SFM-loan-Rest-Api/websocket.go

package main

import (
	"encoding/json"
	"fmt"
	"github.com/brianvoe/gofakeit/v6"
	"github.com/gorilla/websocket"
	log "github.com/sirupsen/logrus"
	"net/http"
	"time"
)

// We'll need to define an upgradeToWs
// this will require a Read and Write buffer size
var upgradeToWs = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
}

func apiV1WebSocketHandler(w http.ResponseWriter, r *http.Request) {
	upgradeToWs.CheckOrigin = func(r *http.Request) bool { return true }
	ws, err := upgradeToWs.Upgrade(w, r, nil)
	if err != nil {
		log.Println("cannot upgrade websocket", err)
		return
	}

	mid := apiV1GetMachineId(r)
	wsq.MapMidToConnection(mid, ws)

	// helpful log statement to show connections
	log.Println("Websocket Api/V1: Client Connected", mid)

	wsReader(ws)
}

func wsReader(conn *websocket.Conn) {
	wsq.addConnection(conn)
	for {

		stillExist := wsq.has(conn)
		if !stillExist {
			return // the connection has been removed.
		}

		// read in a message
		messageType, p, err := conn.ReadMessage()
		if err != nil {
			wsq.del(conn)
			log.Println(err)
			return
		}
		// print out that message for clarity
		// fmt.Println(string(p))

		if err := conn.WriteMessage(messageType, p); err != nil {
			wsq.del(conn)
			log.Println(err)
			return
		}

		if string(p) == "send dummy string for 500 times" {
			go wsDummySender(conn)
		}
	}
}

func WsBroadCast(msg string) {
	wsq.wsDoBroadcast(msg, "")
}

func WsSend(To string, msg map[string]string) {
	b, e := json.Marshal(msg)
	if e != nil {
		log.Error("cannot broadcast websocket message, cannot convert to json", msg)
	}

	conn := wsq.getConnBySessionId(To)
	if conn != nil {
		err := conn.WriteMessage(websocket.TextMessage, b)
		if err != nil {
			wsq.del(conn)
		}
	}
}

func WsBroadCastExceptMe(me string, msg map[string]string) {
	b, e := json.Marshal(msg)
	if e == nil {
		wsq.wsDoBroadcast(string(b), me)
	}
}

func wsDummySender(conn *websocket.Conn) {
	//write subsequent 5 copies, each after 1 second
	log.Info("start sending server data to client ..")
	p := "dummy string from server "
	for i := 1; i < 500; i++ {
		time.Sleep(1 * time.Second)
		//msg := fmt.Sprintf("copy %d, %s, %s", i, p, wsDummyString()) // 4M long string no issue
		msg := fmt.Sprintf("copy %d, %s ", i, p)
		log.Info("dummy sender is working, ", msg)
		if err := conn.WriteMessage(websocket.TextMessage, []byte(msg)); err != nil {
			log.Println("wsDummySender stopped on error: ", err)
			return
		}
	}
}

func wsDummyString() string {
	s := gofakeit.LetterN(4096000) // 4M
	return s
}