// SHA-512. Adapted from LibTomCrypt. This code is Public Domain
#include "hash.h"

#include <blue/core/hash.h>
#include <stdint.h>
#include <string.h>

static const uint64_t K[80]
	= {0x428a2f98d728ae22ULL, 0x7137449123ef65cdULL, 0xb5c0fbcfec4d3b2fULL,
           0xe9b5dba58189dbbcULL, 0x3956c25bf348b538ULL, 0x59f111f1b605d019ULL,
           0x923f82a4af194f9bULL, 0xab1c5ed5da6d8118ULL, 0xd807aa98a3030242ULL,
           0x12835b0145706fbeULL, 0x243185be4ee4b28cULL, 0x550c7dc3d5ffb4e2ULL,
           0x72be5d74f27b896fULL, 0x80deb1fe3b1696b1ULL, 0x9bdc06a725c71235ULL,
           0xc19bf174cf692694ULL, 0xe49b69c19ef14ad2ULL, 0xefbe4786384f25e3ULL,
           0x0fc19dc68b8cd5b5ULL, 0x240ca1cc77ac9c65ULL, 0x2de92c6f592b0275ULL,
           0x4a7484aa6ea6e483ULL, 0x5cb0a9dcbd41fbd4ULL, 0x76f988da831153b5ULL,
           0x983e5152ee66dfabULL, 0xa831c66d2db43210ULL, 0xb00327c898fb213fULL,
           0xbf597fc7beef0ee4ULL, 0xc6e00bf33da88fc2ULL, 0xd5a79147930aa725ULL,
           0x06ca6351e003826fULL, 0x142929670a0e6e70ULL, 0x27b70a8546d22ffcULL,
           0x2e1b21385c26c926ULL, 0x4d2c6dfc5ac42aedULL, 0x53380d139d95b3dfULL,
           0x650a73548baf63deULL, 0x766a0abb3c77b2a8ULL, 0x81c2c92e47edaee6ULL,
           0x92722c851482353bULL, 0xa2bfe8a14cf10364ULL, 0xa81a664bbc423001ULL,
           0xc24b8b70d0f89791ULL, 0xc76c51a30654be30ULL, 0xd192e819d6ef5218ULL,
           0xd69906245565a910ULL, 0xf40e35855771202aULL, 0x106aa07032bbd1b8ULL,
           0x19a4c116b8d2d0c8ULL, 0x1e376c085141ab53ULL, 0x2748774cdf8eeb99ULL,
           0x34b0bcb5e19b48a8ULL, 0x391c0cb3c5c95a63ULL, 0x4ed8aa4ae3418acbULL,
           0x5b9cca4f7763e373ULL, 0x682e6ff3d6b2b8a3ULL, 0x748f82ee5defb2fcULL,
           0x78a5636f43172f60ULL, 0x84c87814a1f0ab72ULL, 0x8cc702081a6439ecULL,
           0x90befffa23631e28ULL, 0xa4506cebde82bde9ULL, 0xbef9a3f7b2c67915ULL,
           0xc67178f2e372532bULL, 0xca273eceea26619cULL, 0xd186b8c721c0c207ULL,
           0xeada7dd6cde0eb1eULL, 0xf57d4f7fee6ed178ULL, 0x06f067aa72176fbaULL,
           0x0a637dc5a2c898a6ULL, 0x113f9804bef90daeULL, 0x1b710b35131c471bULL,
           0x28db77f523047d84ULL, 0x32caab7b40c72493ULL, 0x3c9ebe0a15c9bebcULL,
           0x431d67c49c100d4cULL, 0x4cc5d4becb3e42b6ULL, 0x597f299cfc657e2aULL,
           0x5fcb6fab3ad6faecULL, 0x6c44198c4a475817ULL};

static uint32_t min(uint32_t x, uint32_t y)
{
	return x < y ? x : y;
}

static void store64(uint64_t x, unsigned char *y)
{
	for (int i = 0; i != 8; ++i)
		y[i] = (x >> ((7 - i) * 8)) & 255;
}

