ahsah 2.0.0

use crate::traits::HashAlgorithm;
use crate::utils::{big_sigma, ch, maj, small_sigma};

const MESSAGE_SCHEDULE_SIZE: usize = 80;
const BLOCK_SIZE: usize = 128;
const HASH_SIZE_U64: usize = 8;

const H: [u64; HASH_SIZE_U64] = [
    0x6a09e667f3bcc908,
    0xbb67ae8584caa73b,
    0x3c6ef372fe94f82b,
    0xa54ff53a5f1d36f1,
    0x510e527fade682d1,
    0x9b05688c2b3e6c1f,
    0x1f83d9abfb41bd6b,
    0x5be0cd19137e2179,
];

const K: [u64; MESSAGE_SCHEDULE_SIZE] = [
    0x428a2f98d728ae22,
    0x7137449123ef65cd,
    0xb5c0fbcfec4d3b2f,
    0xe9b5dba58189dbbc,
    0x3956c25bf348b538,
    0x59f111f1b605d019,
    0x923f82a4af194f9b,
    0xab1c5ed5da6d8118,
    0xd807aa98a3030242,
    0x12835b0145706fbe,
    0x243185be4ee4b28c,
    0x550c7dc3d5ffb4e2,
    0x72be5d74f27b896f,
    0x80deb1fe3b1696b1,
    0x9bdc06a725c71235,
    0xc19bf174cf692694,
    0xe49b69c19ef14ad2,
    0xefbe4786384f25e3,
    0x0fc19dc68b8cd5b5,
    0x240ca1cc77ac9c65,
    0x2de92c6f592b0275,
    0x4a7484aa6ea6e483,
    0x5cb0a9dcbd41fbd4,
    0x76f988da831153b5,
    0x983e5152ee66dfab,
    0xa831c66d2db43210,
    0xb00327c898fb213f,
    0xbf597fc7beef0ee4,
    0xc6e00bf33da88fc2,
    0xd5a79147930aa725,
    0x06ca6351e003826f,
    0x142929670a0e6e70,
    0x27b70a8546d22ffc,
    0x2e1b21385c26c926,
    0x4d2c6dfc5ac42aed,
    0x53380d139d95b3df,
    0x650a73548baf63de,
    0x766a0abb3c77b2a8,
    0x81c2c92e47edaee6,
    0x92722c851482353b,
    0xa2bfe8a14cf10364,
    0xa81a664bbc423001,
    0xc24b8b70d0f89791,
    0xc76c51a30654be30,
    0xd192e819d6ef5218,
    0xd69906245565a910,
    0xf40e35855771202a,
    0x106aa07032bbd1b8,
    0x19a4c116b8d2d0c8,
    0x1e376c085141ab53,
    0x2748774cdf8eeb99,
    0x34b0bcb5e19b48a8,
    0x391c0cb3c5c95a63,
    0x4ed8aa4ae3418acb,
    0x5b9cca4f7763e373,
    0x682e6ff3d6b2b8a3,
    0x748f82ee5defb2fc,
    0x78a5636f43172f60,
    0x84c87814a1f0ab72,
    0x8cc702081a6439ec,
    0x90befffa23631e28,
    0xa4506cebde82bde9,
    0xbef9a3f7b2c67915,
    0xc67178f2e372532b,
    0xca273eceea26619c,
    0xd186b8c721c0c207,
    0xeada7dd6cde0eb1e,
    0xf57d4f7fee6ed178,
    0x06f067aa72176fba,
    0x0a637dc5a2c898a6,
    0x113f9804bef90dae,
    0x1b710b35131c471b,
    0x28db77f523047d84,
    0x32caab7b40c72493,
    0x3c9ebe0a15c9bebc,
    0x431d67c49c100d4c,
    0x4cc5d4becb3e42b6,
    0x597f299cfc657e2a,
    0x5fcb6fab3ad6faec,
    0x6c44198c4a475817,
];

#[derive(Debug)]
pub struct Sha512 {
    data: Vec<u8>,
    hashes: [u64; HASH_SIZE_U64],
    bytes_len: usize,
}

impl HashAlgorithm for Sha512 {
    const BLOCK_SIZE: usize = BLOCK_SIZE;
    const HASH_SIZE: usize = 64;
    const LENGTH_SIZE: usize = 16;
    const LENGTH_IS_BIG_ENDIAN: bool = true;

    fn new() -> Self {
        Self {
            data: Vec::new(),
            hashes: H,
            bytes_len: 0,
        }
    }

    fn data_mut(&mut self) -> &mut Vec<u8> {
        &mut self.data
    }

    fn data(&self) -> &[u8] {
        &self.data
    }

    fn bytes_len(&self) -> usize {
        self.bytes_len
    }

    fn set_bytes_len(&mut self, len: usize) {
        self.bytes_len = len;
    }

    fn process_block(&mut self, block: &[u8]) {
        // Decode 128 bytes into 16 u64 words (big-endian)
        let mut chunk = [0u64; 16];
        for (i, c) in chunk.iter_mut().enumerate() {
            let offset = i * 8;
            *c = u64::from_be_bytes([
                block[offset],
                block[offset + 1],
                block[offset + 2],
                block[offset + 3],
                block[offset + 4],
                block[offset + 5],
                block[offset + 6],
                block[offset + 7],
            ]);
        }

        // Message schedule
        let mut w = [0u64; MESSAGE_SCHEDULE_SIZE];
        w[..16].copy_from_slice(&chunk);
        for i in 16..MESSAGE_SCHEDULE_SIZE {
            let s0 = small_sigma(w[i - 15], (1, 8, 7));
            let s1 = small_sigma(w[i - 2], (19, 61, 6));
            w[i] = s0
                .wrapping_add(s1)
                .wrapping_add(w[i - 16])
                .wrapping_add(w[i - 7]);
        }

        // Compression
        let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut h] = self.hashes;
        for i in 0..MESSAGE_SCHEDULE_SIZE {
            let sum1 = big_sigma(e, (14, 18, 41));
            let ch_val = ch(e, f, g);
            let temp1 = h
                .wrapping_add(sum1)
                .wrapping_add(ch_val)
                .wrapping_add(K[i])
                .wrapping_add(w[i]);
            let sum0 = big_sigma(a, (28, 34, 39));
            let maj_val = maj(a, b, c);
            let temp2 = sum0.wrapping_add(maj_val);
            h = g;
            g = f;
            f = e;
            e = d.wrapping_add(temp1);
            d = c;
            c = b;
            b = a;
            a = temp1.wrapping_add(temp2);
        }

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

    fn encode_length(buf: &mut Vec<u8>, total_bits: u128) {
        buf.extend_from_slice(&total_bits.to_be_bytes());
    }

    fn hash_string(&self) -> String {
        format!(
            "{:016x}{:016x}{:016x}{:016x}{:016x}{:016x}{:016x}{:016x}",
            self.hashes[0],
            self.hashes[1],
            self.hashes[2],
            self.hashes[3],
            self.hashes[4],
            self.hashes[5],
            self.hashes[6],
            self.hashes[7]
        )
    }
}