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use crate::arithmetic::bits_384::limbs::*;
use crate::arithmetic::utils::Bits;
use rand_core::RngCore;

pub const fn zero() -> [u64; 6] {
    [0, 0, 0, 0, 0, 0]
}

pub const fn one(r2: [u64; 6], p: [u64; 6], inv: u64) -> [u64; 6] {
    to_mont_form([1, 0, 0, 0, 0, 0], r2, p, inv)
}

pub const fn from_u64(val: u64) -> [u64; 6] {
    [val, 0, 0, 0, 0, 0]
}

pub const fn from_u512(
    limbs: [u64; 12],
    r2: [u64; 6],
    r3: [u64; 6],
    p: [u64; 6],
    inv: u64,
) -> [u64; 6] {
    let a = mul(
        [limbs[0], limbs[1], limbs[2], limbs[3], limbs[4], limbs[5]],
        r2,
        p,
        inv,
    );
    let b = mul(
        [limbs[6], limbs[7], limbs[8], limbs[9], limbs[10], limbs[11]],
        r3,
        p,
        inv,
    );
    add(a, b, p)
}

pub const fn to_mont_form(val: [u64; 6], r2: [u64; 6], p: [u64; 6], inv: u64) -> [u64; 6] {
    mul(val, r2, p, inv)
}

pub fn to_bits(val: [u64; 6]) -> Bits {
    let mut index = 384;
    let mut bits: [u8; 384] = [0; 384];
    for mut x in val {
        for _ in 0..64 {
            index -= 1;
            bits[index] = (x & 1) as u8;
            x >>= 1;
        }
    }
    bits.to_vec()
}

pub fn random_limbs(
    mut rand: impl RngCore,
    r2: [u64; 6],
    r3: [u64; 6],
    p: [u64; 6],
    inv: u64,
) -> [u64; 6] {
    from_u512(
        [
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
            rand.next_u64(),
        ],
        r2,
        r3,
        p,
        inv,
    )
}

pub const fn little_fermat(p: [u64; 6]) -> [u64; 6] {
    sub(zero(), [2, 0, 0, 0, 0, 0], p)
}