/* Copyright (C) 2013
 * swift project Community / Contributors
 *
 * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
 * directory of this distribution. No part of swift project, including this file, may be copied, modified, propagated,
 * or distributed except according to the terms contained in the LICENSE file.
 */

//! \file

#ifndef BLACKMISC_MATH_MATHUTILS_H
#define BLACKMISC_MATH_MATHUTILS_H

#include "blackmisc/blackmiscexport.h"

#include <QRandomGenerator>
#include <QtCore/qmath.h>
#include <QPair>
#include <cmath>
#include <numeric>

namespace BlackMisc
{
    namespace Math
    {
        //! Math utils
        class BLACKMISC_EXPORT CMathUtils
        {
        public:
            //! No objects, just static
            CMathUtils() = delete;

            //! Calculates the square of x
            static inline double square(double x)
            {
                return x * x;
            }

            //! Calculates x to the power of three
            static inline double cubic(const double x)
            {
                return x * x * x;
            }

            //! Calculates the real cubic root
            static double cubicRootReal(double x);

            //! Utility round method
            static double round(double value, int digits);

            //! Utility round method, returning as string
            static QString roundAsString(double value, int digits);

            //! Round by given epsilon
            static double roundEpsilon(double value, double epsilon);

            //! Epsilon safe equal
            //! @{
            static bool epsilonEqual(float v1, float v2, float epsilon = 1E-06f);
            static bool epsilonEqual(double v1, double v2, double epsilon = 1E-06);
            static bool epsilonEqualLimits(double v1, double v2) { return qAbs(v1 - v2) <= std::numeric_limits<double>::epsilon(); }
            //! @}

            //! Epsilon safe zero
            //! @{
            static bool epsilonZero(double v, double epsilon) { return epsilonEqual(v, 0.0, epsilon); }
            static bool epsilonZero(double v) { return epsilonEqual(v, 0.0, 1E-06); }
            static inline bool epsilonZeroLimits(double v) { return qAbs(v) <= std::numeric_limits<double>::epsilon(); }
            //! @}

            //! Nearest integer not greater in magnitude than value, correcting for epsilon
            static inline double trunc(double value, double epsilon = 1e-10)
            {
                return value < 0 ? ceil(value - epsilon) : floor(value + epsilon);
            }

            //! Fractional part of value
            static inline double fract(double value)
            {
                double unused;
                return modf(value, &unused);
            }

            //! PI / 2
            static const double &PIHALF()
            {
                static double pi = 2.0 * qAtan(1.0);
                return pi;
            }

            //! PI
            static const double &PI()
            {
                static double pi = 4.0 * qAtan(1.0);
                return pi;
            }

            //! PI * 2
            static const double &PI2()
            {
                static double pi2 = 8.0 * qAtan(1.0);
                return pi2;
            }

            //! Degrees to radians
            static double deg2rad(double degree);

            //! Radians to degrees
            static double rad2deg(double radians);

            //! Normalize: -180< degrees ≤180
            static double normalizeDegrees180(double degrees);

            //! Normalize: 0≤ degrees <360
            static double normalizeDegrees360(double degrees);

            //! Thread-local random generator
            static QRandomGenerator &randomGenerator();

            //! Random number between low and high
            static int randomInteger(int low, int high);

            //! Random double 0-max
            static double randomDouble(double max = 1);

            //! Random boolean
            static bool randomBool();

            //! Round numToRound to the nearest multiple of divisor
            static int roundToMultipleOf(int value, int divisor);

            //! Fractional part as integer string, e.g. 3.12 -> 12 / 3.012 -> 012
            //! \remark because of leading 0 returned as string
            static QString fractionalPartAsString(double value, int width = -1);

            //! Calculate the sum
            static double sum(const QList<double> &values);

            //! Calculate the mean
            static double mean(const QList<double> &values);

            //! Calculate the standard deviation
            static double standardDeviation(const QList<double> &values);

            //! Standard deviation (first) and mean (second)
            static QPair<double, double> standardDeviationAndMean(const QList<double> &values);

        private:
            //! Calculate the variance
            static double variance(const QList<double> &values);

            //! The squared differences to mean
            static QList<double> squaredDifferences(const QList<double> &values);

            //! The squared differences to mean
            static QList<double> squaredDifferences(const QList<double> &values, double meanValue);
        };
    } // namespace
} // namespace

#endif // guard