Add monitoring of the current public IP

Ref #4

This commit adds an active monitoring of the current public IP. If a
change is detected, then a message is sent to the given Telegram
channel. Add a few tests for the main monitoring logic.

tracker/bot/bot.go

@@ -3,6 +3,7 @@ package bot
 import (
 	"context"
 	"fmt"
+	"net"
 	"time"
 
 	"git.faercol.me/faercol/public-ip-tracker/tracker/config"
@@ -11,11 +12,17 @@ import (
 )
 
 type Notifier struct {
-	ctx          context.Context
-	cancel       context.CancelFunc
-	tgBot        *bot.ConcreteBot
-	notifChannel int64
-	ipGetter     *ip.IPGetter
+	ctx         context.Context
+	cancel      context.CancelFunc
+	tgBot       bot.Bot
+	tgChatID    int64
+	ipGetter    ip.IPGetter
+	timeGetter  func() time.Time
+	currentIP   net.IP
+	frequency   time.Duration
+	errChan     chan error
+	changesChan chan net.IP
+	exitChan    chan struct{}
 }
 
 func (n *Notifier) SendInitMessage() error {
@@ -24,22 +31,67 @@ func (n *Notifier) SendInitMessage() error {
 		return fmt.Errorf("failed to get current public IP: %w", err)
 	}
 
-	initMsg := fmt.Sprintf("Public IP tracker initialized at %v, public IP is %s", time.Now(), publicIP)
-	if err := n.tgBot.SendMessage(n.ctx, n.notifChannel, initMsg); err != nil {
+	n.currentIP = publicIP
+	currentTime := n.timeGetter()
+
+	initMsg := fmt.Sprintf("Public IP tracker initialized at %v, public IP is %s", currentTime, publicIP)
+	if err := n.tgBot.SendMessage(n.ctx, n.tgChatID, initMsg); err != nil {
 		return fmt.Errorf("failed to send initialization message: %w", err)
 	}
 	return nil
 }
 
+func (n *Notifier) sendUpdatedIPMsg() error {
+	updateMsg := fmt.Sprintf("Public IP has been changed, is now %s", n.currentIP)
+	if err := n.tgBot.SendMessage(n.ctx, n.tgChatID, updateMsg); err != nil {
+		return fmt.Errorf("failed to send update message: %w", err)
+	}
+	return nil
+}
+
+func (n *Notifier) Run() {
+	for {
+		select {
+		case <-time.After(n.frequency):
+			newIP, err := n.ipGetter.GetCurrentPublicIP(n.ctx)
+			if err != nil {
+				n.errChan <- fmt.Errorf("failed to update public IP: %w", err)
+				continue
+			}
+			if !newIP.Equal(n.currentIP) {
+				n.currentIP = newIP
+				if err := n.sendUpdatedIPMsg(); err != nil {
+					n.errChan <- err
+				}
+			}
+		case <-n.ctx.Done():
+			n.exitChan <- struct{}{}
+			return
+		}
+	}
+}
+
+func (n *Notifier) ErrChan() <-chan error {
+	return n.errChan
+}
+
+func (n *Notifier) Exit() <-chan struct{} {
+	return n.exitChan
+}
+
 func New(ctx context.Context, config *config.Config) *Notifier {
 	subCtx, cancel := context.WithCancel(ctx)
 	tgBot := bot.New(config.Telegram.Token)
 
 	return &Notifier{
-		ctx:          subCtx,
-		cancel:       cancel,
-		tgBot:        tgBot,
-		notifChannel: config.Telegram.ChannelID,
-		ipGetter:     ip.New(),
+		ctx:        subCtx,
+		cancel:     cancel,
+		tgBot:      tgBot,
+		tgChatID:   config.Telegram.ChannelID,
+		timeGetter: time.Now,
+		ipGetter:   ip.New(),
+		errChan:    make(chan error, 10),
+		exitChan:   make(chan struct{}, 1),
+		frequency:  config.PollingFrequency,
 	}
 }

