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use std::arch::aarch64;

pub fn iterate_bitboard(bb: Bitboard) -> u32 {
    let mut i = 0;
    for pos in bb {
        i += pos;
    }
    i
}

#[inline(always)]
fn pop_lsb(n: &mut u64) -> u32 {
    let ret = n.trailing_zeros();
    *n = *n & n.wrapping_sub(1);
    ret
}

#[derive(Clone, Copy)]
pub struct Bitboard(aarch64::uint64x2_t);
pub struct BitboardIterator([u64; 2]);

impl Iterator for BitboardIterator {
    type Item = u32;

// #[inline(always)]
    fn next(&mut self) -> Option<Self::Item> {
        if self.0[0] != 0 {
            return Some(pop_lsb(&mut self.0[0]) + 1);
        }
        if self.0[1] != 0 {
            return Some(pop_lsb(&mut self.0[1]) + 64);
        }
        None
    }
}

impl IntoIterator for Bitboard {
    type Item = u32;
    type IntoIter = BitboardIterator;

fn into_iter(self) -> Self::IntoIter {
        unsafe {
            let u = std::mem::MaybeUninit::<[u64; 2]>::uninit();
            aarch64::vst1q_u64(u.as_ptr() as *mut _, self.0);
            BitboardIterator(u.assume_init())
        }
    }
}