// Implementation of an Arrow2 array that holds non Arrow2 data types.

// Modified from the implementation of real Arrow2 Arrays here:
// https://docs.rs/arrow2/latest/src/arrow2/array/mod.rs.html
// https://docs.rs/arrow2/latest/src/arrow2/array/primitive/mod.rs.html

// The license for Arrow2 is as follows:

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// Copyright 2020-2022 Jorge C. Leitão

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use arrow2::{
    array::Array,
    bitmap::{
        utils::{BitmapIter, ZipValidity},
        Bitmap,
    },
    buffer::Buffer,
    datatypes::DataType,
};
use common_error::{DaftError, DaftResult};

pub mod compute;
#[cfg(feature = "python")]
pub mod python;

#[derive(Clone, Debug)]
pub struct PseudoArrowArray<T> {
    values: Buffer<T>,
    validity: Option<Bitmap>,
}

impl<T: Send + Sync + Clone + 'static> PseudoArrowArray<T> {
    pub fn try_new(values: Buffer<T>, validity: Option<Bitmap>) -> DaftResult<Self> {
        if validity
            .clone()
            .map_or(false, |vd| vd.len() != values.len())
        {
            Err(DaftError::ValueError(format!(
                "validity mask length {} must match the number of values {}",
                validity.unwrap().len(),
                values.len(),
            )))
        } else {
            Ok(Self { values, validity })
        }
    }

    pub fn new(values: Buffer<T>, validity: Option<Bitmap>) -> Self {
        Self::try_new(values, validity).unwrap()
    }

    #[inline]
    pub fn values(&self) -> &Buffer<T> {
        &self.values
    }

    #[inline]
    pub fn iter(&self) -> ZipValidity<&T, std::slice::Iter<T>, BitmapIter> {
        ZipValidity::new_with_validity(self.values().iter(), self.validity())
    }
}

impl<T: Send + Sync + Clone + 'static> Array for PseudoArrowArray<T> {
    #[inline]
    fn as_any(&self) -> &dyn std::any::Any {
        self
    }

    #[inline]
    fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
        self
    }

    #[inline]
    fn len(&self) -> usize {
        self.values.len()
    }

    #[inline]
    fn data_type(&self) -> &DataType {
        unimplemented!("PseudoArrowArray does not hold real Arrow DataTypes")
    }

    #[inline]
    fn slice(&mut self, offset: usize, length: usize) {
        assert!(
            offset + length <= self.len(),
            "offset + length may not exceed length of array"
        );
        unsafe { self.slice_unchecked(offset, length) }
    }

    #[inline]
    unsafe fn slice_unchecked(&mut self, offset: usize, length: usize) {
        self.validity.as_mut().and_then(|bitmap| {
            bitmap.slice_unchecked(offset, length);
            (bitmap.unset_bits() > 0).then_some(bitmap)
        });
        self.values.slice_unchecked(offset, length);
    }

    #[inline]
    fn to_boxed(&self) -> Box<dyn Array> {
        Box::new(self.clone())
    }

    fn validity(&self) -> Option<&Bitmap> {
        self.validity.as_ref()
    }

    fn with_validity(&self, validity: Option<Bitmap>) -> Box<dyn Array> {
        Box::new(Self {
            values: self.values.clone(),
            validity,
        })
    }

    #[inline]
    fn null_count(&self) -> usize {
        self.validity()
            .as_ref()
            .map(|x| x.unset_bits())
            .unwrap_or(0)
    }

    fn change_type(&mut self, _: arrow2::datatypes::DataType) {
        unimplemented!("PseudoArray doesn't hold a data type and therefore does not support the change_type API.")
    }
}
