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#![no_std]

/// Computes total size of all provided const arrays.
#[macro_export]
macro_rules! concat_arrays_size {
    ($( $array:tt ),*) => {{
        0 $(+ $array.len())*
    }};
}

/// Concatenates provided const arrays.
#[macro_export]
macro_rules! concat_arrays {
    ($t:ty; $( $array:tt ),*; $init_value:expr) => ({
        const __ARRAY_SIZE__: usize = $crate::concat_arrays_size!($($array),*);
        const __CONCAT__: [$t; __ARRAY_SIZE__] = {
        let mut result = [$init_value; __ARRAY_SIZE__];
        let mut result_index = 0;

        $(
        let mut index = 0;
        while index < $array.len() {
                result[result_index] = $array[index];
                result_index += 1;
                index += 1;
        }
        )*
        ["Initialization Failed"][(result_index != __ARRAY_SIZE__) as usize];
        result
        };
        __CONCAT__
    });
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_simple_concat() {
        const A: [u32; 3] = [1, 2, 3];
        const B: [u32; 3] = [4, 5, 6];
        const C: [u32; concat_arrays_size!(A, B)] = concat_arrays!(u32; A, B; u32::MIN);
        assert_eq!([1, 2, 3, 4, 5, 6], C);
    }

    #[test]
    fn test_different_sizes() {
        const A: [u32; 3] = [1, 2, 3];
        const B: [u32; 2] = [4, 5];
        const C: [u32; concat_arrays_size!(A, B)] = concat_arrays!(u32; A, B; u32::MIN);
        assert_eq!([1, 2, 3, 4, 5], C);
    }
}