package main

import "fmt"

func skip32Encrypt(number uint32, key string) uint32 {
	return skip32(number, key, true)
}

func skip32Decrypt(number uint32, key string) uint32 {
	return skip32(number, key, false)
}

var _SKIP32_FTABLE = [256]byte{
	0xa3, 0xd7, 0x09, 0x83, 0xf8, 0x48,
	0xf6, 0xf4, 0xb3, 0x21, 0x15, 0x78, 0x99, 0xb1, 0xaf, 0xf9, 0xe7,
	0x2d, 0x4d, 0x8a, 0xce, 0x4c, 0xca, 0x2e, 0x52, 0x95, 0xd9, 0x1e,
	0x4e, 0x38, 0x44, 0x28, 0x0a, 0xdf, 0x02, 0xa0, 0x17, 0xf1, 0x60,
	0x68, 0x12, 0xb7, 0x7a, 0xc3, 0xe9, 0xfa, 0x3d, 0x53, 0x96, 0x84,
	0x6b, 0xba, 0xf2, 0x63, 0x9a, 0x19, 0x7c, 0xae, 0xe5, 0xf5, 0xf7,
	0x16, 0x6a, 0xa2, 0x39, 0xb6, 0x7b, 0x0f, 0xc1, 0x93, 0x81, 0x1b,
	0xee, 0xb4, 0x1a, 0xea, 0xd0, 0x91, 0x2f, 0xb8, 0x55, 0xb9, 0xda,
	0x85, 0x3f, 0x41, 0xbf, 0xe0, 0x5a, 0x58, 0x80, 0x5f, 0x66, 0x0b,
	0xd8, 0x90, 0x35, 0xd5, 0xc0, 0xa7, 0x33, 0x06, 0x65, 0x69, 0x45,
	0x00, 0x94, 0x56, 0x6d, 0x98, 0x9b, 0x76, 0x97, 0xfc, 0xb2, 0xc2,
	0xb0, 0xfe, 0xdb, 0x20, 0xe1, 0xeb, 0xd6, 0xe4, 0xdd, 0x47, 0x4a,
	0x1d, 0x42, 0xed, 0x9e, 0x6e, 0x49, 0x3c, 0xcd, 0x43, 0x27, 0xd2,
	0x07, 0xd4, 0xde, 0xc7, 0x67, 0x18, 0x89, 0xcb, 0x30, 0x1f, 0x8d,
	0xc6, 0x8f, 0xaa, 0xc8, 0x74, 0xdc, 0xc9, 0x5d, 0x5c, 0x31, 0xa4,
	0x70, 0x88, 0x61, 0x2c, 0x9f, 0x0d, 0x2b, 0x87, 0x50, 0x82, 0x54,
	0x64, 0x26, 0x7d, 0x03, 0x40, 0x34, 0x4b, 0x1c, 0x73, 0xd1, 0xc4,
	0xfd, 0x3b, 0xcc, 0xfb, 0x7f, 0xab, 0xe6, 0x3e, 0x5b, 0xa5, 0xad,
	0x04, 0x23, 0x9c, 0x14, 0x51, 0x22, 0xf0, 0x29, 0x79, 0x71, 0x7e,
	0xff, 0x8c, 0x0e, 0xe2, 0x0c, 0xef, 0xbc, 0x72, 0x75, 0x6f, 0x37,
	0xa1, 0xec, 0xd3, 0x8e, 0x62, 0x8b, 0x86, 0x10, 0xe8, 0x08, 0x77,
	0x11, 0xbe, 0x92, 0x4f, 0x24, 0xc5, 0x32, 0x36, 0x9d, 0xcf, 0xf3,
	0xa6, 0xbb, 0xac, 0x5e, 0x6c, 0xa9, 0x13, 0x57, 0x25, 0xb5, 0xe3,
	0xbd, 0xa8, 0x3a, 0x01, 0x05, 0x59, 0x2a, 0x46,
}

func _skip32_g(key []byte, k uint32, w uint32) uint32 {
	g1 := w >> 8
	g2 := w & 0xFF
	g3 := (uint32(_SKIP32_FTABLE[g2^uint32(key[(4*k)%10]&0xFF)])) ^ g1
	g4 := (uint32(_SKIP32_FTABLE[g3^uint32(key[(4*k+1)%10]&0xFF)])) ^ g2
	g5 := (uint32(_SKIP32_FTABLE[g4^uint32(key[(4*k+2)%10]&0xFF)])) ^ g3
	g6 := (uint32(_SKIP32_FTABLE[g5^uint32(key[(4*k+3)%10]&0xFF)])) ^ g4

	return (g5 << 8) + g6
}

func skip32(value uint32, key string, encypt bool) uint32 {
	buf := [...]uint32{
		((value >> 24) & 0xff),
		((value >> 16) & 0xff),
		((value >> 8) & 0xff),
		((value >> 0) & 0xff),
	}
	keySlice := []byte(key)
	var kstep int32
	var k int32

	if encypt {
		kstep = 1
		k = 0
	} else {
		kstep = -1
		k = 23
	}

	wl := (buf[0] << 8) + buf[1]
	wr := (buf[2] << 8) + buf[3]
	for i := 0; i < 12; i++ {
		wr ^= _skip32_g(keySlice, uint32(k), wl) ^ uint32(k)
		k += kstep
		wl ^= _skip32_g(keySlice, uint32(k), wr) ^ uint32(k)
		k += kstep
	}
	buf[0] = (wr >> 8)
	buf[1] = (wr & 0xFF)
	buf[2] = (wl >> 8)
	buf[3] = (wl & 0xFF)

	return ((buf[0]) << 24) | ((buf[1]) << 16) | ((buf[2]) << 8) | (buf[3])
}

func main() {
	var a uint32 = 2
	k := "0123456789"
	e := skip32Encrypt(a, k)
	fmt.Println(e)
	fmt.Println(skip32Decrypt(e, k))
}