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// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// OpenEthereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with OpenEthereum.  If not, see <http://www.gnu.org/licenses/>.

/// The precomputed values for BLAKE2b [from the spec](https://tools.ietf.org/html/rfc7693#section-2.7)
/// There are 10 16-byte arrays - one for each round
/// the entries are calculated from the sigma constants.
const SIGMA: [[usize; 16]; 10] = [
    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
    [14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3],
    [11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4],
    [7, 9, 3, 1, 13, 12, 11, 14, 2, 6, 5, 10, 4, 0, 15, 8],
    [9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13],
    [2, 12, 6, 10, 0, 11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9],
    [12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11],
    [13, 11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10],
    [6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4, 10, 5],
    [10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0],
];

/// IV is the initialization vector for BLAKE2b. See https://tools.ietf.org/html/rfc7693#section-2.6
/// for details.
const IV: [u64; 8] = [
    0x6a09e667f3bcc908,
    0xbb67ae8584caa73b,
    0x3c6ef372fe94f82b,
    0xa54ff53a5f1d36f1,
    0x510e527fade682d1,
    0x9b05688c2b3e6c1f,
    0x1f83d9abfb41bd6b,
    0x5be0cd19137e2179,
];

#[inline(always)]
/// The G mixing function. See https://tools.ietf.org/html/rfc7693#section-3.1
fn g(v: &mut [u64], a: usize, b: usize, c: usize, d: usize, x: u64, y: u64) {
    v[a] = v[a].wrapping_add(v[b]).wrapping_add(x);
    v[d] = (v[d] ^ v[a]).rotate_right(32);
    v[c] = v[c].wrapping_add(v[d]);
    v[b] = (v[b] ^ v[c]).rotate_right(24);
    v[a] = v[a].wrapping_add(v[b]).wrapping_add(y);
    v[d] = (v[d] ^ v[a]).rotate_right(16);
    v[c] = v[c].wrapping_add(v[d]);
    v[b] = (v[b] ^ v[c]).rotate_right(63);
}

/// The Blake2 compression function F. See https://tools.ietf.org/html/rfc7693#section-3.2
/// Takes as an argument the state vector `h`, message block vector `m`, offset
/// counter `t`, final block indicator flag `f`, and number of rounds `rounds`.
/// The state vector provided as the first parameter is modified by the
/// function.
pub fn compress(
    h: &mut [u64; 8], m: [u64; 16], t: [u64; 2], f: bool, rounds: usize,
) {
    let mut v = [0u64; 16];
    v[..h.len()].copy_from_slice(h); // First half from state.
    v[h.len()..].copy_from_slice(&IV); // Second half from IV.

    v[12] ^= t[0];
    v[13] ^= t[1];

    if f {
        v[14] = !v[14] // Invert all bits if the last-block-flag is set.
    }
    for i in 0..rounds {
        // Message word selection permutation for this round.
        let s = &SIGMA[i % 10];
        g(&mut v, 0, 4, 8, 12, m[s[0]], m[s[1]]);
        g(&mut v, 1, 5, 9, 13, m[s[2]], m[s[3]]);
        g(&mut v, 2, 6, 10, 14, m[s[4]], m[s[5]]);
        g(&mut v, 3, 7, 11, 15, m[s[6]], m[s[7]]);

        g(&mut v, 0, 5, 10, 15, m[s[8]], m[s[9]]);
        g(&mut v, 1, 6, 11, 12, m[s[10]], m[s[11]]);
        g(&mut v, 2, 7, 8, 13, m[s[12]], m[s[13]]);
        g(&mut v, 3, 4, 9, 14, m[s[14]], m[s[15]]);
    }

    for i in 0..8 {
        h[i] ^= v[i] ^ v[i + 8];
    }
}

#[cfg(test)]
mod tests {
    use super::compress;
    use rustc_hex::FromHex;

    #[test]
    fn test_blake2_f() {
        // test from https://github.com/ethereum/EIPs/blob/master/EIPS/eip-152.md#example-usage-in-solidity
        let mut h_in = [
            0x6a09e667f2bdc948_u64,
            0xbb67ae8584caa73b_u64,
            0x3c6ef372fe94f82b_u64,
            0xa54ff53a5f1d36f1_u64,
            0x510e527fade682d1_u64,
            0x9b05688c2b3e6c1f_u64,
            0x1f83d9abfb41bd6b_u64,
            0x5be0cd19137e2179_u64,
        ];

