package util

//底层网络通信协议
import (
	"bufio"
	"bytes"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"io"
	"net"
)

const (
	EMPTY_ADDR = "00000000"
)

//读取
type Reader struct {
	conn   net.Conn
	reader *bufio.Reader
	buffer [4]byte
}

//数据包，实际上就是协议定义
type Packet struct {
	//头开始
	Length     int32  //4bit 包长度
	From       string //8bit
	To         string //8bit
	Msgid      string //8bit
	Event      int32  //4bit
	SentToType int32  //4bit
	//头结束
	Raw []byte //数据包，头+数据
}

//返回
func (p *Packet) GetBusinessData() []byte {
	return p.Raw[36:]
}

//
type RawData []byte //流数据

//
func NewReader(c net.Conn) *Reader {
	return &Reader{
		conn:   c,
		reader: bufio.NewReader(c),
	}
}

//读取头部
func (p *Reader) readHeader() (int32, error) {
	buf := p.buffer[:4]
	if _, err := io.ReadFull(p.reader, buf); err != nil {
		return 0, err
	}
	size := int32(binary.BigEndian.Uint32(buf))
	if size < 32 || size > 16384000 {
		return 0, fmt.Errorf("Incorrect frame size (%d)", size)
	}
	return size, nil
}

//读取完整一帧数据，防止粘包
func (p *Reader) readFrame(size int32) (*Packet, error) {
	var buf []byte
	if int(size) <= len(p.buffer) {
		buf = p.buffer[0:size]
	} else {
		buf = make([]byte, size)
	}
	_, err := io.ReadFull(p.reader, buf)
	raw := append(Int2Byte(size), buf...)
	if err == nil {
		//解析包
		packet := &Packet{
			Length:     size,
			From:       string(buf[:8]),
			To:         string(buf[8:16]),
			Msgid:      string(buf[16:24]),
			Event:      Byte2Int(buf[24:28]),
			SentToType: Byte2Int(buf[28:32]),
			//Data:       buf[32:],
			Raw: raw,
		}
		return packet, nil
	}
	return nil, err
}

//读取数据写入队列
func forwardMessage(c net.Conn, queue chan<- *Packet) {
	defer c.Close()
	logReader := NewReader(c)
	for {
		size, err := logReader.readHeader()
		if err != nil {
			break
		}
		packet, err := logReader.readFrame(size)
		if err != nil {
			break
		}
		queue <- packet
	}
}

//从队列中读取数据，定期处理
func processMsg(q <-chan *Packet, parseEvent func(*Packet)) {
	for {
		select {
		case msg := <-q:
			go parseEvent(msg)
		}
	}
}

//封包，输出直接可以写到流中的数据包
func Enpacket(from, to, msgid string, event, sendtotype int, obj interface{}) []byte {
	if len(from) != 8 {
		from = EMPTY_ADDR
	}
	if len(to) != 8 {
		to = EMPTY_ADDR
	}
	if len(msgid) != 8 {
		msgid = EMPTY_ADDR
	}
	var ret []byte
	var bs []byte
	if v, ok := obj.([]byte); ok {
		bs = v
	} else if v, ok := obj.(string); ok {
		bs = []byte(v)
	} else {
		bs, _ = json.Marshal(obj)
	}
	ret = append(Int2Byte(int32(32 + len(bs))))
	ret = append(ret, []byte(from+to+msgid)...)
	ret = append(ret, Int2Byte(int32(event))...)
	ret = append(ret, Int2Byte(int32(sendtotype))...)
	ret = append(ret, bs...)
	return ret
}

//
func Byte2Int(src []byte) int32 {
	var ret int32
	binary.Read(bytes.NewReader(src), binary.BigEndian, &ret)
	return ret
}

//
func Int2Byte(src int32) []byte {
	buf := bytes.NewBuffer([]byte{})
	binary.Write(buf, binary.BigEndian, src)
	return buf.Bytes()
}