tracker/bot/bot_test.go

@@ -0,0 +1,191 @@
+package bot
+
+import (
+	"context"
+	"errors"
+	"net"
+	"testing"
+	"time"
+
+	iptest "git.faercol.me/faercol/public-ip-tracker/tracker/ip/test"
+	"github.com/ahugues/go-telegram-api/structs"
+)
+
+const expectedChatID = 42
+
+// Need to mock the telegram bot, because no mock is provided by my own lib, what a shame.
+type mockTGBot struct {
+	SendMessageProp error
+	SendMessageFunc func(context.Context, int64, string) error
+}
+
+// Do nothing here, it's not used by this bot
+func (mb *mockTGBot) GetMe(ctx context.Context) (structs.User, error) {
+	return structs.User{}, nil
+}
+
+func (mb *mockTGBot) SendMessage(ctx context.Context, chatID int64, content string) error {
+	if mb.SendMessageFunc == nil {
+		return mb.SendMessageProp
+	}
+	return mb.SendMessageFunc(ctx, chatID, content)
+}
+
+func TestInit(t *testing.T) {
+	t.Parallel()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	called := false
+
+	tgBot := mockTGBot{
+		SendMessageFunc: func(ctx context.Context, chatID int64, content string) error {
+			if chatID != expectedChatID {
+				t.Errorf("Unexpected chatID %d", chatID)
+			}
+			if content != "Public IP tracker initialized at 2023-01-28 14:17:12 +0000 UTC, public IP is 198.51.100.42" {
+				t.Errorf("Unexpected message %s", content)
+			}
+			called = true
+			return nil
+		},
+	}
+
+	ipGetter := iptest.TestIPGetter{
+		PublicIPProp: net.ParseIP("198.51.100.42"),
+	}
+
+	bot := Notifier{
+		ctx:        ctx,
+		cancel:     cancel,
+		tgBot:      &tgBot,
+		tgChatID:   expectedChatID,
+		timeGetter: func() time.Time { return time.Date(2023, 1, 28, 14, 17, 12, 0, time.UTC) },
+		ipGetter:   &ipGetter,
+		frequency:  1 * time.Minute,
+	}
+
+	if err := bot.SendInitMessage(); err != nil {
+		t.Fatalf("Unexpected error %s", err.Error())
+	}
+	if !called {
+		t.Error("Telegram bot not called")
+	}
+}
+
+func TestUpdateIP(t *testing.T) {
+	t.Parallel()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	called := false
+
+	tgBot := mockTGBot{
+		SendMessageFunc: func(ctx context.Context, chatID int64, content string) error {
+			if chatID != expectedChatID {
+				t.Errorf("Unexpected chatID %d", chatID)
+			}
+			if content != "Public IP has been changed, is now 198.51.100.42" {
+				t.Errorf("Unexpected message %s", content)
+			}
+			called = true
+			return nil
+		},
+	}
+
+	ipGetter := iptest.TestIPGetter{
+		PublicIPProp: net.ParseIP("198.51.100.42"),
+	}
+
+	bot := Notifier{
+		ctx:        ctx,
+		cancel:     cancel,
+		tgBot:      &tgBot,
+		tgChatID:   expectedChatID,
+		timeGetter: func() time.Time { return time.Date(2023, 1, 28, 14, 17, 12, 0, time.UTC) },
+		currentIP:  net.ParseIP("198.51.100.12"),
+		exitChan:   make(chan struct{}, 1),
+		errChan:    make(chan error, 5),
+		ipGetter:   &ipGetter,
+		frequency:  500 * time.Millisecond,
+	}
+
+	go bot.Run()
+
+	select {
+	case <-bot.Exit():
+		t.Error("Unexpected exit")
+	case <-time.After(1 * time.Second):
+		break
+	}
+
+	cancel()
+
+	select {
+	case <-bot.Exit():
+		break
+	case <-time.After(2 * time.Second):
+		t.Error("Unexpected timeout")
+	}
+
+	select {
+	case err := <-bot.ErrChan():
+		t.Errorf("Unexpected error %s", err.Error())
+	default:
+		break
+	}
+
+	if !called {
+		t.Error("Telegram bot not called")
+	}
+}
+
+func TestUpdateIPNoChange(t *testing.T) {
+	t.Parallel()
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	tgBot := mockTGBot{
+		SendMessageProp: errors.New("should not be called"),
+	}
+
+	ipGetter := iptest.TestIPGetter{
+		PublicIPProp: net.ParseIP("198.51.100.42"),
+	}
+
+	bot := Notifier{
+		ctx:        ctx,
+		cancel:     cancel,
+		tgBot:      &tgBot,
+		tgChatID:   expectedChatID,
+		timeGetter: func() time.Time { return time.Date(2023, 1, 28, 14, 17, 12, 0, time.UTC) },
+		currentIP:  net.ParseIP("198.51.100.42"),
+		exitChan:   make(chan struct{}, 1),
+		errChan:    make(chan error, 5),
+		ipGetter:   &ipGetter,
+		frequency:  100 * time.Millisecond,
+	}
+
+	go bot.Run()
+
+	select {
+	case <-bot.Exit():
+		t.Error("Unexpected exit")
+	case <-time.After(500 * time.Millisecond):
+		break
+	}
+
+	cancel()
+
+	select {
+	case <-bot.Exit():
+		break
+	case <-time.After(2 * time.Second):
+		t.Error("Unexpected timeout")
+	}
+
+	select {
+	case err := <-bot.ErrChan():
+		t.Errorf("Unexpected error %s", err.Error())
+	default:
+		break
+	}
+}

