//build !android

package main

// TODO: rewrite this. Think of another way of admin control

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/hmac"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/binary"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net"

	"github.com/cbeuw/Cloak/internal/client"
	"github.com/cbeuw/Cloak/internal/client/TLS"
	"github.com/cbeuw/Cloak/internal/util"
)

type UserInfo struct {
	UID []byte
	// ALL of the following fields have to be accessed atomically
	SessionsCap uint32
	UpRate      int64
	DownRate    int64
	UpCredit    int64
	DownCredit  int64
	ExpiryTime  int64
}

type administrator struct {
	adminConn net.Conn
	adminUID  []byte
}

func adminHandshake(sta *client.State) *administrator {
	fmt.Println("Enter the ip:port of your server")
	var addr string
	fmt.Scanln(&addr)
	fmt.Println("Enter the admin UID")
	var b64AdminUID string
	fmt.Scanln(&b64AdminUID)
	adminUID, err := base64.StdEncoding.DecodeString(b64AdminUID)
	if err != nil {
		log.Println(err)
		return nil
	}

	sta.UID = adminUID

	remoteConn, err := net.Dial("tcp", addr)
	if err != nil {
		log.Println(err)
		return nil
	}

	clientHello := TLS.ComposeInitHandshake(sta)
	_, err = remoteConn.Write(clientHello)

	// Three discarded messages: ServerHello, ChangeCipherSpec and Finished
	discardBuf := make([]byte, 1024)
	for c := 0; c < 3; c++ {
		_, err = util.ReadTLS(remoteConn, discardBuf)
		if err != nil {
			log.Printf("Reading discarded message %v: %v\n", c, err)
			return nil
		}
	}

	reply := TLS.ComposeReply()
	_, err = remoteConn.Write(reply)
	a := &administrator{remoteConn, adminUID}
	return a
}

func (a *administrator) getCommand() []byte {
	fmt.Println("Select your command")
	fmt.Println(`1       listActiveUsers         none            []uids
2       listAllUsers            none            []userinfo
3       getUserInfo             uid             userinfo
4       addNewUser              userinfo        ok`)
	var cmd string
	fmt.Scanln(&cmd)
	switch cmd {
	case "1":
		return a.request([]byte{0x01})
	case "2":
		return a.request([]byte{0x02})
	case "3":
		fmt.Println("Enter UID")
		var b64UID string
		fmt.Scanln(&b64UID)
		UID, _ := base64.StdEncoding.DecodeString(b64UID)
		return a.request(append([]byte{0x03}, UID...))
	case "4":
		var uinfo UserInfo
		var b64UID string
		fmt.Printf("UID:")
		fmt.Scanln(&b64UID)
		UID, _ := base64.StdEncoding.DecodeString(b64UID)
		uinfo.UID = UID
		fmt.Printf("SessionsCap:")
		fmt.Scanf("%d", &uinfo.SessionsCap)
		fmt.Printf("UpRate:")
		fmt.Scanf("%d", &uinfo.UpRate)
		fmt.Printf("DownRate:")
		fmt.Scanf("%d", &uinfo.DownRate)
		fmt.Printf("UpCredit:")
		fmt.Scanf("%d", &uinfo.UpCredit)
		fmt.Printf("DownCredit:")
		fmt.Scanf("%d", &uinfo.DownCredit)
		fmt.Printf("ExpiryTime:")
		fmt.Scanf("%d", &uinfo.ExpiryTime)
		marshed, _ := json.Marshal(uinfo)
		return a.request(append([]byte{0x04}, marshed...))
	default:
		return nil
	}
}

// protocol: 0[TLS record layer 5 bytes]5[IV 16 bytes]21[data][hmac 32 bytes]
func (a *administrator) request(data []byte) []byte {
	dataLen := len(data)

	buf := make([]byte, 5+16+dataLen+32)
	buf[0] = 0x17
	buf[1] = 0x03
	buf[2] = 0x03
	binary.BigEndian.PutUint16(buf[3:5], uint16(16+dataLen+32))

	rand.Read(buf[5:21]) //iv
	copy(buf[21:], data)
	block, _ := aes.NewCipher(a.adminUID[0:16])
	stream := cipher.NewCTR(block, buf[5:21])
	stream.XORKeyStream(buf[21:21+dataLen], buf[21:21+dataLen])

	mac := hmac.New(sha256.New, a.adminUID[16:32])
	mac.Write(buf[5 : 21+dataLen])
	copy(buf[21+dataLen:], mac.Sum(nil))

	return buf
}

var ErrInvalidMac = errors.New("Mac mismatch")

func (a *administrator) checkAndDecrypt(data []byte) ([]byte, error) {
	macIndex := len(data) - 32
	mac := hmac.New(sha256.New, a.adminUID[16:32])
	mac.Write(data[5:macIndex])
	expected := mac.Sum(nil)
	if !hmac.Equal(data[macIndex:], expected) {
		return nil, ErrInvalidMac
	}

	iv := data[5:21]
	ret := data[21:macIndex]
	block, _ := aes.NewCipher(a.adminUID[0:16])
	stream := cipher.NewCTR(block, iv)
	stream.XORKeyStream(ret, ret)
	return ret, nil
}