http.Flusher compatiability about scs HOT 20 CLOSED

package main

import (
	"fmt"
	"github.com/alexedwards/scs/v2"
	"github.com/gorilla/mux"
	"github.com/r3labs/sse/v2"
	"github.com/rs/cors"
	"net/http"
	"time"
)

func main() {
	server := Server{
		Router:           mux.NewRouter(),
		ServerSentEvents: sse.New(),
		SessionManager:   scs.New(),
	}

	server.Start()
}

type Server struct {
	Router           *mux.Router
	ServerSentEvents *sse.Server
	SessionManager   *scs.SessionManager
}

func (server *Server) Start() {
	server.Router.Handle("/outlook/loading", server.handleOutlookLoading())

	corsHandler := cors.New(cors.Options{
		AllowedOrigins:   []string{"http://localhost:3000", "http://127.0.0.1:3000"},
		AllowedMethods:   []string{http.MethodGet, http.MethodPost, http.MethodDelete},
		AllowCredentials: true,
	}).Handler(server.Router)

	fmt.Println("Starting the server...")
	// TODO - The handleOutlookLoading will not work with the session manager.
	fmt.Println(http.ListenAndServe(":1337", server.SessionManager.LoadAndSave(corsHandler)))
	
	// The following works:
	//fmt.Println(http.ListenAndServe(":1337", corsHandler))
}

func (server *Server) handleOutlookLoading() http.HandlerFunc {
	return func(responseWriter http.ResponseWriter, request *http.Request) {
		server.ServerSentEvents.CreateStream("test")

		go func() {
			for {
				server.ServerSentEvents.Publish("test", &sse.Event{Data: []byte("hello")})
				time.Sleep(time.Second)
			}
		}()

		server.ServerSentEvents.ServeHTTP(responseWriter, request)
	}
}

package main

import (
	"fmt"
	"github.com/alexedwards/scs/v2"
	"github.com/r3labs/sse/v2"
	"net/http"
	"time"
)

func main() {
	server := Server{
		Router:           http.NewServeMux(),
		ServerSentEvents: sse.New(),
		SessionManager:   scs.New(),
	}

	server.Start()
}

type Server struct {
	Router           *http.ServeMux
	ServerSentEvents *sse.Server
	SessionManager   *scs.SessionManager
}

func (server *Server) Start() {
	server.Router.Handle("/outlook/loading", server.handleOutlookLoading())

	fmt.Println("Starting the server...")
	// TODO - The handleOutlookLoading will not work with the session manager.
	fmt.Println(http.ListenAndServe(":1337", server.SessionManager.LoadAndSave(server.Router)))

	// The following works:
	//fmt.Println(http.ListenAndServe(":1337", server.Router))
}

func (server *Server) handleOutlookLoading() http.HandlerFunc {
	return func(responseWriter http.ResponseWriter, request *http.Request) {
		server.ServerSentEvents.CreateStream("test")

		go func() {
			for {
				server.ServerSentEvents.Publish("test", &sse.Event{Data: []byte("hello")})
				time.Sleep(time.Second)
			}
		}()

		server.ServerSentEvents.ServeHTTP(responseWriter, request)
	}
}

func (bw *bufferedResponseWriter) Flush() {
	if flusher, ok := bw.ResponseWriter.(http.Flusher); ok {
		flusher.Flush()
	}
}

fmt.Printf("Type of ResponseWriter: %T\n", w)
flusher, ok := w.(http.Flusher)
if !ok {
    http.Error(w, "Streaming unsupported!", http.StatusInternalServerError)
    return
}

r.Use(app.sessionManager.LoadAndSave)

type middleware struct {
	store *scs.SessionManager
}

func Middleware(store *scs.SessionManager) func(next http.Handler) http.Handler {
	middleware := &middleware{
		store: store,
	}
	return middleware.Handler
}

