#![allow(clippy::many_single_char_names)]

use crate::consts::{BLOCK_LEN, K64X2};

use core::convert::TryInto;

fn add(a: [u64; 2], b: [u64; 2]) -> [u64; 2] {

    [a[0].wrapping_add(b[0]), a[1].wrapping_add(b[1])]

}

/// Not an intrinsic, but works like an unaligned load.

fn sha512load(v0: [u64; 2], v1: [u64; 2]) -> [u64; 2] {

    [v1[1], v0[0]]

}

/// Performs 2 rounds of the SHA-512 message schedule update.

pub fn sha512_schedule_x2(v0: [u64; 2], v1: [u64; 2], v4to5: [u64; 2], v7: [u64; 2]) -> [u64; 2] {

    // sigma 0

    fn sigma0(x: u64) -> u64 {

        ((x << 63) | (x >> 1)) ^ ((x << 56) | (x >> 8)) ^ (x >> 7)

    }

    // sigma 1

    fn sigma1(x: u64) -> u64 {

        ((x << 45) | (x >> 19)) ^ ((x << 3) | (x >> 61)) ^ (x >> 6)

    }

    let [w1, w0] = v0;

    let [_, w2] = v1;

    let [w10, w9] = v4to5;

    let [w15, w14] = v7;

    let w16 = sigma1(w14)

        .wrapping_add(w9)

        .wrapping_add(sigma0(w1))

        .wrapping_add(w0);

    let w17 = sigma1(w15)

        .wrapping_add(w10)

        .wrapping_add(sigma0(w2))

        .wrapping_add(w1);

    [w17, w16]

}

/// Performs one round of the SHA-512 message block digest.

pub fn sha512_digest_round(

    ae: [u64; 2],

    bf: [u64; 2],

    cg: [u64; 2],

    dh: [u64; 2],

    wk0: u64,

) -> [u64; 2] {

    macro_rules! big_sigma0 {

        ($a:expr) => {

            ($a.rotate_right(28) ^ $a.rotate_right(34) ^ $a.rotate_right(39))

        };

    }

    macro_rules! big_sigma1 {

        ($a:expr) => {

            ($a.rotate_right(14) ^ $a.rotate_right(18) ^ $a.rotate_right(41))

        };

    }

    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 [a0, e0] = ae;

    let [b0, f0] = bf;

    let [c0, g0] = cg;

    let [d0, h0] = dh;

    // 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, _, _, _, e1, _, _, _) = (

        x0.wrapping_add(y0),

        a0,

        b0,

        c0,

        x0.wrapping_add(d0),

        e0,

        f0,

        g0,

    );

    [a1, e1]

}

/// Process a block with the SHA-512 algorithm.

pub fn sha512_digest_block_u64(state: &mut [u64; 8], block: &[u64; 16]) {

    let k = &K64X2;

    macro_rules! schedule {

        ($v0:expr, $v1:expr, $v4:expr, $v5:expr, $v7:expr) => {

            sha512_schedule_x2($v0, $v1, sha512load($v4, $v5), $v7)

        };

    }

    macro_rules! rounds4 {

        ($ae:ident, $bf:ident, $cg:ident, $dh:ident, $wk0:expr, $wk1:expr) => {{

            let [u, t] = $wk0;

            let [w, v] = $wk1;

            $dh = sha512_digest_round($ae, $bf, $cg, $dh, t);

            $cg = sha512_digest_round($dh, $ae, $bf, $cg, u);

            $bf = sha512_digest_round($cg, $dh, $ae, $bf, v);

            $ae = sha512_digest_round($bf, $cg, $dh, $ae, w);

        }};

    }

    let mut ae = [state[0], state[4]];

    let mut bf = [state[1], state[5]];

    let mut cg = [state[2], state[6]];

    let mut dh = [state[3], state[7]];

    // Rounds 0..20

    let (mut w1, mut w0) = ([block[3], block[2]], [block[1], block[0]]);

    rounds4!(ae, bf, cg, dh, add(k[0], w0), add(k[1], w1));

    let (mut w3, mut w2) = ([block[7], block[6]], [block[5], block[4]]);

    rounds4!(ae, bf, cg, dh, add(k[2], w2), add(k[3], w3));

    let (mut w5, mut w4) = ([block[11], block[10]], [block[9], block[8]]);

    rounds4!(ae, bf, cg, dh, add(k[4], w4), add(k[5], w5));

    let (mut w7, mut w6) = ([block[15], block[14]], [block[13], block[12]]);

    rounds4!(ae, bf, cg, dh, add(k[6], w6), add(k[7], w7));

    let mut w8 = schedule!(w0, w1, w4, w5, w7);

    let mut w9 = schedule!(w1, w2, w5, w6, w8);

    rounds4!(ae, bf, cg, dh, add(k[8], w8), add(k[9], w9));

