gossip.go

package main

import (
	"net/http"
	"log"
	"os"
	"encoding/json"
)

type Message struct {
	Name string `json:"name"`
	Body string `json:"body"`
}

type Client struct {
	Channel chan <- Message
}

func handleMessages(messageChan <- chan Message, addChan <- chan Client, removeChan <- chan Client) {
	channels := make(map[Client] chan <- Message)

	for {
		select {
		case message := <- messageChan:
			log.Print("New message: ", message.Body)
			for _, channel := range channels {
				go func (c chan <- Message) {
					c <- message
				}(channel)
			}
		case client := <- addChan:
			log.Print("Client connected: ", client)
			channels[client] = client.Channel
		case client := <- removeChan:
			log.Print("Client disconnected: ", client)
			delete(channels, client)
		}
	}
}

func handleStream(messageChan chan <- Message, addChan chan <- Client, removeChan chan <- Client, writer http.ResponseWriter, request *http.Request) {
	writer.Header().Set("Content-Type", "text/event-stream")
	writer.Header().Set("Access-Control-Allow-Origin", "*")
	writer.WriteHeader(200)

	channel := make(chan Message)
	client  := Client{channel}

	addChan <- client

	for {
		message := <- channel
		data, _ := json.Marshal(message)
		if _, error := writer.Write([]byte("data: " + string(data) + "\n\n")); error != nil {
			log.Print("Write: ", error)
			break
		}
		writer.(http.Flusher).Flush()
	}

	removeChan <- client
}

func handleMessage(messageChan chan <- Message, writer http.ResponseWriter, request *http.Request) {
	request.ParseForm()
	message := request.FormValue("message")
	name    := request.FormValue("name")
	messageChan <- Message{name, message}
	writer.WriteHeader(200)
}

func main() {
	messagesChan := make(chan Message)
	addChan      := make(chan Client)
	removeChan   := make(chan Client)

	go handleMessages(messagesChan, addChan, removeChan)

	http.HandleFunc("/", func (writer http.ResponseWriter, request *http.Request) {
		http.ServeFile(writer, request, "static/index.html")
	})
	http.HandleFunc("/static/", func (writer http.ResponseWriter, request *http.Request) {
		http.ServeFile(writer, request, request.URL.Path[1:])
	})
	http.HandleFunc("/stream", func (writer http.ResponseWriter, request *http.Request) {
		handleStream(messagesChan, addChan, removeChan, writer, request)
	})
	http.HandleFunc("/messages", func (writer http.ResponseWriter, request *http.Request) {
		handleMessage(messagesChan, writer, request)
	})

	port := "8080"

	if portFromEnv := os.Getenv("PORT"); portFromEnv != "" {
		port = portFromEnv
	}

	log.Print("Starting server on port ", port)

	http.ListenAndServe(":" + port, nil)
}