/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef _DECAF_UTIL_RANDOM_H_
#define _DECAF_UTIL_RANDOM_H_

#include <decaf/lang/exceptions/IllegalArgumentException.h>
#include <decaf/util/Config.h>
#include <vector>
#include <cmath>

namespace decaf{
namespace util{

    /**
     * Random Value Generator which is used to generate a stream of pseudorandom numbers.
     * <p>
     * The algorithms implemented by class Random use a protected utility method that
     * on each invocation can supply up to 32 pseudorandomly generated bits.
     *
     * @since 1.0
     */
    class DECAF_API Random {
    private:

        static unsigned long long multiplier;

        /**
         * The boolean value indicating if the second Gaussian number is available.
         */
        bool haveNextNextGaussian;

        /**
         * It is associated with the internal state of this generator.
         */
        unsigned long long seed;

        /**
         * The second Gaussian generated number.
         */
        double nextNextGaussian;

    public:

        /**
         * Construct a random generator with the current time of day in
         * milliseconds as the initial state.
         *
         * @see #setSeed
         */
        Random();

        /**
         * Construct a random generator with the given <code>seed</code>
         * as the initial state.
         *
         * @param seed the seed that will determine the initial state of
         * this random number generator
         *
         * @see #setSeed
         */
        Random(unsigned long long seed);

        virtual ~Random();

    public:

        /**
         * Answers the next pseudo-random, uniformly distributed boolean
         * value generated by this generator.
         *
         * @return boolean a pseudo-random, uniformly distributed boolean
         * value
         */
        bool nextBoolean();

        /**
         * Generates a normally distributed random double number between
         * 0.0 inclusively and 1.0 exclusively.
         *
         * @return double
         *
         * @see #nextFloat
         */
        double nextDouble();

        /**
         * Generates a normally distributed random float number between
         * 0.0 inclusively and 1.0 exclusively.
         *
         * @return float a random float number between 0.0 and 1.0
         *
         * @see #nextDouble
         */
        float nextFloat();

        /**
         * Pseudo-randomly generates (approximately) a normally
         * distributed <code>double</code> value with mean 0.0 and a
         * standard deviation value of <code>1.0</code> using the <i>polar
         * method</i> of G. E. P. Box, M.  E. Muller, and G. Marsaglia, as
         * described by Donald E. Knuth in <i>The Art of Computer
         * Programming, Volume 2: Seminumerical Algorithms</i>, section
         * 3.4.1, subsection C, algorithm P
         *
         * @return double
         *
         * @see #nextDouble
         */
        double nextGaussian();

        /**
         * Generates a uniformly distributed 32-bit <code>int</code> value
         * from the this random number sequence.
         *
         * @return int uniformly distributed <code>int</code> value
         *
         * @see #next
         * @see #nextLong
         */
        int nextInt();

        /**
         * Returns to the caller a new pseudo-random integer value which
         * is uniformly distributed between 0 (inclusively) and the value
         * of <code>n</code> (exclusively).
         *
         * @param n
         *      The int value that defines the max value of the return.
         *
         * @return the next pseudo random int value.
         *
         * @throws IllegalArgumentException if n is less than or equal to zero.
         */
        int nextInt(int n);

        /**
         * Generates a uniformly distributed 64-bit <code>int</code> value
         * from the this random number sequence.
         *
         * @return 64-bit <code>int</code> random number
         *
         * @see #next
         * @see #nextInt()
         * @see #nextInt(int)
         */
        long long nextLong();

    public: // Virtual Methods

        /**
         * Modifies the byte array by a random sequence of bytes generated
         * by this random number generator.
         *
         * @param buf non-null array to contain the new random bytes
         *
         * @see #next
         */
        virtual void nextBytes(std::vector<unsigned char>& buf);

        /**
         * Modifies the byte array by a random sequence of bytes generated
         * by this random number generator.
         *
         * @param buf non-null array to contain the new random bytes
         *
         * @see #next
         *
         * @throw NullPointerException if buff is NULL
         * @throw IllegalArgumentException if size is negative
         */
        virtual void nextBytes(unsigned char* buf, int size);

        /**
         * Modifies the seed using linear congruential formula presented
         * in <i>The Art of Computer Programming, Volume 2</i>, Section
         * 3.2.1.
         *
         * @param seed the seed that alters the state of the random number
         * generator
         *
         * @see #next
         * @see #Random()
         * @see #Random(long)
         */
        virtual void setSeed(unsigned long long seed);

    protected: // Virtual method used by all non-virtual methods in Random.

        /**
         * Answers a pseudo-random uniformly distributed <code>int</code>
         * value of the number of bits specified by the argument
         * <code>bits</code> as described by Donald E. Knuth in <i>The Art
         * of Computer Programming, Volume 2: Seminumerical
         * Algorithms</i>, section 3.2.1.
         *
         * @return int a pseudo-random generated int number
         * @param bits number of bits of the returned value
         *
         * @see #nextBytes
         * @see #nextDouble
         * @see #nextFloat
         * @see #nextInt()
         * @see #nextInt(int)
         * @see #nextGaussian
         * @see #nextLong
         */
        virtual int next(int bits);

    };

}}

#endif /*_DECAF_UTIL_RANDOM_H_*/