gdg-counter-website/main.go

package main

import (
	"encoding/json"
	"log"
	"net/http"

	"github.com/r3labs/sse/v2"
)

func main() {
	mux := http.NewServeMux()

	setupRoutes(mux)

	server := http.Server{
		Addr:    ":4000",
		Handler: mux,
	}

	log.Printf("Starting server on port 4000...")
	log.Fatal(server.ListenAndServe())
}

func broadcastCounterUpdate(srv *sse.Server, id string, value int) {
	bytes, err := json.Marshal(value)
	if err != nil {
		log.Fatal(err)
	}

	srv.Publish(id, &sse.Event{Data: bytes})
}

func setupRoutes(mux *http.ServeMux) {
	sseServer := sse.New()
	sseServer.CreateStream("new-counter-value")

	counter := 0

	// 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)
			return
		}

		w.Header().Set("Content-Type", "application/json")

		err := json.NewEncoder(w).Encode("ok")
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
	})

	mux.HandleFunc("/api/value", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		err := json.NewEncoder(w).Encode(counter)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
	})

	mux.HandleFunc("/api/increment", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
			return
		}

		counter++

		w.Header().Set("Content-Type", "application/json")
		err := json.NewEncoder(w).Encode(counter)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}

		broadcastCounterUpdate(sseServer, "new-counter-value", counter)
	})

	mux.HandleFunc("/api/decrement", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
			return
		}

		counter--

		w.Header().Set("Content-Type", "application/json")
		err := json.NewEncoder(w).Encode(counter)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}

		broadcastCounterUpdate(sseServer, "new-counter-value", counter)
	})

	// Static Files
	mux.Handle("/", http.FileServer(http.Dir("./dist/")))
}