#![allow(clippy::many_single_char_names)]

use crate::consts::BLOCK_LEN;

use core::convert::TryInto;

#[inline(always)]

fn shl(v: [u32; 4], o: u32) -> [u32; 4] {

    [v[0] >> o, v[1] >> o, v[2] >> o, v[3] >> o]

}

#[inline(always)]

fn shr(v: [u32; 4], o: u32) -> [u32; 4] {

    [v[0] << o, v[1] << o, v[2] << o, v[3] << o]

}

#[inline(always)]

fn or(a: [u32; 4], b: [u32; 4]) -> [u32; 4] {

    [a[0] | b[0], a[1] | b[1], a[2] | b[2], a[3] | b[3]]

}

#[inline(always)]

fn xor(a: [u32; 4], b: [u32; 4]) -> [u32; 4] {

    [a[0] ^ b[0], a[1] ^ b[1], a[2] ^ b[2], a[3] ^ b[3]]

}

#[inline(always)]

fn add(a: [u32; 4], b: [u32; 4]) -> [u32; 4] {

    [

        a[0].wrapping_add(b[0]),

        a[1].wrapping_add(b[1]),

        a[2].wrapping_add(b[2]),

        a[3].wrapping_add(b[3]),

    ]

}

fn sha256load(v2: [u32; 4], v3: [u32; 4]) -> [u32; 4] {

    [v3[3], v2[0], v2[1], v2[2]]

}

fn sha256swap(v0: [u32; 4]) -> [u32; 4] {

    [v0[2], v0[3], v0[0], v0[1]]

}

fn sha256msg1(v0: [u32; 4], v1: [u32; 4]) -> [u32; 4] {

    // sigma 0 on vectors

    #[inline]

    fn sigma0x4(x: [u32; 4]) -> [u32; 4] {

        let t1 = or(shl(x, 7), shr(x, 25));

        let t2 = or(shl(x, 18), shr(x, 14));

        let t3 = shl(x, 3);

        xor(xor(t1, t2), t3)

    }

    add(v0, sigma0x4(sha256load(v0, v1)))

}

fn sha256msg2(v4: [u32; 4], v3: [u32; 4]) -> [u32; 4] {

    macro_rules! sigma1 {

        ($a:expr) => {

            $a.rotate_right(17) ^ $a.rotate_right(19) ^ ($a >> 10)

        };

    }

    let [x3, x2, x1, x0] = v4;

    let [w15, w14, _, _] = v3;

    let w16 = x0.wrapping_add(sigma1!(w14));

    let w17 = x1.wrapping_add(sigma1!(w15));

    let w18 = x2.wrapping_add(sigma1!(w16));

    let w19 = x3.wrapping_add(sigma1!(w17));

    [w19, w18, w17, w16]

}

fn sha256_digest_round_x2(cdgh: [u32; 4], abef: [u32; 4], wk: [u32; 4]) -> [u32; 4] {

    macro_rules! big_sigma0 {

        ($a:expr) => {

            ($a.rotate_right(2) ^ $a.rotate_right(13) ^ $a.rotate_right(22))

        };

    }

    macro_rules! big_sigma1 {

        ($a:expr) => {

            ($a.rotate_right(6) ^ $a.rotate_right(11) ^ $a.rotate_right(25))

        };

    }

    macro_rules! bool3ary_202 {

        ($a:expr, $b:expr, $c:expr) => {

            $c ^ ($a & ($b ^ $c))

        };

    } // Choose, MD5F, SHA1C

    macro_rules! bool3ary_232 {

        ($a:expr, $b:expr, $c:expr) => {

            ($a & $b) ^ ($a & $c) ^ ($b & $c)

        };

    } // Majority, SHA1M

    let [_, _, wk1, wk0] = wk;

    let [a0, b0, e0, f0] = abef;

    let [c0, d0, g0, h0] = cdgh;

    // a round

    let x0 = big_sigma1!(e0)

        .wrapping_add(bool3ary_202!(e0, f0, g0))

        .wrapping_add(wk0)

        .wrapping_add(h0);

    let y0 = big_sigma0!(a0).wrapping_add(bool3ary_232!(a0, b0, c0));

    let (a1, b1, c1, d1, e1, f1, g1, h1) = (

        x0.wrapping_add(y0),

        a0,

        b0,

        c0,

        x0.wrapping_add(d0),

        e0,

        f0,

        g0,

    );

