package ss

import (
	"crypto/hmac"
	"crypto/sha1"
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"net"
	"os"
	"strconv"

	"bitbucket.org/snail/proxy/utils"
)

const leakyBufSize = 4108 // data.len(2) + hmacsha1(10) + data(4096)
const maxNBuf = 2048

var leakyBuf = utils.NewLeakyBuf(maxNBuf, leakyBufSize)

func IsFileExists(path string) (bool, error) {
	stat, err := os.Stat(path)
	if err == nil {
		if stat.Mode()&os.ModeType == 0 {
			return true, nil
		}
		return false, errors.New(path + " exists but is not regular file")
	}
	if os.IsNotExist(err) {
		return false, nil
	}
	return false, err
}

func HmacSha1(key []byte, data []byte) []byte {
	hmacSha1 := hmac.New(sha1.New, key)
	hmacSha1.Write(data)
	return hmacSha1.Sum(nil)[:10]
}

func otaConnectAuth(iv, key, data []byte) []byte {
	return append(data, HmacSha1(append(iv, key...), data)...)
}

func otaReqChunkAuth(iv []byte, chunkId uint32, data []byte) []byte {
	nb := make([]byte, 2)
	binary.BigEndian.PutUint16(nb, uint16(len(data)))
	chunkIdBytes := make([]byte, 4)
	binary.BigEndian.PutUint32(chunkIdBytes, chunkId)
	header := append(nb, HmacSha1(append(iv, chunkIdBytes...), data)...)
	return append(header, data...)
}

const (
	idType  = 0 // address type index
	idIP0   = 1 // ip addres start index
	idDmLen = 1 // domain address length index
	idDm0   = 2 // domain address start index

	typeIPv4 = 1 // type is ipv4 address
	typeDm   = 3 // type is domain address
	typeIPv6 = 4 // type is ipv6 address

	lenIPv4     = net.IPv4len + 2 // ipv4 + 2port
	lenIPv6     = net.IPv6len + 2 // ipv6 + 2port
	lenDmBase   = 2               // 1addrLen + 2port, plus addrLen
	lenHmacSha1 = 10
)

func GetRequest(conn *Conn) (host string, err error) {

	// buf size should at least have the same size with the largest possible
	// request size (when addrType is 3, domain name has at most 256 bytes)
	// 1(addrType) + 1(lenByte) + 255(max length address) + 2(port) + 10(hmac-sha1)
	buf := make([]byte, 269)
	// read till we get possible domain length field
	if _, err = io.ReadFull(conn, buf[:idType+1]); err != nil {
		return
	}

	var reqStart, reqEnd int
	addrType := buf[idType]
	switch addrType & AddrMask {
	case typeIPv4:
		reqStart, reqEnd = idIP0, idIP0+lenIPv4
	case typeIPv6:
		reqStart, reqEnd = idIP0, idIP0+lenIPv6
	case typeDm:
		if _, err = io.ReadFull(conn, buf[idType+1:idDmLen+1]); err != nil {
			return
		}
		reqStart, reqEnd = idDm0, idDm0+int(buf[idDmLen])+lenDmBase
	default:
		err = fmt.Errorf("addr type %d not supported", addrType&AddrMask)
		return
	}

	if _, err = io.ReadFull(conn, buf[reqStart:reqEnd]); err != nil {
		return
	}

	// Return string for typeIP is not most efficient, but browsers (Chrome,
	// Safari, Firefox) all seems using typeDm exclusively. So this is not a
	// big problem.
	switch addrType & AddrMask {
	case typeIPv4:
		host = net.IP(buf[idIP0 : idIP0+net.IPv4len]).String()
	case typeIPv6:
		host = net.IP(buf[idIP0 : idIP0+net.IPv6len]).String()
	case typeDm:
		host = string(buf[idDm0 : idDm0+int(buf[idDmLen])])
	}
	// parse port
	port := binary.BigEndian.Uint16(buf[reqEnd-2 : reqEnd])
	host = net.JoinHostPort(host, strconv.Itoa(int(port)))

	return
}

type ClosedFlag struct {
	flag bool
}

func (flag *ClosedFlag) SetClosed() {
	flag.flag = true
}

func (flag *ClosedFlag) IsClosed() bool {
	return flag.flag
}