#include "md5calc.hpp"

#include <cstring>

#include "../strings/xstring.hpp"
#include "../strings/vstring.hpp"

#include "../io/read.hpp"

#include "cxxstdio.hpp"
#include "random.hpp"
#include "utils.hpp"

#include "../poison.hpp"

// auxilary data
/*
sin() constant table
# Reformatted output of:
echo 'scale=40; obase=16; for (i=1;i<=64;i++) print 2^32 * sin(i), "\n"' |
bc | sed 's/^-//;s/^/0x/;s/\..*$/,/'
*/
static
const uint32_t T[64] =
{
    // used by round 1
    0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, //0
    0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, //4
    0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be, //8
    0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821, //12
    // used by round 2
    0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa, //16
    0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8, //20
    0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, //24
    0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a, //28
    // used by round 3
    0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c, //32
    0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, //36
    0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05, //40
    0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665, //44
    // used by round 4
    0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, //48
    0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1, //52
    0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1, //56
    0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391, //60
};

// auxilary functions
// note - the RFC defines these by non-CS conventions: or=v, and=(empty)
static
uint32_t rotate_left(uint32_t val, unsigned shift)
{
    return val << shift | val >> (32 - shift);
}

static
uint32_t F(uint32_t X, uint32_t Y, uint32_t Z)
{
    return (X & Y) | (~X & Z);
}
static
uint32_t G(uint32_t X, uint32_t Y, uint32_t Z)
{
    return (X & Z) | (Y & ~Z);
}
static
uint32_t H(uint32_t X, uint32_t Y, uint32_t Z)
{
    return X ^ Y ^ Z;
}
static
uint32_t I(uint32_t X, uint32_t Y, uint32_t Z)
{
    return Y ^ (X | ~Z);
}

static
const struct
{
    uint8_t k : 4;
    uint8_t : 0;
    uint8_t s : 5;
//    uint8_t i : 6; just increments constantly, from 1 .. 64 over all rounds
}
MD5_round1[16] =
{
    { 0,  7}, { 1, 12}, { 2, 17}, { 3, 22},
    { 4,  7}, { 5, 12}, { 6, 17}, { 7, 22},
    { 8,  7}, { 9, 12}, {10, 17}, {11, 22},
    {12,  7}, {13, 12}, {14, 17}, {15, 22},
},
MD5_round2[16] =
{
    { 1,  5}, { 6,  9}, {11, 14}, { 0, 20},
    { 5,  5}, {10,  9}, {15, 14}, { 4, 20},
    { 9,  5}, {14,  9}, { 3, 14}, { 8, 20},
    {13,  5}, { 2,  9}, { 7, 14}, {12, 20},
},
MD5_round3[16] =
{
    { 5,  4}, { 8, 11}, {11, 16}, {14, 23},
    { 1,  4}, { 4, 11}, { 7, 16}, {10, 23},
    {13,  4}, { 0, 11}, { 3, 16}, { 6, 23},
    { 9,  4}, {12, 11}, {15, 16}, { 2, 23},
},
MD5_round4[16] =
{
    { 0,  6}, { 7, 10}, {14, 15}, { 5, 21},
    {12,  6}, { 3, 10}, {10, 15}, { 1, 21},
    { 8,  6}, {15, 10}, { 6, 15}, {13, 21},
    { 4,  6}, {11, 10}, { 2, 15}, { 9, 21},
};


void MD5_init(MD5_state* state)
{
    // in the RFC, these are specified as bytes, interpreted as little-endian
    state->val[0] = 0x67452301;
    state->val[1] = 0xEFCDAB89;
    state->val[2] = 0x98BADCFE;
    state->val[3] = 0x10325476;
}

