// Copyright 2010 Complete Genomics, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you
// may not use this file except in compliance with the License. You
// may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.

// Adapted based on http://www.fourmilab.ch/md5/ on Jan 21, 2010. In
// md5.c at that URL, it says:
//
// "This code implements the MD5 message-digest algorithm.  The
// algorithm is due to Ron Rivest. This code was written by Colin Plumb
// in 1993, no copyright is claimed.  This code is in the public domain;
// do with it what you wish."
//
// "Equivalent code is available from RSA Data Security, Inc.  This code
// has been tested against that, and is equivalent, except that you
// don't need to include two pages of legalese with every copy."

#include "cgatools/core.hpp"
#include "cgatools/util/Exception.hpp"
#include "cgatools/util/Md5.hpp"
#include <boost/detail/endian.hpp>
#include <stdio.h>
#include <string.h>

namespace cgatools { namespace util {

    Md5Digest::Md5Digest()
    {
        digest_.assign(0);
    }
    
    Md5Digest::Md5Digest(const void* val)
    {
        set(val);
    }
    
    void Md5Digest::set(const void* vval)
    {
        const uint8_t* val = reinterpret_cast<const uint8_t*>(vval);
        std::copy(val, val+16, digest_.begin());
    }

    const void* Md5Digest::data() const
    {
        return digest_.data();
    }

    std::string Md5Digest::hex() const
    {
        char buf[33];
        for (size_t ii=0; ii<digest_.size(); ii++)
            sprintf(buf+ii*2, "%02x", digest_[ii]);
        buf[32]=0;
        return std::string(buf);
    }

    bool operator==(const Md5Digest& lhs, const Md5Digest& rhs)
    {
        return 0 == memcmp(lhs.data(), rhs.data(), lhs.size());
    }

#if defined(BOOST_LITTLE_ENDIAN)
    #define byteReverse(buf, len) (void(0)) /* Nothing */
#elif defined(BOOST_BIG_ENDIAN)
    /*
     * Note: this code is harmless on little-endian machines.
     */
    void byteReverse(unsigned char* buf, unsigned longs)
        {
            uint32_t t;
            do {
                t = (uint32_t) ((unsigned) buf[3] << 8 | buf[2]) << 16 |
                    ((unsigned) buf[1] << 8 | buf[0]);
                *(uint32_t *) buf = t;
                buf += 4;
            } while (--longs);
        }
#else
    #error failed to detect byte order
#endif

    Md5Context::Md5Context()
    {
        init();
    }

    void Md5Context::init()
    {
        buf_[0] = 0x67452301;
        buf_[1] = 0xefcdab89;
        buf_[2] = 0x98badcfe;
        buf_[3] = 0x10325476;

        bits_.assign(0);
    }

    void Md5Context::update(const void *vbuf, size_t length)
    {
        const uint8_t* buf = reinterpret_cast<const uint8_t*>(vbuf);

        /* Update bitcount */

        uint32_t t = bits_[0];
        if ((bits_[0] = t + ((uint32_t) length << 3)) < t)
            bits_[1]++;         /* Carry from low to high */
        bits_[1] += length >> 29;

        t = (t >> 3) & 0x3f;    /* Bytes already in shsInfo->data */

        /* Handle any leading odd-sized chunks */

        if (t) {
            unsigned char *p = (unsigned char *) in_.c_array() + t;

            t = 64 - t;
            if (length < t) {
                memcpy(p, buf, length);
                return;
            }
            memcpy(p, buf, t);
            byteReverse(in_, 16);
            transform();
            buf += t;
            length -= t;
        }
        /* Process data in 64-byte chunks */

        while (length >= 64) {
            memcpy(in_.c_array(), buf, 64);
            byteReverse(in_, 16);
            transform();
            buf += 64;
            length -= 64;
        }

        /* Handle any remaining bytes of data. */

        memcpy(in_.c_array(), buf, length);
    }

    Md5Digest Md5Context::getDigest() const
    {
        Md5Context context(*this);
        context.final();
        return Md5Digest(&context.buf_[0]);
    }

    std::string Md5Context::hexDigest() const
    {
        return getDigest().hex();
    }

    void Md5Context::final()
    {
        unsigned count;
        unsigned char *p;

        /* Compute number of bytes mod 64 */
        count = (bits_[0] >> 3) & 0x3F;

        /* Set the first char of padding to 0x80.  This is safe since there is
           always at least one byte free */
        p = in_.c_array() + count;
        *p++ = 0x80;

        /* Bytes of padding needed to make 64 bytes */
        count = 64 - 1 - count;

        /* Pad out to 56 mod 64 */
        if (count < 8) {
            /* Two lots of padding:  Pad the first block to 64 bytes */
            memset(p, 0, count);
            byteReverse(in_, 16);
            transform();

            /* Now fill the next block with 56 bytes */
            memset(in_.c_array(), 0, 56);
        } else {
            /* Pad block to 56 bytes */
            memset(p, 0, count - 8);
        }
        byteReverse(in_, 14);

        /* Append length in bits and transform */
        ((uint32_t *) in_.c_array())[14] = bits_[0];
        ((uint32_t *) in_.c_array())[15] = bits_[1];

        transform();
        byteReverse((unsigned char *) buf_, 4);
    }

    /* The four core functions - F1 is optimized somewhat */

    /* #define F1(x, y, z) (x & y | ~x & z) */
    #define F1(x, y, z) (z ^ (x & (y ^ z)))
    #define F2(x, y, z) F1(z, x, y)
    #define F3(x, y, z) (x ^ y ^ z)
    #define F4(x, y, z) (y ^ (x | ~z))

    /* This is the central step in the MD5 algorithm. */
    #define MD5STEP(f, w, x, y, z, data, s) \
        ( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )

    /*
     * The core of the MD5 algorithm, this alters an existing MD5 hash to
     * reflect the addition of 16 longwords of new data.  MD5Update blocks
     * the data and converts bytes into longwords for this routine.
     */
    void Md5Context::transform()
    {
        uint32_t* in = reinterpret_cast<uint32_t*>(in_.c_array());
        register uint32_t a, b, c, d;

        a = buf_[0];
        b = buf_[1];
        c = buf_[2];
        d = buf_[3];

        MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
        MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
        MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
        MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
        MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
        MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
        MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
        MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
        MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
        MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
        MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
        MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
        MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
        MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
        MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
        MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);

        MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
        MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
        MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
        MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
        MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
        MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
        MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
        MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
        MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
        MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
        MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
        MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
        MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
        MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
        MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
        MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);

        MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
        MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
        MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
        MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
        MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
        MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
        MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
        MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
        MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
        MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
        MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
        MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
        MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
        MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
        MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
        MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);

        MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
        MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
        MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
        MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
        MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
        MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
        MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
        MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
        MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
        MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
        MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
        MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
        MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
        MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
        MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
        MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);

        buf_[0] += a;
        buf_[1] += b;
        buf_[2] += c;
        buf_[3] += d;
    }

} } // cgatools::util
