#include<hgl/util/hash/Hash.h>

namespace hgl
{
    namespace util
    {
        namespace
        {
            #define ROTLEFT(a,b) (((a) << (b)) | ((a) >> (32-(b))))
            #define ROTRIGHT(a,b) (((a) >> (b)) | ((a) << (32-(b))))

            #define CH(x,y,z) (((x) & (y)) ^ (~(x) & (z)))
            #define MAJ(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
            #define EP0(x) (ROTRIGHT(x,2) ^ ROTRIGHT(x,13) ^ ROTRIGHT(x,22))
            #define EP1(x) (ROTRIGHT(x,6) ^ ROTRIGHT(x,11) ^ ROTRIGHT(x,25))
            #define SIG0(x) (ROTRIGHT(x,7) ^ ROTRIGHT(x,18) ^ ((x) >> 3))
            #define SIG1(x) (ROTRIGHT(x,17) ^ ROTRIGHT(x,19) ^ ((x) >> 10))

            /**************************** VARIABLES *****************************/
            constexpr uint32 k[64] =
            {
                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
            };
        }//namespace

        class SHA256:public Hash
        {
            enum
            {
                BLOCK_SIZE  = 64,
                DIGEST_SIZE = 32
            };

            uint32 state[8];
            uint8 data[64];  // SHA data buffer
            uint64 bitlen;
            uint32 datalen;

            uint32 m[64];

        private:

            void sha256_transform()
            {
                uint32 a, b, c, d, e, f, g, h, i, j, t1, t2;

                for (i = 0, j = 0; i < 16; ++i, j += 4)
                    m[i] = (data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]);

                for ( ; i < 64; ++i)
                    m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];

                a = state[0];
                b = state[1];
                c = state[2];
                d = state[3];
                e = state[4];
                f = state[5];
                g = state[6];
                h = state[7];

                for (i = 0; i < 64; ++i) {
                    t1 = h + EP1(e) + CH(e,f,g) + k[i] + m[i];
                    t2 = EP0(a) + MAJ(a,b,c);
                    h = g;
                    g = f;
                    f = e;
                    e = d + t1;
                    d = c;
                    c = b;
                    b = a;
                    a = t1 + t2;
                }

                state[0] += a;
                state[1] += b;
                state[2] += c;
                state[3] += d;
                state[4] += e;
                state[5] += f;
                state[6] += g;
                state[7] += h;
            }

        public:

            SHA256():Hash(DIGEST_SIZE,"SHA256"){}

            void Init()override
            {
                state[0] = 0x6a09e667;
                state[1] = 0xbb67ae85;
                state[2] = 0x3c6ef372;
                state[3] = 0xa54ff53a;
                state[4] = 0x510e527f;
                state[5] = 0x9b05688c;
                state[6] = 0x1f83d9ab;
                state[7] = 0x5be0cd19;

                bitlen=0;
                datalen=0;
                memset(data, 0, sizeof(data));
            }

            void Update(const void *input,uint count)override
            {
                const uint8 *u8input=(const uint8 *)input;
                uint32 size;

                while(count>0)
                {
                    size=BLOCK_SIZE-datalen;

                    if(size>count)
                        size=count;

                    memcpy(data+datalen,u8input,size);
                    datalen+=size;
                    count-=size;
                    u8input+=size;

                    if (datalen == BLOCK_SIZE)
                    {
                        sha256_transform();
                        bitlen += 512;
                        datalen = 0;
                    }
                }
            }

            void Final(void *result)override
            {
                uint32 i;

                i = datalen;

                // Pad whatever data is left in the buffer.
                if (datalen < 56)
                {
                    data[i++] = 0x80;

                    memset(data+i,0,56-i);
                }
                else
                {
                    data[i++] = 0x80;

                    memset(data+i,0,64-i);

                    sha256_transform();
                    memset(data, 0, 56);
                }

                // Append to the padding the total message's length in bits and transform.
                bitlen += datalen * 8;
                data[63] = bitlen;
                data[62] = bitlen >> 8;
                data[61] = bitlen >> 16;
                data[60] = bitlen >> 24;
                data[59] = bitlen >> 32;
                data[58] = bitlen >> 40;
                data[57] = bitlen >> 48;
                data[56] = bitlen >> 56;
                sha256_transform();

                // Since this implementation uses little endian byte ordering and SHA uses big endian,
                // reverse all the bytes when copying the final state to the output hash.

                uint8 *hash=(uint8 *)result;

                for (i = 0; i < 4; ++i)
                {
                    hash[i]      = (state[0] >> (24 - i * 8)) & 0x000000ff;
                    hash[i + 4]  = (state[1] >> (24 - i * 8)) & 0x000000ff;
                    hash[i + 8]  = (state[2] >> (24 - i * 8)) & 0x000000ff;
                    hash[i + 12] = (state[3] >> (24 - i * 8)) & 0x000000ff;
                    hash[i + 16] = (state[4] >> (24 - i * 8)) & 0x000000ff;
                    hash[i + 20] = (state[5] >> (24 - i * 8)) & 0x000000ff;
                    hash[i + 24] = (state[6] >> (24 - i * 8)) & 0x000000ff;
                    hash[i + 28] = (state[7] >> (24 - i * 8)) & 0x000000ff;
                }
            }
        };//class SHA256

        template<> Hash *CreateHash<HASH::SHA256>()
        {
            return(new SHA256);
        }
    }//namespace util
}//namespace hgl