void MD5_do_block(MD5_state* state, MD5_block block)
{
#define X block.data
#define a state->val[(16 - i) % 4]
#define b state->val[(17 - i) % 4]
#define c state->val[(18 - i) % 4]
#define d state->val[(19 - i) % 4]
    // save the values
    const MD5_state saved = *state;
    // round 1
    for (int i = 0; i < 16; i++)
    {
#define k MD5_round1[i].k
#define s MD5_round1[i].s
        a = b + rotate_left(a + F(b, c, d) + X[k] + T[i + 0x0], s);
#undef k
#undef s
    }
    // round 2
    for (int i = 0; i < 16; i++)
    {
#define k MD5_round2[i].k
#define s MD5_round2[i].s
        a = b + rotate_left(a + G(b, c, d) + X[k] + T[i + 0x10], s);
#undef k
#undef s
    }
    // round 3
    for (int i = 0; i < 16; i++)
    {
#define k MD5_round3[i].k
#define s MD5_round3[i].s
        a = b + rotate_left(a + H(b, c, d) + X[k] + T[i + 0x20], s);
#undef k
#undef s
    }
    // round 4
    for (int i = 0; i < 16; i++)
    {
#define k MD5_round4[i].k
#define s MD5_round4[i].s
        a = b + rotate_left(a + I(b, c, d) + X[k] + T[i + 0x30], s);
#undef k
#undef s
    }
    // adjust state based on original
    state->val[0] += saved.val[0];
    state->val[1] += saved.val[1];
    state->val[2] += saved.val[2];
    state->val[3] += saved.val[3];
#undef a
#undef b
#undef c
#undef d
}

void MD5_to_bin(MD5_state state, md5_binary& out)
{
    for (int i = 0; i < 0x10; i++)
        out[i] = state.val[i / 4] >> 8 * (i % 4);
}

static
const char hex[] = "0123456789abcdef";

void MD5_to_str(MD5_state state, md5_string& out_)
{
    md5_binary bin;
    MD5_to_bin(state, bin);
    char out[0x20];
    for (int i = 0; i < 0x10; i++)
        out[2 * i] = hex[bin[i] >> 4],
        out[2 * i + 1] = hex[bin[i] & 0xf];
    out_ = stringish<md5_string>(XString(out, out + 0x20, nullptr));
}

MD5_state MD5_from_string(XString msg)
{
    MD5_state state;
    MD5_init(&state);
    MD5_block block;
    const uint64_t msg_full_len = msg.size();
    while (msg.size() >= 64)
    {
        for (int i = 0; i < 0x10; i++)
            X[i] = msg[4 * i + 0] | msg[4 * i + 1] << 8 | msg[4 * i + 2] << 16 | msg[4 * i + 3] << 24;
        MD5_do_block(&state, block);
        msg = msg.xslice_t(64);
    }
    // now pad 1-512 bits + the 64-bit length - may be two blocks
    uint8_t buf[0x40] = {};
    really_memcpy(buf, reinterpret_cast<const uint8_t *>(msg.data()), msg.size());
    buf[msg.size()] = 0x80; // a single one bit
    if (64 - msg.size() > 8)
    {
        for (int i = 0; i < 8; i++)
            buf[0x38 + i] = (msg_full_len * 8) >> (i * 8);
    }
    for (int i = 0; i < 0x10; i++)
        X[i] = buf[4 * i + 0] | buf[4 * i + 1] << 8 | buf[4 * i + 2] << 16 | buf[4 * i + 3] << 24;
    MD5_do_block(&state, block);
    if (64 - msg.size() <= 8)
    {
        really_memset0(buf, 0x38);
        for (int i = 0; i < 8; i++)
            buf[0x38 + i] = (msg_full_len * 8) >> (i * 8);
        for (int i = 0; i < 0x10; i++)
            X[i] = buf[4 * i + 0] | buf[4 * i + 1] << 8 | buf[4 * i + 2] << 16 | buf[4 * i + 3] << 24;
        MD5_do_block(&state, block);
    }
    return state;
}

// TODO - refactor MD5 into a stream, and merge the implementations
// I once implemented an ostream that does it ...
MD5_state MD5_from_FILE(io::ReadFile& in)
{
    uint64_t total_len = 0;

    uint8_t buf[0x40];
    uint8_t block_len = 0;

    MD5_state state;
    MD5_init(&state);

