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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::integer_vector::IntegerVector;
use crate::natural::Natural;
use malachite_base::num::arithmetic::traits::{ContentChained, Gcd, GcdAssign};
use malachite_base::num::basic::traits::One;
// Returns the GCD of `gcd` and the absolute values of the elements of `xs`, where `abs` gives the
// absolute value of an element.
//
// This is equivalent to `_fmpz_vec_content_chained` from `fmpz_vec/content_chained.c`, FLINT 3.6.0.
pub(crate) fn content_chained_helper<T>(
xs: &[T],
abs: impl Fn(&T) -> &Natural,
mut gcd: Natural,
) -> Natural {
// Zeros make no difference, so they are skipped at both ends.
let Some(start) = xs.iter().position(|c| *abs(c) != 0u32) else {
return gcd;
};
let end = xs.iter().rposition(|c| *abs(c) != 0u32).unwrap();
let mut xs = &xs[start..=end];
// An element of absolute value 1 makes the GCD 1. Only the ends are checked, since for the
// coefficients of a polynomial they are the likeliest to be ±1.
if let [first, .., last] = xs
&& (*abs(first) == 1u32 || *abs(last) == 1u32)
{
return Natural::ONE;
}
// The elements are taken in pairs from both ends, stopping as soon as the GCD reaches 1.
while gcd != 1u32
&& let [first, middle @ .., last] = xs
{
gcd.gcd_assign(abs(first).gcd(abs(last)));
xs = middle;
}
if gcd != 1u32
&& let [middle] = xs
{
gcd.gcd_assign(abs(middle));
}
gcd
}
// Returns the GCD of `x` and the absolute values of the elements of `xs`.
//
// This is equivalent to `_fmpz_vec_content_chained` from `fmpz_vec/content_chained.c`, FLINT 3.6.0.
#[doc(hidden)]
#[inline]
pub fn integers_content_chained(xs: &[Integer], x: &Natural) -> Natural {
content_chained_helper(xs, Integer::unsigned_abs_ref, x.clone())
}
impl ContentChained<Natural> for IntegerVector {
type Output = Natural;
/// Computes the GCD of `x` and the elements of an [`IntegerVector`], taking the vector by value
/// and `x` by value.
///
/// The GCD of `x` and the elements of the 0-dimensional vector, or of a vector of zeros, is
/// `x`. The computation stops as soon as the GCD reaches 1.
///
/// $$
/// f(v, x) = \gcd(x, v_0, v_1, \ldots, v_{n-1}),
/// $$
///
/// where $n$ is the dimension of $v$.
///
/// # Worst-case complexity
/// $T(n) = O(n (\log n)^2 \log\log n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is the total number of bits of the
/// elements and of `x`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ContentChained;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_nz::integer_vector::IntegerVector;
/// use malachite_nz::natural::Natural;
///
/// let v = IntegerVector::from_str("(-6, 4, -10)").unwrap();
/// assert_eq!(v.clone().content_chained(Natural::from(4u32)), 2u32);
/// assert_eq!(v.content_chained(Natural::ZERO), 2u32);
/// let v = IntegerVector::from_str("()").unwrap();
/// assert_eq!(v.content_chained(Natural::from(6u32)), 6u32);
/// ```
///
/// This is equivalent to `_fmpz_vec_content_chained` from `fmpz_vec/content_chained.c`, FLINT
/// 3.6.0.
#[inline]
fn content_chained(self, x: Natural) -> Natural {
content_chained_helper(&self.elements, Integer::unsigned_abs_ref, x)
}
}
impl ContentChained<&Natural> for IntegerVector {
type Output = Natural;
/// Computes the GCD of `x` and the elements of an [`IntegerVector`], taking the vector by value
/// and `x` by reference.
///
/// The GCD of `x` and the elements of the 0-dimensional vector, or of a vector of zeros, is
/// `x`. The computation stops as soon as the GCD reaches 1.
///
/// $$
/// f(v, x) = \gcd(x, v_0, v_1, \ldots, v_{n-1}),
/// $$
///
/// where $n$ is the dimension of $v$.
