/**
 * 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;

public class RandomGenerator {

    /**
     * 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 = (int) Math
                .floor(doubleRangeRandom(lowLimit, upLimit + 1) - 1E-10);
        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 + Math.random() * (upLimit - lowLimit);
        return (num);
    }

    public static int[] randomSelection(int maxNum, int times) {
        if (times <= 0)
            return new int[0];
        int realTimes = Math.min(maxNum, times);
        boolean[] flags = new boolean[maxNum];
        boolean isBelowHalf = times < maxNum * 0.5;
        int virtualTimes = realTimes;
        if (!isBelowHalf) {
            virtualTimes = maxNum - realTimes;
        }
        int i = 0;
        int upper = maxNum - 1;
        int[] indices = new int[realTimes];

        while (i < virtualTimes) {
            indices[i] = intRangeRandom(0, upper);
            if (!flags[indices[i]]) {
                flags[indices[i]] = true;
                i++;
            }
        }
        if (!isBelowHalf) {
            int j = 0;
            for (i = 0; i < maxNum; i++) {
                if (flags[i] == isBelowHalf) {
                    indices[j] = i;
                    j++;
                    if (j == realTimes)
                        break;
                }
            }
        }
        return indices;
    }
}