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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::{ModPowerOf2AddMulShl, ModPowerOf2AddMulShlAssign};
use crate::num::basic::unsigneds::PrimitiveUnsigned;
fn assert_reduced<T: PrimitiveUnsigned>(x: T, y: T, z: T, pow: u64) {
assert!(pow <= T::WIDTH);
assert!(
x.significant_bits() <= pow,
"x must be reduced mod 2^pow, but {x} >= 2^{pow}"
);
assert!(
y.significant_bits() <= pow,
"y must be reduced mod 2^pow, but {y} >= 2^{pow}"
);
assert!(
z.significant_bits() <= pow,
"z must be reduced mod 2^pow, but {z} >= 2^{pow}"
);
}
// When `bits` is at least `pow`, the shifted product vanishes modulo `2^pow`. Otherwise `bits` is
// less than `T::WIDTH`, so the shift is valid.
fn mod_power_of_2_add_mul_shl<T: PrimitiveUnsigned>(x: T, y: T, z: T, bits: u64, pow: u64) -> T {
assert_reduced(x, y, z, pow);
if bits >= pow {
x
} else {
x.wrapping_add(y.wrapping_mul(z) << bits)
.mod_power_of_2(pow)
}
}
macro_rules! impl_mod_power_of_2_add_mul_shl {
($t:ident) => {
impl ModPowerOf2AddMulShl<$t> for $t {
type Output = $t;
/// Adds a number and the product of two other numbers, shifted left by `bits`, modulo
/// $2^k$. All three inputs must be already reduced modulo $2^k$.
///
/// $f(x, y, z, b, k) = w$, where $x, y, z, w < 2^k$ and $x + yz2^b \equiv w \mod 2^k$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Panics
/// Panics if `pow` is greater than `Self::WIDTH` or if `self`, `y`, or `z` are greater
/// than or equal to $2^k$.
///
/// # Examples
/// See [here](super::mod_power_of_2_add_mul_shl#mod_power_of_2_add_mul_shl).
#[inline]
fn mod_power_of_2_add_mul_shl(self, y: $t, z: $t, bits: u64, pow: u64) -> $t {
mod_power_of_2_add_mul_shl(self, y, z, bits, pow)
}
}
impl ModPowerOf2AddMulShlAssign<$t> for $t {
/// Adds the product of two numbers, shifted left by `bits`, to a third number modulo
/// $2^k$, in place. All three inputs must be already reduced modulo $2^k$.
///
/// $x \gets w$, where $x, y, z, w < 2^k$ and $x + yz2^b \equiv w \mod 2^k$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Panics
/// Panics if `pow` is greater than `Self::WIDTH` or if `self`, `y`, or `z` are greater
/// than or equal to $2^k$.
///
/// # Examples
/// See [here](super::mod_power_of_2_add_mul_shl#mod_power_of_2_add_mul_shl_assign).
#[inline]
fn mod_power_of_2_add_mul_shl_assign(&mut self, y: $t, z: $t, bits: u64, pow: u64) {
*self = mod_power_of_2_add_mul_shl(*self, y, z, bits, pow);
}
}
};
}
apply_to_unsigneds!(impl_mod_power_of_2_add_mul_shl);