package zsshrpc_server

import (
	"fmt"
	"golang.org/x/crypto/ssh"
	"net"
)

type ZSshRpcSessionContext struct {
	NetConn          net.Conn
	ServerConn       *ssh.ServerConn
	NewChannelChan   <-chan ssh.NewChannel
	ReqChan          <-chan *ssh.Request
	OperationHandler ZSshRpcOperationHandler
	Logger           SvrLogFunc
}

type ZSshRpcChannelContext struct {
	Channel      ssh.Channel
	ReqChan      <-chan *ssh.Request
	SessionCtx   *ZSshRpcSessionContext
	Logger       SvrLogFunc
	RxState      ZSshRpcChState
	RxMethod     ZSshRpcMethod
	RxBuf        ThreadSafeBuffer
	UriStr       string
	JsonStr      string
	ResponseData ZSshRpcOperationResponse
}

func HandleNewSession(conn net.Conn, sshcfg *ssh.ServerConfig, logger SvrLogFunc, handler ZSshRpcOperationHandler, IOBlockSize int) {
	sconn, schan, reqchan, err := ssh.NewServerConn(conn, sshcfg)
	if err != nil {
		logger(SvrLogLevel_WARNING, fmt.Sprintf("Failed Handling Session From Client '%v'", conn.RemoteAddr()), err)
		return
	}
	rpcSessCtx := &ZSshRpcSessionContext{
		NetConn:          conn,
		ServerConn:       sconn,
		NewChannelChan:   schan,
		ReqChan:          reqchan,
		OperationHandler: handler,
		Logger:           logger,
	}
	go ssh.DiscardRequests(reqchan)
	go handleChannels(rpcSessCtx, IOBlockSize)
}

func try(Logger SvrLogFunc) {
	if err := recover(); err != nil {
		var einf error
		switch err.(type) {
		case error:
			einf = err.(error)
			break
		default:
			einf = nil
			break
		}
		Logger(SvrLogLevel_WARNING, "Internal Error Recovered", einf)
	}
}

func handleChannels(ctx *ZSshRpcSessionContext, IOBlockSize int) {
	defer try(ctx.Logger)
	for newchan := range ctx.NewChannelChan {
		go handleChannel(ctx, newchan, IOBlockSize)
	}
}

func handleChannel(sessctx *ZSshRpcSessionContext, nch ssh.NewChannel, IOBlockSize int) {
	defer try(sessctx.Logger)
	if nch.ChannelType() == "zsshrpc" {
		ch, req, err := nch.Accept()
		if err != nil {
			sessctx.Logger(SvrLogLevel_INFO, fmt.Sprintf("Failed Handler Channel From '%v'", sessctx.NetConn.RemoteAddr()), err)
			sessctx.ServerConn.Close()
		} else {
			chctx := &ZSshRpcChannelContext{
				SessionCtx: sessctx,
				Channel:    ch,
				ReqChan:    req,
				Logger:     sessctx.Logger,
				RxState:    ChannelState_IDLE,
			}
			go handleZSshRpcChannel(chctx, IOBlockSize)
		}
	} else {
		sessctx.Logger(SvrLogLevel_INFO, fmt.Sprintf("Unsupported Channel Type '%s' From Client '%v'", nch.ChannelType(), sessctx.NetConn.RemoteAddr()), nil)
		nch.Reject(ssh.UnknownChannelType, "Unsupported Channel Type.")
		sessctx.ServerConn.Close()
	}
}

func readChannelData(b []byte, recvBufLen int, chctx *ZSshRpcChannelContext) {
	for {
		rl, err := chctx.Channel.Read(b)
		if err != nil || rl == 0 {
			break
		}
		if rl < recvBufLen {
			if rl != 0 {
				if b[rl-1] == 0 {
					chctx.RxBuf.Write(b[:rl-1])
					break
				} else {
					chctx.RxBuf.Write(b[:rl])
				}
			}
		} else {
			if b[recvBufLen-1] == 0 {
				chctx.RxBuf.Write(b[:recvBufLen-1])
				break
			} else {
				chctx.RxBuf.Write(b)
			}
		}
	}
}

