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use crate::constants::{CRYPTO_SHORTHASH_SIPHASH24_BYTES, CRYPTO_SHORTHASH_SIPHASH24_KEYBYTES};
use crate::utils::load_u64_le;

pub(crate) type Hash = [u8; CRYPTO_SHORTHASH_SIPHASH24_BYTES];
pub(crate) type Key = [u8; CRYPTO_SHORTHASH_SIPHASH24_KEYBYTES];

fn rotl64(x: u64, b: u64) -> u64 {
    (x << b) | (x >> (64 - b))
}

pub(crate) fn siphash24(output: &mut Hash, input: &[u8], key: &Key) {
    // "somepseudorandomlygeneratedbytes"
    let mut v0 = 0x736f6d6570736575u64;
    let mut v1 = 0x646f72616e646f6du64;
    let mut v2 = 0x6c7967656e657261u64;
    let mut v3 = 0x7465646279746573u64;

    let k0 = load_u64_le(&key[..8]);
    let k1 = load_u64_le(&key[8..]);

    v3 ^= k1;
    v2 ^= k0;
    v1 ^= k1;
    v0 ^= k0;

    let round = |v0: &mut u64, v1: &mut u64, v2: &mut u64, v3: &mut u64| {
        *v0 = v0.wrapping_add(*v1);
        *v1 = rotl64(*v1, 13);
        *v1 ^= *v0;
        *v0 = rotl64(*v0, 32);
        *v2 = v2.wrapping_add(*v3);
        *v3 = rotl64(*v3, 16);
        *v3 ^= *v2;
        *v0 = v0.wrapping_add(*v3);
        *v3 = rotl64(*v3, 21);
        *v3 ^= *v0;
        *v2 = v2.wrapping_add(*v1);
        *v1 = rotl64(*v1, 17);
        *v1 ^= *v2;
        *v2 = rotl64(*v2, 32);
    };

    for chunk in input.chunks_exact(8) {
        let m = load_u64_le(chunk);
        v3 ^= m;
        round(&mut v0, &mut v1, &mut v2, &mut v3);
        round(&mut v0, &mut v1, &mut v2, &mut v3);
        v0 ^= m;
    }

    let mut b = (input.len() as u64) << 56;

    let remainder = input.chunks_exact(8).remainder();

    for i in (0..remainder.len()).rev() {
        b |= (remainder[i] as u64) << (i * 8);
    }

    v3 ^= b;
    round(&mut v0, &mut v1, &mut v2, &mut v3);
    round(&mut v0, &mut v1, &mut v2, &mut v3);
    v0 ^= b;
    v2 ^= 0xff;
    round(&mut v0, &mut v1, &mut v2, &mut v3);
    round(&mut v0, &mut v1, &mut v2, &mut v3);
    round(&mut v0, &mut v1, &mut v2, &mut v3);
    round(&mut v0, &mut v1, &mut v2, &mut v3);
    b = v0 ^ v1 ^ v2 ^ v3;

