#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "util.h"
#include "sha2.h"
#include "scrypt.h"

/**
 * Name  RFC    Description
 * pass  P      Passphrase, an octet string.
 * salt  S      Salt, an octet string.
 * cost  N      CPU/Memory cost parameter
 * bs    r      Block size parameter.
 * par   p      Parallelization parameter
 * len?  dkLen  Intended output length
 * in    B      Input data
 * out   B'     Output data
 */

/* Types */
typedef void hash_t(uint8_t *out, const uint8_t *in, int len);

/* Helpers */
#if 0
static int mod(uint8_t out[64], uint8_t in[64])
{
}

static void copy(uint8_t out[64], uint8_t in[64])
{
}

static void xor(uint8_t out[64], uint8_t a[64], uint8_t b[64])
{
}
#endif

/* HMAC */
static void hmac_gen(hash_t hash,
		uint8_t *out, int nout,
		const uint8_t *key, int nkey,
		const uint8_t *msg, int nmsg)
{
	uint8_t *fix  = alloc0(nout);
	uint8_t *ipad = alloc0(nout+nmsg);
	uint8_t *opad = alloc0(nout+nout);

	/* Fixup key */
	if (nkey > nout)
		hash(fix, key, nkey);
	else
		memcpy(fix, key, nkey);

	/* Create pad strings */
	for (int i = 0; i < nout; i++) {
		opad[i] = 0x5c ^ fix[i];
		ipad[i] = 0x36 ^ fix[i];
	}

	/* Run hashes - hash(o+hash(i+msg)) */
	memcpy(ipad+nout, msg, nmsg);
	hash(opad+nout, ipad, nout+nmsg);
	hash(out, opad, nout+nout);

	/* Cleanup */
	free(fix);
	free(opad);
	free(ipad);
}

/* PBKDF2 */
static void pbkdf2_gen(uint8_t *out, int nout,
		const uint8_t *pass, int npass,
		const uint8_t *salt, int nsalt,
		int iter)
{
	int      nbuf = nsalt + 4;
	uint8_t *buf  = alloc0(nbuf);
	memcpy(buf, salt, nsalt);

	const int nptr = 256/8;

	for (int i = 0; i < nout/nptr; i++) {
		uint8_t *ptr = &out[i*nptr];

		buf[nsalt+0] = ((i+1) & 0xFF000000) >> 030;
		buf[nsalt+1] = ((i+1) & 0x00FF0000) >> 020;
		buf[nsalt+2] = ((i+1) & 0x0000FF00) >> 010;
		buf[nsalt+3] = ((i+1) & 0x000000FF) >> 000;

		hmac_gen(sha256_hash, ptr, nptr, pass, npass, buf, nbuf);
		for (int j = 1; j < iter; j++)
			hmac_gen(sha256_hash, ptr, nptr, pass, npass, ptr, nptr);
	}

	free(buf);
}

static void pbkdf2_gen_str(uint8_t *out, int nout,
		const char *pass, const char *salt, int iter)
{
	pbkdf2_gen(out, nout,
		(const uint8_t *)pass, strlen(pass),
		(const uint8_t *)salt, strlen(salt), iter);
}

/* Salsa20/8 */
static void salsa(uint8_t out[64], uint8_t in[64])
{
}

/* scrypt */
#if 0
static void block_mix(uint8_t *out[64], uint8_t *in[64], int bs)
{
	// xor each block with the last block
	// alternat first/second half for result

	uint8_t tmp[64]
	for (int i = 0; i < 2*r; i++) {
		int o = bs*(i%2) + (i/2);
	        xor(tmp, in[2*r - 1], in[i]);
	        salsa(out[o], tmp);
	}
}

static void ro_mix(uint8_t *out[128], uint8_t *in[128], int cost, int bs)
{
	// generate vector of size cost
	// randomly collapse vector as output

	uint8_t *state[64];
	uint8_t *mixed[64];
	uint8_t *tmp[64];

