// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// 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 crate::data::{ArrayData, count_nulls};

use arrow_buffer::ArrowNativeType;

use num_integer::Integer;

use super::equal_range;

fn lengths_equal<T: ArrowNativeType + Integer>(lhs: &[T], rhs: &[T]) -> bool {

    // invariant from `base_equal`

    debug_assert_eq!(lhs.len(), rhs.len());

    if lhs.is_empty() {

        return true;

    }

    if lhs[0] == T::zero() && rhs[0] == T::zero() {

        return lhs == rhs;

    };

    // The expensive case, e.g.

    // [0, 2, 4, 6, 9] == [4, 6, 8, 10, 13]

    lhs.windows(2)

        .zip(rhs.windows(2))

        .all(|(lhs_offsets, rhs_offsets)| {

            // length of left == length of right

            (lhs_offsets[1] - lhs_offsets[0]) == (rhs_offsets[1] - rhs_offsets[0])

        })

}

pub(super) fn list_equal<T: ArrowNativeType + Integer>(

    lhs: &ArrayData,

    rhs: &ArrayData,

    lhs_start: usize,

    rhs_start: usize,

    len: usize,

) -> bool {

    let lhs_offsets = lhs.buffer::<T>(0);

    let rhs_offsets = rhs.buffer::<T>(0);

    // There is an edge-case where a n-length list that has 0 children, results in panics.

    // For example; an array with offsets [0, 0, 0, 0, 0] has 4 slots, but will have

    // no valid children.

    // Under logical equality, the child null bitmap will be an empty buffer, as there are

    // no child values. This causes panics when trying to count set bits.

    //

    // We caught this by chance from an accidental test-case, but due to the nature of this

    // crash only occurring on list equality checks, we are adding a check here, instead of

    // on the buffer/bitmap utilities, as a length check would incur a penalty for almost all

    // other use-cases.

    //

    // The solution is to check the number of child values from offsets, and return `true` if

    // they = 0. Empty arrays are equal, so this is correct.

    //

    // It's unlikely that one would create a n-length list array with no values, where n > 0,

    // however, one is more likely to slice into a list array and get a region that has 0

    // child values.

    // The test that triggered this behaviour had [4, 4] as a slice of 1 value slot.

    // For the edge case that zero length list arrays are always equal.

    if len == 0 {

        return true;

    }

    let lhs_child_length = lhs_offsets[lhs_start + len].to_usize().unwrap()

        - lhs_offsets[lhs_start].to_usize().unwrap();

    let rhs_child_length = rhs_offsets[rhs_start + len].to_usize().unwrap()

        - rhs_offsets[rhs_start].to_usize().unwrap();

    if lhs_child_length == 0 && 
lhs_child_length == rhs_child_length0
 {

        return true;

    }

    let lhs_values = &lhs.child_data()[0];

    let rhs_values = &rhs.child_data()[0];

    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 != rhs_null_count {

        return false;

    }

    if lhs_null_count == 0 && 
rhs_null_count == 03
 {

        lhs_child_length == rhs_child_length

            && lengths_equal(

                &lhs_offsets[lhs_start..lhs_start + len],

                &rhs_offsets[rhs_start..rhs_start + len],

            )

            && equal_range(

                lhs_values,

                rhs_values,

                lhs_offsets[lhs_start].to_usize().unwrap(),

                rhs_offsets[rhs_start].to_usize().unwrap(),

                lhs_child_length,

            )

    } else {

        // get a ref of the parent null buffer bytes, to use in testing for nullness

        let lhs_nulls = lhs.nulls().unwrap();

        let rhs_nulls = rhs.nulls().unwrap();

        // with nulls, we need to compare item by item whenever it is not null

        // TODO: Could potentially compare runs of not NULL values

        
(0..len)11
.
all11
(|i| {

            let lhs_pos = lhs_start + i;

            let rhs_pos = rhs_start + i;

            let lhs_is_null = lhs_nulls.is_null(lhs_pos);

            let rhs_is_null = rhs_nulls.is_null(rhs_pos);

            if lhs_is_null != rhs_is_null {

                return false;

            }

            let lhs_offset_start = lhs_offsets[lhs_pos].to_usize().unwrap();

            let lhs_offset_end = lhs_offsets[lhs_pos + 1].to_usize().unwrap();

            let rhs_offset_start = rhs_offsets[rhs_pos].to_usize().unwrap();

            let rhs_offset_end = rhs_offsets[rhs_pos + 1].to_usize().unwrap();

            let lhs_len = lhs_offset_end - lhs_offset_start;

            let rhs_len = rhs_offset_end - rhs_offset_start;

            lhs_is_null

                || (lhs_len == rhs_len

                    && equal_range(

                        lhs_values,

                        rhs_values,

                        lhs_offset_start,

                        rhs_offset_start,

                        lhs_len,

                    ))

        })

    }

}