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//! Contains the concatenate kernel
//!
//! Example:
//!
//! ```
//! use arrow2::array::Utf8Array;
//! use arrow2::compute::concatenate::concatenate;
//!
//! let arr = concatenate(&[
//!     &Utf8Array::<i32>::from_slice(["hello", "world"]),
//!     &Utf8Array::<i32>::from_slice(["!"]),
//! ]).unwrap();
//! assert_eq!(arr.len(), 3);
//! ```

use crate::array::{growable::make_growable, Array};
use crate::error::{ArrowError, Result};

/// Concatenate multiple [Array] of the same type into a single [`Array`].
pub fn concatenate(arrays: &[&dyn Array]) -> Result<Box<dyn Array>> {
    if arrays.is_empty() {
        return Err(ArrowError::InvalidArgumentError(
            "concat requires input of at least one array".to_string(),
        ));
    }

    if arrays
        .iter()
        .any(|array| array.data_type() != arrays[0].data_type())
    {
        return Err(ArrowError::InvalidArgumentError(
            "It is not possible to concatenate arrays of different data types.".to_string(),
        ));
    }

    let lengths = arrays.iter().map(|array| array.len()).collect::<Vec<_>>();
    let capacity = lengths.iter().sum();

    let mut mutable = make_growable(arrays, false, capacity);

    for (i, len) in lengths.iter().enumerate() {
        mutable.extend(i, 0, *len)
    }

    Ok(mutable.as_box())
}