/*
MIT License

Copyright (c) 2021 Jérémy LAMBERT (SystemGlitch)

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

#ifndef SHA256_H
#define SHA256_H

#include <string>
#include <array>

class SHA256 {

public:
    SHA256();
    void update(const uint8_t * data, size_t length);
    void update(const std::string &data);
    uint8_t * digest();

    static std::string toString(const uint8_t * digest);

private:
    uint8_t  m_data[64];
    uint32_t m_blocklen;
    uint64_t m_bitlen;
    uint32_t m_state[8]; //A, B, C, D, E, F, G, H

    static constexpr std::array<uint32_t, 64> K = {
        0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,
        0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
        0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,
        0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
        0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,
        0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
        0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,
        0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
        0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,
        0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
        0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,
        0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
        0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,
        0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
        0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,
        0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
    };

    static uint32_t rotr(uint32_t x, uint32_t n);
    static uint32_t choose(uint32_t e, uint32_t f, uint32_t g);
    static uint32_t majority(uint32_t a, uint32_t b, uint32_t c);
    static uint32_t sig0(uint32_t x);
    static uint32_t sig1(uint32_t x);
    void transform();
    void pad();
    void revert(uint8_t * hash);
};

#endif // SHA256_H
