use crate::utils::gt_by;

use std::{cmp::Ordering, iter::from_generator};
/// Sorts a slice of data using the cocktail sort algorithm.
///
/// # Examples
///
/// ```
/// # use sort_steps::{cocktail_sort};
/// let numbers = [5, 9, 3, 6, 8, 2, 1, 7, 4];
/// println!("Cocktail Sort Steps:");
/// for (i, v) in cocktail_sort(&numbers).enumerate() {
///     println!("#{:02}: {:?}", i, v);
/// }
/// ```
pub fn cocktail_sort<T>(v: &[T]) -> impl Iterator<Item = Vec<T>>
where
    T: Clone + PartialOrd,
{
    cocktail_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::{cocktail_sort_by};
/// let numbers = [5, 9, 3, 6, 8, 2, 1, 7, 4];
/// println!("Cocktail Sort Steps:");
/// for (i, v) in cocktail_sort_by(&numbers, |a, b| a.partial_cmp(b)).enumerate() {
///     println!("#{:02}: {:?}", i, v);
/// }
/// ```
pub fn cocktail_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 start = 0;
    let mut end = n - 1;
    let mut swapped = true;
    from_generator(move || {
        yield state.to_vec();
        while swapped {
            swapped = false;

            // Sort left to right
            for i in start..end {
                if gt_by(&state[i], &state[i + 1], compare) {
                    state.swap(i, i + 1);
                    yield state.to_vec();
                    swapped = true;
                }
            }

            // If nothing was swapped, the array is sorted
            if !swapped {
                break;
            }

            // Update the end index
            end -= 1;
            swapped = false;

            // Sort right to left
            for i in (start..end).rev() {
                if gt_by(&state[i], &state[i + 1], compare) {
                    state.swap(i, i + 1);
                    yield state.to_vec();
                    swapped = true;
                }
            }

            // Update the start index
            start += 1;
        }
    })
}