package dpack

import (
	"bytes"
	"encoding/binary"
	"errors"
	"github.com/aceld/zinx/zlog"
	"github.com/aceld/zinx/zpack"
	"time"

	"github.com/aceld/zinx/zconf"
	"github.com/aceld/zinx/ziface"
)

// +---------------+---------------+--------------------+----------------+-------------------
// |    开始标志     |     type       |     秒时间戳       |  长度           |     消息体
// | 0xffff(2byte) |  uint8(1byte)  |     uint32(4byte) |  uint16(2byte) |    bytes(N byte)
// +---------------+---------------+--------------------+----------------+-------------------

var defaultHeaderLen uint32 = 9

type DataPack struct{}

// NewDataPack initializes a packing and unpacking instance
// (封包拆包实例初始化方法)
func NewDataPack() ziface.IDataPack {
	return &DataPack{}
}

// GetHeadLen returns the length of the message header
// (获取包头长度方法)
func (dp *DataPack) GetHeadLen() uint32 {
	//ID uint32(4 bytes) +  DataLen uint32(4 bytes)
	return defaultHeaderLen
}

// Pack packs the message (compresses the data)
// (封包方法,压缩数据)
func (dp *DataPack) Pack(msg ziface.IMessage) ([]byte, error) {
	zlog.Ins().InfoF("my pack: %v", msg)
	// Create a buffer to store the bytes
	// (创建一个存放bytes字节的缓冲)
	dataBuff := bytes.NewBuffer([]byte{})

	// Write the oxffff
	if err := binary.Write(dataBuff, binary.BigEndian, uint16(0xffff)); err != nil {
		return nil, err
	}
	//Write the type
	if err := binary.Write(dataBuff, binary.BigEndian, uint8(msg.GetMsgID())); err != nil {
		return nil, err
	}

	//Write the timestamp
	if err := binary.Write(dataBuff, binary.BigEndian, uint32(time.Now().Unix())); err != nil {
		return nil, err
	}

	//Write the length
	if err := binary.Write(dataBuff, binary.BigEndian, uint16(msg.GetDataLen())); err != nil {
		return nil, err
	}

	// Write the data
	if err := binary.Write(dataBuff, binary.BigEndian, msg.GetData()); err != nil {
		return nil, err
	}

	return dataBuff.Bytes(), nil
}

// Unpack unpacks the message (decompresses the data)
// (拆包方法,解压数据)
func (dp *DataPack) Unpack(binaryData []byte) (ziface.IMessage, error) {
	// Create an ioReader for the input binary data
	dataBuff := bytes.NewReader(binaryData)

	// Only unpack the header information to obtain the data length and message ID
	// (只解压head的信息，得到dataLen和msgID)
	msg := &zpack.Message{}

	// Read the startSign
	var startSign uint16
	if err := binary.Read(dataBuff, binary.BigEndian, &startSign); err != nil {
		return nil, err
	}

	// Read the msgID
	var msgType uint
	if err := binary.Read(dataBuff, binary.BigEndian, &msgType); err != nil {
		return nil, err
	}
	msg.ID = uint32(msgType)

	// read timeStamp
	var timeStamp uint32
	if err := binary.Read(dataBuff, binary.BigEndian, &timeStamp); err != nil {
		return nil, err
	}

	// Read the data length
	var length uint16
	if err := binary.Read(dataBuff, binary.BigEndian, &length); err != nil {
		return nil, err
	}
	msg.DataLen = uint32(length)

	// Check whether the data length exceeds the maximum allowed packet size
	// (判断dataLen的长度是否超出我们允许的最大包长度)
	if zconf.GlobalObject.MaxPacketSize > 0 && msg.GetDataLen() > zconf.GlobalObject.MaxPacketSize {
		return nil, errors.New("too large msg data received")
	}

	// Only the header data needs to be unpacked, and then another data read is performed from the connection based on the header length
	// (这里只需要把head的数据拆包出来就可以了，然后再通过head的长度，再从conn读取一次数据)
	return msg, nil
}