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use std::sync::Arc;

use crate::{
    array::{Array, Offset, Utf8Array},
    bitmap::MutableBitmap,
};

use super::{
    utils::{build_extend_null_bits, extend_offset_values, extend_offsets, ExtendNullBits},
    Growable,
};

/// Concrete [`Growable`] for the [`Utf8Array`].
pub struct GrowableUtf8<'a, O: Offset> {
    arrays: Vec<&'a Utf8Array<O>>,
    validity: MutableBitmap,
    values: Vec<u8>,
    offsets: Vec<O>,
    length: O, // always equal to the last offset at `offsets`.
    extend_null_bits: Vec<ExtendNullBits<'a>>,
}

impl<'a, O: Offset> GrowableUtf8<'a, O> {
    /// Creates a new [`GrowableUtf8`] bound to `arrays` with a pre-allocated `capacity`.
    /// # Panics
    /// If `arrays` is empty.
    pub fn new(arrays: Vec<&'a Utf8Array<O>>, mut use_validity: bool, capacity: usize) -> Self {
        // if any of the arrays has nulls, insertions from any array requires setting bits
        // as there is at least one array with nulls.
        if arrays.iter().any(|array| array.null_count() > 0) {
            use_validity = true;
        };

        let extend_null_bits = arrays
            .iter()
            .map(|array| build_extend_null_bits(*array, use_validity))
            .collect();

        let mut offsets = Vec::with_capacity(capacity + 1);
        let length = O::default();
        offsets.push(length);

        Self {
            arrays: arrays.to_vec(),
            values: Vec::with_capacity(0),
            offsets,
            length,
            validity: MutableBitmap::with_capacity(capacity),
            extend_null_bits,
        }
    }

    fn to(&mut self) -> Utf8Array<O> {
        let validity = std::mem::take(&mut self.validity);
        let offsets = std::mem::take(&mut self.offsets);
        let values = std::mem::take(&mut self.values);

        #[cfg(debug_assertions)]
        {
            crate::array::specification::try_check_offsets_and_utf8(&offsets, &values).unwrap();
        }

        unsafe {
            Utf8Array::<O>::try_new_unchecked(
                self.arrays[0].data_type().clone(),
                offsets.into(),
                values.into(),
                validity.into(),
            )
            .unwrap()
        }
    }
}

impl<'a, O: Offset> Growable<'a> for GrowableUtf8<'a, O> {
    fn extend(&mut self, index: usize, start: usize, len: usize) {
        (self.extend_null_bits[index])(&mut self.validity, start, len);

        let array = self.arrays[index];
        let offsets = array.offsets();
        let values = array.values();

        extend_offsets::<O>(
            &mut self.offsets,
            &mut self.length,
            &offsets[start..start + len + 1],
        );
        // values
        extend_offset_values::<O>(&mut self.values, offsets, values, start, len);
    }

    fn extend_validity(&mut self, additional: usize) {
        self.offsets
            .resize(self.offsets.len() + additional, self.length);
        self.validity.extend_constant(additional, false);
    }

    fn as_arc(&mut self) -> Arc<dyn Array> {
        Arc::new(self.to())
    }

    fn as_box(&mut self) -> Box<dyn Array> {
        Box::new(self.to())
    }
}

impl<'a, O: Offset> From<GrowableUtf8<'a, O>> for Utf8Array<O> {
    fn from(mut val: GrowableUtf8<'a, O>) -> Self {
        val.to()
    }
}