package main

import "fmt"

func teaEncrypt(v [2]uint32, k [4]uint32) [2]uint32 {
	var v0, v1, sum uint32 = v[0], v[1], 0   /* set up */
	var delta uint32 = 0x9e3779b9            /* a key schedule constant */
	k0, k1, k2, k3 := k[0], k[1], k[2], k[3] /* cache key */
	for i := 0; i < 32; i++ {                /* basic cycle start */
		sum += delta
		v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1)
		v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3)
	} /* end cycle */
	v[0] = v0
	v[1] = v1
	return v
}

func teaDecrypt(v [2]uint32, k [4]uint32) [2]uint32 {
	var v0, v1, sum uint32 = v[0], v[1], 0xC6EF3720 /* set up */
	var delta uint32 = 0x9e3779b9                   /* a key schedule constant */
	k0, k1, k2, k3 := k[0], k[1], k[2], k[3]        /* cache key */
	for i := 0; i < 32; i++ {                       /* basic cycle start */
		v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3)
		v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1)
		sum -= delta
	} /* end cycle */
	v[0] = v0
	v[1] = v1
	return v
}

func xteaEncrypt(rounds uint32, v [2]uint32, k [4]uint32) [2]uint32 { // encipher
	var v0, v1, sum, delta, i uint32 = v[0], v[1], 0, 0x9E3779B9, 0
	for ; i < rounds; i++ {
		v0 += (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + k[sum&3])
		sum += delta
		v1 += (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + k[(sum>>11)&3])
	}
	v[0] = v0
	v[1] = v1
	return v
}

func xteaDecrypt(rounds uint32, v [2]uint32, k [4]uint32) [2]uint32 { //decipher
	var v0, v1, delta, sum, i uint32 = v[0], v[1], 0x9E3779B9, 0, 0
	sum = delta * rounds
	for ; i < rounds; i++ {
		v1 -= (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + k[(sum>>11)&3])
		sum -= delta
		v0 -= (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + k[sum&3])
	}
	v[0] = v0
	v[1] = v1
	return v
}

func xxteaMX(z, y, sum uint32, key [4]uint32, p, e uint) uint32 {
	return (((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (key[(p&3)^e] ^ z)))
}

func xxtea(v []uint32, n int, k [4]uint32) { // btea
	var y, z, sum uint32
	var p, rounds, e uint
	var delta uint32 = 0x9e3779b9
	if n > 1 { /* Coding Part */
		rounds = uint(6 + 52/n)
		sum = 0
		z = v[n-1]
		for {
			sum += delta
			e = uint((sum >> 2) & 3)
			for p = 0; p < uint(n-1); p++ {
				y = v[p+1]
				v[p] += xxteaMX(z, y, sum, k, p, e)
				z = v[p]
			}
			y = v[0]
			v[n-1] += xxteaMX(z, y, sum, k, p, e)
			z = v[n-1]
			rounds--
			if rounds == 0 {
				break
			}
		}
	} else if n < -1 { /* Decoding Part */
		n = -n
		rounds = uint(6 + 52/n)
		sum = uint32(rounds) * delta
		y = v[0]
		for {
			e = uint((sum >> 2) & 3)
			for p = uint(n - 1); p > 0; p-- {
				z = v[p-1]
				v[p] -= xxteaMX(z, y, sum, k, p, e)
				y = v[p]
			}
			z = v[n-1]
			v[0] -= xxteaMX(z, y, sum, k, p, e)
			y = v[0]
			sum -= delta
			rounds--
			if rounds == 0 {
				break
			}
		}
	}
}

func xxteaEncrypt(v []uint32, k [4]uint32) {
	xxtea(v, len(v), k)
}

func xxteaDecrypt(v []uint32, k [4]uint32) {
	xxtea(v, -len(v), k)
}

func main() {
	var v = [2]uint32{1, 2}
	var vv = [4]uint32{1, 2, 3, 4}
	var k = [4]uint32{2, 2, 3, 4}
	v = teaEncrypt(v, k)
	fmt.Println(v)
	v = teaDecrypt(v, k)
	fmt.Println(v)
	v = xteaEncrypt(32, v, k)
	fmt.Println(v)
	v = xteaDecrypt(32, v, k)
	fmt.Println(v)
	xxteaEncrypt(vv[:], k)
	fmt.Println(vv)
	xxteaDecrypt(vv[:], k)
	fmt.Println(vv)
}