        let m = [
            0x0000000000636261_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
            0x0000000000000000_u64,
        ];
        let c = [3, 0];
        let f = true;
        let rounds = 12;
        let h_out: [u64; 8] = [
            0x0D4D1C983FA580BA_u64,
            0xE9F6129FB697276A_u64,
            0xB7C45A68142F214C_u64,
            0xD1A2FFDB6FBB124B_u64,
            0x2D79AB2A39C5877D_u64,
            0x95CC3345DED552C2_u64,
            0x5A92F1DBA88AD318_u64,
            0x239900D4ED8623B9_u64,
        ];

        compress(&mut h_in, m, c, f, rounds);

        assert_eq!(h_in, h_out);
    }

    fn to_u64_slice(vec: &[u8], slice: &mut [u64]) {
        vec.chunks(8).enumerate().for_each(|(index, val)| {
            slice[index] = u64::from_le_bytes([
                val[0], val[1], val[2], val[3], val[4], val[5], val[6], val[7],
            ])
        })
    }

    #[test]
    fn test_vectors_from_eip() {
        let vec = vec![
            (
                // Test vector 4
                "0000000048c9bdf267e6096a3ba7ca8485ae67bb2bf894fe72f36e3cf1361d5f3af54fa5d182e6ad7f520e511f6c3e2b8c68059b6bbd41fbabd9831f79217e1319cde05b61626300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000001",
                "08c9bcf367e6096a3ba7ca8485ae67bb2bf894fe72f36e3cf1361d5f3af54fa5d282e6ad7f520e511f6c3e2b8c68059b9442be0454267ce079217e1319cde05b",
            ),
            (   // test vector 5
                "0000000c48c9bdf267e6096a3ba7ca8485ae67bb2bf894fe72f36e3cf1361d5f3af54fa5d182e6ad7f520e511f6c3e2b8c68059b6bbd41fbabd9831f79217e1319cde05b61626300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000001",
                "ba80a53f981c4d0d6a2797b69f12f6e94c212f14685ac4b74b12bb6fdbffa2d17d87c5392aab792dc252d5de4533cc9518d38aa8dbf1925ab92386edd4009923",
            ),
            (
                // Test vector 6
                "0000000c48c9bdf267e6096a3ba7ca8485ae67bb2bf894fe72f36e3cf1361d5f3af54fa5d182e6ad7f520e511f6c3e2b8c68059b6bbd41fbabd9831f79217e1319cde05b61626300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000000",
                "75ab69d3190a562c51aef8d88f1c2775876944407270c42c9844252c26d2875298743e7f6d5ea2f2d3e8d226039cd31b4e426ac4f2d3d666a610c2116fde4735",
            ),
            (
                // Test vector 7
                "0000000148c9bdf267e6096a3ba7ca8485ae67bb2bf894fe72f36e3cf1361d5f3af54fa5d182e6ad7f520e511f6c3e2b8c68059b6bbd41fbabd9831f79217e1319cde05b61626300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000001",
                "b63a380cb2897d521994a85234ee2c181b5f844d2c624c002677e9703449d2fba551b3a8333bcdf5f2f7e08993d53923de3d64fcc68c034e717b9293fed7a421",
            ),
            // Test vector 8 – u32::MAX rounds – too slow to run
//			(
//				"ffffffff48c9bdf267e6096a3ba7ca8485ae67bb2bf894fe72f36e3cf1361d5f3af54fa5d182e6ad7f520e511f6c3e2b8c68059b6bbd41fbabd9831f79217e1319cde05b61626300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000001",
//				"fc59093aafa9ab43daae0e914c57635c5402d8e3d2130eb9b3cc181de7f0ecf9b22bf99a7815ce16419e200e01846e6b5df8cc7703041bbceb571de6631d2615",
//			),
        ];
        for (hex, output) in vec {
            let hex = hex;
            let bytes: Vec<u8> = hex.from_hex().unwrap();

            assert_eq!(bytes.len(), 213);

            let mut h = [0u64; 8];
            let mut m = [0u64; 16];
            let mut t = [0u64; 2];

            let rounds =
                u32::from_be_bytes([bytes[0], bytes[1], bytes[2], bytes[3]]);
            let f = match bytes[212] {
                1 => true,
                0 => false,
                _ => unreachable!(),
            };

            to_u64_slice(&bytes[4..68], &mut h);
            to_u64_slice(&bytes[68..196], &mut m);
            to_u64_slice(&bytes[196..212], &mut t);

            compress(&mut h, m, t, f, rounds as usize);

            let output: Vec<u8> = output.from_hex().unwrap();

            let mut out = [0u64; 8];
            to_u64_slice(&output[..], &mut out);

            assert_eq!(out, h);
        }
    }
}