    // Rounds 20..40

    w0 = schedule!(w2, w3, w6, w7, w9);

    w1 = schedule!(w3, w4, w7, w8, w0);

    rounds4!(ae, bf, cg, dh, add(k[10], w0), add(k[11], w1));

    w2 = schedule!(w4, w5, w8, w9, w1);

    w3 = schedule!(w5, w6, w9, w0, w2);

    rounds4!(ae, bf, cg, dh, add(k[12], w2), add(k[13], w3));

    w4 = schedule!(w6, w7, w0, w1, w3);

    w5 = schedule!(w7, w8, w1, w2, w4);

    rounds4!(ae, bf, cg, dh, add(k[14], w4), add(k[15], w5));

    w6 = schedule!(w8, w9, w2, w3, w5);

    w7 = schedule!(w9, w0, w3, w4, w6);

    rounds4!(ae, bf, cg, dh, add(k[16], w6), add(k[17], w7));

    w8 = schedule!(w0, w1, w4, w5, w7);

    w9 = schedule!(w1, w2, w5, w6, w8);

    rounds4!(ae, bf, cg, dh, add(k[18], w8), add(k[19], w9));

    // Rounds 40..60

    w0 = schedule!(w2, w3, w6, w7, w9);

    w1 = schedule!(w3, w4, w7, w8, w0);

    rounds4!(ae, bf, cg, dh, add(k[20], w0), add(k[21], w1));

    w2 = schedule!(w4, w5, w8, w9, w1);

    w3 = schedule!(w5, w6, w9, w0, w2);

    rounds4!(ae, bf, cg, dh, add(k[22], w2), add(k[23], w3));

    w4 = schedule!(w6, w7, w0, w1, w3);

    w5 = schedule!(w7, w8, w1, w2, w4);

    rounds4!(ae, bf, cg, dh, add(k[24], w4), add(k[25], w5));

    w6 = schedule!(w8, w9, w2, w3, w5);

    w7 = schedule!(w9, w0, w3, w4, w6);

    rounds4!(ae, bf, cg, dh, add(k[26], w6), add(k[27], w7));

    w8 = schedule!(w0, w1, w4, w5, w7);

    w9 = schedule!(w1, w2, w5, w6, w8);

    rounds4!(ae, bf, cg, dh, add(k[28], w8), add(k[29], w9));

    // Rounds 60..80

    w0 = schedule!(w2, w3, w6, w7, w9);

    w1 = schedule!(w3, w4, w7, w8, w0);

    rounds4!(ae, bf, cg, dh, add(k[30], w0), add(k[31], w1));

    w2 = schedule!(w4, w5, w8, w9, w1);

    w3 = schedule!(w5, w6, w9, w0, w2);

    rounds4!(ae, bf, cg, dh, add(k[32], w2), add(k[33], w3));

    w4 = schedule!(w6, w7, w0, w1, w3);

    w5 = schedule!(w7, w8, w1, w2, w4);

    rounds4!(ae, bf, cg, dh, add(k[34], w4), add(k[35], w5));

    w6 = schedule!(w8, w9, w2, w3, w5);

    w7 = schedule!(w9, w0, w3, w4, w6);

    rounds4!(ae, bf, cg, dh, add(k[36], w6), add(k[37], w7));

    w8 = schedule!(w0, w1, w4, w5, w7);

    w9 = schedule!(w1, w2, w5, w6, w8);

    rounds4!(ae, bf, cg, dh, add(k[38], w8), add(k[39], w9));

    let [a, e] = ae;

    let [b, f] = bf;

    let [c, g] = cg;

    let [d, h] = dh;

    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 [u64; 8], blocks: &[[u8; 128]]) {

    let mut block_u32 = [0u64; 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(8)) {

            *o = u64::from_be_bytes(chunk.try_into().unwrap());

        }

        sha512_digest_block_u64(&mut state_cpy, &block_u32);

    }

    *state = state_cpy;

}