Adding simple visits handler to send a notification on site load with some simple rate limiting and caching

controller.go

@@ -16,8 +16,9 @@ import (
 var token string
 
 type Handler struct {
-	db   *sql.DB
-	ntfy *Ntfy
+	db     *sql.DB
+	ntfy   *Ntfy
+	visits *VisitHandler
 }
 
 func getStaticFile(relPath string, contentType string, w http.ResponseWriter) {
@@ -153,6 +154,7 @@ func SetupAuth() {
 
 func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	fmt.Printf("%s - [%s] (%s) %s\n", time.Now().Format(time.RFC3339), r.RemoteAddr, r.Method, r.URL)
+	h.visits.HandleVisit(r.RemoteAddr)
 
 	switch true {
 	case r.Method == "GET" && r.URL.Path == "/favicon.ico":

main.go

@@ -16,8 +16,10 @@ func main() {
 	db := SetupDatabase()
 	SetupRsvpsTable(db)
 
+	visits := SetupVisitHandler(&VisitHandlerArgs{baseUrl: "http://ip-api.com", rateLimitAmount: 45, rateLimitDurationSeconds: 60})
+
 	SetupAuth()
-	hnd := &Handler{db, ntfy}
+	hnd := &Handler{db, ntfy, visits}
 	fmt.Println("handler ready")
 
 	http.ListenAndServe(":8000", hnd)

ntfy.go

@@ -71,46 +71,6 @@ func SetupNtfyClient() *Ntfy {
 	return &Ntfy{client: tp}
 }
 
-func buildTitle(rsvp *Rsvp) string {
-	builder := new(strings.Builder)
-	if rsvp.Attending {
-		peoplePerson := "people"
-		if rsvp.PartySize == 1 {
-			peoplePerson = "person"
-		}
-		fmt.Fprintf(builder, "%d %s confirmed!", rsvp.PartySize, peoplePerson)
-	} else {
-		fmt.Fprintf(builder, "Someone can't make it")
-	}
-	return builder.String()
-}
-
-func buildMessage(rsvp *Rsvp) string {
-	builder := new(strings.Builder)
-	if rsvp.Attending {
-		builder.WriteString("Here's who is coming 👇")
-		for _, mem := range rsvp.PartyMembers {
-			age := "adult"
-			if mem.Child {
-				age = "👶"
-			} else {
-				age = "🧓"
-			}
-			dp := "n/a"
-			if len(mem.DietaryPreferences) > 0 {
-				dp = mem.DietaryPreferences
-			}
-			fmt.Fprintf(builder, "\n- %s %s, %s", age, mem.Name, dp)
-		}
-	} else {
-		for _, mem := range rsvp.PartyMembers {
-			fmt.Fprintf(builder, "%s\n", mem.Name)
-		}
-		builder.WriteString("can't make it")
-	}
-	return builder.String()
-}
-
 func numberToEmoji(num int64) string {
 	switch num {
 	case 0:
@@ -138,7 +98,47 @@ func numberToEmoji(num int64) string {
 	}
 }
 
-func buildTags(rsvp *Rsvp) []string {
+func buildRsvpTitle(rsvp *Rsvp) string {
+	builder := new(strings.Builder)
+	if rsvp.Attending {
+		peoplePerson := "people"
+		if rsvp.PartySize == 1 {
+			peoplePerson = "person"
+		}
+		fmt.Fprintf(builder, "%d %s confirmed!", rsvp.PartySize, peoplePerson)
+	} else {
+		fmt.Fprintf(builder, "Someone can't make it")
+	}
+	return builder.String()
+}
+
+func buildRsvpMessage(rsvp *Rsvp) string {
+	builder := new(strings.Builder)
+	if rsvp.Attending {
+		builder.WriteString("Here's who is coming 👇")
+		for _, mem := range rsvp.PartyMembers {
+			age := "adult"
+			if mem.Child {
+				age = "👶"
+			} else {
+				age = "🧓"
+			}
+			dp := "n/a"
+			if len(mem.DietaryPreferences) > 0 {
+				dp = mem.DietaryPreferences
+			}
+			fmt.Fprintf(builder, "\n- %s %s, %s", age, mem.Name, dp)
+		}
+	} else {
+		for _, mem := range rsvp.PartyMembers {
+			fmt.Fprintf(builder, "%s\n", mem.Name)
+		}
+		builder.WriteString("can't make it")
+	}
+	return builder.String()
+}
+
+func buildRsvpTags(rsvp *Rsvp) []string {
 	if rsvp.Attending {
 		return []string{"white_check_mark", numberToEmoji(rsvp.PartySize)}
 	} else {
@@ -146,18 +146,46 @@ func buildTags(rsvp *Rsvp) []string {
 	}
 }
 
