package DataStructures.Heaps;

import java.util.ArrayList;
import java.util.List;

/**
 * Heap tree where a node's key is higher than or equal to its parent's and lower than or equal
 * to its children's.
 *
 * @author Nicolas Renard
 */
public class MinHeap implements Heap {

    private final List minHeap;

    public MinHeap(List listElements) {
        minHeap = new ArrayList();
        for (HeapElement heapElement : listElements) {
            if (heapElement != null) insertElement(heapElement);
            else System.out.println("Null element. Not added to heap");
        }
        if (minHeap.size() == 0) System.out.println("No element has been added, empty heap.");
    }

    // Get the element at a given index. The key for the list is equal to index value - 1
    public HeapElement getElement(int elementIndex) {
        if ((elementIndex  minHeap.size()))
            throw new IndexOutOfBoundsException("Index out of heap range");
        return minHeap.get(elementIndex - 1);
    }

    // Get the key of the element at a given index
    private double getElementKey(int elementIndex) {
        return minHeap.get(elementIndex - 1).getKey();
    }

    // Swaps two elements in the heap
    private void swap(int index1, int index2) {
        HeapElement temporaryElement = minHeap.get(index1 - 1);
        minHeap.set(index1 - 1, minHeap.get(index2 - 1));
        minHeap.set(index2 - 1, temporaryElement);
    }

    // Toggle an element up to its right place as long as its key is lower than its parent's
    private void toggleUp(int elementIndex) {
        double key = minHeap.get(elementIndex - 1).getKey();
        while (getElementKey((int) Math.floor(elementIndex / 2)) > key) {
            swap(elementIndex, (int) Math.floor(elementIndex / 2));
            elementIndex = (int) Math.floor(elementIndex / 2);
        }
    }

    // Toggle an element down to its right place as long as its key is higher
    // than any of its children's
    private void toggleDown(int elementIndex) {
        double key = minHeap.get(elementIndex - 1).getKey();
        boolean wrongOrder = (key > getElementKey(elementIndex * 2)) || (key > getElementKey(Math.min(elementIndex * 2, minHeap.size())));
        while ((2 * elementIndex  getElementKey(elementIndex * 2)) || (key > getElementKey(Math.min(elementIndex * 2, minHeap.size())));

        }
    }

    private HeapElement extractMin() {
        HeapElement result = minHeap.get(0);
        deleteElement(0);
        return result;
    }

    @Override
    public void insertElement(HeapElement element) {
        minHeap.add(element);
        toggleUp(minHeap.size());

    }

    @Override
    public void deleteElement(int elementIndex) {
        if (minHeap.isEmpty())
            try {
                throw new EmptyHeapException("Attempt to delete an element from an empty heap");
            } catch (EmptyHeapException e) {
                e.printStackTrace();
            }
        if ((elementIndex > minHeap.size()) || (elementIndex  getElementKey(elementIndex * 2))))
            toggleDown(elementIndex);
    }

    @Override
    public HeapElement getElement() throws EmptyHeapException {
        try {
            return extractMin();
        } catch (Exception e) {
            throw new EmptyHeapException("Heap is empty. Error retrieving element");
        }
    }
}