use crate::utils::gt_by;
use std::{cmp::Ordering, iter::from_generator};

/// Sorts a slice of data using the comb sort algorithm.
///
/// # Examples
///
/// ```
/// # use sort_steps::{comb_sort};
/// let numbers = [5, 9, 3, 6, 8, 2, 1, 7, 4];
/// println!("Comb Sort Steps:");
/// for (i, v) in comb_sort(&numbers).enumerate() {
///     println!("#{:02}: {:?}", i, v);
/// }
/// ```
pub fn comb_sort<T>(v: &[T]) -> impl Iterator<Item = Vec<T>>
where
    T: Clone + PartialOrd,
{
    comb_sort_by(v, |a, b| a.partial_cmp(b))
}

/// Sorts a slice of data using the cocktail sort algorithm with a custom comparator.
///
/// # Examples
///
/// ```
/// # use sort_steps::{comb_sort_by};
/// let numbers = [5, 9, 3, 6, 8, 2, 1, 7, 4];
/// println!("Comb Sort Steps:");
/// for (i, v) in comb_sort_by(&numbers, |a, b| a.partial_cmp(b)).enumerate() {
///     println!("#{:02}: {:?}", i, v);
/// }
/// ```
pub fn comb_sort_by<T, F>(v: &[T], compare: F) -> impl Iterator<Item = Vec<T>>
where
    F: Fn(&T, &T) -> Option<Ordering> + Copy,
    T: Clone,
{
    let n = v.len();
    let mut state = v.to_vec();
    let mut gap = n;
    let mut swapped = true;

    from_generator(move || {
        yield state.to_vec();
        while gap > 1 || swapped {
            gap = (4 * gap) / 5;
            if gap < 1 {
                gap = 1;
            }
            let mut i = 0;
            swapped = false;
            while i + gap < n {
                if gt_by(&state[i], &state[i + gap], compare) {
                    state.swap(i, i + gap);
                    swapped = true;
                }
                i += 1;
                yield state.to_vec();
            }
        }
    })
}