/************************************************************************
 ************************************************************************
    FAUST compiler
    Copyright (C) 2021 GRAME, Centre National de Creation Musicale
    ---------------------------------------------------------------------
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2.1 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 ************************************************************************
 ************************************************************************/

#ifndef SHA_KEY_H
#define SHA_KEY_H

#include <stdint.h>

#include "faust/export.h"

/*
 SHA-1 in C (see: https://github.com/clibs/sha1/blob/master/sha1.h)
 By Steve Reid <steve@edmweb.com>
 100% Public Domain
 */

#define SHA1HANDSOFF

typedef struct {
    uint32_t      state[5];
    uint32_t      count[2];
    unsigned char buffer[64];
} SHA1_CTX;

#define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))

/* blk0() and blk() perform the initial expand. */
/* I got the idea of expanding during the round function from SSLeay */
#if BYTE_ORDER == LITTLE_ENDIAN
#define blk0(i) \
    (block->l[i] = (rol(block->l[i], 24) & 0xFF00FF00) | (rol(block->l[i], 8) & 0x00FF00FF))
#elif BYTE_ORDER == BIG_ENDIAN
#define blk0(i) block->l[i]
#else
#error "Endianness not defined!"
#endif
#define blk(i)                                                                 \
    (block->l[i & 15] = rol(block->l[(i + 13) & 15] ^ block->l[(i + 8) & 15] ^ \
                                block->l[(i + 2) & 15] ^ block->l[i & 15],     \
                            1))

/* (R0+R1), R2, R3, R4 are the different operations used in SHA1 */
#define R0(v, w, x, y, z, i)                                     \
    z += ((w & (x ^ y)) ^ y) + blk0(i) + 0x5A827999 + rol(v, 5); \
    w = rol(w, 30);
#define R1(v, w, x, y, z, i)                                    \
    z += ((w & (x ^ y)) ^ y) + blk(i) + 0x5A827999 + rol(v, 5); \
    w = rol(w, 30);
#define R2(v, w, x, y, z, i)                            \
    z += (w ^ x ^ y) + blk(i) + 0x6ED9EBA1 + rol(v, 5); \
    w = rol(w, 30);
#define R3(v, w, x, y, z, i)                                          \
    z += (((w | x) & y) | (w & x)) + blk(i) + 0x8F1BBCDC + rol(v, 5); \
    w = rol(w, 30);
#define R4(v, w, x, y, z, i)                            \
    z += (w ^ x ^ y) + blk(i) + 0xCA62C1D6 + rol(v, 5); \
    w = rol(w, 30);

/* Hash a single 512-bit block. This is the core of the algorithm. */
inline void SHA1Transform(uint32_t state[5], const unsigned char buffer[64])
{
    uint32_t a, b, c, d, e;

    typedef union {
        unsigned char c[64];
        uint32_t      l[16];
    } CHAR64LONG16;

