with file db

.gitignore

@@ -1,2 +1,4 @@
 dist/
 node_modules/
+
+*.local*

go.mod

@@ -1,9 +1,3 @@
 module gdg-counter-website
 
 go 1.19
-
-require (
-	github.com/r3labs/sse/v2 v2.10.0 // indirect
-	golang.org/x/net v0.0.0-20191116160921-f9c825593386 // indirect
-	gopkg.in/cenkalti/backoff.v1 v1.1.0 // indirect
-)

go.sum

@@ -1,15 +0,0 @@
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/r3labs/sse/v2 v2.10.0 h1:hFEkLLFY4LDifoHdiCN/LlGBAdVJYsANaLqNYa1l/v0=
-github.com/r3labs/sse/v2 v2.10.0/go.mod h1:Igau6Whc+F17QUgML1fYe1VPZzTV6EMCnYktEmkNJ7I=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/net v0.0.0-20191116160921-f9c825593386 h1:ktbWvQrW08Txdxno1PiDpSxPXG6ndGsfnJjRRtkM0LQ=
-golang.org/x/net v0.0.0-20191116160921-f9c825593386/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-gopkg.in/cenkalti/backoff.v1 v1.1.0 h1:Arh75ttbsvlpVA7WtVpH4u9h6Zl46xuptxqLxPiSo4Y=
-gopkg.in/cenkalti/backoff.v1 v1.1.0/go.mod h1:J6Vskwqd+OMVJl8C33mmtxTBs2gyzfv7UDAkHu8BrjI=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

main.go

@@ -4,8 +4,6 @@ import (
 	"encoding/json"
 	"log"
 	"net/http"
-
-	"github.com/r3labs/sse/v2"
 )
 
 func main() {
@@ -22,25 +20,68 @@ func main() {
 	log.Fatal(server.ListenAndServe())
 }
 
-func broadcastCounterUpdate(srv *sse.Server, id string, value int) {
-	bytes, err := json.Marshal(value)
-	if err != nil {
-		log.Fatal(err)
+type Store interface {
+	Count() (int, error)
+	Increment() (int, error)
+	Decrement() (int, error)
+}
+
+const StoreFilename = "store.local.json"
+
+type fileStore struct {
+	Counter int `json:"counter"`
+}
+
+func (db *fileStore) Count() (int, error) {
+	if err := readOrCreateJson(StoreFilename, db); err != nil {
+		return 0, err
 	}
 
-	srv.Publish(id, &sse.Event{Data: bytes})
+	return db.Counter, nil
+}
+
+func (db *fileStore) Increment() (int, error) {
+	if err := readOrCreateJson(StoreFilename, db); err != nil {
+		return 0, err
+	}
+
+	db.Counter++
+
+	if err := writeJson(StoreFilename, db); err != nil {
+		return 0, err
+	}
+
+	return db.Counter, nil
+}
+
+func (db *fileStore) Decrement() (int, error) {
+	if err := readOrCreateJson(StoreFilename, db); err != nil {
+		return 0, err
+	}
+
+	db.Counter--
+
+	if err := writeJson(StoreFilename, db); err != nil {
+		return 0, err
+	}
+
+	return db.Counter, nil
 }
 
 func setupRoutes(mux *http.ServeMux) {
-	sseServer := sse.New()
-	sseServer.CreateStream("new-counter-value")
+	var db Store = &fileStore{Counter: 0}
+	{
+		initialCount, err := db.Count()
+		if err != nil {
+			log.Fatalf(`Unable to create store: %v`, err)
+			return
+		}
 
-	counter := 0
+		log.Printf(`Store correctly initialized, count: %v`, initialCount)
+	}
 
 	// API Routes
 
-	mux.HandleFunc("/api/events", sseServer.ServeHTTP)
-
 	mux.HandleFunc("/api/status", func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodGet {
 			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
@@ -62,12 +103,17 @@ func setupRoutes(mux *http.ServeMux) {
 			return
 		}
 
-		w.Header().Set("Content-Type", "application/json")
-		err := json.NewEncoder(w).Encode(counter)
+		count, err := db.Count()
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
 		}
+
+		w.Header().Set("Content-Type", "application/json")
+		if err := json.NewEncoder(w).Encode(count); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
 	})
 
 	mux.HandleFunc("/api/increment", func(w http.ResponseWriter, r *http.Request) {
@@ -76,16 +122,17 @@ func setupRoutes(mux *http.ServeMux) {
 			return
 		}
 
-		counter++
-
-		w.Header().Set("Content-Type", "application/json")
-		err := json.NewEncoder(w).Encode(counter)
+		newCount, err := db.Increment()
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
 		}
 
-		broadcastCounterUpdate(sseServer, "new-counter-value", counter)
+		w.Header().Set("Content-Type", "application/json")
+		if err := json.NewEncoder(w).Encode(newCount); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
 	})
 
 	mux.HandleFunc("/api/decrement", func(w http.ResponseWriter, r *http.Request) {
@@ -94,16 +141,17 @@ func setupRoutes(mux *http.ServeMux) {
 			return
 		}
 
-		counter--
-
-		w.Header().Set("Content-Type", "application/json")
-		err := json.NewEncoder(w).Encode(counter)
+		newCount, err := db.Decrement()
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
 		}
 
-		broadcastCounterUpdate(sseServer, "new-counter-value", counter)
+		w.Header().Set("Content-Type", "application/json")
+		if err := json.NewEncoder(w).Encode(newCount); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
 	})
 
 	// Static Files

src/main.js

@@ -1,26 +1,27 @@
 const counterElement = document.querySelector('#counter-value')
+const incrementButton = document.querySelector('#btn-increment')
+const decrementButton = document.querySelector('#btn-decrement')
 
 function updateCounter(value) {
     counterElement.textContent = `Counter: ${value}`
 }
 
-const counterTickSource = new EventSource('/api/events?stream=new-counter-value')
-counterTickSource.addEventListener('message', e => {
-    const data = JSON.parse(e.data)
+incrementButton.addEventListener('click', async () => {
+    const res = await fetch('/api/increment', { method: 'POST' })
+    const data = await res.json()
     updateCounter(data)
 })
 
-const incrementButton = document.querySelector('#btn-increment')
-const decrementButton = document.querySelector('#btn-decrement')
-
-incrementButton.addEventListener('click', () => {
-    fetch('/api/increment', { method: 'POST' })
+decrementButton.addEventListener('click', async () => {
+    const res = await fetch('/api/decrement', { method: 'POST' })
+    const data = await res.json()
+    updateCounter(data)
 })
 
-decrementButton.addEventListener('click', () => {
-    fetch('/api/decrement', { method: 'POST' })
-})
+async function main() {
+    const res = await fetch('/api/value')
+    const data = await res.json()
+    updateCounter(data)
+}
 
-fetch('/api/value')
-    .then(res => res.json())
-    .then(data => updateCounter(data))
+main()

utils.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+)
+
+func readOrCreateJson(filename string, value any) error {
+	f, err := os.Open(filename)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return writeJson(filename, value)
+		}
+
+		return err
+	}
+	defer f.Close()
+
+	if json.NewDecoder(f).Decode(value); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func writeJson(filename string, value any) error {
+	f, err := os.Create(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	enc := json.NewEncoder(f)
+	enc.SetIndent("", "    ")
+	if err := enc.Encode(value); err != nil {
+		return err
+	}
+
+	return nil
+}