package tls

import (
	"crypto/tls"
	"errors"
	"fmt"
	"github.com/net-byte/vtun/common/xproto"
	"log"
	"net"
	"time"

	"github.com/golang/snappy"
	"github.com/net-byte/vtun/common/cache"
	"github.com/net-byte/vtun/common/cipher"
	"github.com/net-byte/vtun/common/config"
	"github.com/net-byte/vtun/common/counter"
	"github.com/net-byte/vtun/common/netutil"
	"github.com/net-byte/water"
)

// StartClient starts the tls client
func StartClient(iFace *water.Interface, config config.Config) {
	log.Println("vtun tls client started")
	go tunToTLS(config, iFace)
	tlsConfig := &tls.Config{
		InsecureSkipVerify: config.TLSInsecureSkipVerify,
		MinVersion:         tls.VersionTLS13,
		CurvePreferences:   []tls.CurveID{tls.CurveP521, tls.CurveP384, tls.CurveP256},
		CipherSuites: []uint16{
			tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
			tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
			tls.TLS_RSA_WITH_AES_256_GCM_SHA384,
			tls.TLS_RSA_WITH_AES_256_CBC_SHA,
			tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
			tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
			tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
		},
	}
	if config.TLSSni != "" {
		tlsConfig.ServerName = config.TLSSni
	}
	for {
		conn, err := tls.Dial("tcp", config.ServerAddr, tlsConfig)
		if err != nil {
			time.Sleep(3 * time.Second)
			netutil.PrintErr(err, config.Verbose)
			continue
		}
		cache.GetCache().Set("tlsConn", conn, 24*time.Hour)
		tlsToTun(config, conn, iFace)
		cache.GetCache().Delete("tlsConn")
	}
}

// tunToTLS sends packets from tun to tls
func tunToTLS(config config.Config, iFace *water.Interface) {
	authKey := xproto.ParseAuthKeyFromString(config.Key)
	buffer := make([]byte, config.BufferSize)
	for {
		n, err := iFace.Read(buffer)
		if err != nil {
			netutil.PrintErr(err, config.Verbose)
			continue
		}
		b := buffer[:n]
		if v, ok := cache.GetCache().Get("tlsConn"); ok {
			if config.Obfs {
				b = cipher.XOR(b)
			}
			if config.Compress {
				b = snappy.Encode(nil, b)
			}
			tlsConn := v.(net.Conn)
			ph := &xproto.ClientSendPacketHeader{
				ProtocolVersion: xproto.ProtocolVersion,
				Key:             authKey,
				Length:          len(b),
			}
			_, err := tlsConn.Write(ph.Bytes())
			if err != nil {
				netutil.PrintErr(err, config.Verbose)
				continue
			}
			n, err := tlsConn.Write(b[:])
			if err != nil {
				netutil.PrintErr(err, config.Verbose)
				continue
			}
			counter.IncrWrittenBytes(n)
		}
	}
}

// tlsToTun sends packets from tls to tun
func tlsToTun(config config.Config, tlsConn net.Conn, iFace *water.Interface) {
	defer func(tlsConn net.Conn) {
		err := tlsConn.Close()
		if err != nil {
			netutil.PrintErr(err, config.Verbose)
		}
	}(tlsConn)
	header := make([]byte, xproto.ServerSendPacketHeaderLength)
	packet := make([]byte, config.BufferSize)
	for {
		n, err := tlsConn.Read(header)
		if err != nil {
			netutil.PrintErr(err, config.Verbose)
			break
		}
		if n != xproto.ServerSendPacketHeaderLength {
			netutil.PrintErr(errors.New(fmt.Sprintf("received length <%d> not equals <%d>!", n, xproto.ServerSendPacketHeaderLength)), config.Verbose)
			break
		}
		ph := xproto.ParseServerSendPacketHeader(header[:n])
		if ph == nil {
			netutil.PrintErr(errors.New("ph == nil"), config.Verbose)
			break
		}
		n, err = tlsConn.Read(packet[:ph.Length])
		if err != nil {
			netutil.PrintErr(err, config.Verbose)
			break
		}
		if n != ph.Length {
			netutil.PrintErr(errors.New(fmt.Sprintf("received length <%d> not equals <%d>!", n, ph.Length)), config.Verbose)
			break
		}
		b := packet[:n]
		if config.Compress {
			b, err = snappy.Decode(nil, b)
			if err != nil {
				netutil.PrintErr(err, config.Verbose)
				break
			}
		}
		if config.Obfs {
			b = cipher.XOR(b)
		}
		n, err = iFace.Write(b)
		if err != nil {
			netutil.PrintErr(err, config.Verbose)
			break
		}
		counter.IncrReadBytes(n)
	}
}