#ifdef SHA1HANDSOFF
    CHAR64LONG16 block[1]; /* use array to appear as a pointer */
    memcpy(block, buffer, 64);
#else
    /* The following had better never be used because it causes the
     * pointer-to-const buffer to be cast into a pointer to non-const.
     * And the result is written through. I threw a "const" in, hoping
     * this will cause a diagnostic.
     */
    CHAR64LONG16* block = (const CHAR64LONG16*)buffer;
#endif
    /* Copy context->state[] to working vars */
    a = state[0];
    b = state[1];
    c = state[2];
    d = state[3];
    e = state[4];
    /* 4 rounds of 20 operations each. Loop unrolled. */
    R0(a, b, c, d, e, 0);
    R0(e, a, b, c, d, 1);
    R0(d, e, a, b, c, 2);
    R0(c, d, e, a, b, 3);
    R0(b, c, d, e, a, 4);
    R0(a, b, c, d, e, 5);
    R0(e, a, b, c, d, 6);
    R0(d, e, a, b, c, 7);
    R0(c, d, e, a, b, 8);
    R0(b, c, d, e, a, 9);
    R0(a, b, c, d, e, 10);
    R0(e, a, b, c, d, 11);
    R0(d, e, a, b, c, 12);
    R0(c, d, e, a, b, 13);
    R0(b, c, d, e, a, 14);
    R0(a, b, c, d, e, 15);
    R1(e, a, b, c, d, 16);
    R1(d, e, a, b, c, 17);
    R1(c, d, e, a, b, 18);
    R1(b, c, d, e, a, 19);
    R2(a, b, c, d, e, 20);
    R2(e, a, b, c, d, 21);
    R2(d, e, a, b, c, 22);
    R2(c, d, e, a, b, 23);
    R2(b, c, d, e, a, 24);
    R2(a, b, c, d, e, 25);
    R2(e, a, b, c, d, 26);
    R2(d, e, a, b, c, 27);
    R2(c, d, e, a, b, 28);
    R2(b, c, d, e, a, 29);
    R2(a, b, c, d, e, 30);
    R2(e, a, b, c, d, 31);
    R2(d, e, a, b, c, 32);
    R2(c, d, e, a, b, 33);
    R2(b, c, d, e, a, 34);
    R2(a, b, c, d, e, 35);
    R2(e, a, b, c, d, 36);
    R2(d, e, a, b, c, 37);
    R2(c, d, e, a, b, 38);
    R2(b, c, d, e, a, 39);
    R3(a, b, c, d, e, 40);
    R3(e, a, b, c, d, 41);
    R3(d, e, a, b, c, 42);
    R3(c, d, e, a, b, 43);
    R3(b, c, d, e, a, 44);
    R3(a, b, c, d, e, 45);
    R3(e, a, b, c, d, 46);
    R3(d, e, a, b, c, 47);
    R3(c, d, e, a, b, 48);
    R3(b, c, d, e, a, 49);
    R3(a, b, c, d, e, 50);
    R3(e, a, b, c, d, 51);
    R3(d, e, a, b, c, 52);
    R3(c, d, e, a, b, 53);
    R3(b, c, d, e, a, 54);
    R3(a, b, c, d, e, 55);
    R3(e, a, b, c, d, 56);
    R3(d, e, a, b, c, 57);
    R3(c, d, e, a, b, 58);
    R3(b, c, d, e, a, 59);
    R4(a, b, c, d, e, 60);
    R4(e, a, b, c, d, 61);
    R4(d, e, a, b, c, 62);
    R4(c, d, e, a, b, 63);
    R4(b, c, d, e, a, 64);
    R4(a, b, c, d, e, 65);
    R4(e, a, b, c, d, 66);
    R4(d, e, a, b, c, 67);
    R4(c, d, e, a, b, 68);
    R4(b, c, d, e, a, 69);
    R4(a, b, c, d, e, 70);
    R4(e, a, b, c, d, 71);
    R4(d, e, a, b, c, 72);
    R4(c, d, e, a, b, 73);
    R4(b, c, d, e, a, 74);
    R4(a, b, c, d, e, 75);
    R4(e, a, b, c, d, 76);
    R4(d, e, a, b, c, 77);
    R4(c, d, e, a, b, 78);
    R4(b, c, d, e, a, 79);
    /* Add the working vars back into context.state[] */
    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
    state[4] += e;
    /* Wipe variables */
    a = b = c = d = e = 0;
#ifdef SHA1HANDSOFF
    memset(block, '\0', sizeof(block));
#endif
}

/* SHA1Init - Initialize new context */
inline void SHA1Init(SHA1_CTX* context)
{
    /* SHA1 initialization constants */
    context->state[0] = 0x67452301;
    context->state[1] = 0xEFCDAB89;
    context->state[2] = 0x98BADCFE;
    context->state[3] = 0x10325476;
    context->state[4] = 0xC3D2E1F0;
    context->count[0] = context->count[1] = 0;
}

