package util

import (
	"bytes"
	"net"
	"time"
)

//
type UdpClient struct {
	Local   string
	Connect *net.UDPConn
	BufSize int
}

//指令
const (
	OP_NOOP = byte(iota)
	OP_JOIN
	OP_BYE
	OP_SAY_ONLINE
	OP_TYPE_DATA
	OP_GET_DOWNLOADERCODE     //上报下载器代码
	OP_WILLCHANGEIP           //将要切换IP
	OP_PUSH_DOWNLOADERCODES   //
	OP_DELETE_DOWNLOADERCODES //需要删除
	OP_SEND_EMAIL             //发送邮件
)

//
func (c *UdpClient) Listen(fn func(byte, []byte, *net.UDPAddr)) {
	listenAddr, _ := net.ResolveUDPAddr("udp4", c.Local)
	c.Connect, _ = net.ListenUDP("udp4", listenAddr)
	go c.readUdp(fn)
}

//写
func (c *UdpClient) WriteUdp(data []byte /*写入数据*/, act byte /*动作*/, toaddr *net.UDPAddr /*目标端地址*/) error {
	bs := make([]byte, 1)
	bs[0] = act
	sizebs := Int2Byte(int32(len(data)))
	bs = append(bs, sizebs...)
	bs = append(bs, data...)
	if len(bs) > c.BufSize {
		bs = bs[:c.BufSize]
	} else if len(bs) < c.BufSize {
		bs = append(bs, bytes.Repeat([]byte{0}, c.BufSize-len(bs))...)
	}
	for i := 0; i < 5; i++ { //尝试5次
		_, err := c.Connect.WriteToUDP(bs, toaddr)
		if err == nil {
			break
		}
		time.Sleep(1 * time.Second)
	}
	return nil
}

//读
func (c *UdpClient) readUdp(fn func(byte, []byte, *net.UDPAddr)) {
	for {
		head := make([]byte, c.BufSize)
		n, ra, err := c.Connect.ReadFromUDP(head)
		if err != nil || n == 0 { //取不到数据
			time.Sleep(1 * time.Second)
			continue
		}
		size := int(Byte2Int(head[1:5]))
		if size < 1 { //无数据，仅仅是控制指令
			go fn(head[0], []byte{}, ra)
		} else {
			if size > c.BufSize-5 {
				size = c.BufSize - 5
			}
			go fn(head[0], head[5:5+size], ra)
		}
	}
}