sse.go

package main

import (
	"fmt"
	"net/http"
	"sync"
)

// Broadcaster sends messages to ALL connected clients
type Broadcaster struct {
	mu      sync.RWMutex
	clients map[chan string]bool
}

var broadcast = &Broadcaster{
	clients: make(map[chan string]bool),
}

func (b *Broadcaster) Subscribe() chan string {
	b.mu.Lock()
	defer b.mu.Unlock()
	ch := make(chan string, 10)
	b.clients[ch] = true
	return ch
}

func (b *Broadcaster) Unsubscribe(ch chan string) {
	b.mu.Lock()
	defer b.mu.Unlock()
	delete(b.clients, ch)
	close(ch)
}

func (b *Broadcaster) Send(msg string) {
	b.mu.RLock()
	defer b.mu.RUnlock()
	for ch := range b.clients {
		select {
		case ch <- msg:
		default:
			// Client buffer full, skip
		}
	}
}

func handleSSE(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("X-Accel-Buffering", "no")

	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "SSE not supported", http.StatusInternalServerError)
		return
	}

	// Subscribe this client
	clientChan := broadcast.Subscribe()
	defer broadcast.Unsubscribe(clientChan)

	// Send initial connection event
	fmt.Fprintf(w, "event: connected\ndata: {\"status\":\"connected\"}\n\n")
	flusher.Flush()

	for {
		select {
		case <-r.Context().Done():
			return
		case msg := <-clientChan:
			fmt.Fprintf(w, "event: sse-toast\ndata: %s\n\n", msg)
			flusher.Flush()
		}
	}
}