massflip/client.go

package main

import (
	"encoding/json"
	"log"
	"net/http"
	"strings"
	"time"

	"github.com/gorilla/websocket"
	"golang.org/x/time/rate"
)

// code adapted from the gorilla websocket chat demo code

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{' '}
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
}

// Client is a 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

	username string

	auth bool

	limiter rate.Limiter
}

type Auth struct {
	Type     string `json:"type"`
	Username string `json:"username"`
	Key      string `json:"key"`
}

// readPump pumps messages from the websocket connection to the hub.
//
// The application runs readPump in a per-connection goroutine. The application
// ensures that there is at most one reader on a connection by executing all
// reads from this goroutine.
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 })
	c.limiter = *rate.NewLimiter(1, 5)
	for {
		_, message, err := c.conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
				log.Printf("error: %v", err)
			}
			break
		}
		if !c.limiter.Allow() {
			c.send <- []byte("{\"type\":\"chaterror\",\"error\":\"You are sending messages too quickly\"}")
			continue
		}
		var v Auth
		err = json.Unmarshal(message, &v)
		if err == nil {
			// check for authorization messages
			if v.Type == "auth" {
				// bind the WS client to the username (useful)
				c.username = strings.ToLower(v.Username)
				// if auth key matches session, they are authorized to bet/chat etc
				if DBGetUserByUsername(c.username).Session == v.Key {
					c.auth = true
				}
				// if the user has bet (and then reloaded the page) send them their state
				if c.hub.allUsers[c.username] != "" {
					c.send <- []byte("{\"type\":\"state\",\"value\":true,\"bet\":\"" + c.hub.allUsers[c.username] + "\"}")
				}
				continue
			}
		}
		// only authorized clients are allowed to push to the Hub
		if c.auth {
			c.hub.broadcast <- message
		}
	}
}

// writePump pumps messages from the hub to the websocket connection.
//
// A goroutine running writePump is started for each connection. The
// application ensures that there is at most one writer to a connection by
// executing all writes from this goroutine.
func (c *Client) writePump() {
	ticker := time.NewTicker(pingPeriod)
	defer func() {
		ticker.Stop()
		c.conn.Close()
	}()
	for {
		select {
		case message, ok := <-c.send:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if !ok {
				// The hub closed the channel.
				c.conn.WriteMessage(websocket.CloseMessage, []byte{})
				return
			}

			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:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
				return
			}
		}
	}
}

// serveWs handles websocket requests from the peer.
func serveWs(hub *Hub, w http.ResponseWriter, r *http.Request) {
	upgrader.CheckOrigin = func(r *http.Request) bool { return true }
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println(err)
		return
	}
	client := &Client{hub: hub, conn: conn, send: make(chan []byte, 256)}
	client.hub.register <- client

	// Allow collection of memory referenced by the caller by doing all work in
	// new goroutines.
	go client.writePump()
	go client.readPump()
}