qfall-math 0.1.1

Mathematical foundations for rapid prototyping of lattice-based cryptography
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// Copyright © 2025 Niklas Siemer
//
// This file is part of qFALL-math.
//
// qFALL-math is free software: you can redistribute it and/or modify it under
// the terms of the Mozilla Public License Version 2.0 as published by the
// Mozilla Foundation. See <https://mozilla.org/en-US/MPL/2.0/>.

//! [`NTTPolynomialRingZq`] containts the NTT representations of polynomials.

use crate::{
    integer::Z,
    integer_mod_q::{ModulusPolynomialRingZq, mat_ntt_polynomial_ring_zq::print_vec_z},
};
use derive_more::Display;
use serde::{Deserialize, Serialize};
use std::fmt;

mod arithmetic;
mod cmp;
mod from;
mod get;
mod sample;

/// [`NTTPolynomialRingZq`] contains the NTT representation of some polynomial with respect to
/// a [`NTTBasisPolynomialRingZq`](super::NTTBasisPolynomialRingZq) that itself isn't aware of.
///
/// Attributes
/// - `poly`: holds the coefficients
/// - `modulus`: the [`ModulusPolynomialRingZq`] defining the modulus `q`, the ring `Z_q[X]/f(X)`, and
///   the NTT transform [`NTTBasisPolynomialRingZq`](crate::integer_mod_q::NTTBasisPolynomialRingZq)
///
/// # Examples
/// ```
/// use qfall_math::integer_mod_q::{Modulus, PolynomialRingZq, NTTPolynomialRingZq, ModulusPolynomialRingZq};
/// use std::str::FromStr;
/// // Setup modulus with capability to perform NTT transform
/// let mut modulus = ModulusPolynomialRingZq::from_str("5  1 0 0 0 1 mod 257").unwrap();
/// modulus.set_ntt_unchecked(64);
///
/// // sample random polynomial
/// let rnd = NTTPolynomialRingZq::sample_uniform(&modulus);
/// // or instantiate polynomial from PolynomialRingZq (or PolyOverZq)
///
/// let poly_ring = PolynomialRingZq::sample_uniform(&modulus);
/// let ntt_poly_ring = NTTPolynomialRingZq::from(&poly_ring);
///
/// // multiply, add and subtract objects
/// let mod_q = Modulus::from(modulus.get_q());
/// let mut tmp_ntt = ntt_poly_ring * &rnd;
/// tmp_ntt += &rnd;
/// tmp_ntt -= &rnd;
///
/// // Return to PolynomialRingZq
/// let res = tmp_ntt.inv_ntt();
/// ```
#[derive(PartialEq, Eq, Serialize, Deserialize, Display, Clone)]
#[display("{} / {}", print_vec_z(&self.poly), self.modulus)]
pub struct NTTPolynomialRingZq {
    pub poly: Vec<Z>,
    pub modulus: ModulusPolynomialRingZq,
}

impl fmt::Debug for NTTPolynomialRingZq {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let short_print = print_vec_z(&self.poly);
        let a: Vec<&str> = short_print.split_whitespace().collect();
        let short_print = format!("{}{} ..., {}{}", a[0], a[1], a[a.len() - 2], a[a.len() - 1]);

        write!(
            f,
            "NTTPolynomialRingZq {{poly: {}, modulus: {}, storage: {{poly: {:?}, modulus: {:?}}}}}",
            short_print, self.modulus, self.poly, self.modulus
        )
    }
}