update communication

server/go.mod

@@ -1,3 +1,5 @@
 module sirlab.de/go/knyc
 
 go 1.16
+
+require github.com/imkira/go-observer v1.0.3

server/go.sum

@@ -0,0 +1,2 @@
+github.com/imkira/go-observer v1.0.3 h1:l45TYAEeAB4L2xF6PR2gRLn2NE5tYhudh33MLmC7B80=
+github.com/imkira/go-observer v1.0.3/go.mod h1:zLzElv2cGTHufQG17IEILJMPDg32TD85fFgKyFv00wU=

server/knyc.go

@@ -2,22 +2,78 @@ package main
 
 import (
 	"fmt"
+	"github.com/imkira/go-observer"
 	"net/http"
 	"sirlab.de/go/knyc/handler"
+	"strconv"
+	"time"
 )
 
+type Value struct {
+	value int
+}
+
+type Engine struct {
+	payload observer.Property
+}
+
+var engine Engine
+
+func (engine Engine) runEngine() {
+	for {
+		value := engine.payload.Value().(Value)
+		fmt.Printf("sleep: %d\n", value.value)
+		time.Sleep(1 * time.Second)
+		value.value++
+		engine.payload.Update(value)
+	}
+}
+
+func syncFactory(payload observer.Property) func(http.ResponseWriter, *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		refId, err := strconv.Atoi(r.URL.Query().Get("ref"))
+		if err != nil {
+			refId = -1
+		}
+
+		stream := payload.Observe()
+		var value Value
+		for {
+			value = stream.Value().(Value)
+			if value.value > refId {
+				break
+			}
+
+			select {
+			case <-stream.Changes():
+				stream.Next()
+			}
+		}
+
+		w.Header().Add("Content-Type", "text/plain")
+		fmt.Fprintf(w, "%d (%d)\n", value.value, refId)
+	}
+}
+
 func main() {
 	app := handler.NewAuthMux()
 	http.Handle("/", app)
 
 	app.PublicHandleFunc("/__intern__/exit", handler.Exit)
 
+	payload := observer.NewProperty(Value{value: 19})
+	sync := syncFactory(payload)
+	app.PublicHandleFunc("/sync", sync)
+
 	// hanlde login page
 	fsHandler := http.FileServer(http.Dir("../client/dist/"))
 
 	// default handler
 	app.PublicHandle("/", fsHandler)
 
+	engine.payload = payload
+	go engine.runEngine()
+
 	// start listening
 	fmt.Println("http://localhost:32039")
 	http.ListenAndServe(":32039", nil)