package main

import (
	"errors"
	"fmt"
	"net"
	"sync"
	"time"
)

func main() {
	var wg sync.WaitGroup
	conn, err := net.ListenUDP("udp4", &net.UDPAddr{Port: 30000})
	if err != nil {
		panic(err)
	}
	fmt.Printf("Listening on %v\n", conn.LocalAddr().String())
	wg.Add(1)
	inchan := make(chan string)
	t := time.NewTimer(time.Minute)
	go readProc(&wg, conn, inchan)
loop:
	for {
		select {
		case s := <-inchan:
			fmt.Printf("got %s\n", s)
			if s == "stop" {
				fmt.Println("stop stop", s)
				conn.Close()
				break loop
			}
		case timeStamp := <-t.C:
			conn.Close()
			fmt.Printf("Time Stop %v\n", timeStamp)
			break loop
		}
	}
	fmt.Println("Exiting")
	wg.Wait()

}

func readProc(wg *sync.WaitGroup, conn *net.UDPConn, inchan chan string) {
	defer wg.Done()
	var n int
	var addr *net.UDPAddr
	var err error
	for {
		buf := make([]byte, 1000)
		n, addr, err = conn.ReadFromUDP(buf)
		if err != nil {
			if errors.Is(err, net.ErrClosed) {
				fmt.Println("Socket closed")
			} else {
				fmt.Printf("Got some other error: %v\n", err.Error())
			}
			return
		}
		fmt.Printf("Received %v bytes from %v\n", n, addr.String())
		inchan <- string(buf[:n])
	}
}