aasumitro · December 6, 2020 08:13
diff --git a/websocket_example.go b/websocket_example.go
 package main

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

 	"github.com/gorilla/websocket"
 	"github.com/justinas/alice"
 )

 var err error

 func logMiddleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		log.Println(r.URL.Path)
 		next.ServeHTTP(w, r)
 	})
 }

 func main() {
 	logger := alice.New(logMiddleware)
 	http.Handle("/", logger.Then(http.HandlerFunc(indexHandler)))
 	http.Handle("/ws", logger.Then(http.HandlerFunc(wsHandler)))
 	http.ListenAndServe(":8080", nil)
 }

 func wsHandler(w http.ResponseWriter, r *http.Request) {
 	conn, err := websocket.Upgrade(w, r, w.Header(), 1024, 1024)
 	if err != nil {
 		http.Error(w, "Could not open websocket connection", http.StatusBadRequest)
 	}
 	go echo(conn)
 }

 func echo(conn *websocket.Conn) {
 	for {
 		cp := getCurrencyPayload()
 		if err = conn.WriteJSON(cp); err != nil {
 			log.Println(err)
 		}
 		time.Sleep(15 * time.Second)
 	}
 }

 func getCurrencyPayload() []interface{} {
 	type CurrencyPayload []interface{}
 	var cp CurrencyPayload
 	var myClient = &http.Client{Timeout: 10 * time.Second}
 	url := "https://api.coinmarketcap.com/v1/ticker/"
 	r, err := myClient.Get(url)
 	if err != nil {
 		log.Println(err)
 	}
 	defer r.Body.Close()
 	err = json.NewDecoder(r.Body).Decode(&cp)
 	if err != nil {
 		log.Println(err)
 	}
 	return cp
 }

 func indexHandler(w http.ResponseWriter, r *http.Request) {
 	fmt.Fprint(w, indexTemplate)
 }

 const indexTemplate = `
 <html>
 <head>
  <title>websocket example</title>
 	<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
  <style>
   .glyphicon.glyphicon-one-fine-full-dot {
    margin-bottom: -.8em;
    overflow: hidden;
   }
   .glyphicon.glyphicon-one-fine-full-dot:before {
    content:"\25cf";
   }
  </style>
 </head>
 <body>
  <div class="container"> 
   <h1>Cryptocurrency Tracker</h1>
 	 <h5>Status: <span id="link_status"><span style="color:yellow;" class="glyphicon glyphicon-one-fine-full-dot"></span> Connecting...</span></h5>
   <ul id="currencies">
   </ul>
  </div>
  <script type="text/javascript">
   $(function () {
    var ws;
    if (window.WebSocket === undefined) {
     alert("Your browser does not support WebSockets.");
     return;
    } else {
     ws = initWS();
    }
    function initWS() {
     var socket = new WebSocket("ws://localhost:8080/ws"),
     clist = $("#currencies")
 		 link = $("#link_status")
     socket.onopen = function() {
      console.log("Socket is open.");
 			link.html("<span style='color:green;' class='glyphicon glyphicon-one-fine-full-dot'></span> Connected");
     };
     socket.onmessage = function(e) {
      console.log("Received data.");
 			clist.empty();
 			$.each(JSON.parse(e.data), function(key, value) {
 				clist.append("<li>" + value.name + " | " + value.symbol + " | $" + value.price_usd + " | " + value.percent_change_24h + "%</li>")
 			});
     }
     socket.onclose = function() {
      console.log("Socket closed.");
 			link.html("<span style='color:red;' class='glyphicon glyphicon-one-fine-full-dot'></span> Disconnected")
 			setTimeout(function(){initWS()}, 5000);
     }
     return socket;
    }
   });
  </script>
 </body>
 </html>
 `
	package main

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

	"github.com/gorilla/websocket"
	"github.com/justinas/alice"
	)

	var err error

	func logMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
	log.Println(r.URL.Path)
	next.ServeHTTP(w, r)
	})
	}

	func main() {
	logger := alice.New(logMiddleware)
	http.Handle("/", logger.Then(http.HandlerFunc(indexHandler)))
	http.Handle("/ws", logger.Then(http.HandlerFunc(wsHandler)))
	http.ListenAndServe(":8080", nil)
	}

	func wsHandler(w http.ResponseWriter, r *http.Request) {
	conn, err := websocket.Upgrade(w, r, w.Header(), 1024, 1024)
	if err != nil {
	http.Error(w, "Could not open websocket connection", http.StatusBadRequest)
	}
	go echo(conn)
	}

	func echo(conn *websocket.Conn) {
	for {
	cp := getCurrencyPayload()
	if err = conn.WriteJSON(cp); err != nil {
	log.Println(err)
	}
	time.Sleep(15 * time.Second)
	}
	}

	func getCurrencyPayload() []interface{} {
	type CurrencyPayload []interface{}
	var cp CurrencyPayload
	var myClient = &http.Client{Timeout: 10 * time.Second}
	url := "https://api.coinmarketcap.com/v1/ticker/"
	r, err := myClient.Get(url)
	if err != nil {
	log.Println(err)
	}
	defer r.Body.Close()
	err = json.NewDecoder(r.Body).Decode(&cp)
	if err != nil {
	log.Println(err)
	}
	return cp
	}

	func indexHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprint(w, indexTemplate)
	}

	const indexTemplate = `
	<html>
	<head>
	<title>websocket example</title>
	<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
	<style>
	.glyphicon.glyphicon-one-fine-full-dot {
	margin-bottom: -.8em;
	overflow: hidden;
	}
	.glyphicon.glyphicon-one-fine-full-dot:before {
	content:"\25cf";
	}
	</style>
	</head>
	<body>
	<div class="container">
	<h1>Cryptocurrency Tracker</h1>
	<h5>Status: <span id="link_status"><span style="color:yellow;" class="glyphicon glyphicon-one-fine-full-dot"></span> Connecting...</span></h5>
	<ul id="currencies">
	</ul>
	</div>
	<script type="text/javascript">
	$(function () {
	var ws;
	if (window.WebSocket === undefined) {
	alert("Your browser does not support WebSockets.");
	return;
	} else {
	ws = initWS();
	}
	function initWS() {
	var socket = new WebSocket("ws://localhost:8080/ws"),
	clist = $("#currencies")
	link = $("#link_status")
	socket.onopen = function() {
	console.log("Socket is open.");
	link.html("<span style='color:green;' class='glyphicon glyphicon-one-fine-full-dot'></span> Connected");
	};
	socket.onmessage = function(e) {
	console.log("Received data.");
	clist.empty();
	$.each(JSON.parse(e.data), function(key, value) {
	clist.append("<li>" + value.name + " \| " + value.symbol + " \| $" + value.price_usd + " \| " + value.percent_change_24h + "%</li>")
	});
	}
	socket.onclose = function() {
	console.log("Socket closed.");
	link.html("<span style='color:red;' class='glyphicon glyphicon-one-fine-full-dot'></span> Disconnected")
	setTimeout(function(){initWS()}, 5000);
	}
	return socket;
	}
	});
	</script>
	</body>
	</html>
	`