Simple HTTP stream messaging server

httq.go

package main

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"strings"
	"sync"
)

type Channel struct {
	sync.Mutex
	Refcount int64
	Msgbuf   chan []byte
}

func main() {
	var mu sync.Mutex
	channels := make(map[string]*Channel)
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		channel := strings.TrimPrefix(r.URL.Path, "/")
		if r.Method != http.MethodGet && r.Method != http.MethodPost {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}
		mu.Lock()
		ch, ok := channels[channel]
		if !ok {
			ch := &Channel{Msgbuf: make(chan []byte)}
			channels[channel] = ch
		}
		mu.Unlock()
		ch.Lock()
		ch.Refcount++
		ch.Unlock()
		switch r.Method {
		case http.MethodGet:
			msg := <-ch.Msgbuf
			w.Write(msg)
		case http.MethodPost:
			msg, _ := ioutil.ReadAll(r.Body)
			ch.Msgbuf <- msg
		}
		ch.Lock()
		ch.Refcount--
		if ch.Refcount <= 0 {
			mu.Lock()
			delete(channels, channel)
			mu.Unlock()
		}
		ch.Unlock()
	})
	addr := os.Getenv("HTTQ_ADDR")
	if err := http.ListenAndServe(addr, nil); err != nil {
		fmt.Fprintf(os.Stderr, "listen: %v\n", err)
		os.Exit(1)
	}
}