Misc.

main.go

@@ -5,22 +5,43 @@ import (
 	"html/template"
 	"log"
 	"net/http"
-	"time"
 )
 
 type handler = func(http.ResponseWriter, *http.Request)
 
-func generateHandler(file string, handler func(), data func() any) handler {
-	tmpl := template.Must(template.ParseFiles(fmt.Sprintf("templates/%s", file)))
+func generateHandler(
+	file string,
+	handler func(http.ResponseWriter, *http.Request),
+	data func(http.ResponseWriter, *http.Request) any,
+	methods []string,
+) handler {
+	var tmpl *template.Template
+	if file != "" {
+		tmpl = template.Must(template.ParseFiles(fmt.Sprintf("templates/%s", file)))
+	}
 	return func(w http.ResponseWriter, r *http.Request) {
-		handler()
-		w.Header().Set("Content-Type", "text/html; charset=utf-8")
-		tmpl.Execute(w, data())
+		for _, method := range methods {
+			if method == r.Method {
+				goto ok
+			}
+		}
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		return
+	ok:
+		handler(w, r)
+		if tmpl != nil {
+			w.Header().Set("Content-Type", "text/html; charset=utf-8")
+			tmpl.Execute(w, data(w, r))
+		}
 	}
 }
 
-func generateSseHandler(handler func(http.ResponseWriter, *http.Request)) handler {
+func generateSseHandler(handler handler) handler {
 	return func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet {
+			w.WriteHeader(http.StatusMethodNotAllowed)
+			return
+		}
 		w.Header().Set("Content-Type", "text/event-stream")
 		w.Header().Set("Cache-Control", "no-cache")
 		w.Header().Set("Connection", "keep-alive")
@@ -29,25 +50,116 @@ func generateSseHandler(handler func(http.ResponseWriter, *http.Request)) handle
 	}
 }
 
-func generateCounter() handler {
+type client = chan []event
+
+type clientSet struct {
+	clients map[client]bool
+}
+
+func newClientSet() clientSet {
+	return clientSet{make(map[client]bool)}
+}
+
+func (clients clientSet) broadcast(events ...event) {
+	for client := range clients.clients {
+		client <- events
+	}
+}
+
+func (clients clientSet) playerCountEvent(offset int) event {
+	playerCount := len(clients.clients) + offset
+	var data string
+	if playerCount == 0 {
+		data = "No players online."
+	} else {
+		data = fmt.Sprintf("%d player%s online.", playerCount, map[bool]string{true: "", false: "s"}[playerCount == 1])
+	}
+	return event{eventPlayerCount, data}
+}
+
+func (clients clientSet) broadcastPlayerCount(offset int) {
+	clients.broadcast(clients.playerCountEvent(offset))
+}
+
+func (clients clientSet) broadcastWord(word string) {
+	clients.broadcast(
+		event{eventWord, fmt.Sprintf("<div>%s</div>", word)},
+		event{eventNavigate, fmt.Sprintf("https://jisho.org/search/%s", word)},
+	)
+}
+
+func (clients clientSet) connect(client client) {
+	// Channels are blocking.
+	// Client initialization is waiting for connect() to complete.
+	// If we try to braodcast to it before connect() is done,
+	// the channel handling logic wouldn't have started yet,
+	// and broadcast() would be freeze.
+	// Therefore, we must broadcast an offset player count first,
+	// then actually add the client.
+	clients.broadcastPlayerCount(1)
+	clients.clients[client] = true
+}
+
+func (clients clientSet) disconnect(client client) {
+	delete(clients.clients, client)
+	clients.broadcastPlayerCount(0)
+}
+
+var clients = newClientSet()
+
+type event struct {
+	eventName string
+	data      string
+}
+
+func (event event) encode() string {
+	return fmt.Sprintf("event: %s\ndata: %s\n\n", event.eventName, event.data)
+}
+
+const eventWord = "word"
+const eventPlayerCount = "players"
+const eventNavigate = "navigate"
+
+func generateWordBroadcaster() handler {
 	return generateSseHandler(func(w http.ResponseWriter, r *http.Request) {
-		tick := time.Tick(500 * time.Millisecond)
+		sendEvent := func(events ...event) {
+			for _, event := range events {
+				fmt.Fprint(w, event.encode())
+			}
+			w.(http.Flusher).Flush()
+		}
+		sendEvent(clients.playerCountEvent(1))
 		ctx := r.Context()
+		channel := make(client)
+		clients.connect(channel)
 	outer:
-		for i := 0; ; i++ {
+		for {
 			select {
 			case <-ctx.Done():
+				clients.disconnect(channel)
 				break outer
-			case <-tick:
-				fmt.Fprintf(w, "event: count\ndata: <div>%d</div>\n\n", i)
-				w.(http.Flusher).Flush()
+			case events := <-channel:
+				sendEvent(events...)
 			}
 		}
 	})
 }
 