static uint64_t load64(const unsigned char *y)
{
	uint64_t res = 0;
	for (int i = 0; i != 8; ++i)
		res |= (uint64_t)(y[i]) << ((7 - i) * 8);
	return res;
}

static uint64_t Ch(uint64_t x, uint64_t y, uint64_t z)
{
	return z ^ (x & (y ^ z));
}
static uint64_t Maj(uint64_t x, uint64_t y, uint64_t z)
{
	return ((x | y) & z) | (x & y);
}
static uint64_t Rot(uint64_t x, uint64_t n)
{
	return (x >> (n & 63)) | (x << (64 - (n & 63)));
}
static uint64_t Sh(uint64_t x, uint64_t n)
{
	return x >> n;
}
static uint64_t Sigma0(uint64_t x)
{
	return Rot(x, 28) ^ Rot(x, 34) ^ Rot(x, 39);
}
static uint64_t Sigma1(uint64_t x)
{
	return Rot(x, 14) ^ Rot(x, 18) ^ Rot(x, 41);
}
static uint64_t Gamma0(uint64_t x)
{
	return Rot(x, 1) ^ Rot(x, 8) ^ Sh(x, 7);
}
static uint64_t Gamma1(uint64_t x)
{
	return Rot(x, 19) ^ Rot(x, 61) ^ Sh(x, 6);
}
static void RND(
	uint64_t W[], uint64_t *t0, uint64_t *t1, uint64_t a, uint64_t b,
	uint64_t c, uint64_t *d, uint64_t e, uint64_t f, uint64_t g,
	uint64_t *h, uint64_t i)
{
	*t0 = *h + Sigma1(e) + Ch(e, f, g) + K[i] + W[i];
	*t1 = Sigma0(a) + Maj(a, b, c);
	*d += *t0;
	*h = *t0 + *t1;
}

static void sha_compress(struct b_hash_ctx *md, const unsigned char *buf)
{
	uint64_t S[8], W[80], t0, t1;

	// Copy state into S
	for (int i = 0; i < 8; i++) {
		S[i] = md->ctx_state.sha2_512.state[i];
	}

	// Copy the state into 1024-bits into W[0..15]
	for (int i = 0; i < 16; i++) {
		W[i] = load64(buf + (8 * i));
	}

	// Fill W[16..79]
	for (int i = 16; i < 80; i++) {
		W[i] = Gamma1(W[i - 2]) + W[i - 7] + Gamma0(W[i - 15]) + W[i - 16];
	}

	// Compress

	for (int i = 0; i < 80; i += 8) {
		RND(W, &t0, &t1, S[0], S[1], S[2], &S[3], S[4], S[5], S[6],
		    &S[7], i + 0);
		RND(W, &t0, &t1, S[7], S[0], S[1], &S[2], S[3], S[4], S[5],
		    &S[6], i + 1);
		RND(W, &t0, &t1, S[6], S[7], S[0], &S[1], S[2], S[3], S[4],
		    &S[5], i + 2);
		RND(W, &t0, &t1, S[5], S[6], S[7], &S[0], S[1], S[2], S[3],
		    &S[4], i + 3);
		RND(W, &t0, &t1, S[4], S[5], S[6], &S[7], S[0], S[1], S[2],
		    &S[3], i + 4);
		RND(W, &t0, &t1, S[3], S[4], S[5], &S[6], S[7], S[0], S[1],
		    &S[2], i + 5);
		RND(W, &t0, &t1, S[2], S[3], S[4], &S[5], S[6], S[7], S[0],
		    &S[1], i + 6);
		RND(W, &t0, &t1, S[1], S[2], S[3], &S[4], S[5], S[6], S[7],
		    &S[0], i + 7);
	}

	// Feedback
	for (int i = 0; i < 8; i++)
		md->ctx_state.sha2_512.state[i]
			= md->ctx_state.sha2_512.state[i] + S[i];
}

