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use std::cmp::min;

use arrow_buffer::buffer::BooleanBuffer;
use arrow_buffer::BooleanBufferBuilder;
use num_traits::AsPrimitive;
use vortex_dtype::NativePType;
use vortex_error::{vortex_panic, VortexExpect as _};

use crate::value_at_index;

pub fn runend_bool_encode_slice(elements: &BooleanBuffer) -> (Vec<u64>, bool) {
    let mut iter = elements.set_slices();
    let Some((start, end)) = iter.next() else {
        return (vec![elements.len() as u64], false);
    };

    let mut ends = Vec::new();
    let first_bool = start == 0;
    if !first_bool {
        ends.push(start as u64)
    }
    ends.push(end as u64);
    for (s, e) in iter {
        ends.push(s as u64);
        ends.push(e as u64);
    }

    let last_end = ends.last().vortex_expect(
        "RunEndBoolArray cannot have empty run ends (by construction); this should be impossible",
    );
    if *last_end != elements.len() as u64 {
        ends.push(elements.len() as u64)
    }

    (ends, first_bool)
}

#[inline]
pub fn trimmed_ends_iter<E: NativePType + AsPrimitive<usize> + Ord>(
    run_ends: &[E],
    offset: usize,
    length: usize,
) -> impl Iterator<Item = usize> + use<'_, E> {
    let offset_e = E::from_usize(offset).unwrap_or_else(|| {
        vortex_panic!(
            "offset {} cannot be converted to {}",
            offset,
            std::any::type_name::<E>()
        )
    });
    let length_e = E::from_usize(length).unwrap_or_else(|| {
        vortex_panic!(
            "length {} cannot be converted to {}",
            length,
            std::any::type_name::<E>()
        )
    });
    run_ends
        .iter()
        .copied()
        .map(move |v| v - offset_e)
        .map(move |v| min(v, length_e))
        .map(|v| v.as_())
}

pub fn runend_bool_decode_slice(
    run_ends_iter: impl Iterator<Item = usize>,
    start: bool,
    length: usize,
) -> BooleanBuffer {
    let mut decoded = BooleanBufferBuilder::new(length);
    for (idx, end) in run_ends_iter.enumerate() {
        decoded.append_n(end - decoded.len(), value_at_index(idx, start));
    }
    BooleanBuffer::from(decoded)
}

#[cfg(test)]
mod test {
    use arrow_buffer::BooleanBuffer;
    use itertools::Itertools;
    use rand::prelude::StdRng;
    use rand::{Rng, SeedableRng};
    use vortex_array::array::{BoolArray, PrimitiveArray};
    use vortex_array::compute::slice;
    use vortex_array::validity::Validity;
    use vortex_array::IntoArrayVariant;

    use crate::compress::{runend_bool_decode_slice, runend_bool_encode_slice, trimmed_ends_iter};
    use crate::decode_runend_bool;

    #[test]
    fn encode_bool() {
        let encoded =
            runend_bool_encode_slice(&BooleanBuffer::from([true, true, false, true].as_slice()));
        assert_eq!(encoded, (vec![2, 3, 4], true))
    }

    #[test]
    fn encode_bool_false_true_end() {
        let mut input = vec![false; 66];
        input.extend([true, true]);
        let encoded = runend_bool_encode_slice(&BooleanBuffer::from(input));
        assert_eq!(encoded, (vec![66, 68], false))
    }

    #[test]
    fn encode_bool_false() {
        let encoded =
            runend_bool_encode_slice(&BooleanBuffer::from([false, false, true, false].as_slice()));
        assert_eq!(encoded, (vec![2, 3, 4], false))
    }

    #[test]
    fn encode_decode_bool() {
        let input = [true, true, false, true, true, false];
        let (ends, start) = runend_bool_encode_slice(&BooleanBuffer::from(input.as_slice()));
        let ends_iter = trimmed_ends_iter(ends.as_slice(), 0, input.len());

        let decoded = runend_bool_decode_slice(ends_iter, start, input.len());
        assert_eq!(decoded, BooleanBuffer::from(input.as_slice()))
    }

    #[test]
    fn encode_decode_bool_false_start() {
        let input = [false, false, true, true, false, true, true, false];
        let (ends, start) = runend_bool_encode_slice(&BooleanBuffer::from(input.as_slice()));
        let ends_iter = trimmed_ends_iter(ends.as_slice(), 0, input.len());

        let decoded = runend_bool_decode_slice(ends_iter, start, input.len());
        assert_eq!(decoded, BooleanBuffer::from(input.as_slice()))
    }

    #[test]
    fn encode_decode_bool_false_start_long() {
        let mut input = vec![true; 1024];
        input.extend([false, true, false, true].as_slice());
        let (ends, start) = runend_bool_encode_slice(&BooleanBuffer::from(input.as_slice()));
        let ends_iter = trimmed_ends_iter(ends.as_slice(), 0, input.len());

        let decoded = runend_bool_decode_slice(ends_iter, start, input.len());
        assert_eq!(decoded, BooleanBuffer::from(input.as_slice()))
    }

    #[test]
    fn encode_decode_random() {
        let mut rng = StdRng::seed_from_u64(4352);
        let input = (0..1024 * 4).map(|_x| rng.gen::<bool>()).collect_vec();
        let (ends, start) = runend_bool_encode_slice(&BooleanBuffer::from(input.as_slice()));
        let ends_iter = trimmed_ends_iter(ends.as_slice(), 0, input.len());

        let decoded = runend_bool_decode_slice(ends_iter, start, input.len());
        assert_eq!(decoded, BooleanBuffer::from(input.as_slice()))
    }

    #[test]
    fn encode_decode_offset_array() {
        let mut rng = StdRng::seed_from_u64(39451);
        let input = (0..1024 * 8 - 61).map(|_x| rng.gen::<bool>()).collect_vec();
        let b = BoolArray::from_iter(input.clone());
        let b = slice(b, 3, 1024 * 8 - 66).unwrap().into_bool().unwrap();
        let (ends, start) = runend_bool_encode_slice(&b.boolean_buffer());
        let ends = PrimitiveArray::from(ends);

        let decoded = decode_runend_bool(&ends, start, Validity::NonNullable, 0, 1024 * 8 - 69)
            .unwrap()
            .into_bool()
            .unwrap()
            .boolean_buffer()
            .iter()
            .collect_vec();
        assert_eq!(input[3..1024 * 8 - 66], decoded)
    }
}