/* Run your data through this. */
inline void SHA1Update(SHA1_CTX* context, const unsigned char* data, uint32_t len)
{
    uint32_t i;
    uint32_t j;

    j = context->count[0];
    if ((context->count[0] += len << 3) < j) {
        context->count[1]++;
    }
    context->count[1] += (len >> 29);
    j = (j >> 3) & 63;
    if ((j + len) > 63) {
        memcpy(&context->buffer[j], data, (i = 64 - j));
        SHA1Transform(context->state, context->buffer);
        for (; i + 63 < len; i += 64) {
            SHA1Transform(context->state, &data[i]);
        }
        j = 0;
    } else {
        i = 0;
    }
    memcpy(&context->buffer[j], &data[i], len - i);
}

/* Add padding and return the message digest. */
void SHA1Final(unsigned char digest[20], SHA1_CTX* context)
{
    unsigned      i;
    unsigned char finalcount[8];
    unsigned char c;

#if 0 /* untested "improvement" by DHR */
    /* Convert context->count to a sequence of bytes
     * in finalcount.  Second element first, but
     * big-endian order within element.
     * But we do it all backwards.
     */
    unsigned char* fcp = &finalcount[8];
    
    for (i = 0; i < 2; i++) {
        uint32_t t = context->count[i];
        int j;
        for (j = 0; j < 4; t >>= 8, j++) {
            *--fcp = (unsigned char)t
        }
    }
#else
    for (i = 0; i < 8; i++) {
        finalcount[i] = (unsigned char)((context->count[(i >= 4 ? 0 : 1)] >> ((3 - (i & 3)) * 8)) &
                                        255); /* Endian independent */
    }
#endif
    c = 0200;
    SHA1Update(context, &c, 1);
    while ((context->count[0] & 504) != 448) {
        c = 0000;
        SHA1Update(context, &c, 1);
    }
    SHA1Update(context, finalcount, 8); /* Should cause a SHA1Transform() */
    for (i = 0; i < 20; i++) {
        digest[i] = (unsigned char)((context->state[i >> 2] >> ((3 - (i & 3)) * 8)) & 255);
    }
    /* Wipe variables */
    memset(context, '\0', sizeof(*context));
    memset(&finalcount, '\0', sizeof(finalcount));
}

inline void SHA1(char* hash_out, const char* str, unsigned int len)
{
    SHA1_CTX ctx;
    SHA1Init(&ctx);
    for (unsigned int ii = 0; ii < len; ii += 1) {
        SHA1Update(&ctx, (const unsigned char*)str + ii, 1);
    }
    SHA1Final((unsigned char*)hash_out, &ctx);
}

// External C++ libfaust API

LIBFAUST_API std::string generateSHA1(const std::string& data)
{
    SHA1_CTX      ctx;
    unsigned char obuf[20] = {0};

    SHA1Init(&ctx);
    SHA1Update(&ctx, (unsigned char const*)data.c_str(), data.size());
    SHA1Final(obuf, &ctx);

    std::string sha_key;
    for (int i = 0; i < 20; i++) {
        const char* H  = "0123456789ABCDEF";
        char        c1 = H[(obuf[i] >> 4)];
        char        c2 = H[(obuf[i] & 15)];
        sha_key += c1;
        sha_key += c2;
    }

    return sha_key;
}

// External C libfaust API

extern "C" FAUST_API void generateCSHA1(const char* data, char* sha_key)
{
    SHA1_CTX      ctx;
    unsigned char obuf[20] = {0};

    SHA1Init(&ctx);
    SHA1Update(&ctx, (unsigned char const*)data, strlen(data));
    SHA1Final(obuf, &ctx);

    // convert SHA1 key into hexadecimal string
    for (int i = 0; i < 20; i++) {
        const char* H  = "0123456789ABCDEF";
        char        c1 = H[(obuf[i] >> 4)];
        char        c2 = H[(obuf[i] & 15)];

        *sha_key = c1;
        sha_key++;
        *sha_key = c2;
        sha_key++;
    }
    *sha_key = '\0';  // Null terminate the string
}

#endif
