package Receivers

import (
	"encoding/hex"
	"errors"
	"fmt"
	"gitee.com/ling-bin/network/netInterface"
)

var (
	maxLen = 65535 //允许最大包容量，超过会异常（网卡极限:64k）
)

//策略分包器
type DynamicReceiver struct {
	currentReceiver netInterface.IReceiver   //当前分包器
	Receivers       []netInterface.IReceiver //分包器集合
	ReceiverLen     int                      //分包器个数
	IsPackStart     bool                     //是否开始分包
	IsSingle        bool                     //是否只有一个分包算法
}

//策略分包器
func NewDynamicReceiver () *DynamicReceiver {
	return  &DynamicReceiver{
		IsPackStart: false,
		Receivers:   nil,
	}
}

//分包处理
func (d *DynamicReceiver) Receiver(conn netInterface.IConnection, buffer []byte) (err error) {
	//1.查看有没有待分包数据
	var newBuf []byte
	cacheBf := conn.GetBytesCache()
	if cacheBf.Len() != 0 {
		cacheBf.Write(buffer)
		newBuf = cacheBf.Bytes()
	} else {
		newBuf = buffer
	}

	//长度超长直接踢连接
	if cacheBf.Len() > maxLen {
		conn.Stop()
		msg:=fmt.Sprint(" buffer out maxLen [", cacheBf.Len(), "]数据：",hex.EncodeToString(newBuf[:]))
		cacheBf.Reset()
		return errors.New(msg)
	}
	totalLen := len(newBuf)
	startIndex := 0
	skipCount := 0
	for {
		if startIndex == totalLen {
			//刚好完成或未找到分包算法就清理缓存跳出函数
			cacheBf.Reset()
			if skipCount > 0 {
				return errors.New(fmt.Sprint("查找分包算法跳过[", skipCount, "]字节完整数据:", hex.EncodeToString(newBuf[:])))
			}
			break
		}
		if d.IsPackStart { //确认当前包分包算法
			iReceiver := d.selectReceiver(conn, newBuf[startIndex:])
			if iReceiver == nil {
				//后移一位查找分包算法
				startIndex++
				skipCount++
				continue
			}
			d.currentReceiver = iReceiver
			d.IsPackStart = false
		}
		//分包处理[内部也有可能跳过，需要具体分包算法处理]
		bytes, handleIndex := d.currentReceiver.Receiver(conn, newBuf[startIndex:])
		if len(bytes) == 0 {
			if startIndex+handleIndex < totalLen {
				//没有找到则重置缓存，重新设置缓存
				cacheBf.Reset()
				cacheBf.Write(newBuf[startIndex+handleIndex:])
			}
			break
		}
		//找到一包处理后继续找
		conn.OnReceiveCompleted(bytes)
		d.IsPackStart = true
		startIndex += handleIndex
	}
	return nil
}

//选择分包器
func (d *DynamicReceiver) selectReceiver(conn netInterface.IConnection, buffer []byte) netInterface.IReceiver {
	//单个分包算法直接跳过认包逻辑
	if d.IsSingle {
		isMe := d.Receivers[0].IsMeHandle(conn, buffer)
		if isMe {
			return d.Receivers[0]
		}
		return nil
	}

    //找到符合的分包器
	for i := 0; i < d.ReceiverLen; i++ {
		isMe := d.Receivers[i].IsMeHandle(conn, buffer)
		if isMe {
			return d.Receivers[i]
		}
	}
	return nil
}