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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::num::arithmetic::traits::{ModPowerOf2IsReduced, ModPowerOf2Neg, ModPowerOf2NegAssign};
use crate::num::basic::unsigneds::PrimitiveUnsigned;
use crate::unsigned_vector::UnsignedVector;
fn assert_reduced<T: PrimitiveUnsigned>(v: &UnsignedVector<T>, pow: u64) {
assert!(
pow <= T::WIDTH,
"pow must be at most T::WIDTH, but it is {pow}"
);
assert!(
v.mod_power_of_2_is_reduced(pow),
"self must be reduced mod 2^pow, but {v} has an element >= 2^{pow}"
);
}
// Negates every element modulo 2^pow.
fn negate<T: PrimitiveUnsigned>(elements: &mut [T], pow: u64) {
for x in elements {
*x = x.wrapping_neg().mod_power_of_2(pow);
}
}
impl<T: PrimitiveUnsigned> ModPowerOf2Neg for UnsignedVector<T> {
type Output = Self;
/// Negates an [`UnsignedVector`] modulo $2^k$, taking the vector by value. The elements must
/// already be reduced modulo $2^k$.
///
/// Each element $x$ becomes $-x \bmod 2^k$: $2^k - x$ if $x$ is nonzero, and 0 if it is zero.
/// The dimension is unchanged.
///
/// $$
/// f(v, k) = -v \bmod 2^k.
/// $$
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.dimension()`.
///
/// # Panics
/// Panics if `pow` is greater than `T::WIDTH`, or if any element of `self` is greater than or
/// equal to $2^k$.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModPowerOf2Neg;
/// use malachite_base::unsigned_vector::UnsignedVector;
///
/// let v = UnsignedVector::<u8>::from_str("(5, 1, 3)").unwrap();
/// assert_eq!(v.mod_power_of_2_neg(3).to_string(), "(3, 7, 5)");
///
/// // A zero element stays zero.
/// let v = UnsignedVector::<u8>::from_str("(0, 1)").unwrap();
/// assert_eq!(v.mod_power_of_2_neg(8).to_string(), "(0, 255)");
/// ```
///
/// This is equivalent to `_nmod_vec_neg` from `nmod_vec/neg.c`, FLINT 3.6.0, with the modulus
/// $2^k$.
#[inline]
fn mod_power_of_2_neg(mut self, pow: u64) -> Self {
self.mod_power_of_2_neg_assign(pow);
self
}
}
impl<T: PrimitiveUnsigned> ModPowerOf2Neg for &UnsignedVector<T> {
type Output = UnsignedVector<T>;
/// Negates an [`UnsignedVector`] modulo $2^k$, taking the vector by reference. The elements
/// must already be reduced modulo $2^k$.
///
/// Each element $x$ becomes $-x \bmod 2^k$: $2^k - x$ if $x$ is nonzero, and 0 if it is zero.
/// The dimension is unchanged.
///
/// $$
/// f(v, k) = -v \bmod 2^k.
/// $$
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.dimension()`.
///
/// # Panics
/// Panics if `pow` is greater than `T::WIDTH`, or if any element of `self` is greater than or
/// equal to $2^k$.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModPowerOf2Neg;
/// use malachite_base::unsigned_vector::UnsignedVector;
///
/// let v = UnsignedVector::<u8>::from_str("(5, 1, 3)").unwrap();
/// assert_eq!((&v).mod_power_of_2_neg(3).to_string(), "(3, 7, 5)");
/// ```
///
/// This is equivalent to `_nmod_vec_neg` from `nmod_vec/neg.c`, FLINT 3.6.0, with the modulus
/// $2^k$.
#[inline]
fn mod_power_of_2_neg(self, pow: u64) -> UnsignedVector<T> {
assert_reduced(self, pow);
let mut elements = self.elements.clone();
negate(&mut elements, pow);
UnsignedVector { elements }
}
}
impl<T: PrimitiveUnsigned> ModPowerOf2NegAssign for UnsignedVector<T> {
/// Negates an [`UnsignedVector`] modulo $2^k$, in place. The elements must already be reduced
/// modulo $2^k$.
///
/// See [`mod_power_of_2_neg`](ModPowerOf2Neg::mod_power_of_2_neg).
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.dimension()`.
///
/// # Panics
/// Panics if `pow` is greater than `T::WIDTH`, or if any element of `self` is greater than or
/// equal to $2^k$.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModPowerOf2NegAssign;
/// use malachite_base::unsigned_vector::UnsignedVector;
///
/// let mut v = UnsignedVector::<u8>::from_str("(5, 1, 3)").unwrap();
/// v.mod_power_of_2_neg_assign(3);
/// assert_eq!(v.to_string(), "(3, 7, 5)");
/// ```
#[inline]
fn mod_power_of_2_neg_assign(&mut self, pow: u64) {
assert_reduced(self, pow);
negate(&mut self.elements, pow);
}
}