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feat: add cmd/ssechat as ServerSentEvents demo
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parent
ef78d2fa05
commit
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3
cmd/ssechat/go.mod
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3
cmd/ssechat/go.mod
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module github.com/therootcompany/golib/cmd/ssechat
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go 1.25.4
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154
cmd/ssechat/index.html
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154
cmd/ssechat/index.html
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<!doctype html>
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<html lang="en">
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<head>
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<meta charset="UTF-8" />
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<meta name="viewport" content="width=device-width, initial-scale=1.0" />
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<title>SSE Chat Room</title>
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<style>
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body {
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font-family: system-ui, sans-serif;
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margin: 0;
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padding: 1rem;
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background: #f8f9fa;
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color: #111;
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}
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header {
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text-align: center;
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margin-bottom: 1.5rem;
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}
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#messages {
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background: white;
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border: 1px solid #ddd;
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border-radius: 8px;
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padding: 1rem;
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height: 60vh;
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overflow-y: auto;
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font-family: monospace;
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white-space: pre-wrap;
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margin-bottom: 1rem;
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}
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form {
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display: flex;
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gap: 0.5rem;
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max-width: 600px;
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margin: 0 auto;
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}
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input[type="text"] {
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flex: 1;
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padding: 0.8rem;
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border: 1px solid #ccc;
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border-radius: 6px;
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font-size: 1rem;
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}
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button {
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padding: 0.8rem 1.5rem;
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background: #0066cc;
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color: white;
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border: none;
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border-radius: 6px;
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cursor: pointer;
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font-weight: 600;
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}
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button:hover {
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background: #0055aa;
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}
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.msg {
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margin: 0.4rem 0;
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}
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.msg.system {
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color: #666;
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font-style: italic;
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}
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.msg.user {
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color: #0066cc;
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}
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</style>
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</head>
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<body>
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<header>
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<h1>Simple SSE Chat Room</h1>
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<p>Everyone sees the same messages in real time</p>
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</header>
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<div id="messages"></div>
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<form id="chat-form">
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<input
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type="text"
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id="nickname"
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placeholder="Your name"
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value="Guest"
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style="width: 140px"
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/>
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<input
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type="text"
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id="message"
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placeholder="Type a message..."
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autocomplete="off"
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required
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/>
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<button type="submit">Send</button>
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</form>
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<script>
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const messagesDiv = document.getElementById("messages");
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const form = document.getElementById("chat-form");
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const msgInput = document.getElementById("message");
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const nickInput = document.getElementById("nickname");
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// Connect to SSE
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const evtSource = new EventSource("/api/events");
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evtSource.onmessage = (event) => {
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const data = JSON.parse(event.data);
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appendMessage(`${data.time} • ${data.nick}: ${data.text}`);
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};
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evtSource.addEventListener("system", (event) => {
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const data = JSON.parse(event.data);
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appendMessage(`${data.time} • ${data.text}`, "system");
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});
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evtSource.onerror = () => {
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appendMessage("[Connection lost — reconnecting...]", "system");
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};
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function appendMessage(text, kind = "user") {
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const line = document.createElement("div");
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line.className = `msg ${kind}`;
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line.textContent = text;
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messagesDiv.appendChild(line);
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messagesDiv.scrollTop = messagesDiv.scrollHeight;
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}
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// Send message on form submit
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form.addEventListener("submit", async (e) => {
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e.preventDefault();
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const text = msgInput.value.trim();
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if (!text) return;
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const nick = nickInput.value.trim() || "Anonymous";
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try {
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await fetch("/api/send", {
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method: "POST",
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headers: {
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"Content-Type": "application/x-www-form-urlencoded",
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},
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body: new URLSearchParams({ nick, text }),
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});
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msgInput.value = "";
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msgInput.focus();
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} catch (err) {
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appendMessage("[Failed to send message]", "system");
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}
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});
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// Initial welcome
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appendMessage(
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"Welcome to the chat! Type below to join the conversation.",
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"system"
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);
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</script>
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</body>
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</html>
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118
cmd/ssechat/main.go
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118
cmd/ssechat/main.go
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package main
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import (
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_ "embed"
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"encoding/json"
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"fmt"
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"log"
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"net/http"
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"time"
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)
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//go:embed index.html
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var indexHTML []byte
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type Message struct {
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Time string `json:"time"`
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Nick string `json:"nick"`
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Text string `json:"text"`