// flusherResponseWriter wraps http.ResponseController and http.ResponseWriter so that we pass an
// http.Flusher compatible ResponseWriter to the next handler. This is done because scs's middleware
// wraps ResponseWriter and we need to re-expose http.Flusher for the sse library.
type flusherResponseWriter struct {
	*http.ResponseController
	http.ResponseWriter
}

func (w flusherResponseWriter) Flush() {
	err := w.ResponseController.Flush()
	if err != nil {
		panic(err)
	}
}

func (w flusherResponseWriter) Unwrap() http.ResponseWriter {
	return w.ResponseWriter
}

var _ http.Flusher = flusherResponseWriter{}

func (m *middleware) Handler(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ctx := r.Context()

		rc := http.NewResponseController(w)
		flusher := &flusherResponseWriter{
			ResponseController: rc,
			ResponseWriter:     w,
		}
		next.ServeHTTP(flusher, r.WithContext(ctx))
	})
}

type flusherResponseWriter struct {
	*http.ResponseController
	http.ResponseWriter
}

func (w *flusherResponseWriter) Flush() {
	if err := w.ResponseController.Flush(); err != nil {
		panic(err)
	}
}

func (w *flusherResponseWriter) Unwrap() http.ResponseWriter {
	return w.ResponseWriter
}

var _ http.Flusher = &flusherResponseWriter{}

func WrapWithFlusher(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		rc := http.NewResponseController(w)
		flusher := &flusherResponseWriter{
			ResponseController: rc,
			ResponseWriter:     w,
		}
		next.ServeHTTP(flusher, r)
	})
}

r := chi.NewRouter()
r.Use(middleware.RealIP)
r.Use(middleware.Recoverer)
r.Use(app.sessionManager.LoadAndSave)
r.Use(WrapWithFlusher)

func handleStatusUpdates(w http.ResponseWriter, r *http.Request) {

	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("Access-Control-Allow-Origin", "*")
        fmt.Printf("Type of ResponseWriter: %T\n", w)
	flusher, ok := w.(http.Flusher)
		if !ok {
			http.Error(w, "Streaming unsupported!", http.StatusInternalServerError)
			return
		}
	for {
		// logic .... 
		// ... 
		flusher.Flush() // panics
		time.Sleep(StatusUpdateInterval)
	}
}

package main

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"time"

	"github.com/alexedwards/scs/v2"
)

var sessionManager = scs.New()

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("/flush", flushHandler)
	mux.HandleFunc("/get", getHandler)

	http.ListenAndServe(":4000", sessionManager.LoadAndSave(mux))
}

func flushHandler(w http.ResponseWriter, r *http.Request) {
	sessionManager.Put(r.Context(), "message", "Hello from a flushing handler!")

	rc := http.NewResponseController(w)

	for i := 0; i < 5; i++ {
		fmt.Fprintf(w, "Write %d\n", i)

		err := rc.Flush()
		if err != nil {
			log.Println(err)
			return
		}

		time.Sleep(time.Second)
	}
}

func getHandler(w http.ResponseWriter, r *http.Request) {
	msg := sessionManager.GetString(r.Context(), "message")
	io.WriteString(w, msg)
}

require github.com/alexedwards/scs/v2 v2.5.1

package main

import (
	"fmt"
	"log"
	"net/http"
	"time"

	"github.com/alexedwards/scs/v2"
)

var sessionManager *scs.SessionManager

func main() {

	sessionManager = scs.New()
	sessionManager.Lifetime = 24 * time.Hour

	mux := http.NewServeMux()
	mux.HandleFunc("/sse", sseHandler)
	mux.HandleFunc("/", indexHandler)

	log.Println("Server started on localhost:4000")
	http.ListenAndServe("localhost:4000", sessionManager.LoadAndSave(mux))
}

func sseHandler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("Access-Control-Allow-Origin", "*")

	// Create a new ResponseController for flushing
	rc := http.NewResponseController(w)

	for {
		currentTime := time.Now().Format(time.RFC1123)
		data := fmt.Sprintf("data: %s\n\n", currentTime)
		_, writeErr := w.Write([]byte(data))
		if writeErr != nil {
			log.Printf("Error writing to client: %v", writeErr)
			return
		}

		// Use the ResponseController to flush the data
		flushErr := rc.Flush()
		if flushErr != nil {
			log.Printf("Error flushing data to client: %v", flushErr)
			return
		}

		time.Sleep(1 * time.Second)
	}
}

func indexHandler(w http.ResponseWriter, r *http.Request) {
	html := `
		<!DOCTYPE html>
		<html lang="en">
		<head>
			<meta charset="UTF-8">
			<title>SSE with Go</title>
		</head>
		<body>
			<h1>Server Sent Events with Go</h1>
			<div id="sse-data"></div>
			<script>
				const eventSource = new EventSource("/sse");
				eventSource.onmessage = function(event) {
					document.getElementById("sse-data").innerHTML = event.data;
				};
			</script>
		</body>
		</html>
	`
	w.Write([]byte(html))
}