#include "heap.h"

static int parent(int i) {
    return (i > 0) ? (i - 1) / 2 : -1;
}

static int left_child(int i) {
    return i * 2 + 1;
}

static int right_child(int i) {
    return i * 2 + 2;
}

static int left_sibling(int i) {
    return (i % 2 == 0) ? i - 1 : -1;
}

static int right_sibling(int i) {
    return (i % 2 == 1) ? i + 1 : -1;
}

static int index_of_larger_child(int i, dlos_Heap *h) {
    int larger = left_child(i);
    if (larger >= h->size) {
        return -1;
    }
    if (larger + 1 < h->size && h->compare(&h->arr[larger], &h->arr[larger + 1]) > 0) {
        larger = larger + 1;
    }
    return larger;
}

void dlos_node_swap(dlos_ComparableNode *arr, int a, int b) {
    dlos_ComparableNode temp = arr[a];
    arr[a] = arr[b];
    arr[b] = temp;
}

void dlos_sift_down(int i, dlos_Heap *h) {
    int target = index_of_larger_child(i, h);
    while (target > 0 && h->compare(&h->arr[i], &h->arr[target]) > 0) {
        dlos_node_swap(h->arr, i, target);
        i = target;
        target = index_of_larger_child(i, h);
    }
}

void dlos_max_heap(dlos_Heap *h) {
    for (int i = parent(h->size - 1); i >= 0; i--) {
        dlos_sift_down(i, h);
    }
}