package broadcast

import (
	"fmt"
	"github.com/gogf/greuse"
	"strconv"
	"strings"
	"sync"
	"time"
)

var (
	port = 31995
	lport = 31996

	lock sync.Mutex    //同一时刻只能有一个线程在执行搜索
)


//广播收集其他节点信息
func BroadCast() ([]string, error) {
	lock.Lock()
	defer lock.Unlock()

	retCh := make(chan []string)
	go startRecv(retCh)

	conn, err := greuse.Dial("udp", "0.0.0.0:"+strconv.Itoa(lport), "255.255.255.255:"+strconv.Itoa(port))

	if err != nil {
		fmt.Println("err:", err)
	} else {
		defer conn.Close()

		n,err := conn.Write([]byte("who are you?"))
		if err != nil || n == 0 {
			fmt.Println("conn.Write err:", err, " n:", n)
		}
	}

	nodes := <-retCh

	return nodes, nil
}

func startRecv(rCh chan []string) {
	conn, err := greuse.ListenPacket("udp", "0.0.0.0:"+strconv.Itoa(lport))

	if err != nil {
		fmt.Println("startRecv ListenPacket err:", err)
		rCh <- []string{}
		return
	}
	//10秒钟之内收到的返回，即认为是在线的
	conn.SetReadDeadline(time.Now().Add(time.Second * 1))
	ch := time.After(time.Second * 4)
	var nodes []string
Loop:
	for {
		select {
		case <-ch:
			fmt.Println("<-ch")
			break Loop
		default:
			ret := make([]byte, 1024)
			n, from, e := conn.ReadFrom(ret)
			if e == nil && n >0 {
				arr := strings.Split(from.String(), ":")
				if len(arr) == 2 {
					nodes = append(nodes, arr[0])
				}
				fmt.Println("read message from udp:", string(ret), " from:", from)
			} else {
				time.Sleep(time.Millisecond * 100)
			}
		}
	}
	rCh <- nodes
}