main.go

package main

import (
	"context"
	"fmt"

	"time"

	"github.com/gorilla/websocket"
	"github.com/labstack/echo/v4"

	"github.com/rs/zerolog"
	"github.com/rs/zerolog/log"
	"github.com/rs/zerolog/pkgerrors"
)

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

type wsclient struct {
	id   string
	conn *websocket.Conn
	msg  chan<- message
}

type wsMessage struct {
	messageType int
	payload     []byte
}

type message struct {
	clientID string
	wsMessage
	err error
}

func (c wsclient) reciever() {
	defer 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 })
	for {
		mt, p, err := c.conn.ReadMessage()
		if err != nil {
			c.msg <- message{clientID: c.id, err: err}
			return
		}
		c.msg <- message{clientID: c.id, wsMessage: wsMessage{messageType: mt, payload: p}, err: nil}
	}
}

func (c wsclient) runSender() chan<- wsMessage {
	snd := make(chan wsMessage)
	go func() {
		ticker := time.NewTicker(pingPeriod)
		defer func() {
			c.conn.Close()
			ticker.Stop()
		}()
		for {
			select {
			case <-ticker.C:
				c.conn.SetWriteDeadline(time.Now().Add(writeWait))
				if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
					c.msg <- message{clientID: c.id, err: err}
					return
				}
			case m, ok := <-snd:
				if !ok {
					return
				}
				if err := c.conn.WriteMessage(m.messageType, m.payload); err != nil {
					c.msg <- message{clientID: c.id, err: err}
					return
				}
			}
		}
	}()

	return snd
}

func (c wsclient) connect(msg chan<- message) chan<- wsMessage {
	c.msg = msg
	go c.reciever()
	snd := c.runSender()
	return snd
}

func runEchoServer(ctx context.Context) chan<- wsclient {
	register := make(chan wsclient)

	go func() {
		snds := make(map[string]chan<- wsMessage)
		msg := make(chan message)
		for {
			select {
			case <-ctx.Done():
				return
			case client := <-register:
				snds[client.id] = client.connect(msg)
			case m := <-msg:
				if m.err != nil {
					close(snds[m.clientID])
					delete(snds, m.clientID)
					continue
				}
				for _, snd := range snds {
					snd <- wsMessage{messageType: m.messageType, payload: m.payload}
				}
			}
		}
	}()

	return register
}

func hub(registrar chan<- wsclient) func(c echo.Context) error {
	i := 0
	return func(c echo.Context) error {
		i++
		w := c.Response()
		r := c.Request()

		conn, err := upgrader.Upgrade(w, r, nil)
		if err != nil {
			return err
		}

		registrar <- wsclient{id: fmt.Sprintf("hello%d", i), conn: conn}

		return nil
	}
}

func main() {
	zerolog.TimeFieldFormat = time.RFC3339Nano
	zerolog.ErrorStackMarshaler = pkgerrors.MarshalStack
	zerolog.SetGlobalLevel(zerolog.DebugLevel)

	e := echo.New()

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	registrar := runEchoServer(ctx)

	e.HTTPErrorHandler = func(err error, c echo.Context) {
		log.Debug().Err(err).Msg(fmt.Sprintf("%+v", err))
		e.DefaultHTTPErrorHandler(err, c)
	}

	e.GET("/ws", hub(registrar))

	e.Static("/", "./web")

	e.Logger.Fatal(e.Start(":8080"))
}