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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::{ModSubMul, ModSubMulAssign};
use crate::num::basic::unsigneds::PrimitiveUnsigned;
fn assert_reduced<T: PrimitiveUnsigned>(x: T, y: T, z: T, m: T) {
assert!(x < m, "x must be reduced mod m, but {x} >= {m}");
assert!(y < m, "y must be reduced mod m, but {y} >= {m}");
assert!(z < m, "z must be reduced mod m, but {z} >= {m}");
}
#[inline]
fn mod_sub_mul<T: PrimitiveUnsigned>(x: T, y: T, z: T, m: T) -> T {
assert_reduced(x, y, z, m);
x.mod_sub(y.mod_mul(z, m), m)
}
#[inline]
fn mod_sub_mul_assign<T: PrimitiveUnsigned>(x: &mut T, y: T, z: T, m: T) {
assert_reduced(*x, y, z, m);
x.mod_sub_assign(y.mod_mul(z, m), m);
}
macro_rules! impl_mod_sub_mul {
($t:ident) => {
impl ModSubMul<$t> for $t {
type Output = $t;
/// Subtracts the product of two numbers from a third number, modulo a fourth number
/// $m$. All three inputs must be already reduced modulo $m$.
///
/// $f(x, y, z, m) = w$, where $x, y, z, w < m$ and $x - yz \equiv w \mod m$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Panics
/// Panics if `self`, `y`, or `z` are greater than or equal to `m`.
///
/// # Examples
/// See [here](super::mod_sub_mul#mod_sub_mul).
#[inline]
fn mod_sub_mul(self, y: $t, z: $t, m: $t) -> $t {
mod_sub_mul(self, y, z, m)
}
}
impl ModSubMulAssign<$t> for $t {
/// Subtracts the product of two numbers from a third number, modulo a fourth number
/// $m$, in place. All three inputs must be already reduced modulo $m$.
///
/// $x \gets w$, where $x, y, z, w < m$ and $x - yz \equiv w \mod m$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Panics
/// Panics if `self`, `y`, or `z` are greater than or equal to `m`.
///
/// # Examples
/// See [here](super::mod_sub_mul#mod_sub_mul_assign).
#[inline]
fn mod_sub_mul_assign(&mut self, y: $t, z: $t, m: $t) {
mod_sub_mul_assign(self, y, z, m);
}
}
};
}
apply_to_unsigneds!(impl_mod_sub_mul);