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}
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var sse = NewSSEChannel()
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func main() {
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mux := http.NewServeMux()
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// Serve static HTML
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//mux.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.Dir("static"))))
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mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
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if r.URL.Path != "/" {
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http.NotFound(w, r)
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return
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}
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w.Header().Set("Content-Type", "text/html")
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w.Write(indexHTML)
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})
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// SSE endpoint
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mux.HandleFunc("GET /api/events", handleSSE)
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// POST endpoint to send messages
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mux.HandleFunc("POST /api/send", handleSend)
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log.Println("Server running on :8080")
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log.Fatal(http.ListenAndServe(":8080", mux))
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}
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func handleSSE(w http.ResponseWriter, r *http.Request) {
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w.Header().Set("Content-Type", "text/event-stream")
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w.Header().Set("Cache-Control", "no-cache")
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w.Header().Set("Connection", "keep-alive")
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w.Header().Set("X-Accel-Buffering", "no") // helps nginx / some proxies
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flusher, ok := w.(http.Flusher)
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if !ok {
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http.Error(w, "Streaming unsupported", http.StatusInternalServerError)
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return
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}
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sse.Subscribe(AddrStr(r.RemoteAddr))
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defer sse.Unsubscribe(AddrStr(r.RemoteAddr))
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fmt.Fprintf(w, "event: system\ndata: {\"time\":\"%s\",\"text\":\"You joined the room\"}\n\n", time.Now().Format("15:04"))
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flusher.Flush()
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// Forward messages to this client
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for {
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select {
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case <-r.Context().Done():
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return
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case msg, ok := <-sse.Member(AddrStr(r.RemoteAddr)).C:
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if !ok {
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return
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}
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// SSE format: one data: line with the full JSON
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if msg.Event != "" {
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fmt.Fprintf(w, "event: %s\n", msg.Event)
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}
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fmt.Fprintf(w, "%s: %s\n\n", msg.Type, msg.Data)
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flusher.Flush()
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}
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}
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}
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func handleSend(w http.ResponseWriter, r *http.Request) {
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if r.Method != http.MethodPost {
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http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
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return
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}
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if err := r.ParseForm(); err != nil {
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http.Error(w, "Bad form", http.StatusBadRequest)
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return
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}
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nick := r.FormValue("nick")
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text := r.FormValue("text")
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if text == "" {
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http.Error(w, "Message required", http.StatusBadRequest)
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return
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}
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if nick == "" {
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nick = "Anonymous"
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}
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// In the broadcast loop (handleSend)
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msg := Message{
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Time: time.Now().Format("15:04"),
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Nick: nick,
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Text: text,
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}
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payload, _ := json.Marshal(msg)
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sse.Broadcast(payload)
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w.WriteHeader(http.StatusAccepted)
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}
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92
cmd/ssechat/sse.go
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92
cmd/ssechat/sse.go
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package main
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import (
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"fmt"
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"sync"
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"time"
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)
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type AddrStr string
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type ServerSentEvent struct {
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Type string
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Event string
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ID string
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Data []byte
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}
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type SSEMember struct {
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C chan ServerSentEvent
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ticker *time.Ticker
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}
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type SSEChannel struct {
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clients map[AddrStr]SSEMember
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clientsMu sync.Mutex
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}
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func NewSSEChannel() *SSEChannel {
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return &SSEChannel{
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clients: make(map[AddrStr]SSEMember),
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}
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}
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func (c *SSEChannel) Subscribe(addr AddrStr) {
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ch := make(chan ServerSentEvent, 16)
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m := SSEMember{
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ch,
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time.NewTicker(15 * time.Second),
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}
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c.clientsMu.Lock()
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c.clients[addr] = m
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c.clientsMu.Unlock()
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go func() {
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for range m.ticker.C {
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m.C <- ServerSentEvent{
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"",
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"",
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"",
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[]byte("heartbeat"),
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}
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}
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}()
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}
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func (c *SSEChannel) Member(addr AddrStr) SSEMember {
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c.clientsMu.Lock()
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defer c.clientsMu.Unlock()
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m := c.clients[addr]
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return m
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}
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func (c *SSEChannel) Broadcast(payload []byte) {
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c.clientsMu.Lock()
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defer c.clientsMu.Unlock()
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for _, m := range c.clients {
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// drop-on-full (best effort delivery)
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select {
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case m.C <- ServerSentEvent{
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Type: "data",
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Event: "message",
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ID: fmt.Sprintf("%d", time.Now().UnixMilli()), // or use atomic counter
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Data: payload,
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}:
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// client was able to receive
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default:
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// client is backed up
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}
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}
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}
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func (c *SSEChannel) Unsubscribe(addr AddrStr) {
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c.clientsMu.Lock()
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defer c.clientsMu.Unlock()
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m := c.clients[addr]
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delete(c.clients, addr)
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// ticker must be stopped BEFORE closing channel
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m.ticker.Stop()
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close(m.C)
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}
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