    MD5_block block;

    while (true)
    {
        size_t rv = in.get(sign_cast<char *>(buf + block_len), 0x40 - block_len);
        if (!rv)
            break;
        total_len += 8 * rv; // in bits
        block_len += rv;
        if (block_len != 0x40)
            continue;
        for (int i = 0; i < 0x10; i++)
            X[i] = buf[4 * i + 0] | buf[4 * i + 1] << 8 | buf[4 * i + 2] << 16 | buf[4 * i + 3] << 24;
        MD5_do_block(&state, block);
        block_len = 0;
    }
    // no more input, just pad and append the length
    buf[block_len] = 0x80;
    really_memset0(buf + block_len + 1, 0x40 - block_len - 1);
    if (block_len < 0x38)
    {
        for (int i = 0; i < 8; i++)
            buf[0x38 + i] = total_len >> i * 8;
    }
    for (int i = 0; i < 0x10; i++)
        X[i] = buf[4 * i + 0] | buf[4 * i + 1] << 8 | buf[4 * i + 2] << 16 | buf[4 * i + 3] << 24;
    MD5_do_block(&state, block);
    if (0x38 <= block_len)
    {
        really_memset0(buf, 0x38);
        for (int i = 0; i < 8; i++)
            buf[0x38 + i] = total_len >> i * 8;
        for (int i = 0; i < 0x10; i++)
            X[i] = buf[4 * i + 0] | buf[4 * i + 1] << 8 | buf[4 * i + 2] << 16 | buf[4 * i + 3] << 24;
        MD5_do_block(&state, block);
    }
    return state;
}


// Hash a password with a salt.
// Whoever wrote this FAILS programming
AccountCrypt MD5_saltcrypt(AccountPass key, SaltString salt)
{
    char cbuf[64] {};

    // hash the key then the salt
    // buf ends up as a 64-char NUL-terminated string
    md5_string tbuf, tbuf2;
    MD5_to_str(MD5_from_string(key), tbuf);
    MD5_to_str(MD5_from_string(salt), tbuf2);
    const auto it = std::copy(tbuf.begin(), tbuf.end(), std::begin(cbuf));
    auto it2 = std::copy(tbuf2.begin(), tbuf2.end(), it);
    assert(it2 == std::end(cbuf));

    md5_string tbuf3;
    MD5_to_str(MD5_from_string(XString(std::begin(cbuf), it2, nullptr)), tbuf3);

    VString<31> obuf;

    // This truncates the string, but we have to keep it like that for compatibility
    SNPRINTF(obuf, 32, "!%s$%s", salt, tbuf3);
    return stringish<AccountCrypt>(obuf);
}

SaltString make_salt(void)
{
    char salt[5];
    for (int i = 0; i < 5; i++)
        // 126 would probably actually be okay
        salt[i] = random_::in(48, 125);
    return stringish<SaltString>(XString(salt + 0, salt + 5, nullptr));
}

bool pass_ok(AccountPass password, AccountCrypt crypted)
{
    // crypted is like !salt$hash
    auto begin = crypted.begin() + 1;
    auto end = std::find(begin, crypted.end(), '$');
    SaltString salt = stringish<SaltString>(crypted.xislice(begin, end));

    return crypted == MD5_saltcrypt(password, salt);
}

// [M|h]ashes up an IP address and a secret key
// to return a hopefully unique masked IP.
IP4Address MD5_ip(IP4Address ip)
{
    static SaltString secret = make_salt();

    // MD5sum a secret + the IP address
    VString<31> ipbuf;
    SNPRINTF(ipbuf, 32, "%s %s", ip, secret);
    md5_binary obuf;
    MD5_to_bin(MD5_from_string(ipbuf), obuf);

    // Fold the md5sum to 32 bits, pack the bytes to an in_addr
    return IP4Address({
            static_cast<uint8_t>(obuf[0] ^ obuf[1] ^ obuf[8] ^ obuf[9]),
            static_cast<uint8_t>(obuf[2] ^ obuf[3] ^ obuf[10] ^ obuf[11]),
            static_cast<uint8_t>(obuf[4] ^ obuf[5] ^ obuf[12] ^ obuf[13]),
            static_cast<uint8_t>(obuf[6] ^ obuf[7] ^ obuf[14] ^ obuf[15]),
    });
}