	copy(state, in);

	for (i = 0; i < cost; i++) {
		copy(mixed[i], state);
		block_mix(state, state);
	}

	for (i = 0; i < cost; i++) {
		int j = mod(state, cost);
		xor(tmp, state, mixed[j]);
		block_mix(state, tmp);
	}

	copy(out, state);
}

static void scrypt_run(uint8_t out[64],
		char *pass, char *salt,
		int cost, int bs, int par, int len)
{
	// hash pass/salt into large buffer
	// mix each buffer (in parallel)
	// combine bubers into output

	sha256_hmac(buf, pass, salt, 1, par * 128 * bs);

	for (i = 0; i < par; i++)
		buf[i] = ro_mix(buf[i], cost, bs);

	sha256_hmac(out, pass, buf, 1, len);
}
#endif

/* Entry point */
void scrypt_hash(uint8_t *in, uint8_t *sum)
{
	*sum = 0;
}

/* Tests */
#if 0
static void test_script(void)
{
	/* Parameters */
	const int   cost = 1024;
	const int   bs   = 1;
	const int   par  = 1;
	const int   len  = 32;

	/* Input data */
	const char *pass = "hello";
	const char *salt = "world";

	/* Output data */
	static uint8_t out[32];

	/* Run the hash */
	scrypt_hash(out, pass, salt, par, bs, len);

	/* Print output */
}
#endif

static void test_keygen(void)
{
	const uint8_t truth0[] = {
		0x55, 0xac, 0x04, 0x6e, 0x56, 0xe3, 0x08, 0x9f,
		0xec, 0x16, 0x91, 0xc2, 0x25, 0x44, 0xb6, 0x05,
		0xf9, 0x41, 0x85, 0x21, 0x6d, 0xde, 0x04, 0x65,
		0xe6, 0x8b, 0x9d, 0x57, 0xc2, 0x0d, 0xac, 0xbc,
		0x49, 0xca, 0x9c, 0xcc, 0xf1, 0x79, 0xb6, 0x45,
		0x99, 0x16, 0x64, 0xb3, 0x9d, 0x77, 0xef, 0x31,
		0x7c, 0x71, 0xb8, 0x45, 0xb1, 0xe3, 0x0b, 0xd5,
		0x09, 0x11, 0x20, 0x41, 0xd3, 0xa1, 0x97, 0x83,
	};

	const uint8_t truth1[] = {
		0x4d, 0xdc, 0xd8, 0xf6, 0x0b, 0x98, 0xbe, 0x21,
		0x83, 0x0c, 0xee, 0x5e, 0xf2, 0x27, 0x01, 0xf9,
		0x64, 0x1a, 0x44, 0x18, 0xd0, 0x4c, 0x04, 0x14,
		0xae, 0xff, 0x08, 0x87, 0x6b, 0x34, 0xab, 0x56,
		0xa1, 0xd4, 0x25, 0xa1, 0x22, 0x58, 0x33, 0x54,
		0x9a, 0xdb, 0x84, 0x1b, 0x51, 0xc9, 0xb3, 0x17,
		0x6a, 0x27, 0x2b, 0xde, 0xbb, 0xa1, 0xd0, 0x78,
		0x47, 0x8f, 0x62, 0xb3, 0x97, 0xf3, 0x3c, 0x8d,
	};

	uint8_t out0[64] = {};
	uint8_t out1[64] = {};

	//             output     password    salt    iters
	pbkdf2_gen_str(out0, 64,  "passwd",   "salt", 1);
	//pbkdf2_gen_str(out1, 64,  "Password", "NaCl", 80000);

	hexdump("\nTest #1", NULL, truth0, 64);
	hexdump("",          NULL, out0,   64);

	hexdump("\nTest #2", NULL, truth1, 64);
	hexdump("",          NULL, out1,   64);

	(void)salsa;
	(void)pbkdf2_gen;
	(void)hmac_gen;
}

void scrypt_test(void)
{
	test_keygen();
}