-func BuildNtfyMessage(topic string, rsvp *Rsvp) *gotfy.Message {
+func BuildRsvpMessage(topic string, rsvp *Rsvp) *gotfy.Message {
 	return &gotfy.Message{
 		Topic:    topic,
-		Message:  buildMessage(rsvp),
-		Title:    buildTitle(rsvp),
-		Tags:     buildTags(rsvp),
+		Message:  buildRsvpMessage(rsvp),
+		Title:    buildRsvpTitle(rsvp),
+		Tags:     buildRsvpTags(rsvp),
 		Priority: gotfy.Default,
 	}
 }
 
 func (n *Ntfy) PublishNewRsvpNotification(rsvp *Rsvp) (string, error) {
-	resp, err := n.client.SendMessage(context.Background(), BuildNtfyMessage("collinenlucy_nl", rsvp))
+	resp, err := n.client.SendMessage(context.Background(), BuildRsvpMessage("collinenlucy_nl", rsvp))
+
+	if err != nil {
+		return "", err
+	}
+
+	return resp.ID, nil
+}
+
+func buildVisitTitle(visit *Visit) string {
+	return "Someone visited!"
+}
+
+func buildVisitMessage(visit *Visit) string {
+	return fmt.Sprintf("Got a visit from %s (%s)", visit.Location, visit.RemoteAddr)
+}
+
+func BuildVisitMessage(topic string, visit *Visit) *gotfy.Message {
+	return &gotfy.Message{
+		Topic:    topic,
+		Message:  buildVisitMessage(visit),
+		Title:    buildVisitTitle(visit),
+		Tags:     []string{"eyes"},
+		Priority: gotfy.Default,
+	}
+}
+
+func (n *Ntfy) PublishNewVisitNotification(visit *Visit) (string, error) {
+	resp, err := n.client.SendMessage(context.Background(), BuildVisitMessage("collinenlucy_nl", visit))
 
 	if err != nil {
 		return "", err

ntfy_test.go

@@ -11,7 +11,7 @@ func TestBuildNtfyMessage(t *testing.T) {
 			{Name: "test", Child: false, DietaryPreferences: ""},
 		},
 	}
-	msg := BuildNtfyMessage("test", rsvp)
+	msg := BuildRsvpMessage("test", rsvp)
 
 	if msg.Topic != "test" {
 		t.Fatal("message topic is incorrect")
@@ -34,7 +34,7 @@ func TestBuildNtfyMessage(t *testing.T) {
 			{Name: "test", Child: false, DietaryPreferences: ""},
 		},
 	}
-	msg = BuildNtfyMessage("test", rsvp)
+	msg = BuildRsvpMessage("test", rsvp)
 
 	if msg.Topic != "test" {
 		t.Fatal("message topic is incorrect")
@@ -58,7 +58,7 @@ func TestBuildNtfyMessage(t *testing.T) {
 			{Name: "test2", Child: true, DietaryPreferences: "no tobacco"},
 		},
 	}
-	msg = BuildNtfyMessage("test", rsvp)
+	msg = BuildRsvpMessage("test", rsvp)
 
 	if msg.Topic != "test" {
 		t.Fatal("message topic is incorrect")

