "127.0.0.1 localhost\n")
+
+	peers := map[netip.Addr]*Peer{
+		netip.MustParseAddr("10.11.12.1"):  peer("hub"),
+		netip.MustParseAddr("10.11.12.10"): peer("laptop"),
+	}
+
+	if err := updateHosts(path, "mynet.local", peers); err != nil {
+		t.Fatal(err)
+	}
+
+	inside, outside := readManagedSection(t, path, "mynet.local")
+
+	sort.Strings(inside)
+	want := []string{
+		"10.11.12.1 hub.mynet.local",
+		"10.11.12.10 laptop.mynet.local",
+	}
+	if strings.Join(inside, "\n") != strings.Join(want, "\n") {
+		t.Errorf("managed section = %v, want %v", inside, want)
+	}
+
+	if !contains(outside, "127.0.0.1 localhost") {
+		t.Errorf("original content lost; outside = %v", outside)
+	}
+}
+
+func TestUpdateHosts_ReplacesExistingSection(t *testing.T) {
+	path := writeTempHosts(t, "127.0.0.1 localhost\n")
+
+	// First write.
+	first := map[netip.Addr]*Peer{
+		netip.MustParseAddr("10.11.12.1"): peer("hub"),
+	}
+	if err := updateHosts(path, "mynet.local", first); err != nil {
+		t.Fatal(err)
+	}
+
+	// Second write with a different set of peers.
+	second := map[netip.Addr]*Peer{
+		netip.MustParseAddr("10.11.12.20"): peer("phone"),
+	}
+	if err := updateHosts(path, "mynet.local", second); err != nil {
+		t.Fatal(err)
+	}
+
+	inside, outside := readManagedSection(t, path, "mynet.local")
+
+	if len(inside) != 1 || inside[0] != "10.11.12.20 phone.mynet.local" {
+		t.Errorf("section not replaced; inside = %v", inside)
+	}
+	if contains(inside, "10.11.12.1 hub.mynet.local") {
+		t.Errorf("stale entry remained; inside = %v", inside)
+	}
+	if !contains(outside, "127.0.0.1 localhost") {
+		t.Errorf("original content lost; outside = %v", outside)
+	}
+}
+
+func TestUpdateHosts_SkipsEmptyNames(t *testing.T) {
+	path := writeTempHosts(t, "127.0.0.1 localhost\n")
+
+	peers := map[netip.Addr]*Peer{
+		netip.MustParseAddr("10.11.12.1"):  peer("hub"),
+		netip.MustParseAddr("10.11.12.99"): peer(""), // no name
+	}
+	if err := updateHosts(path, "mynet.local", peers); err != nil {
+		t.Fatal(err)
+	}
+
+	inside, _ := readManagedSection(t, path, "mynet.local")
+	if len(inside) != 1 || inside[0] != "10.11.12.1 hub.mynet.local" {
+		t.Errorf("expected only named peer; inside = %v", inside)
+	}
+}
+
+func TestUpdateHosts_Idempotent(t *testing.T) {
+	path := writeTempHosts(t, "127.0.0.1 localhost\n")
+
+	peers := map[netip.Addr]*Peer{
+		netip.MustParseAddr("10.11.12.1"): peer("hub"),
+	}
+	if err := updateHosts(path, "mynet.local", peers); err != nil {
+		t.Fatal(err)
+	}
+	first, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := updateHosts(path, "mynet.local", peers); err != nil {
+		t.Fatal(err)
+	}
+	second, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(first) != string(second) {
+		t.Errorf("repeated update changed file:\nfirst:\n%s\nsecond:\n%s", first, second)
+	}
+}
+
+func contains(ss []string, s string) bool {
+	for _, x := range ss {
+		if x == s {
+			return true
+		}
+	}
+	return false
+}