package net.abhinavsarkar.algorist.sort;

import java.util.Arrays;
import net.abhinavsarkar.algorist.Sorter;

public class HeapSorter<T> implements Sorter<T>
{
    @Override
    public T[] sort(T[] input, Comparator<T> comparator)
    {
        if (input.length <= 1) {
            return input;
        }

        heapify(input, comparator);
        deheapify(input, comparator);
        return input;
    }

    private void heapify(T[] input, Comparator<T> comparator)
    {
        for (int i = (input.length - 1)/2; i >= 0; i--) {
            bubbleDown(input, i, input.length, comparator);
        }
    }

    private void deheapify(T[] input, Comparator<T> comparator)
    {
        for (int i = input.length; i > 1; i--) {
            swap(input, 0, i - 1);
            bubbleDown(input, 0, i - 1, comparator);
        }
    }

    private void bubbleDown(T[] input, int index, int size, Comparator<T> comparator) {
        int maxIdx = index;
        maxIdx = getMaxIdx(input, index * 2 + 1, maxIdx, size, comparator);
        maxIdx = getMaxIdx(input, index * 2 + 2, maxIdx, size, comparator);
        if (index != maxIdx) {
            swap(input, index, maxIdx);
            bubbleDown(input, maxIdx, size, comparator);
        }
    }

    private int getMaxIdx(T[] input, int childIndex, int minIndex, int size, Comparator<T> comparator)
    {
        return childIndex < size && comparator.compare(input[minIndex], input[childIndex]) < 0 ?
                childIndex : minIndex;
    }

    private void swap(T[] input, int i, int j)
    {
        if (i == j) {
            return;
        }
        T temp = input[i];
        input[i] = input[j];
        input[j] = temp;
    }

    public static void main(String[] args)
    {
        Sorter<String> sorter = new HeapSorter<>();
        String[] sorted =
                sorter.sort(new String[]{"abhinav", "sarkar", "barista", "jordan", "zebra", "data"},
                        (s, anotherString) -> anotherString.compareTo(s));
        System.out.println(Arrays.toString(sorted));
    }
}