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use vortex_dtype::match_each_native_ptype;
use vortex_error::VortexResult;

use crate::array::primitive::PrimitiveArray;
use crate::compute::unary::FillForwardFn;
use crate::validity::ArrayValidity;
use crate::{Array, IntoArray};

impl FillForwardFn for PrimitiveArray {
    fn fill_forward(&self) -> VortexResult<Array> {
        let validity = self.logical_validity();
        let Some(nulls) = validity.to_null_buffer()? else {
            return Ok(self.clone().into());
        };
        match_each_native_ptype!(self.ptype(), |$T| {
            let maybe_null_slice = self.maybe_null_slice::<$T>();
            let mut last_value = $T::default();
            let filled = maybe_null_slice
                .iter()
                .zip(nulls.into_iter())
                .map(|(v, valid)| {
                    if valid {
                        last_value = *v;
                    }
                    last_value
                })
                .collect::<Vec<_>>();
            Ok(filled.into_array())
        })
    }
}

#[cfg(test)]
mod test {
    use crate::array::primitive::PrimitiveArray;
    use crate::array::BoolArray;
    use crate::compute::unary::fill_forward;
    use crate::validity::{ArrayValidity, Validity};
    use crate::IntoArray;

    #[test]
    fn leading_none() {
        let arr = PrimitiveArray::from_nullable_vec(vec![None, Some(8u8), None, Some(10), None])
            .into_array();
        let p = fill_forward(&arr).unwrap().as_primitive();
        assert_eq!(p.maybe_null_slice::<u8>(), vec![0, 8, 8, 10, 10]);
        assert!(p.logical_validity().all_valid());
    }

    #[test]
    fn all_none() {
        let arr =
            PrimitiveArray::from_nullable_vec(vec![Option::<u8>::None, None, None, None, None])
                .into_array();

        let p = fill_forward(&arr).unwrap().as_primitive();
        assert_eq!(p.maybe_null_slice::<u8>(), vec![0, 0, 0, 0, 0]);
        assert!(p.logical_validity().all_valid());
    }

    #[test]
    fn nullable_non_null() {
        let arr = PrimitiveArray::from_vec(
            vec![8u8, 10u8, 12u8, 14u8, 16u8],
            Validity::Array(BoolArray::from(vec![true, true, true, true, true]).into_array()),
        )
        .into_array();
        let p = fill_forward(&arr).unwrap().as_primitive();
        assert_eq!(p.maybe_null_slice::<u8>(), vec![8, 10, 12, 14, 16]);
        assert!(p.logical_validity().all_valid());
    }
}