package main

import (
	"errors"
	"fmt"
	"io"
	"log"
	"net"
	"strconv"
	"strings"
	"sync"

	"github.com/pyke369/golang-support/rcache"
)

// Server represents the server
type OpenVpnMgt struct {
	port       string
	m          sync.RWMutex
	debug      bool
	VpnRemotes []string            `json:"remotes"`
	vpnServers map[int]*OpenVpnSrv `json:"sessions"`
}

// NewServer returns a pointer to a new server
func NewVPNServer(port string, debug bool) *OpenVpnMgt {
	return &OpenVpnMgt{
		port:       port,
		debug:      debug,
		vpnServers: make(map[int]*OpenVpnSrv),
	}
}

func (s *OpenVpnMgt) Lock() {
	s.m.Lock()
}

func (s *OpenVpnMgt) Unlock() {
	s.m.Unlock()
}

// Run starts a the server
func (s *OpenVpnMgt) Run() {

	// get the endpoint list
	if err := s.getServerList(); err != nil {
		log.Println(err)
		return
	}

	// Resolve the passed port into an address
	addrs, err := net.ResolveTCPAddr("tcp", s.port)
	if err != nil {
		log.Println(err)
		return
	}
	// start listening to client connections
	listener, err := net.ListenTCP("tcp", addrs)
	if err != nil {
		log.Println(err)
		return
	}
	// Infinite loop since we dont want the server to shut down
	for {
		// Accept the incomming connections
		conn, err := listener.Accept()
		if err != nil {
			// continue accepting connection even if an error occurs (if error occurs dont shut down)
			continue
		}
		// run it as a go routine to allow multiple clients to connect at the same time
		go s.handleConn(conn)
	}
}

func (s *OpenVpnMgt) GetSession(remote int) (error, *OpenVpnSrv) {
	if vpnServer, ok := s.vpnServers[remote]; ok {
		return nil, vpnServer
	}
	return errors.New(fmt.Sprintf("unknown session %d", vpnServers)), nil
}

func (s *OpenVpnMgt) SetRemote(server string, remote int) error {
	// check if the session is valid
	err, session := s.GetSession(remote)
	if err != nil {
		return err
	}

	for _, r := range s.VpnRemotes {
		if r != server {
			continue
		}
		return session.SetRemote(server)
	}

	return errors.New(fmt.Sprintf("unknown remote %s", server))
}

// send the version command on all vpn servers. Kind of useless
func (s *OpenVpnMgt) Version() (error, map[int][]string) {
	var err error
	ret := make(map[int][]string)
	for remote, srv := range s.vpnServers {
		err, msg := srv.Version()
		if err == nil {
			ret[remote] = msg
		}
	}
	return err, ret
}

// main loop for a given openvpn server
func (s *OpenVpnMgt) handleConn(conn net.Conn) {
	remote := conn.RemoteAddr().String()
	pidRegexp := rcache.Get("^SUCCESS: pid=([0-9]+)$")
	//  >REMOTE:vpn.example.com,1194,udp
	remoteRegexp := rcache.Get("^>REMOTE:(.*),([0-9]*),(.*)$")

	defer conn.Close()

	vpnServer := NewOpenVpnSrv(conn)

	// most response are multilined, use response to concatenate them
	response := []string{}

	// remove bogus clients
	line, err := vpnServer.session.GetLine()
	if err != nil {
		log.Println(err)
		return
	}
	if line != ">INFO:OpenVPN Management Interface Version 1 -- type 'help' for more info\r\n" {
		log.Println("Bogus Client")
		return
	}

	log.Printf("Valid openvpn connected from %s\n", remote)

	go session.sendCommand([]string{"pid"})

	for {
		line, err := session.GetLine()

		// manage basic errors
		switch {
		case err == io.EOF:
			log.Println("Reached EOF - close this connection.\n")
			return
		case err != nil:
			log.Println("Error reading line. Got: '"+line+"'\n", err)
			return
		}
		line = strings.Trim(line, "\n\r ")

		if s.debug && strings.Index(line, "password") == -1 {
			log.Print(line)
		}

		// manage exit commands
		for _, terminator := range []string{"quit", "exit"} {
			if line == terminator || strings.HasPrefix(line, terminator+" ") {
				log.Println("server disconnected")
				return
			}
		}

		// get the PID
		match := pidRegexp.FindStringSubmatch(line)
		if len(match) == 2 {
			pid, _ := strconv.Atoi(match[1])
			s.Lock()
			s.vpnServers[pid] = vpnServer
			s.Unlock()
			defer delete(s.vpnServers, pid)
		}

		// manage all "terminator" lines
		for _, terminator := range []string{"END", ">CLIENT:ENV,END", "SUCCESS", "ERROR"} {
			if strings.HasPrefix(line, terminator) {
				vpnServer.Response(response)
				response = nil
				line = ""
				break
			}
		}

		remoteMatch := remoteRegexp.FindStringSubmatch(line)
		switch {
		// command successfull, we can ignore
		case strings.HasPrefix(line, ">SUCCESS: client-deny command succeeded"):
		case strings.HasPrefix(line, ">HOLD"):
			go vpnServer.waitForRelase()
		case len(remoteMatch) > 0:
			go vpnServer.ValidRemote(remoteMatch[1], remoteMatch[2], remoteMatch[3])
		default:
			response = append(response, line)
		}
	}
}