_content/talks/2012/chat/both/chat.go

// +build ignore,OMIT

package main

import (
	"fmt"
	"io"
	"log"
	"net"
	"net/http"
	"time"

	"golang.org/x/net/websocket"
)

const listenAddr = "localhost:4000"

func main() {
	go netListen() // HL
	http.HandleFunc("/", rootHandler)
	http.Handle("/socket", websocket.Handler(socketHandler))
	err := http.ListenAndServe(listenAddr, nil)
	if err != nil {
		log.Fatal(err)
	}
}

func netListen() {
	l, err := net.Listen("tcp", "localhost:4001")
	if err != nil {
		log.Fatal(err)
	}
	for {
		c, err := l.Accept()
		if err != nil {
			log.Fatal(err)
		}
		go match(c)
	}
}

type socket struct {
	io.Reader
	io.Writer
	done chan bool
}

func (s socket) Close() error {
	s.done <- true
	return nil
}

var chain = NewChain(2) // 2-word prefixes

func socketHandler(ws *websocket.Conn) {
	r, w := io.Pipe()
	go func() {
		_, err := io.Copy(io.MultiWriter(w, chain), ws)
		w.CloseWithError(err)
	}()
	s := socket{r, ws, make(chan bool)}
	go match(s)
	<-s.done
}

var partner = make(chan io.ReadWriteCloser)

func match(c io.ReadWriteCloser) {
	fmt.Fprint(c, "Waiting for a partner...")
	select {
	case partner <- c:
		// now handled by the other goroutine
	case p := <-partner:
		chat(p, c)
	case <-time.After(5 * time.Second):
		chat(Bot(), c)
	}
}

func chat(a, b io.ReadWriteCloser) {
	fmt.Fprintln(a, "Found one! Say hi.")
	fmt.Fprintln(b, "Found one! Say hi.")
	errc := make(chan error, 1)
	go cp(a, b, errc)
	go cp(b, a, errc)
	if err := <-errc; err != nil {
		log.Println(err)
	}
	a.Close()
	b.Close()
}

func cp(w io.Writer, r io.Reader, errc chan<- error) {
	_, err := io.Copy(w, r)
	errc <- err
}

// Bot returns an io.ReadWriteCloser that responds to
// each incoming write with a generated sentence.
func Bot() io.ReadWriteCloser {
	r, out := io.Pipe() // for outgoing data
	return bot{r, out}
}

type bot struct {
	io.ReadCloser
	out io.Writer
}

func (b bot) Write(buf []byte) (int, error) {
	go b.speak()
	return len(buf), nil
}

func (b bot) speak() {
	time.Sleep(time.Second)
	msg := chain.Generate(10) // at most 10 words
	b.out.Write([]byte(msg))
}