package main


import (
"fmt"
"net"
"os"
"time"
)


const (
MAX_CONN_NUM = 10
)

//服務處理函式，如果處理過程過於複雜，可以啟動一定量的協程來做（協程池），

//處理完後再發回去通過通道，實現非同步處理的方式

//echo server Goroutine
func EchoFunc(conn net.Conn) {
defer conn.Close()
buf := make([]byte, 1024)
for {
_, err := conn.Read(buf)
if err != nil {
//println("Error reading:", err.Error())
return
}
//send reply
_, err = conn.Write(buf)
if err != nil {
//println("Error send reply:", err.Error())
return
}
}
}


//initial listener and run
func main() {
listener, err := net.Listen("tcp", "0.0.0.0:8088")
if err != nil {
fmt.Println("error listening:", err.Error())
os.Exit(1)
}
defer listener.Close()


fmt.Printf("running ...\n")


var cur_conn_num int = 0
conn_chan := make(chan net.Conn)
ch_conn_change := make(chan int)


go func() {
for conn_change := range ch_conn_change {
cur_conn_num += conn_change
}
}()


go func() {
for _ = range time.Tick(1e8) {
fmt.Printf("cur conn num: %f\n", cur_conn_num)
}
}()


for i := 0; i < MAX_CONN_NUM; i++ {
go func() {
for conn := range conn_chan {
ch_conn_change <- 1
EchoFunc(conn)
ch_conn_change <- -1
}
}()
}


for {
conn, err := listener.Accept()
if err != nil {
println("Error accept:", err.Error())
return
}
conn_chan <- conn
}
}