/***********************************************************************
 * Software License Agreement (BSD License)
 *
 * Copyright 2008-2009  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
 * Copyright 2008-2009  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
 *
 * THE BSD LICENSE
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *************************************************************************/

#ifndef RANDOM_H
#define RANDOM_H

#include <algorithm>
#include <cstdlib>
#include <cassert>
#include <flann/general.h>

namespace flann
{

/**
 * Seeds the random number generator
 */
FLANN_EXPORT void seed_random(unsigned int seed);

/*
 * Generates a random double value.
 */
FLANN_EXPORT double rand_double(double high = 1.0, double low = 0);

/*
 * Generates a random integer value.
 */
FLANN_EXPORT int rand_int(int high = RAND_MAX, int low = 0);


/**
 * Random number generator that returns a distinct number from
 * the [0,n) interval each time.
 *
 * TODO: improve on this to use a generator function instead of an
 * array of randomly permuted numbers
 */
class UniqueRandom
{
    int* vals;
    int size;
    int counter;

public:
    /**
     * Constructor.
     * Params:
     *     n = the size of the interval from which to generate
     *       random numbers.
     */
    UniqueRandom(int n) : vals(NULL) {
        init(n);
    }

    ~UniqueRandom() {
        delete[] vals;
    }

    /**
     * Initializes the number generator.
     * Params:
     *   n = the size of the interval from which to generate
     *       random numbers.
     */
    void init(int n) {
        // create and initialize an array of size n
        if (vals == NULL || n != size) {
            delete[] vals;
            size = n;
            vals = new int[size];
        }
        for (int i = 0;i < size;++i) {
            vals[i] = i;
        }

        // shuffle the elements in the array
        // Fisher-Yates shuffle
        for (int i = size;i > 0;--i) {
//    int rand = cast(int) (drand48() * n);
            int rnd = rand_int(i);
            assert(rnd >= 0 && rnd < i);
            std::swap(vals[i-1], vals[rnd]);
        }

        counter = 0;
    }

    /**
     * Return a distinct random integer in greater or equal to 0 and less
     * than 'n' on each call. It should be called maximum 'n' times.
     * Returns: a random integer
     */
    int next() {
        if (counter == size) {
            return -1;
        }
        else {
            return vals[counter++];
        }
    }
};

}

#endif //RANDOM_H