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package nl.hsac.fitnesse.util;

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

/**
 * Helper for random values.
 */
public class RandomUtil {
    private Random random = new SecureRandom();

    /**
     * Generates random number below a certain value.
     *
     * @param max max (non-inclusive) value for returned number.
     * @return random number
     */
    public int random(int max) {
        return random.nextInt(max);
    }

    /**
     * Creates a random string consisting only of supplied characters.
     *
     * @param permitted string consisting of permitted characters.
     * @param length    length of string to create.
     * @return random string.
     */
    public String randomString(String permitted, int length) {
        StringBuilder result = new StringBuilder(length);
        int maxIndex = permitted.length();
        for (int i = 0; i < length; i++) {
            int index = random(maxIndex);
            char value = permitted.charAt(index);
            result.append(value);
        }
        return result.toString();
    }

    /**
     * Picks and returns a random value from the supplied array.
     * Does not work for arrays of 'primitives' (e.g. int[] or byte[]).
     *
     * @param  type of element.
     * @param elements the array from which a value will be picked.
     * @return random element from the array of values.
     */
    public  T randomElement(T[] elements) {
        return elements[random(elements.length)];
    }

    /**
     * Creates a random split in an integer, resulting in two integers.
     * These two integers added together will result in the original input
     * Minimal input value is 2
     *
     * @param inputValue integer that needs to be split.
     * @return array with two integers.
     */
    public int[] getRandomSplit(int inputValue) {
        if (inputValue < 2) {
            throw new IllegalArgumentException("Minimal possible value to split is 2");
        }
        int firstValue = random(inputValue - 1) + 1; //+1 so it will never become 0
        int secondValue = inputValue - firstValue;//
        int split[] = {firstValue, secondValue};
        return split;
    }
}