//! gnome sort algorithm.
//!
//! **O(N²)**

mod utils;

/// Sort in ascending order using a gnome sort algorithm.
/// 
/// ```rust
/// use buldak::gnome;
///
/// let mut nums = [1, 4, 2, 3, 5, 111, 234, 21, 13];
/// gnome::sort(&mut nums);
/// assert_eq!(nums, [1, 2, 3, 4, 5, 13, 21, 111, 234]);
/// ```
pub fn sort<T>(array: &mut [T])
where
    T: std::cmp::Ord,
{
    sort_by(array, |l, r| l.cmp(r))
}

/// Sort in descending order using a gnome sort algorithm.
/// 
/// ```rust
/// use buldak::gnome;
///
/// let mut nums = [1, 4, 2, 3, 5, 111, 234, 21, 13];
/// gnome::sort_reverse(&mut nums);
/// assert_eq!(nums, [234, 111, 21, 13, 5, 4, 3, 2, 1]);
/// ```
pub fn sort_reverse<T>(array: &mut [T])
where
    T: std::cmp::Ord,
{
    sort_by(array, |l, r| l.cmp(r).reverse())
}

/// It takes a comparator function to determine the order,
/// and sorts it using a gnome sort algorithm.
/// 
/// ```rust
/// use buldak::gnome;
///
/// let mut nums = [1, 4, 2, 3, 5, 111, 234, 21, 13];
/// gnome::sort_by(&mut nums, |l, r| l.cmp(r));
/// assert_eq!(nums, [1, 2, 3, 4, 5, 13, 21, 111, 234]);
/// ```
pub fn sort_by<T, F>(array: &mut [T], compare: F)
where
    T: std::cmp::Ord,
    F: Fn(&T, &T) -> std::cmp::Ordering,
{
    _gnome_sort_impl(array, compare);
}

fn _gnome_sort_impl<T, F>(array: &mut [T], compare: F)
where
    T: std::cmp::Ord,
    F: Fn(&T, &T) -> std::cmp::Ordering,
{
    let mut pos = 0;

    while pos < array.len() {
        if pos == 0 || compare(&array[pos], &array[pos - 1]) != std::cmp::Ordering::Less {
            pos += 1;
        } else {
            utils::swap(array, pos, pos - 1);
            pos -= 1;
        }
    }
}