// SHA256 block step.
// In its own file so that a faster assembly or C version
// can be substituted easily.

const K: [u32; 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,
];

const CHUNK: usize = 64;

pub fn block_generic<const N: usize, const IS_224: bool>(
    dig: &mut super::Sha256<N, IS_224>,
    mut p: &[u8],
) {
    let mut w = [0u32; 64];
    let (mut h0, mut h1, mut h2, mut h3, mut h4, mut h5, mut h6, mut h7) = (
        dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4], dig.h[5], dig.h[6], dig.h[7],
    );

    while p.len() >= CHUNK {
        // Can interlace the computation of w with the
        // rounds below if needed for speed.
        (0..16).for_each(|i| {
            let j = i * 4;
            w[i] = ((p[j] as u32) << 24)
                | ((p[j + 1] as u32) << 16)
                | ((p[j + 2] as u32) << 8)
                | (p[j + 3] as u32);
        });

        for i in 16..64 {
            let v1 = w[i - 2];
            let t1 = v1.rotate_right(17) ^ v1.rotate_right(19) ^ (v1 >> 10);
            let v2 = w[i - 15];
            let t2 = v2.rotate_right(7) ^ v2.rotate_right(18) ^ (v2 >> 3);
            w[i] = t1
                .wrapping_add(w[i - 7])
                .wrapping_add(t2)
                .wrapping_add(w[i - 16]);
        }

        let (mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut h) =
            (h0, h1, h2, h3, h4, h5, h6, h7);

        for i in 0..64 {
            let t1 = h
                .wrapping_add(e.rotate_right(6) ^ e.rotate_right(11) ^ e.rotate_right(25))
                .wrapping_add((e & f) ^ (!e & g))
                .wrapping_add(K[i])
                .wrapping_add(w[i]);

            let t2 = (a.rotate_right(2) ^ a.rotate_right(13) ^ a.rotate_right(22))
                .wrapping_add((a & b) ^ (a & c) ^ (b & c));

            h = g;
            g = f;
            f = e;
            e = d.wrapping_add(t1);
            d = c;
            c = b;
            b = a;
            a = t1.wrapping_add(t2);
        }

        h0 = h0.wrapping_add(a);
        h1 = h1.wrapping_add(b);
        h2 = h2.wrapping_add(c);
        h3 = h3.wrapping_add(d);
        h4 = h4.wrapping_add(e);
        h5 = h5.wrapping_add(f);
        h6 = h6.wrapping_add(g);
        h7 = h7.wrapping_add(h);

        p = &p[CHUNK..];
    }

    dig.h[0] = h0;
    dig.h[1] = h1;
    dig.h[2] = h2;
    dig.h[3] = h3;
    dig.h[4] = h4;
    dig.h[5] = h5;
    dig.h[6] = h6;
    dig.h[7] = h7;
}
