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use std::ops::BitAnd;

use arrow_buffer::bit_util::ceil;
use arrow_buffer::{BooleanBuffer, MutableBuffer};
use vortex_dtype::{match_each_native_ptype, NativePType};
use vortex_error::VortexResult;

use crate::array::primitive::PrimitiveArray;
use crate::array::BoolArray;
use crate::compute::{CompareFn, Operator};
use crate::validity::Validity;
use crate::{Array, IntoArray, IntoArrayVariant};

impl CompareFn for PrimitiveArray {
    fn compare(&self, other: &Array, operator: Operator) -> VortexResult<Array> {
        let other = other.clone().into_primitive()?;

        let match_mask = match_each_native_ptype!(self.ptype(), |$T| {
            apply_predicate(self.maybe_null_slice::<$T>(), other.maybe_null_slice::<$T>(), operator.to_fn::<$T>())
        });

        let lhs_validity = self
            .validity()
            .to_logical(self.len())
            .to_null_buffer()?
            .map(|b| b.into_inner());
        let rhs_validity = other
            .validity()
            .to_logical(self.len())
            .to_null_buffer()?
            .map(|b| b.into_inner());

        let validity_buffer = match (lhs_validity, rhs_validity) {
            (Some(l), Some(r)) => Some(l.bitand(&r)),
            (Some(b), None) | (None, Some(b)) => Some(b),
            _ => None,
        };

        let validity = validity_buffer
            .map(Validity::from)
            .unwrap_or(Validity::AllValid);

        Ok(BoolArray::try_new(match_mask, validity)?.into_array())
    }
}

fn apply_predicate<T: NativePType, F: Fn(T, T) -> bool>(
    lhs: &[T],
    rhs: &[T],
    f: F,
) -> BooleanBuffer {
    const BLOCK_SIZE: usize = u64::BITS as usize;

    let len = lhs.len();
    let reminder = len % BLOCK_SIZE;
    let block_count = len / BLOCK_SIZE;

    let mut buffer = MutableBuffer::new(ceil(len, BLOCK_SIZE) * 8);

    for block in 0..block_count {
        let mut packed_block = 0_u64;
        for bit_idx in 0..BLOCK_SIZE {
            let idx = bit_idx + block * BLOCK_SIZE;
            let r = f(lhs[idx], rhs[idx]);
            packed_block |= (r as u64) << bit_idx;
        }

        unsafe {
            buffer.push_unchecked(packed_block);
        }
    }

    if reminder != 0 {
        let mut packed_block = 0_u64;
        for bit_idx in 0..reminder {
            let idx = bit_idx + block_count * BLOCK_SIZE;
            let r = f(lhs[idx], rhs[idx]);
            packed_block |= (r as u64) << bit_idx;
        }

        unsafe {
            buffer.push_unchecked(packed_block);
        }
    }

    BooleanBuffer::new(buffer.into(), 0, len)
}

#[cfg(test)]
#[allow(clippy::panic_in_result_fn)]
mod test {
    use itertools::Itertools;

    use super::*;
    use crate::compute::compare;
    use crate::IntoArrayVariant;

    fn to_int_indices(indices_bits: BoolArray) -> Vec<u64> {
        let filtered = indices_bits
            .boolean_buffer()
            .iter()
            .enumerate()
            .filter_map(|(idx, v)| {
                let valid_and_true = indices_bits.validity().is_valid(idx) & v;
                valid_and_true.then_some(idx as u64)
            })
            .collect_vec();
        filtered
    }

    #[test]
    fn test_basic_comparisons() -> VortexResult<()> {
        let arr = PrimitiveArray::from_nullable_vec(vec![
            Some(1i32),
            Some(2),
            Some(3),
            Some(4),
            None,
            Some(5),
            Some(6),
            Some(7),
            Some(8),
            None,
            Some(9),
            None,
        ])
        .into_array();

        let matches = compare(&arr, &arr, Operator::Eq)?.into_bool()?;
        assert_eq!(to_int_indices(matches), [0u64, 1, 2, 3, 5, 6, 7, 8, 10]);

        let matches = compare(&arr, &arr, Operator::NotEq)?.into_bool()?;
        let empty: [u64; 0] = [];
        assert_eq!(to_int_indices(matches), empty);

        let other = PrimitiveArray::from_nullable_vec(vec![
            Some(1i32),
            Some(2),
            Some(3),
            Some(4),
            None,
            Some(6),
            Some(7),
            Some(8),
            Some(9),
            None,
            Some(10),
            None,
        ])
        .into_array();

        let matches = compare(&arr, &other, Operator::Lte)?.into_bool()?;
        assert_eq!(to_int_indices(matches), [0u64, 1, 2, 3, 5, 6, 7, 8, 10]);

        let matches = compare(&arr, &other, Operator::Lt)?.into_bool()?;
        assert_eq!(to_int_indices(matches), [5u64, 6, 7, 8, 10]);

        let matches = compare(&other, &arr, Operator::Gte)?.into_bool()?;
        assert_eq!(to_int_indices(matches), [0u64, 1, 2, 3, 5, 6, 7, 8, 10]);

        let matches = compare(&other, &arr, Operator::Gt)?.into_bool()?;
        assert_eq!(to_int_indices(matches), [5u64, 6, 7, 8, 10]);
        Ok(())
    }
}