    output.copy_from_slice(&b.to_le_bytes());
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_siphash24() {
        let vectors: [[u8; 8]; 64] = [
            [0x31, 0x0e, 0x0e, 0xdd, 0x47, 0xdb, 0x6f, 0x72],
            [0xfd, 0x67, 0xdc, 0x93, 0xc5, 0x39, 0xf8, 0x74],
            [0x5a, 0x4f, 0xa9, 0xd9, 0x09, 0x80, 0x6c, 0x0d],
            [0x2d, 0x7e, 0xfb, 0xd7, 0x96, 0x66, 0x67, 0x85],
            [0xb7, 0x87, 0x71, 0x27, 0xe0, 0x94, 0x27, 0xcf],
            [0x8d, 0xa6, 0x99, 0xcd, 0x64, 0x55, 0x76, 0x18],
            [0xce, 0xe3, 0xfe, 0x58, 0x6e, 0x46, 0xc9, 0xcb],
            [0x37, 0xd1, 0x01, 0x8b, 0xf5, 0x00, 0x02, 0xab],
            [0x62, 0x24, 0x93, 0x9a, 0x79, 0xf5, 0xf5, 0x93],
            [0xb0, 0xe4, 0xa9, 0x0b, 0xdf, 0x82, 0x00, 0x9e],
            [0xf3, 0xb9, 0xdd, 0x94, 0xc5, 0xbb, 0x5d, 0x7a],
            [0xa7, 0xad, 0x6b, 0x22, 0x46, 0x2f, 0xb3, 0xf4],
            [0xfb, 0xe5, 0x0e, 0x86, 0xbc, 0x8f, 0x1e, 0x75],
            [0x90, 0x3d, 0x84, 0xc0, 0x27, 0x56, 0xea, 0x14],
            [0xee, 0xf2, 0x7a, 0x8e, 0x90, 0xca, 0x23, 0xf7],
            [0xe5, 0x45, 0xbe, 0x49, 0x61, 0xca, 0x29, 0xa1],
            [0xdb, 0x9b, 0xc2, 0x57, 0x7f, 0xcc, 0x2a, 0x3f],
            [0x94, 0x47, 0xbe, 0x2c, 0xf5, 0xe9, 0x9a, 0x69],
            [0x9c, 0xd3, 0x8d, 0x96, 0xf0, 0xb3, 0xc1, 0x4b],
            [0xbd, 0x61, 0x79, 0xa7, 0x1d, 0xc9, 0x6d, 0xbb],
            [0x98, 0xee, 0xa2, 0x1a, 0xf2, 0x5c, 0xd6, 0xbe],
            [0xc7, 0x67, 0x3b, 0x2e, 0xb0, 0xcb, 0xf2, 0xd0],
            [0x88, 0x3e, 0xa3, 0xe3, 0x95, 0x67, 0x53, 0x93],
            [0xc8, 0xce, 0x5c, 0xcd, 0x8c, 0x03, 0x0c, 0xa8],
            [0x94, 0xaf, 0x49, 0xf6, 0xc6, 0x50, 0xad, 0xb8],
            [0xea, 0xb8, 0x85, 0x8a, 0xde, 0x92, 0xe1, 0xbc],
            [0xf3, 0x15, 0xbb, 0x5b, 0xb8, 0x35, 0xd8, 0x17],
            [0xad, 0xcf, 0x6b, 0x07, 0x63, 0x61, 0x2e, 0x2f],
            [0xa5, 0xc9, 0x1d, 0xa7, 0xac, 0xaa, 0x4d, 0xde],
            [0x71, 0x65, 0x95, 0x87, 0x66, 0x50, 0xa2, 0xa6],
            [0x28, 0xef, 0x49, 0x5c, 0x53, 0xa3, 0x87, 0xad],
            [0x42, 0xc3, 0x41, 0xd8, 0xfa, 0x92, 0xd8, 0x32],
            [0xce, 0x7c, 0xf2, 0x72, 0x2f, 0x51, 0x27, 0x71],
            [0xe3, 0x78, 0x59, 0xf9, 0x46, 0x23, 0xf3, 0xa7],
            [0x38, 0x12, 0x05, 0xbb, 0x1a, 0xb0, 0xe0, 0x12],
            [0xae, 0x97, 0xa1, 0x0f, 0xd4, 0x34, 0xe0, 0x15],
            [0xb4, 0xa3, 0x15, 0x08, 0xbe, 0xff, 0x4d, 0x31],
            [0x81, 0x39, 0x62, 0x29, 0xf0, 0x90, 0x79, 0x02],
            [0x4d, 0x0c, 0xf4, 0x9e, 0xe5, 0xd4, 0xdc, 0xca],
            [0x5c, 0x73, 0x33, 0x6a, 0x76, 0xd8, 0xbf, 0x9a],
            [0xd0, 0xa7, 0x04, 0x53, 0x6b, 0xa9, 0x3e, 0x0e],
            [0x92, 0x59, 0x58, 0xfc, 0xd6, 0x42, 0x0c, 0xad],
            [0xa9, 0x15, 0xc2, 0x9b, 0xc8, 0x06, 0x73, 0x18],
            [0x95, 0x2b, 0x79, 0xf3, 0xbc, 0x0a, 0xa6, 0xd4],
            [0xf2, 0x1d, 0xf2, 0xe4, 0x1d, 0x45, 0x35, 0xf9],
            [0x87, 0x57, 0x75, 0x19, 0x04, 0x8f, 0x53, 0xa9],
            [0x10, 0xa5, 0x6c, 0xf5, 0xdf, 0xcd, 0x9a, 0xdb],
            [0xeb, 0x75, 0x09, 0x5c, 0xcd, 0x98, 0x6c, 0xd0],
            [0x51, 0xa9, 0xcb, 0x9e, 0xcb, 0xa3, 0x12, 0xe6],
            [0x96, 0xaf, 0xad, 0xfc, 0x2c, 0xe6, 0x66, 0xc7],
            [0x72, 0xfe, 0x52, 0x97, 0x5a, 0x43, 0x64, 0xee],
            [0x5a, 0x16, 0x45, 0xb2, 0x76, 0xd5, 0x92, 0xa1],
            [0xb2, 0x74, 0xcb, 0x8e, 0xbf, 0x87, 0x87, 0x0a],
            [0x6f, 0x9b, 0xb4, 0x20, 0x3d, 0xe7, 0xb3, 0x81],
            [0xea, 0xec, 0xb2, 0xa3, 0x0b, 0x22, 0xa8, 0x7f],
            [0x99, 0x24, 0xa4, 0x3c, 0xc1, 0x31, 0x57, 0x24],
            [0xbd, 0x83, 0x8d, 0x3a, 0xaf, 0xbf, 0x8d, 0xb7],
            [0x0b, 0x1a, 0x2a, 0x32, 0x65, 0xd5, 0x1a, 0xea],
            [0x13, 0x50, 0x79, 0xa3, 0x23, 0x1c, 0xe6, 0x60],
            [0x93, 0x2b, 0x28, 0x46, 0xe4, 0xd7, 0x06, 0x66],
            [0xe1, 0x91, 0x5f, 0x5c, 0xb1, 0xec, 0xa4, 0x6c],
            [0xf3, 0x25, 0x96, 0x5c, 0xa1, 0x6d, 0x62, 0x9f],
            [0x57, 0x5f, 0xf2, 0x8e, 0x60, 0x38, 0x1b, 0xe5],
            [0x72, 0x45, 0x06, 0xeb, 0x4c, 0x32, 0x8a, 0x95],
        ];

        let mut key = Key::default();
        for (i, item) in key.iter_mut().enumerate() {
            *item = i as u8;
        }

        for (i, item) in vectors.iter().enumerate() {
            let mut input = vec![0u8; i];
            for (j, item) in input.iter_mut().enumerate().take(i) {
                *item = j as u8;
            }

            let mut output = Hash::default();

            siphash24(&mut output, &input, &key);

            assert_eq!(output, *item);
        }
    }
}