add websocket chat example

joeybloggs · joeybloggs · commit 32f438e8672b · 2016-07-20T14:22:50.000-04:00
diff --git a/examples/websockets/main.go b/examples/websockets/main.go
@@ -0,0 +1,317 @@
+// Copyright 2016 Dean Karn.
+// Copyright 2013 The Gorilla WebSocket Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"html/template"
+	"log"
+	"net/http"
+	"time"
+
+	"github.com/go-playground/lars"
+	"github.com/go-playground/lars/examples/middleware/logging-recovery"
+	"github.com/gorilla/websocket"
+)
+
+func main() {
+
+	go hub.run()
+
+	l := lars.New()
+	l.Use(middleware.LoggingAndRecovery)
+
+	l.Get("/", homeHandler)
+	l.WebSocket(upgrader, "/ws", ws)
+
+	err := http.ListenAndServe(":4444", l.Serve())
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ws(c lars.Context) {
+
+	client := &Client{hub: hub, conn: c.WebSocket(), send: make(chan []byte, 256)}
+	client.hub.register <- client
+
+	go client.writePump()
+	client.readPump()
+}
+
+func homeHandler(c lars.Context) {
+
+	t, err := template.New("home").Parse(tmpl)
+	if err != nil {
+		log.Println("Unable to parse upgrade html")
+		http.Error(c.Response(), http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+		return
+	}
+
+	err = t.Execute(c.Response(), c.Request().Host)
+	if err != nil {
+		log.Println("Unable to Execute Upgrade Template")
+		http.Error(c.Response(), http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+		return
+	}
+}
+
+// normally the below would be split into multiple files, but for the sake of an easily runnable
+// example is all in one file.
+
+const (
+	// Time allowed to write a message to the peer.
+	writeWait = 10 * time.Second
+
+	// Time allowed to read the next pong message from the peer.
+	pongWait = 60 * time.Second
+
+	// Send pings to peer with this period. Must be less than pongWait.
+	pingPeriod = (pongWait * 9) / 10
+
+	// Maximum message size allowed from peer.
+	maxMessageSize = 512
+)
+
+var (
+	newline  = []byte{'\n'}
+	space    = []byte{' '}
+	upgrader = websocket.Upgrader{
+		ReadBufferSize:  1024,
+		WriteBufferSize: 1024,
+		CheckOrigin: func(r *http.Request) bool {
+			o := r.Header.Get(lars.Origin)
+			return o == "http://localhost:4444"
+		},
+	}
+	tmpl = `<!DOCTYPE html>
+<html lang="en">
+<head>
+<title>Chat Example</title>
+<script type="text/javascript">
+window.onload = function () {
+    var conn;
+    var msg = document.getElementById("msg");
+    var log = document.getElementById("log");
+
+    function appendLog(item) {
+        var doScroll = log.scrollTop === log.scrollHeight - log.clientHeight;
+        log.appendChild(item);
+        if (doScroll) {
+            log.scrollTop = log.scrollHeight - log.clientHeight;
+        }
+    }
+
+    document.getElementById("form").onsubmit = function () {
+        if (!conn) {
+            return false;
+        }
+        if (!msg.value) {
+            return false;
+        }
+        conn.send(msg.value);
+        msg.value = "";
+        return false;
+    };
+
+    if (window["WebSocket"]) {
+        conn = new WebSocket("ws://{{$}}/ws");
+        conn.onclose = function (evt) {
+            var item = document.createElement("div");
+            item.innerHTML = "<b>Connection closed.</b>";
+            appendLog(item);
+        };
+        conn.onmessage = function (evt) {
+            var messages = evt.data.split('\n');
+            for (var i = 0; i < messages.length; i++) {
+                var item = document.createElement("div");
+                item.innerText = messages[i];
+                appendLog(item);
+            }
+        };
+    } else {
+        var item = document.createElement("div");
+        item.innerHTML = "<b>Your browser does not support WebSockets.</b>";
+        appendLog(item);
+    }
+};
+</script>
+<style type="text/css">
+html {
+    overflow: hidden;
+}
+
+body {
+    overflow: hidden;
+    padding: 0;
+    margin: 0;
+    width: 100%;
+    height: 100%;
+    background: gray;
+}
+
+#log {
+    background: white;
+    margin: 0;
+    padding: 0.5em 0.5em 0.5em 0.5em;
+    position: absolute;
+    top: 0.5em;
+    left: 0.5em;
+    right: 0.5em;
+    bottom: 3em;
+    overflow: auto;
+}
+
+#form {
+    padding: 0 0.5em 0 0.5em;
+    margin: 0;
+    position: absolute;
+    bottom: 1em;
+    left: 0px;
+    width: 100%;
+    overflow: hidden;
+}
+
+</style>
+</head>
+<body>
+<div id="log"></div>
+<form id="form">
+    <input type="submit" value="Send" />
+    <input type="text" id="msg" size="64"/>
+</form>
+</body>
+</html>`
+	hub = newHub()
+)
+
+// Client is an middleman between the websocket connection and the hub.
