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// Copyright © 2026 Mikhail Hogrefe
//
// This file is part of Malachite.
//
// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.
use crate::natural::Natural;
use malachite_base::num::arithmetic::traits::{
ModPowerOf2Neg, ModPowerOf2NegAssign, NegModPowerOf2, NegModPowerOf2Assign,
};
use malachite_base::num::logic::traits::SignificantBits;
impl ModPowerOf2Neg for Natural {
type Output = Self;
/// Negates a [`Natural`] modulo $2^k$. The input must be already reduced modulo $2^k$. The
/// [`Natural`] is taken by value.
///
/// $f(x, k) = y$, where $x, y < 2^k$ and $-x \equiv y \mod 2^k$.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `pow`.
///
/// # Panics
/// Panics if `self` is greater than or equal to $2^k$.
///
/// # Examples
/// ```
/// use malachite_base::num::arithmetic::traits::ModPowerOf2Neg;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_nz::natural::Natural;
///
/// assert_eq!(Natural::ZERO.mod_power_of_2_neg(5), 0);
/// assert_eq!(Natural::ZERO.mod_power_of_2_neg(100), 0);
/// assert_eq!(Natural::from(100u32).mod_power_of_2_neg(8), 156);
/// assert_eq!(
/// Natural::from(100u32).mod_power_of_2_neg(100).to_string(),
/// "1267650600228229401496703205276"
/// );
/// ```
#[inline]
fn mod_power_of_2_neg(mut self, pow: u64) -> Self {
assert!(
self.significant_bits() <= pow,
"self must be reduced mod 2^pow, but {self} >= 2^{pow}"
);
self.neg_mod_power_of_2_assign(pow);
self
}
}
impl ModPowerOf2Neg for &Natural {
type Output = Natural;
/// Negates a [`Natural`] modulo $2^k$. The input must be already reduced modulo $2^k$. The
/// [`Natural`] is taken by reference.
///
/// $f(x, k) = y$, where $x, y < 2^k$ and $-x \equiv y \mod 2^k$.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `pow`.
///
/// # Panics
/// Panics if `self` is greater than or equal to $2^k$.
///
/// # Examples
/// ```
/// use malachite_base::num::arithmetic::traits::ModPowerOf2Neg;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_nz::natural::Natural;
///
/// assert_eq!((&Natural::ZERO).mod_power_of_2_neg(5), 0);
/// assert_eq!((&Natural::ZERO).mod_power_of_2_neg(100), 0);
/// assert_eq!((&Natural::from(100u32)).mod_power_of_2_neg(8), 156);
/// assert_eq!(
/// (&Natural::from(100u32)).mod_power_of_2_neg(100).to_string(),
/// "1267650600228229401496703205276"
/// );
/// ```
#[inline]
fn mod_power_of_2_neg(self, pow: u64) -> Natural {
assert!(
self.significant_bits() <= pow,
"self must be reduced mod 2^pow, but {self} >= 2^{pow}"
);
self.neg_mod_power_of_2(pow)
}
}
impl ModPowerOf2NegAssign for Natural {
/// Negates a [`Natural`] modulo $2^k$, in place. The input must be already reduced modulo
/// $2^k$.
///
/// $x \gets y$, where $x, y < 2^p$ and $-x \equiv y \mod 2^p$.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `pow`.
///
/// # Panics
/// Panics if `self` is greater than or equal to $2^k$.
///
/// # Examples
/// ```
/// use malachite_base::num::arithmetic::traits::ModPowerOf2NegAssign;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_nz::natural::Natural;
///
/// let mut n = Natural::ZERO;
/// n.mod_power_of_2_neg_assign(5);
/// assert_eq!(n, 0);
///
/// let mut n = Natural::ZERO;
/// n.mod_power_of_2_neg_assign(100);
/// assert_eq!(n, 0);
///
/// let mut n = Natural::from(100u32);
/// n.mod_power_of_2_neg_assign(8);
/// assert_eq!(n, 156);
///
/// let mut n = Natural::from(100u32);
/// n.mod_power_of_2_neg_assign(100);
/// assert_eq!(n.to_string(), "1267650600228229401496703205276");
/// ```
#[inline]
fn mod_power_of_2_neg_assign(&mut self, pow: u64) {
assert!(
self.significant_bits() <= pow,
"self must be reduced mod 2^pow, but {self} >= 2^{pow}"
);
self.neg_mod_power_of_2_assign(pow);
}
}