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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::integer::Integer;
use crate::natural::arithmetic::balanced_mod_power_of_2::balanced_from_mod_power_of_2;
use core::mem::take;
use malachite_base::num::arithmetic::traits::{
BalancedModPowerOf2, BalancedModPowerOf2Assign, ModPowerOf2,
};
impl BalancedModPowerOf2 for Integer {
type Output = Self;
/// Divides an [`Integer`] by $2^k$, returning the balanced remainder: the representative of
/// `self` modulo $2^k$ that is closest to zero. The [`Integer`] is taken by value.
///
/// The remainder $r$ satisfies $-2^{k-1} < r \leq 2^{k-1}$ and $r \equiv x \bmod 2^k$, which
/// determine it uniquely; for $k = 0$ it is 0. A remainder of exactly $2^{k-1}$ is positive.
/// This is [`balanced_mod`](malachite_base::num::arithmetic::traits::BalancedMod::balanced_mod)
/// with modulus $2^k$.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `pow`.
///
/// # Examples
/// ```
/// use malachite_base::num::arithmetic::traits::BalancedModPowerOf2;
/// use malachite_nz::integer::Integer;
///
/// assert_eq!(Integer::from(23).balanced_mod_power_of_2(3), -1);
/// // a negative value is reduced into the same range
/// assert_eq!(Integer::from(-19).balanced_mod_power_of_2(3), -3);
/// // exactly half the modulus stays positive
/// assert_eq!(Integer::from(-20).balanced_mod_power_of_2(3), 4);
/// ```
#[inline]
fn balanced_mod_power_of_2(self, pow: u64) -> Self {
balanced_from_mod_power_of_2(self.mod_power_of_2(pow), pow)
}
}
impl BalancedModPowerOf2 for &Integer {
type Output = Integer;
/// Divides an [`Integer`] by $2^k$, returning the balanced remainder: the representative of
/// `self` modulo $2^k$ that is closest to zero. The [`Integer`] is taken by reference.
///
/// See the [`BalancedModPowerOf2`] documentation for details.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `pow`.
///
/// # Examples
/// ```
/// use malachite_base::num::arithmetic::traits::BalancedModPowerOf2;
/// use malachite_nz::integer::Integer;
///
/// assert_eq!((&Integer::from(23)).balanced_mod_power_of_2(3), -1);
/// assert_eq!((&Integer::from(-19)).balanced_mod_power_of_2(3), -3);
/// assert_eq!((&Integer::from(-20)).balanced_mod_power_of_2(3), 4);
/// ```
#[inline]
fn balanced_mod_power_of_2(self, pow: u64) -> Integer {
balanced_from_mod_power_of_2(self.mod_power_of_2(pow), pow)
}
}
impl BalancedModPowerOf2Assign for Integer {
/// Divides an [`Integer`] by $2^k$, replacing it by the balanced remainder: the representative
/// of `self` modulo $2^k$ that is closest to zero.
///
/// See the [`BalancedModPowerOf2`] documentation for details.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `pow`.
///
/// # Examples
/// ```
/// use malachite_base::num::arithmetic::traits::BalancedModPowerOf2Assign;
/// use malachite_nz::integer::Integer;
///
/// let mut x = Integer::from(23);
/// x.balanced_mod_power_of_2_assign(3);
/// assert_eq!(x, -1);
/// ```
#[inline]
fn balanced_mod_power_of_2_assign(&mut self, pow: u64) {
*self = take(self).balanced_mod_power_of_2(pow);
}
}