/**
 * Description: For generating random numbers.
 *
 * Author          Create/Modi     Note
 * Xiaofeng Xie    Feb 22, 2001
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * Please acknowledge the author(s) if you use this code in any way.
 *
 * @version 1.0
 * @Since MAOS1.0
 */

package net.adaptivebox.global;

import java.util.Random;
import java.security.SecureRandom;

public class RandomGenerator {
  /**
   * Pseudo-random number generator instance.
   */
  private static Random PRNG = new Random();

  /**
   * Switch between weaker, but faster pseudo-random number generator and
   * stronger, but slower.
   *
   * @param stronger activation of secure pseudo random generator flag
   */
  public static void useStrongerGenerator(boolean stronger) {
    if(stronger == true) {
      PRNG = new SecureRandom();
    } else {
      PRNG = new Random();
    }
  }

  /**
   * This function returns a random integer number between the lowLimit and
   * upLimit.
   *
   * @param lowLimit lower limits upLimit The upper limits (between which the
   *                 random number is to be generated)
   * @return int return value Example: for find [0,1,2]
   */
  public static int intRangeRandom(int lowLimit, int upLimit) {
    int num = lowLimit + PRNG.nextInt(upLimit - lowLimit + 1);
    return num;
  }

  /**
   * This function returns a random float number between the lowLimit and upLimit.
   *
   * @param lowLimit lower limits upLimit The upper limits (between which the
   *                 random number is to be generated)
   * @return double return value
   */
  public static double doubleRangeRandom(double lowLimit, double upLimit) {
    double num = lowLimit + PRNG.nextDouble() * (upLimit - lowLimit);
    return num;
  }

  /**
   * This function returns a random float number between the zero (inclusive) and one (exclusive).
   *
   * @return double value in the range [0, 1)
   */
  public static double doubleZeroOneRandom() {
    return PRNG.nextDouble();
  }

  public static int[] randomSelection(int maxNum, int times) {
    if (maxNum < 0) {
      maxNum = 0;
    }

    if (times < 0) {
      times = 0;
    }

    int[] all = new int[maxNum];
    for (int i = 0; i < all.length; i++) {
      all[i] = i;
    }

    /* https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle */
    int[] indices = new int[Math.min(maxNum, times)];
    for (int i = 0, j, value; i < indices.length; i++) {
      j = intRangeRandom(i, all.length - 1);

      value = all[j];
      all[j] = all[i];
      indices[i] = all[i] = value;
    }

    return indices;
  }
}