tracker/config/config.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"time"
 )
 
 type TelegramConfig struct {
@@ -12,7 +13,13 @@ type TelegramConfig struct {
 }
 
 type Config struct {
-	Telegram *TelegramConfig `json:"telegram"`
+	Telegram         *TelegramConfig
+	PollingFrequency time.Duration
+}
+
+type jsonConfig struct {
+	Telegram         *TelegramConfig `json:"telegram"`
+	PollingFrequency int64           `json:"polling_frequency"`
 }
 
 func New(filepath string) (*Config, error) {
@@ -20,9 +27,12 @@ func New(filepath string) (*Config, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to read config file %q: %w", filepath, err)
 	}
-	var conf Config
-	if err := json.Unmarshal(content, &conf); err != nil {
+	var jsonConf jsonConfig
+	if err := json.Unmarshal(content, &jsonConf); err != nil {
 		return nil, fmt.Errorf("failed to parse config file: %w", err)
 	}
-	return &conf, nil
+	return &Config{
+		Telegram:         jsonConf.Telegram,
+		PollingFrequency: time.Duration(jsonConf.PollingFrequency) * time.Second,
+	}, nil
 }

tracker/go.mod

@@ -2,4 +2,4 @@ module git.faercol.me/faercol/public-ip-tracker/tracker
 
 go 1.16
 
-require github.com/ahugues/go-telegram-api v0.0.0-20230125191847-f1f02f942580
+require github.com/ahugues/go-telegram-api v0.0.0-20230128131122-4d5782beddd0

tracker/go.sum

@@ -1,5 +1,5 @@
-github.com/ahugues/go-telegram-api v0.0.0-20230125191847-f1f02f942580 h1:0EzaHeqTet8yPON8P6kHfHVl9Zb8+eWON0wPco93N7Y=
-github.com/ahugues/go-telegram-api v0.0.0-20230125191847-f1f02f942580/go.mod h1:8I/JWxd9GYM7dHOgGmkRI3Ei1u+nGvzeR2knIMmFw7E=
+github.com/ahugues/go-telegram-api v0.0.0-20230128131122-4d5782beddd0 h1:1R472WmBuKK9Bvt4+rlqj01z1MwlVic3Xzgjvql3PXA=
+github.com/ahugues/go-telegram-api v0.0.0-20230128131122-4d5782beddd0/go.mod h1:8I/JWxd9GYM7dHOgGmkRI3Ei1u+nGvzeR2knIMmFw7E=
 github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/yuin/goldmark v1.4.1/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=

tracker/ip/ip.go

@@ -14,13 +14,17 @@ const ifconfigURL = "https://ifconfig.me"
 const httpMaxRead = 100
 const httpTimeout = 10 * time.Second
 
-type IPGetter struct {
+type IPGetter interface {
+	GetCurrentPublicIP(ctx context.Context) (net.IP, error)
+}
+
+type concreteIPGetter struct {
 	httpClt       *http.Client
 	remoteAddress string
 	timeout       time.Duration
 }
 
-func (c *IPGetter) GetCurrentPublicIP(ctx context.Context) (net.IP, error) {
+func (c *concreteIPGetter) GetCurrentPublicIP(ctx context.Context) (net.IP, error) {
 	reqCtx, cancel := context.WithTimeout(ctx, c.timeout)
 	defer cancel()
 