+type Client struct {
+	hub *Hub
+
+	// The websocket connection.
+	conn *websocket.Conn
+
+	// Buffered channel of outbound messages.
+	send chan []byte
+}
+
+// readPump pumps messages from the websocket connection to the hub.
+func (c *Client) readPump() {
+	defer func() {
+		c.hub.unregister <- c
+		c.conn.Close()
+	}()
+	c.conn.SetReadLimit(maxMessageSize)
+	c.conn.SetReadDeadline(time.Now().Add(pongWait))
+	c.conn.SetPongHandler(func(string) error { c.conn.SetReadDeadline(time.Now().Add(pongWait)); return nil })
+	for {
+		_, message, err := c.conn.ReadMessage()
+		if err != nil {
+			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway) {
+				log.Printf("error: %v", err)
+			}
+			break
+		}
+		message = bytes.TrimSpace(bytes.Replace(message, newline, space, -1))
+		c.hub.broadcast <- message
+	}
+}
+
+// write writes a message with the given message type and payload.
+func (c *Client) write(mt int, payload []byte) error {
+	c.conn.SetWriteDeadline(time.Now().Add(writeWait))
+	return c.conn.WriteMessage(mt, payload)
+}
+
+// writePump pumps messages from the hub to the websocket connection.
+func (c *Client) writePump() {
+	ticker := time.NewTicker(pingPeriod)
+	defer func() {
+		ticker.Stop()
+		c.conn.Close()
+	}()
+	for {
+		select {
+		case message, ok := <-c.send:
+			if !ok {
+				// The hub closed the channel.
+				c.write(websocket.CloseMessage, []byte{})
+				return
+			}
+
+			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
+			w, err := c.conn.NextWriter(websocket.TextMessage)
+			if err != nil {
+				return
+			}
+			w.Write(message)
+
+			// Add queued chat messages to the current websocket message.
+			n := len(c.send)
+			for i := 0; i < n; i++ {
+				w.Write(newline)
+				w.Write(<-c.send)
+			}
+
+			if err := w.Close(); err != nil {
+				return
+			}
+		case <-ticker.C:
+			if err := c.write(websocket.PingMessage, []byte{}); err != nil {
+				return
+			}
+		}
+	}
+}
+
+// hub maintains the set of active clients and broadcasts messages to the
+// clients.
+type Hub struct {
+	// Registered clients.
+	clients map[*Client]bool
+
+	// Inbound messages from the clients.
+	broadcast chan []byte
+
+	// Register requests from the clients.
+	register chan *Client
+
+	// Unregister requests from clients.
+	unregister chan *Client
+}
+
+func newHub() *Hub {
+	return &Hub{
+		broadcast:  make(chan []byte),
+		register:   make(chan *Client),
+		unregister: make(chan *Client),
+		clients:    make(map[*Client]bool),
+	}
+}
+
+func (h *Hub) run() {
+	for {
+		select {
+		case client := <-h.register:
+			h.clients[client] = true
+		case client := <-h.unregister:
+			if _, ok := h.clients[client]; ok {
+				delete(h.clients, client)
+				close(client.send)
+			}
+		case message := <-h.broadcast:
+			for client := range h.clients {
+				select {
+				case client.send <- message:
+				default:
+					close(client.send)
+					delete(h.clients, client)
+				}
+			}
+		}
+	}
+}