    // a round

    let x1 = big_sigma1!(e1)

        .wrapping_add(bool3ary_202!(e1, f1, g1))

        .wrapping_add(wk1)

        .wrapping_add(h1);

    let y1 = big_sigma0!(a1).wrapping_add(bool3ary_232!(a1, b1, c1));

    let (a2, b2, _, _, e2, f2, _, _) = (

        x1.wrapping_add(y1),

        a1,

        b1,

        c1,

        x1.wrapping_add(d1),

        e1,

        f1,

        g1,

    );

    [a2, b2, e2, f2]

}

fn schedule(v0: [u32; 4], v1: [u32; 4], v2: [u32; 4], v3: [u32; 4]) -> [u32; 4] {

    let t1 = sha256msg1(v0, v1);

    let t2 = sha256load(v2, v3);

    let t3 = add(t1, t2);

    sha256msg2(t3, v3)

}

macro_rules! rounds4 {

    ($abef:ident, $cdgh:ident, $rest:expr, $i:expr) => {{

        let t1 = add($rest, crate::consts::K32X4[$i]);

        $cdgh = sha256_digest_round_x2($cdgh, $abef, t1);

        let t2 = sha256swap(t1);

        $abef = sha256_digest_round_x2($abef, $cdgh, t2);

    }};

}

macro_rules! schedule_rounds4 {

    (

        $abef:ident, $cdgh:ident,

        $w0:expr, $w1:expr, $w2:expr, $w3:expr, $w4:expr,

        $i: expr

    ) => {{

        $w4 = schedule($w0, $w1, $w2, $w3);

        rounds4!($abef, $cdgh, $w4, $i);

    }};

}

/// Process a block with the SHA-256 algorithm.

fn sha256_digest_block_u32(state: &mut [u32; 8], block: &[u32; 16]) {

    let mut abef = [state[0], state[1], state[4], state[5]];

    let mut cdgh = [state[2], state[3], state[6], state[7]];

    // Rounds 0..64

    let mut w0 = [block[3], block[2], block[1], block[0]];

    let mut w1 = [block[7], block[6], block[5], block[4]];

    let mut w2 = [block[11], block[10], block[9], block[8]];

    let mut w3 = [block[15], block[14], block[13], block[12]];

    let mut w4;

    rounds4!(abef, cdgh, w0, 0);

    rounds4!(abef, cdgh, w1, 1);

    rounds4!(abef, cdgh, w2, 2);

    rounds4!(abef, cdgh, w3, 3);

    schedule_rounds4!(abef, cdgh, w0, w1, w2, w3, w4, 4);

    schedule_rounds4!(abef, cdgh, w1, w2, w3, w4, w0, 5);

    schedule_rounds4!(abef, cdgh, w2, w3, w4, w0, w1, 6);

    schedule_rounds4!(abef, cdgh, w3, w4, w0, w1, w2, 7);

    schedule_rounds4!(abef, cdgh, w4, w0, w1, w2, w3, 8);

    schedule_rounds4!(abef, cdgh, w0, w1, w2, w3, w4, 9);

    schedule_rounds4!(abef, cdgh, w1, w2, w3, w4, w0, 10);

    schedule_rounds4!(abef, cdgh, w2, w3, w4, w0, w1, 11);

    schedule_rounds4!(abef, cdgh, w3, w4, w0, w1, w2, 12);

    schedule_rounds4!(abef, cdgh, w4, w0, w1, w2, w3, 13);

    schedule_rounds4!(abef, cdgh, w0, w1, w2, w3, w4, 14);

    schedule_rounds4!(abef, cdgh, w1, w2, w3, w4, w0, 15);

    let [a, b, e, f] = abef;

    let [c, d, g, h] = cdgh;

    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 fn compress(state: &mut [u32; 8], blocks: &[[u8; 64]]) {

    let mut block_u32 = [0u32; BLOCK_LEN];

    // since LLVM can't properly use aliasing yet it will make

    // unnecessary state stores without this copy

    let mut state_cpy = *state;

    for block in blocks {

        for (o, chunk) in block_u32.iter_mut().zip(block.chunks_exact(4)) {

            *o = u32::from_be_bytes(chunk.try_into().unwrap());

        }

        sha256_digest_block_u32(&mut state_cpy, &block_u32);

    }

    *state = state_cpy;

}