@@ -52,8 +56,8 @@ func (c *IPGetter) GetCurrentPublicIP(ctx context.Context) (net.IP, error) {
 	return res, nil
 }
 
-func New() *IPGetter {
-	return &IPGetter{
+func New() IPGetter {
+	return &concreteIPGetter{
 		httpClt:       http.DefaultClient,
 		remoteAddress: ifconfigURL,
 		timeout:       httpTimeout,

tracker/ip/ip_test.go

@@ -18,7 +18,7 @@ func TestGetIPOK(t *testing.T) {
 	}))
 	defer mockSrv.Close()
 
-	clt := IPGetter{
+	clt := concreteIPGetter{
 		httpClt:       mockSrv.Client(),
 		remoteAddress: mockSrv.URL,
 		timeout:       1 * time.Second,
@@ -43,7 +43,7 @@ func TestGetIPServerErr(t *testing.T) {
 	}))
 	defer mockSrv.Close()
 
-	clt := IPGetter{
+	clt := concreteIPGetter{
 		httpClt:       mockSrv.Client(),
 		remoteAddress: mockSrv.URL,
 		timeout:       1 * time.Second,
@@ -66,7 +66,7 @@ func TestGetIPUnreachable(t *testing.T) {
 	}))
 	mockSrv.Close()
 
-	clt := IPGetter{
+	clt := concreteIPGetter{
 		httpClt:       mockSrv.Client(),
 		remoteAddress: mockSrv.URL,
 		timeout:       1 * time.Second,
@@ -91,7 +91,7 @@ func TestGetIPInvalidResponse(t *testing.T) {
 	}))
 	defer mockSrv.Close()
 
-	clt := IPGetter{
+	clt := concreteIPGetter{
 		httpClt:       mockSrv.Client(),
 		remoteAddress: mockSrv.URL,
 		timeout:       1 * time.Second,
@@ -117,7 +117,7 @@ func TestGetIPTimeout(t *testing.T) {
 	}))
 	defer mockSrv.Close()
 
-	clt := IPGetter{
+	clt := concreteIPGetter{
 		httpClt:       mockSrv.Client(),
 		remoteAddress: mockSrv.URL,
 		timeout:       1 * time.Millisecond,

tracker/ip/test/ip.go

@@ -0,0 +1,18 @@
+package test
+
+import (
+	"context"
+	"net"
+)
+
+type TestIPGetter struct {
+	PublicIPProp net.IP
+	PublicIPFunc func(ctx context.Context) (net.IP, error)
+}
+
+func (g *TestIPGetter) GetCurrentPublicIP(ctx context.Context) (net.IP, error) {
+	if g.PublicIPFunc == nil {
+		return g.PublicIPProp, nil
+	}
+	return g.PublicIPFunc(ctx)
+}

tracker/main.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"os"
+	"os/signal"
 
 	"git.faercol.me/faercol/public-ip-tracker/tracker/bot"
 	"git.faercol.me/faercol/public-ip-tracker/tracker/config"
@@ -27,6 +29,8 @@ func main() {
 	fmt.Println("Parsing arguments")
 	args := parseArgs()
 
+	mainCtx, cancel := context.WithCancel(context.Background())
+
 	fmt.Println("Parsing config")
 	conf, err := config.New(args.configPath)
 	if err != nil {
@@ -34,10 +38,33 @@ func main() {
 	}
 
 	fmt.Println("Initializing bot")
-	notifBot := bot.New(context.Background(), conf)
+	notifBot := bot.New(mainCtx, conf)
 	if err := notifBot.SendInitMessage(); err != nil {
 		panic(err)
 	}
 
+	fmt.Println("Starting monitoring")
+	go notifBot.Run()
+
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, os.Interrupt)
+
+outerloop:
+	for {
+		select {
+		case <-c:
+			fmt.Println("received cancel")
+			cancel()
+			break outerloop
+		case err := <-notifBot.ErrChan():
+			fmt.Printf("Unexpected error %s", err.Error())
+		case <-notifBot.Exit():
+			fmt.Println("Unexpected exit")
+		}
+	}
+
+	<-notifBot.Exit()
+
 	fmt.Println("OK")
+	os.Exit(0)
 }