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http.go
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http.go
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package showandtell
import (
"context"
"encoding/json"
"log"
"net/http"
"sync"
"time"
"github.com/gorilla/websocket"
"github.com/sirupsen/logrus"
bus "github.com/vardius/message-bus"
)
var (
writeWait = 10 * time.Second
busQueueSize = 100
)
func messageBusClientF(ctx context.Context,
logger logrus.FieldLogger,
cancel context.CancelFunc,
ws *websocket.Conn,
messageBus bus.MessageBus) {
logger = logger.WithFields(logrus.Fields{
"remoteAddr": ws.RemoteAddr().String(),
})
logger.Debug("Handling client connection")
defer cancel()
subscriptionHandler := func(topic string) func(json.RawMessage) {
return func(value json.RawMessage) {
msg := &WebSocketBusMessage{
Value: value,
Topic: topic,
Type: "message",
}
if err := ws.WriteJSON(msg); err != nil {
logger.WithError(err).Error("Failed to write to client, closing connection")
ws.Close()
cancel()
}
}
}
go func() {
for {
msg := &WebSocketBusMessage{}
err := ws.ReadJSON(msg)
if err != nil {
logger.WithError(err).Error("Failed to read message from client, closing connection")
ws.Close()
return
}
logger.Debug("Received msg from client")
switch msg.Type {
case "subscribe":
logger.Debug("Subscribing client")
messageBus.Subscribe(msg.Topic, subscriptionHandler(msg.Topic))
case "unsubscribe":
logger.Debug("Unsubscribing client")
// FIXME, this won't likely work.
messageBus.Unsubscribe(msg.Topic, subscriptionHandler)
case "publish":
logger.Debug("Publishing message")
messageBus.Publish(msg.Topic, msg.Value)
}
}
}()
select {
case <-ctx.Done():
logger.Debug("Context done, closing connection")
ws.Close()
return
}
}
type WebSocketBusMessage struct {
Type string `json:"type"`
Topic string `json:"topic"`
Value json.RawMessage `json:"value"`
}
type PresentationServer struct {
slideDir string
pres *Presentation
ctx context.Context
httpServer *http.Server
indexBytes []byte
wsUpgrader websocket.Upgrader
livereloadConns []*websocket.Conn
centralBus bus.MessageBus
logger logrus.FieldLogger
indexLock *sync.Mutex
}
func NewPresentationServer(ctx context.Context, pres *Presentation, slideDir, addr string) (*PresentationServer, error) {
server := &http.Server{
Addr: addr,
}
p := &PresentationServer{
ctx: ctx,
pres: pres,
slideDir: slideDir,
httpServer: server,
indexLock: &sync.Mutex{},
wsUpgrader: websocket.Upgrader{},
livereloadConns: make([]*websocket.Conn, 0, 100),
centralBus: bus.New(busQueueSize),
logger: logrus.WithField("component", "PresentationServer"),
}
if err := p.Rerender(); err != nil {
return nil, err
}
mux := ServeRevealJS()
mux.Handle("/", http.HandlerFunc(p.serveIndex))
mux.Handle("/livereload", http.HandlerFunc(p.livereloadHandler))
mux.Handle("/messagebus", http.HandlerFunc(p.messagebusHandler))
server.Handler = mux
return p, nil
}
func (p *PresentationServer) serveIndex(w http.ResponseWriter, r *http.Request) {
p.indexLock.Lock()
defer p.indexLock.Unlock()
w.Write(p.indexBytes)
}
func (p *PresentationServer) livereloadHandler(w http.ResponseWriter, r *http.Request) {
logger := p.logger.WithFields(logrus.Fields{
"remoteAddr": r.RemoteAddr,
"url": r.URL.String(),
})
ws, err := p.wsUpgrader.Upgrade(w, r, nil)
if err != nil {
logger.WithError(err).Error("Failed to start websocket connection")
return
}
p.livereloadConns = append(p.livereloadConns, ws)
ctx, cancel := context.WithCancel(p.ctx)
go ping(ctx, cancel, ws)
}
func (p *PresentationServer) messagebusHandler(w http.ResponseWriter, r *http.Request) {
logger := p.logger.WithFields(logrus.Fields{
"remoteAddr": r.RemoteAddr,
"url": r.URL.String(),
})
ws, err := p.wsUpgrader.Upgrade(w, r, nil)
if err != nil {
logger.WithError(err).Error("Failed to start websocket connection")
return
}
ctx, cancel := context.WithCancel(p.ctx)
logger = logger.WithField("messagebus", "websocket")
go messageBusClientF(ctx, logger, cancel, ws, p.centralBus)
}
func ping(ctx context.Context, cancel context.CancelFunc, ws *websocket.Conn) {
ticker := time.NewTicker(time.Second * 10)
defer ticker.Stop()
defer cancel()
for {
select {
case <-ctx.Done():
return
case <-ticker.C:
if err := ws.WriteControl(websocket.PingMessage, []byte{}, time.Now().Add(writeWait)); err != nil {
log.Println("ping:", err)
return
}
}
}
}
func (p *PresentationServer) Rerender() (err error) {
p.indexLock.Lock()
p.indexBytes, err = RenderIndex(p.pres, p.slideDir)
p.indexLock.Unlock()
go func() {
for _, ws := range p.livereloadConns {
logger := p.logger.WithFields(logrus.Fields{
"remoteAddr": ws.RemoteAddr().String(),
})
ws.SetWriteDeadline(time.Now().Add(writeWait))
if err := ws.WriteMessage(websocket.TextMessage, []byte(`Reload`)); err != nil {
logger.WithError(err).Warn("Failed to write reload message to client, closing connection")
// TODO remove connection
ws.Close()
}
}
}()
return
}
func (p *PresentationServer) Close() error {
ctx, cancel := context.WithTimeout(p.ctx, time.Second*15)
defer cancel()
return p.httpServer.Shutdown(ctx)
}
func (p *PresentationServer) Run() {
go func() {
p.httpServer.ListenAndServe()
}()
}