func handleZSshRpcChannel(chctx *ZSshRpcChannelContext, IOBlockSize int) {
	defer try(chctx.Logger)
	ioblockbuf := make([]byte, IOBlockSize)
	waitchan := make(chan int)
	go func() {
		defer try(chctx.Logger)
		for {
			readChannelData(ioblockbuf, IOBlockSize, chctx)
			//chctx.Logger(SvrLogLevel_DEBUG, fmt.Sprintf("<RECV> [len=%d] %s",chctx.RxBuf.Len(), hex.EncodeToString([]byte(chctx.RxBuf.String()))), nil)
			waitchan <- 1
		}
		//io.Copy(&chctx.RxBuf, chctx.Channel)
	}()
	for {
		req := <-chctx.ReqChan
		switch chctx.RxState {
		case ChannelState_IDLE:
			{
				if req.Type == "ZSSHRPC-1.0" {
					chctx.RxState = ChannelState_WAIT_URI
					chctx.RxBuf.Reset()
				}
			}
			break
		case ChannelState_WAIT_URI:
			{
				//chctx.Logger(SvrLogLevel_DEBUG, fmt.Sprintf("[Before URL Clear]Length Of RxBuf: %d", chctx.RxBuf.Len()), nil)
				switch req.Type {
				case "CALL":
					{
						chctx.RxMethod = RpcMethod_CALL
						chctx.RxState = ChannelState_WAIT_JSON
						<-waitchan
						chctx.UriStr = chctx.RxBuf.String()
						chctx.RxBuf.Reset()
					}
					break
				case "ADD":
					{
						chctx.RxMethod = RpcMethod_ADD
						chctx.RxState = ChannelState_WAIT_JSON
						<-waitchan
						chctx.UriStr = chctx.RxBuf.String()
						chctx.RxBuf.Reset()
					}
					break
				case "DEL":
					{
						chctx.RxMethod = RpcMethod_DEL
						chctx.RxState = ChannelState_WAIT_JSON
						<-waitchan
						chctx.UriStr = chctx.RxBuf.String()
						chctx.RxBuf.Reset()
					}
					break
				case "GET":
					{
						chctx.RxMethod = RpcMethod_GET
						chctx.RxState = ChannelState_WAIT_JSON
						<-waitchan
						chctx.UriStr = chctx.RxBuf.String()
						chctx.RxBuf.Reset()
					}
					break
				case "SET":
					{
						chctx.RxMethod = RpcMethod_SET
						chctx.RxState = ChannelState_WAIT_JSON
						<-waitchan
						chctx.UriStr = chctx.RxBuf.String()
						chctx.RxBuf.Reset()
					}
					break
				default:
					{
						chctx.RxState = ChannelState_IDLE
						chctx.RxBuf.Reset()
					}
					break
				}
				chctx.Logger(SvrLogLevel_DEBUG, fmt.Sprint("Recv URI: ", chctx.UriStr), nil)
				//chctx.Logger(SvrLogLevel_DEBUG, fmt.Sprintf("[After URI Clear]Length Of RxBuf: %d", chctx.RxBuf.Len()), nil)
			}
			break
		case ChannelState_WAIT_JSON:
			{
				if req.Type == "ENDREQ" {
					//chctx.Logger(SvrLogLevel_DEBUG, fmt.Sprintf("[Before JSON Clear]Length Of RxBuf: %d", chctx.RxBuf.Len()), nil)
					<-waitchan
					chctx.JsonStr = chctx.RxBuf.String()
					//chctx.Logger(SvrLogLevel_DEBUG, fmt.Sprint("Recv JSON: ", chctx.JsonStr), nil)
					chctx.RxBuf.Reset()
					//chctx.Logger(SvrLogLevel_DEBUG, fmt.Sprintf("[After JSON Clear]Length Of RxBuf: %d", chctx.RxBuf.Len()), nil)
					chctx.RxState = ChannelState_EXEC_HANDLER
					req := ZSshRpcOperationRequest{
						ChannelContext: chctx,
						Method:         chctx.RxMethod,
						URI:            chctx.UriStr,
						JSON:           chctx.JsonStr,
					}
					chctx.ResponseData = chctx.SessionCtx.OperationHandler.HandleOperation(req)
					rcstring := fmt.Sprintf(
						"%d - %s",
						chctx.ResponseData.StatusCode,
						GetResponseStatusCodeString(chctx.ResponseData.StatusCode),
					)
					chctx.Channel.Write([]byte(rcstring))
					chctx.Channel.Write([]byte{0})
					chctx.RxState = ChannelState_WAIT_JSON_READ
				} else {
					chctx.RxState = ChannelState_IDLE
					chctx.RxBuf.Reset()
				}
			}
			break
		case ChannelState_EXEC_HANDLER:
			{
				chctx.RxState = ChannelState_IDLE
				chctx.RxBuf.Reset()
			}
			break
		case ChannelState_WAIT_JSON_READ:
			if req.Type == "GETJSON" {
				chctx.Channel.Write([]byte(chctx.ResponseData.ResponseJSON))
				chctx.Channel.Write([]byte{0})
			}
			chctx.RxState = ChannelState_IDLE
			break
		}
		if req.WantReply {
			req.Reply(true, nil)
		}
	}
}