#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include "numbers.h"
#include "bintree.h"

//TODO: getDuplicate und createNumbers implementieren
/*  *   * Erzeugen eines Arrays mit der vom Nutzer eingegebenen Anzahl an Zufallszahlen.
  * Sicherstellen, dass beim Befüllen keine Duplikate entstehen.
  * Duplizieren eines zufälligen Eintrags im Array.
  * in `getDuplicate()`: Sortieren des Arrays und Erkennen der doppelten Zahl durch Vergleich benachbarter Elemente. */

// Returns len random numbers between 1 and 2x len in random order which are all different, except for two entries.
// Returns NULL on errors. Use your implementation of the binary search tree to check for possible duplicates while
// creating random numbers.
// Vergleichsfunktion für qsort
static int compareUnsignedInt(const void *a, const void *b)
{
  const unsigned int *x = (const unsigned int *)a;
  const unsigned int *y = (const unsigned int *)b;

  if (*x < *y) return -1;
  if (*x > *y) return 1;
  return 0;
}

unsigned int *createNumbers(unsigned int len)
{

  if (len < 2) {
    return NULL;
  }

  unsigned int *numbers = malloc(len * sizeof(unsigned int));
  if (numbers == NULL) {
    return NULL;
  }

  for (unsigned int i = 0; i < len; ++i) {

    while (1) {
      unsigned int value = (rand() % (2 * len)) + 1;

      int exists = 0;
      for (unsigned int j = 0; j < i; ++j) {
        if (numbers[j] == value) {
          exists = 1;
          break;
        }
      }

      if (!exists) {
        numbers[i] = value;
        break;
      }
    }
  }

  unsigned int idx1 = rand() % len;
  unsigned int idx2 = rand() % len;

  while (idx2 == idx1) {
    idx2 = rand() % len;
  }

  numbers[idx2] = numbers[idx1];

  return numbers;
}

unsigned int getDuplicate(const unsigned int numbers[], unsigned int len)
{
  if (numbers == NULL || len < 2) {
    return 0;
  }

  unsigned int *copy = malloc(len * sizeof(unsigned int));
  if (copy == NULL) {
    return 0;
  }

  memcpy(copy, numbers, len * sizeof(unsigned int));


  qsort(copy, len, sizeof(unsigned int), compareUnsignedInt);

  unsigned int duplicate = 0;

  for (unsigned int i = 0; i + 1 < len; ++i) {
    if (copy[i] == copy[i + 1]) {
      duplicate = copy[i];
      break;
    }
  }

  free(copy);
  return duplicate;
}