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use crate::array::{Array, ArrayAccessor, ArrayValuesIter};
use crate::bitmap::utils::{BitmapIter, ZipValidity};
use crate::offset::Offset;

use super::ListArray;

unsafe impl<'a, O: Offset> ArrayAccessor<'a> for ListArray<O> {
    type Item = Box<dyn Array>;

    #[inline]
    unsafe fn value_unchecked(&'a self, index: usize) -> Self::Item {
        self.value_unchecked(index)
    }

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

/// Iterator of values of a [`ListArray`].
pub type ListValuesIter<'a, O> = ArrayValuesIter<'a, ListArray<O>>;

type ZipIter<'a, O> = ZipValidity<Box<dyn Array>, ListValuesIter<'a, O>, BitmapIter<'a>>;

impl<'a, O: Offset> IntoIterator for &'a ListArray<O> {
    type Item = Option<Box<dyn Array>>;
    type IntoIter = ZipIter<'a, O>;

    fn into_iter(self) -> Self::IntoIter {
        self.iter()
    }
}

impl<'a, O: Offset> ListArray<O> {
    /// Returns an iterator of `Option<Box<dyn Array>>`
    pub fn iter(&'a self) -> ZipIter<'a, O> {
        ZipValidity::new_with_validity(ListValuesIter::new(self), self.validity.as_ref())
    }

    /// Returns an iterator of `Box<dyn Array>`
    pub fn values_iter(&'a self) -> ListValuesIter<'a, O> {
        ListValuesIter::new(self)
    }
}

struct Iter<T, I: Iterator<Item = Option<T>>> {
    current: i32,
    offsets: std::vec::IntoIter<i32>,
    values: I,
}

impl<T, I: Iterator<Item = Option<T>> + Clone> Iterator for Iter<T, I> {
    type Item = Option<std::iter::Take<std::iter::Skip<I>>>;

    fn next(&mut self) -> Option<Self::Item> {
        let next = self.offsets.next();
        next.map(|next| {
            let length = next - self.current;
            let iter = self
                .values
                .clone()
                .skip(self.current as usize)
                .take(length as usize);
            self.current = next;
            Some(iter)
        })
    }
}