// Public interface

static void sha_init(struct b_hash_ctx *md)
{
	md->ctx_state.sha2_512.curlen = 0;
	md->ctx_state.sha2_512.length = 0;
	md->ctx_state.sha2_512.state[0] = 0x6a09e667f3bcc908ULL;
	md->ctx_state.sha2_512.state[1] = 0xbb67ae8584caa73bULL;
	md->ctx_state.sha2_512.state[2] = 0x3c6ef372fe94f82bULL;
	md->ctx_state.sha2_512.state[3] = 0xa54ff53a5f1d36f1ULL;
	md->ctx_state.sha2_512.state[4] = 0x510e527fade682d1ULL;
	md->ctx_state.sha2_512.state[5] = 0x9b05688c2b3e6c1fULL;
	md->ctx_state.sha2_512.state[6] = 0x1f83d9abfb41bd6bULL;
	md->ctx_state.sha2_512.state[7] = 0x5be0cd19137e2179ULL;
}

void z__b_sha2_512_update(struct b_hash_ctx *md, const void *src, size_t inlen)
{
	const uint32_t block_size = sizeof md->ctx_state.sha2_512.block;
	const unsigned char *in = (const unsigned char *)src;

	while (inlen > 0) {
		if (md->ctx_state.sha2_512.curlen == 0 && inlen >= block_size) {
			sha_compress(md, in);
			md->ctx_state.sha2_512.length += block_size * 8;
			in += block_size;
			inlen -= block_size;
		} else {
			uint32_t n = min(
				inlen,
				(block_size - md->ctx_state.sha2_512.curlen));
			memcpy(md->ctx_state.sha2_512.block
			               + md->ctx_state.sha2_512.curlen,
			       in, n);
			md->ctx_state.sha2_512.curlen += n;
			in += n;
			inlen -= n;

			if (md->ctx_state.sha2_512.curlen == block_size) {
				sha_compress(md, md->ctx_state.sha2_512.block);
				md->ctx_state.sha2_512.length += 8 * block_size;
				md->ctx_state.sha2_512.curlen = 0;
			}
		}
	}
}

void z__b_sha2_512_finish(struct b_hash_ctx *md, void *out, size_t max)
{
	// Increase the length of the message
	md->ctx_state.sha2_512.length += md->ctx_state.sha2_512.curlen * 8ULL;

	// Append the '1' bit
	md->ctx_state.sha2_512.block[md->ctx_state.sha2_512.curlen++] = 0x80;

	// If the length is currently above 112 bytes we append zeros then compress.
	// Then we can fall back to padding zeros and length encoding like normal.
	if (md->ctx_state.sha2_512.curlen > 112) {
		while (md->ctx_state.sha2_512.curlen < 128)
			md->ctx_state.sha2_512.block[md->ctx_state.sha2_512.curlen++]
				= 0;
		sha_compress(md, md->ctx_state.sha2_512.block);
		md->ctx_state.sha2_512.curlen = 0;
	}

	// Pad upto 120 bytes of zeroes
	// note: that from 112 to 120 is the 64 MSB of the length.  We assume
	// that you won't hash 2^64 bits of data... :-)
	while (md->ctx_state.sha2_512.curlen < 120) {
		md->ctx_state.sha2_512.block[md->ctx_state.sha2_512.curlen++] = 0;
	}

	// Store length
	store64(md->ctx_state.sha2_512.length, md->ctx_state.sha2_512.block + 120);
	sha_compress(md, md->ctx_state.sha2_512.block);

	unsigned char digest[B_DIGEST_LENGTH_SHA2_512];

	// Copy output
	for (int i = 0; i < 8; i++) {
		store64(md->ctx_state.sha2_512.state[i],
		        (unsigned char *)&digest[(8 * i)]);
	}

	memcpy(out, digest, b_min(size_t, sizeof digest, max));
}

struct b_hash_function_ops z__b_sha2_512_ops = {
	.hash_init = sha_init,
	.hash_update = z__b_sha2_512_update,
	.hash_finish = z__b_sha2_512_finish,
};