// Copyright 2016 fatedier, fatedier@gmail.com
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"encoding/json"
	"fmt"
	"io"
	"time"

	"frp/models/consts"
	"frp/models/msg"
	"frp/models/server"
	"frp/utils/conn"
	"frp/utils/log"
)

func ProcessControlConn(l *conn.Listener) {
	for {
		c, err := l.GetConn()
		if err != nil {
			return
		}
		log.Debug("Get new connection, %v", c.GetRemoteAddr())
		go controlWorker(c)
	}
}

// connection from every client and server
func controlWorker(c *conn.Conn) {
	// if login message type is NewWorkConn, don't close this connection
	var closeFlag bool = true
	var s *server.ProxyServer
	defer func() {
		if closeFlag {
			c.Close()
			if s != nil {
				s.Close()
			}
		}
	}()

	// get login message
	buf, err := c.ReadLine()
	if err != nil {
		log.Warn("Read error, %v", err)
		return
	}
	log.Debug("Get msg from frpc: %s", buf)

	cliReq := &msg.ControlReq{}
	if err := json.Unmarshal([]byte(buf), &cliReq); err != nil {
		log.Warn("Parse msg from frpc error: %v : %s", err, buf)
		return
	}

	// do login when type is NewCtlConn or NewWorkConn
	ret, info := doLogin(cliReq, c)
	s, ok := server.ProxyServers[cliReq.ProxyName]
	if !ok {
		log.Warn("ProxyName [%s] is not exist", cliReq.ProxyName)
		return
	}
	// if login type is NewWorkConn, nothing will be send to frpc
	if cliReq.Type != consts.NewWorkConn {
		cliRes := &msg.ControlRes{
			Type: consts.NewCtlConnRes,
			Code: ret,
			Msg:  info,
		}
		byteBuf, _ := json.Marshal(cliRes)
		err = c.Write(string(byteBuf) + "\n")
		if err != nil {
			log.Warn("ProxyName [%s], write to client error, proxy exit", s.Name)
			time.Sleep(1 * time.Second)
			return
		}
	} else {
		closeFlag = false
		return
	}

	// create a channel for sending messages
	msgSendChan := make(chan interface{}, 1024)
	go msgSender(s, c, msgSendChan)
	go noticeUserConn(s, msgSendChan)

	// loop for reading control messages from frpc and deal with different types
	msgReader(s, c, msgSendChan)

	close(msgSendChan)
	log.Info("ProxyName [%s], I'm dead!", s.Name)
	return
}

// when frps get one new user connection, send NoticeUserConn message to frpc and accept one new WorkConn later
func noticeUserConn(s *server.ProxyServer, msgSendChan chan interface{}) {
	for {
		closeFlag := s.WaitUserConn()
		if closeFlag {
			log.Debug("ProxyName [%s], goroutine for noticing user conn is closed", s.Name)
			break
		}
		notice := &msg.ControlRes{
			Type: consts.NoticeUserConn,
		}
		msgSendChan <- notice
		log.Debug("ProxyName [%s], notice client to add work conn", s.Name)
	}
}

// loop for reading messages from frpc after control connection is established
func msgReader(s *server.ProxyServer, c *conn.Conn, msgSendChan chan interface{}) error {
	// for heartbeat
	var heartbeatTimeout bool = false
	timer := time.AfterFunc(time.Duration(server.HeartBeatTimeout)*time.Second, func() {
		heartbeatTimeout = true
		s.Close()
		c.Close()
		log.Error("ProxyName [%s], client heartbeat timeout", s.Name)
	})
	defer timer.Stop()

	for {
		buf, err := c.ReadLine()
		if err != nil {
			if err == io.EOF {
				log.Warn("ProxyName [%s], client is dead!", s.Name)
				return err
			} else if c == nil || c.IsClosed() {
				log.Warn("ProxyName [%s], client connection is closed", s.Name)
				return err
			}
			log.Warn("ProxyName [%s], read error: %v", s.Name, err)
			continue
		}

		cliReq := &msg.ControlReq{}
		if err := json.Unmarshal([]byte(buf), &cliReq); err != nil {
			log.Warn("ProxyName [%s], parse msg from frpc error: %v : %s", s.Name, err, buf)
			continue
		}

		switch cliReq.Type {
		case consts.HeartbeatReq:
			log.Debug("ProxyName [%s], get heartbeat", s.Name)
			timer.Reset(time.Duration(server.HeartBeatTimeout) * time.Second)
			heartbeatRes := msg.ControlRes{
				Type: consts.HeartbeatRes,
			}
			msgSendChan <- heartbeatRes
		default:
			log.Warn("ProxyName [%s}, unsupport msgType [%d]", s.Name, cliReq.Type)
		}
	}
	return nil
}

// loop for sending messages from channel to frpc
func msgSender(s *server.ProxyServer, c *conn.Conn, msgSendChan chan interface{}) {
	for {
		msg, ok := <-msgSendChan
		if !ok {
			break
		}

		buf, _ := json.Marshal(msg)
		err := c.Write(string(buf) + "\n")
		if err != nil {
			log.Warn("ProxyName [%s], write to client error, proxy exit", s.Name)
			s.Close()
			break
		}
	}
}

// if success, ret equals 0, otherwise greater than 0
func doLogin(req *msg.ControlReq, c *conn.Conn) (ret int64, info string) {
	ret = 1
	// check if proxy name exist
	s, ok := server.ProxyServers[req.ProxyName]
	if !ok {
		info = fmt.Sprintf("ProxyName [%s] is not exist", req.ProxyName)
		log.Warn(info)
		return
	}

	// check password
	if req.Passwd != s.Passwd {
		info = fmt.Sprintf("ProxyName [%s], password is not correct", req.ProxyName)
		log.Warn(info)
		return
	}

	// control conn
	if req.Type == consts.NewCtlConn {
		if s.Status != consts.Idle {
			info = fmt.Sprintf("ProxyName [%s], already in use", req.ProxyName)
			log.Warn(info)
			return
		}

		// set infomations from frpc
		s.UseEncryption = req.UseEncryption

		// start proxy and listen for user connections, no block
		err := s.Start()
		if err != nil {
			info = fmt.Sprintf("ProxyName [%s], start proxy error: %v", req.ProxyName, err)
			log.Warn(info)
			return
		}
		log.Info("ProxyName [%s], start proxy success", req.ProxyName)
	} else if req.Type == consts.NewWorkConn {
		// work conn
		if s.Status != consts.Working {
			log.Warn("ProxyName [%s], is not working when it gets one new work connnection", req.ProxyName)
			return
		}
		// the connection will close after join over
		s.RecvNewWorkConn(c)
	} else {
		info = fmt.Sprintf("Unsupport login message type [%d]", req.Type)
		log.Warn("Unsupport login message type [%d]", req.Type)
		return
	}

	ret = 0
	return
}