///
/// # Worst-case complexity
/// $T(n) = O(n (\log n)^2 \log\log n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is the total number of bits of the
/// elements and of `x`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ContentChained;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_nz::integer_vector::IntegerVector;
/// use malachite_nz::natural::Natural;
///
/// let v = IntegerVector::from_str("(-6, 4, -10)").unwrap();
/// assert_eq!(v.clone().content_chained(&Natural::from(4u32)), 2u32);
/// assert_eq!(v.content_chained(&Natural::ZERO), 2u32);
/// let v = IntegerVector::from_str("()").unwrap();
/// assert_eq!(v.content_chained(&Natural::from(6u32)), 6u32);
/// ```
///
/// This is equivalent to `_fmpz_vec_content_chained` from `fmpz_vec/content_chained.c`, FLINT
/// 3.6.0.
#[inline]
fn content_chained(self, x: &Natural) -> Natural {
content_chained_helper(&self.elements, Integer::unsigned_abs_ref, x.clone())
}
}
impl ContentChained<Natural> for &IntegerVector {
type Output = Natural;
/// Computes the GCD of `x` and the elements of an [`IntegerVector`], taking the vector by
/// reference and `x` by value.
///
/// The GCD of `x` and the elements of the 0-dimensional vector, or of a vector of zeros, is
/// `x`. The computation stops as soon as the GCD reaches 1.
///
/// $$
/// f(v, x) = \gcd(x, v_0, v_1, \ldots, v_{n-1}),
/// $$
///
/// where $n$ is the dimension of $v$.
///
/// # Worst-case complexity
/// $T(n) = O(n (\log n)^2 \log\log n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is the total number of bits of the
/// elements and of `x`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ContentChained;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_nz::integer_vector::IntegerVector;
/// use malachite_nz::natural::Natural;
///
/// let v = IntegerVector::from_str("(-6, 4, -10)").unwrap();
/// assert_eq!((&v).content_chained(Natural::from(4u32)), 2u32);
/// assert_eq!((&v).content_chained(Natural::ZERO), 2u32);
/// let v = IntegerVector::from_str("()").unwrap();
/// assert_eq!((&v).content_chained(Natural::from(6u32)), 6u32);
/// ```
///
/// This is equivalent to `_fmpz_vec_content_chained` from `fmpz_vec/content_chained.c`, FLINT
/// 3.6.0.
#[inline]
fn content_chained(self, x: Natural) -> Natural {
content_chained_helper(&self.elements, Integer::unsigned_abs_ref, x)
}
}
impl ContentChained<&Natural> for &IntegerVector {
type Output = Natural;
/// Computes the GCD of `x` and the elements of an [`IntegerVector`], taking the vector by
/// reference and `x` by reference.
///
/// The GCD of `x` and the elements of the 0-dimensional vector, or of a vector of zeros, is
/// `x`. The computation stops as soon as the GCD reaches 1.
///
/// $$
/// f(v, x) = \gcd(x, v_0, v_1, \ldots, v_{n-1}),
/// $$
///
/// where $n$ is the dimension of $v$.
///
/// # Worst-case complexity
/// $T(n) = O(n (\log n)^2 \log\log n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is the total number of bits of the
/// elements and of `x`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ContentChained;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_nz::integer_vector::IntegerVector;
/// use malachite_nz::natural::Natural;
///
/// let v = IntegerVector::from_str("(-6, 4, -10)").unwrap();
/// assert_eq!((&v).content_chained(&Natural::from(4u32)), 2u32);
/// assert_eq!((&v).content_chained(&Natural::ZERO), 2u32);
/// let v = IntegerVector::from_str("()").unwrap();
/// assert_eq!((&v).content_chained(&Natural::from(6u32)), 6u32);
/// ```
///
/// This is equivalent to `_fmpz_vec_content_chained` from `fmpz_vec/content_chained.c`, FLINT
/// 3.6.0.
#[inline]
fn content_chained(self, x: &Natural) -> Natural {
content_chained_helper(&self.elements, Integer::unsigned_abs_ref, x.clone())
}
}