visits.go

@@ -0,0 +1,139 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+)
+
+type Visit struct {
+	RemoteAddr string
+	Location   string
+}
+
+type GeolocationResponse struct {
+	Country    string `json:"country"`
+	City       string `json:"city"`
+	RegionName string `json:"regionName"`
+}
+
+type VisitHandler struct {
+	geolocationApiBaseUrl    string
+	visitsCache              map[string]int64
+	pastRequests             []int64
+	rateLimitAmount          int
+	rateLimitDurationSeconds int
+}
+
+func (v *VisitHandler) buildUrl(ipAddress string) string {
+	return fmt.Sprintf("%s/json/%s?fields=country,regionName,city", v.geolocationApiBaseUrl, ipAddress)
+}
+
+func (v *VisitHandler) limitRate() bool {
+	now := time.Now()
+
+	idxToRemove := make([]int, 0)
+	for idx, ts := range v.pastRequests {
+		if now.Sub(time.Unix(ts, 0)).Seconds() >= float64(v.rateLimitDurationSeconds) {
+			idxToRemove = append(idxToRemove, idx)
+		}
+	}
+
+	for i := len(idxToRemove) - 1; i >= 0; i-- {
+		idx := idxToRemove[i]
+		v.pastRequests = append(v.pastRequests[:idx], v.pastRequests[idx+1:]...)
+	}
+
+	if len(v.pastRequests) == 0 {
+		v.pastRequests = append(v.pastRequests, now.Unix())
+		return true
+	}
+
+	retVal := false
+
+	if len(v.pastRequests) < v.rateLimitAmount {
+		v.pastRequests = append(v.pastRequests, now.Unix())
+		retVal = true
+	}
+
+	return retVal
+}
+
+func (v *VisitHandler) getLocation(ipAddress string) *GeolocationResponse {
+	if !v.limitRate() {
+		return nil
+	}
+
+	resp, err := http.Get(v.buildUrl(ipAddress))
+	if err != nil {
+		return nil
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil
+	}
+
+	var geoResponse GeolocationResponse
+	err = json.Unmarshal(body, &geoResponse)
+	return &geoResponse
+}
+
+func (v *VisitHandler) createVisit(ipAddress string) *Visit {
+	loc := v.getLocation(ipAddress)
+	if loc == nil {
+		return nil
+	}
+
+	locationParts := []string{}
+	if loc.City != "" {
+		locationParts = append(locationParts, loc.City)
+	}
+	if loc.RegionName != "" {
+		locationParts = append(locationParts, loc.RegionName)
+	}
+	if loc.Country != "" {
+		locationParts = append(locationParts, loc.Country)
+	}
+
+	return &Visit{
+		RemoteAddr: ipAddress,
+		Location:   strings.Join(locationParts, ", "),
+	}
+}
+
+func (v *VisitHandler) HandleVisit(remoteAddr string) *Visit {
+	if v.visitsCache == nil {
+		v.visitsCache = make(map[string]int64)
+	}
+
+	if v.visitsCache[remoteAddr] == 0 || time.Since(time.Unix(v.visitsCache[remoteAddr], 0)) > time.Duration(v.rateLimitDurationSeconds) {
+		visit := v.createVisit(remoteAddr)
+		if visit == nil {
+			return nil
+		}
+		v.visitsCache[visit.RemoteAddr] = time.Now().Unix()
+		return visit
+	}
+
+	return nil
+}
+
+type VisitHandlerArgs struct {
+	baseUrl                  string
+	rateLimitAmount          int
+	rateLimitDurationSeconds int
+}
+
+func SetupVisitHandler(args *VisitHandlerArgs) *VisitHandler {
+	return &VisitHandler{
+		geolocationApiBaseUrl:    args.baseUrl,
+		visitsCache:              make(map[string]int64),
+		pastRequests:             make([]int64, 0),
+		rateLimitAmount:          args.rateLimitAmount,
+		rateLimitDurationSeconds: args.rateLimitDurationSeconds,
+	}
+}

