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// distributed with this work for additional information
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// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

use std::mem::size_of;

use crate::array::{data::count_nulls, ArrayData};
use crate::buffer::Buffer;
use crate::util::bit_util::get_bit;

use super::utils::equal_len;

pub(super) fn primitive_equal<T>(
    lhs: &ArrayData,
    rhs: &ArrayData,
    lhs_nulls: Option<&Buffer>,
    rhs_nulls: Option<&Buffer>,
    lhs_start: usize,
    rhs_start: usize,
    len: usize,
) -> bool {
    let byte_width = size_of::<T>();
    let lhs_values = &lhs.buffers()[0].as_slice()[lhs.offset() * byte_width..];
    let rhs_values = &rhs.buffers()[0].as_slice()[rhs.offset() * byte_width..];

    let lhs_null_count = count_nulls(lhs_nulls, lhs_start, len);
    let rhs_null_count = count_nulls(rhs_nulls, rhs_start, len);

    if lhs_null_count == 0 && rhs_null_count == 0 {
        // without nulls, we just need to compare slices
        equal_len(
            lhs_values,
            rhs_values,
            lhs_start * byte_width,
            rhs_start * byte_width,
            len * byte_width,
        )
    } else {
        // get a ref of the null buffer bytes, to use in testing for nullness
        let lhs_null_bytes = lhs_nulls.as_ref().unwrap().as_slice();
        let rhs_null_bytes = rhs_nulls.as_ref().unwrap().as_slice();
        // with nulls, we need to compare item by item whenever it is not null
        (0..len).all(|i| {
            let lhs_pos = lhs_start + i;
            let rhs_pos = rhs_start + i;
            let lhs_is_null = !get_bit(lhs_null_bytes, lhs_pos + lhs.offset());
            let rhs_is_null = !get_bit(rhs_null_bytes, rhs_pos + rhs.offset());

            lhs_is_null
                || (lhs_is_null == rhs_is_null)
                    && equal_len(
                        lhs_values,
                        rhs_values,
                        lhs_pos * byte_width,
                        rhs_pos * byte_width,
                        byte_width, // 1 * byte_width since we are comparing a single entry
                    )
        })
    }
}