pub fn find_by_id_or<Id: PartialEq, Val: Copy>(
    arr: &[(Id, Val)],
    id: Id,
    default: Val,
) -> Val {
    arr.iter()
        .find(|(elem_id, _)| *elem_id == id)
        .map_or(default, |row| row.1)
}

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

    #[test]
    fn when_no_elements_then_return_default() {
        let arr = [];

        let result = find_by_id_or(&arr, 1, 42);

        assert_eq!(result, 42);
    }

    #[test]
    fn when_id_not_in_elements_then_return_default() {
        let arr = [(0, 100), (2, 200)];

        let result = find_by_id_or(&arr, 1, 42);

        assert_eq!(result, 42);
    }

    #[test]
    fn when_id_in_elements_then_return_value() {
        let arr = [(1, 67)];

        let result = find_by_id_or(&arr, 1, 42);

        assert_eq!(result, 67);
    }
}