visits_test.go

@@ -0,0 +1,177 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+)
+
+func TestHandleVisit_Success(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{"country":"Netherlands","regionName":"Noord-Holland","city":"Amsterdam"}`))
+	}))
+	defer server.Close()
+
+	v := SetupVisitHandler(&VisitHandlerArgs{baseUrl: server.URL})
+
+	visit := v.HandleVisit("home.collinduncan.com")
+	if visit == nil {
+		t.FailNow()
+	}
+
+	if visit.Location != "Amsterdam, Noord-Holland, Netherlands" {
+		t.FailNow()
+	}
+}
+
+func TestHandleVisit_NoRegion(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{"country":"Netherlands","city":"Amsterdam"}`))
+	}))
+	defer server.Close()
+
+	v := SetupVisitHandler(&VisitHandlerArgs{baseUrl: server.URL})
+
+	visit := v.HandleVisit("home.collinduncan.com")
+	if visit == nil {
+		t.Fatalf("Location is nil")
+	}
+
+	if visit.Location != "Amsterdam, Netherlands" {
+		t.Fatalf("Location is %s", visit.Location)
+	}
+}
+
+func TestHandleVisit_NoCountry(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{"regionName":"Noord-Holland","city":"Amsterdam"}`))
+	}))
+	defer server.Close()
+
+	v := SetupVisitHandler(&VisitHandlerArgs{baseUrl: server.URL})
+
+	visit := v.HandleVisit("home.collinduncan.com")
+	if visit == nil {
+		t.FailNow()
+	}
+
+	if visit.Location != "Amsterdam, Noord-Holland" {
+		t.FailNow()
+	}
+}
+
+func TestHandleVisit_NoCity(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{"country":"Netherlands","regionName":"Noord-Holland"}`))
+	}))
+	defer server.Close()
+
+	v := SetupVisitHandler(&VisitHandlerArgs{baseUrl: server.URL})
+
+	visit := v.HandleVisit("home.collinduncan.com")
+	if visit == nil {
+		t.FailNow()
+	}
+
+	if visit.Location != "Noord-Holland, Netherlands" {
+		t.FailNow()
+	}
+}
+
+func TestHandleVisit_Nothing(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{}`))
+	}))
+	defer server.Close()
+
+	v := SetupVisitHandler(&VisitHandlerArgs{baseUrl: server.URL})
+
+	visit := v.HandleVisit("home.collinduncan.com")
+	if visit == nil {
+		t.FailNow()
+	}
+
+	if visit.Location != "" {
+		t.FailNow()
+	}
+}
+
+func TestHandleVisit_RateLimit(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{"country":"Netherlands","regionName":"Noord-Holland","city":"Amsterdam"}`))
+	}))
+	defer server.Close()
+
+	v := SetupVisitHandler(&VisitHandlerArgs{
+		baseUrl:                  server.URL,
+		rateLimitAmount:          30,
+		rateLimitDurationSeconds: 1,
+	})
+
+	// pre-limit
+	for i := 0; i < 30; i++ {
+		visit := v.HandleVisit(fmt.Sprintf("home.collinduncan%d.com", i))
+		if visit == nil {
+			t.Fatalf("Failed before rate-limiter %d", i)
+		}
+
+		if visit.Location != "Amsterdam, Noord-Holland, Netherlands" {
+			t.Fatal("Failed before rate-limiter, location")
+		}
+	}
+
+	visit := v.HandleVisit("home.collinduncan90.com")
+	if visit != nil {
+		t.Fatal("Failed to hit rate limiter")
+	}
+
+	time.Sleep(time.Second * 2)
+
+	visit = v.HandleVisit("home.collinduncan90.com")
+	if visit == nil {
+		t.Fatal("Failed after rate-limiter")
+	}
+
+	if visit.Location != "Amsterdam, Noord-Holland, Netherlands" {
+		t.Fatal("Failed after rate-limiter, location")
+	}
+}
+
+func TestHandleVisit_Cache(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{"country":"Netherlands","regionName":"Noord-Holland","city":"Amsterdam"}`))
+	}))
+	defer server.Close()
+
+	v := SetupVisitHandler(&VisitHandlerArgs{baseUrl: server.URL, rateLimitDurationSeconds: 1})
+
+	visit := v.HandleVisit("home.collinduncan.com")
+	if visit == nil {
+		t.FailNow()
+	}
+
+	if visit.Location != "Amsterdam, Noord-Holland, Netherlands" {
+		t.FailNow()
+	}
+
+	visit = v.HandleVisit("home.collinduncan.com")
+	if visit != nil {
+		t.FailNow()
+	}
+
+	time.Sleep(time.Second * 2)
+
+	visit = v.HandleVisit("home.collinduncan.com")
+	if visit == nil {
+		t.FailNow()
+	}
+}