+func generateWordHandler() handler {
+	return generateHandler(
+		"",
+		func(w http.ResponseWriter, r *http.Request) {
+			r.ParseMultipartForm(0)
+			clients.broadcastWord(r.FormValue("word"))
+		},
+		nil,
+		[]string{http.MethodPost},
+	)
+}
+
 func main() {
 	http.Handle("/", http.FileServer(http.Dir("static")))
-	http.HandleFunc("/api/counter", generateCounter())
+	http.HandleFunc("/api/events", generateWordBroadcaster())
+	http.HandleFunc("/api/submit", generateWordHandler())
 	log.Fatal(http.ListenAndServe(":3333", nil))
 }

static/index.html

@@ -4,9 +4,39 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Shiritori</title>
+    <link rel="stylesheet" href="style.css">
     <script src="https://unpkg.com/htmx.org@1.9.3"></script>
 </head>
-<body>
-    <div hx-sse="connect:/api/counter swap:count" hx-swap="beforebegin"></div>
+<body hx-sse="connect:/api/events">
+    <div id="content">
+        <div id="split">
+            <div>
+                <div id="shiritori"
+                    hx-sse="swap:word"
+                    hx-swap="beforeend"
+                    hx-on::sse-message="this.scrollTop = this.scrollHeight">
+                </div>
+                <form
+                    hx-post="/api/submit"
+                    hx-swap="innerHTML"
+                    hx-target="#feedback"
+                    hx-on::after-request="this.querySelector('input[name=word]').value = ''">
+                    <input id="shiritori-input" type="text" name="word">
+                </form>
+            </div>
+            <iframe
+                hx-sse="swap:navigate"
+                hx-on::sse-message="this.src = event.detail.data">
+            </iframe>
+        </div>
+        <p id="shiritori-players"
+            hx-sse="swap:players"
+        ></p>
+        <div style="display: none">
+            <button onclick="changeRoom('lobby')">Back to lobby</button>
+            <div id="feedback"></div>
+            Change room: <input id="room-input" autocomplete="off">
+        </div>
+    </div>
 </body>
 </html>

static/style.css

@@ -0,0 +1,92 @@
+* {
+    font-family: sans-serif;
+    color: ghostwhite;
+}
+body {
+    background: slategrey;
+    font-size: 1.75em;
+    display: flex;
+    height: 100vh;
+    align-items: center;
+    justify-content: center;
+    text-align: center;
+}
+div#content {
+    width: 32em;
+    max-width: 100%;
+}
+div#shiritori p {
+    margin: 0;
+    animation-duration: 1s;
+    animation-name: slidein;
+    animation-fill-mode: forwards;
+    opacity: 0;
+}
+@keyframes slidein {
+    from {
+        transform: translateX(-32px);
+        opacity: 0;
+    }
+
+    to {
+        transform: none;
+        opacity: 1;
+    }
+}
+div#shiritori {
+    padding: 2px;
+    height: 24em;
+    overflow-y: scroll;
+}
+div#shiritori, input#shiritori-input, #split > :last-child {
+    background: rgba(0, 0, 0, 0.25);
+    border: 1px solid;
+    border-radius: 4px;
+    box-sizing: border-box;
+}
+div#shiritori, input#shiritori-input {
+    padding: 0.25em;
+}
+input {
+    font-size: 1em;
+    background: rgba(0, 0, 0, 0.25);
+    border: none;
+    padding: 0.25em;
+}
+input#shiritori-input {
+    width: 100%;
+
+    border-top: none;
+    border-top-left-radius: 0;
+    border-top-right-radius: 0;
+}
+input#shiritori-input:focus {
+    outline: none;
+    background: rgba(0, 0, 0, 0.125);
+}
+div#shiritori {
+    border-bottom: none;
+    border-bottom-left-radius: 0;
+    border-bottom-right-radius: 0;
+}
+#split {
+    display: flex;
+    gap: 0.5em;
+    flex-direction: row;
+}
+#split > * {
+    width: 16em;
+}
+a {
+    text-decoration: none;
+}
+a:hover {
+    border-bottom: 2px solid;
+}
+button {
+    background: rgba(0, 0, 0, 0.25);
+    font-size: inherit;
+    cursor: pointer;
+    padding: 1em;
+    border: 0;
+}