use crate::cryptoutil::read_u32v_be;

#[inline(always)]
pub(crate) fn e0(x: u32) -> u32 {
    x.rotate_right(2) ^ x.rotate_right(13) ^ x.rotate_right(22)
}

#[inline(always)]
pub(crate) fn e1(x: u32) -> u32 {
    x.rotate_right(6) ^ x.rotate_right(11) ^ x.rotate_right(25)
}

#[inline(always)]
fn s0(x: u32) -> u32 {
    x.rotate_right(7) ^ x.rotate_right(18) ^ (x >> 3)
}

#[inline(always)]
fn s1(x: u32) -> u32 {
    x.rotate_right(17) ^ x.rotate_right(19) ^ (x >> 10)
}

// SHA256 64 constants K
pub(crate) const K32: [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,
];

fn digest_block_u32(state: &mut [u32; 8], buf: &[u8]) {
    let mut w = [0u32; 64];

    read_u32v_be(&mut w[0..16], buf);

    unsafe {
        for i in 16..64 {
            *w.get_unchecked_mut(i) = s1(*w.get_unchecked(i - 2))
                .wrapping_add(*w.get_unchecked(i - 7))
                .wrapping_add(s0(*w.get_unchecked(i - 15)))
                .wrapping_add(*w.get_unchecked(i - 16));
        }
    }

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

    macro_rules! round {
        ($a: ident, $b: ident, $c: ident, $d: ident, $e: ident, $f: ident, $g: ident, $h: ident, $i: expr) => {
            let t1 = unsafe {
                $h.wrapping_add(e1($e))
                    .wrapping_add($g ^ ($e & ($f ^ $g)))
                    .wrapping_add(*K32.get_unchecked($i))
                    .wrapping_add(*w.get_unchecked($i))
            };
            let t2 = e0($a).wrapping_add(($a & $b) | ($c & ($a | $b)));
            $d = $d.wrapping_add(t1);
            $h = t1.wrapping_add(t2);
        };
    }

    let mut i = 0;
    while i != 64 {
        round!(a, b, c, d, e, f, g, h, i + 0);
        round!(h, a, b, c, d, e, f, g, i + 1);
        round!(g, h, a, b, c, d, e, f, i + 2);
        round!(f, g, h, a, b, c, d, e, i + 3);
        round!(e, f, g, h, a, b, c, d, i + 4);
        round!(d, e, f, g, h, a, b, c, i + 5);
        round!(c, d, e, f, g, h, a, b, i + 6);
        round!(b, c, d, e, f, g, h, a, i + 7);
        i += 8;
    }

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

pub(crate) fn digest_block(state: &mut [u32; 8], block: &[u8]) {
    let mut i = 0;
    while i < block.len() {
        digest_block_u32(state, &block[i..i + 64]);
        i += 64;
    }
}