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use crate::prelude::*;
use rayon::prelude::*;

unsafe fn idx_to_str(idx: usize, arr: &Utf8Array<i64>) -> Option<&str> {
    if arr.is_valid(idx) {
        Some(arr.value_unchecked(idx))
    } else {
        None
    }
}

impl Utf8Chunked {
    pub fn par_iter_indexed(&self) -> impl IndexedParallelIterator<Item = Option<&str>> {
        assert_eq!(self.chunks.len(), 1);
        let arr = &*self.chunks[0];

        // Safety:
        // guarded by the type system
        let arr = unsafe { &*(arr as *const dyn Array as *const Utf8Array<i64>) };
        (0..arr.len())
            .into_par_iter()
            .map(move |idx| unsafe { idx_to_str(idx, arr) })
    }

    pub fn par_iter(&self) -> impl ParallelIterator<Item = Option<&str>> + '_ {
        self.chunks
            .par_iter()
            .map(move |arr| {
                // Safety:
                // guarded by the type system
                let arr = &**arr;
                let arr = unsafe { &*(arr as *const dyn Array as *const Utf8Array<i64>) };
                (0..arr.len())
                    .into_par_iter()
                    .map(move |idx| unsafe { idx_to_str(idx, arr) })
            })
            .flatten()
    }
}