/////////////////////////////////////////////////////////////////////////////////
//
//  Copyright (C) 2011-2012 Statoil ASA, Ceetron AS
//
//  ResInsight is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  ResInsight 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 General Public License at <http://www.gnu.org/licenses/gpl.html>
//  for more details.
//
/////////////////////////////////////////////////////////////////////////////////

#include "RigStatisticsMath.h"

#include "cvfMath.h"

#include <algorithm>
#include <cassert>
#include <cmath>

//--------------------------------------------------------------------------------------------------
/// A function to do basic statistical calculations
//--------------------------------------------------------------------------------------------------

void RigStatisticsMath::calculateBasicStatistics( const std::vector<double>& values,
                                                  double*                    min,
                                                  double*                    max,
                                                  double*                    sum,
                                                  double*                    range,
                                                  double*                    mean,
                                                  double*                    dev )
{
    double m_min( HUGE_VAL );
    double m_max( -HUGE_VAL );
    double m_mean( HUGE_VAL );
    double m_dev( HUGE_VAL );

    double m_sum      = 0.0;
    double sumSquared = 0.0;

    size_t validValueCount = 0;

    for ( size_t i = 0; i < values.size(); i++ )
    {
        double val = values[i];
        if ( RiaStatisticsTools::isInvalidNumber<double>( val ) ) continue;

        validValueCount++;

        if ( val < m_min ) m_min = val;
        if ( val > m_max ) m_max = val;

        m_sum += val;
        sumSquared += ( val * val );
    }

    if ( validValueCount > 0 )
    {
        m_mean = m_sum / validValueCount;

        // http://en.wikipedia.org/wiki/Standard_deviation#Rapid_calculation_methods
        // Running standard deviation

        double s0 = static_cast<double>( validValueCount );
        double s1 = m_sum;
        double s2 = sumSquared;

        m_dev = sqrt( ( s0 * s2 ) - ( s1 * s1 ) ) / s0;
    }

    if ( min ) *min = m_min;
    if ( max ) *max = m_max;
    if ( sum ) *sum = m_sum;
    if ( range ) *range = m_max - m_min;

    if ( mean ) *mean = m_mean;
    if ( dev ) *dev = m_dev;
}

//--------------------------------------------------------------------------------------------------
/// Algorithm:
/// https://en.wikipedia.org/wiki/Percentile#Third_variant,_'%22%60UNIQ--postMath-00000052-QINU%60%22'
//--------------------------------------------------------------------------------------------------
void RigStatisticsMath::calculateStatisticsCurves( const std::vector<double>& values,
                                                   double*                    p10,
                                                   double*                    p50,
                                                   double*                    p90,
                                                   double*                    mean,
                                                   PercentileStyle            percentileStyle )
{
    CVF_ASSERT( p10 && p50 && p90 && mean );

    if ( values.empty() ) return;

    enum PValue
    {
        P10,
        P50,
        P90
    };

    std::vector<double> sortedValues = values;

    sortedValues.erase( std::remove_if( sortedValues.begin(),
                                        sortedValues.end(),
                                        []( double x ) { return !RiaStatisticsTools::isValidNumber( x ); } ),
                        sortedValues.end() );

    std::sort( sortedValues.begin(), sortedValues.end() );

    double valueSum = std::accumulate( sortedValues.begin(), sortedValues.end(), 0.0 );

    int    valueCount    = (int)sortedValues.size();
    double percentiles[] = { 0.1, 0.5, 0.9 };
    double pValues[]     = { HUGE_VAL, HUGE_VAL, HUGE_VAL };

    for ( int i = P10; i <= P90; i++ )
    {
        // Check valid params
        if ( ( percentiles[i] < 1.0 / ( (double)valueCount + 1 ) ) || ( percentiles[i] > (double)valueCount / ( (double)valueCount + 1 ) ) )
            continue;

        double rank = percentiles[i] * ( valueCount + 1 ) - 1;
        double rankRem;
        double rankFrac = std::modf( rank, &rankRem );
        int    rankInt  = static_cast<int>( rankRem );

        if ( rankInt < valueCount - 1 )
        {
            pValues[i] = sortedValues[rankInt] + rankFrac * ( sortedValues[rankInt + 1] - sortedValues[rankInt] );
        }
        else
        {
            pValues[i] = sortedValues.back();
        }
    }

    *p50 = pValues[P50];

    if ( percentileStyle == PercentileStyle::REGULAR )
    {
        *p10 = pValues[P10];
        *p90 = pValues[P90];
    }
    else
    {
        CVF_ASSERT( percentileStyle == PercentileStyle::SWITCHED );
        *p10 = pValues[P90];
        *p90 = pValues[P10];
    }

    *mean = valueSum / valueCount;
}

//--------------------------------------------------------------------------------------------------
/// Calculate the percentiles of /a inputValues at the pValPosition percentages using the "Nearest Rank"
/// method. This method treats HUGE_VAL as "undefined" values, and ignores these. Will return HUGE_VAL if
/// the inputValues does not contain any valid values
//--------------------------------------------------------------------------------------------------

std::vector<double> RigStatisticsMath::calculateNearestRankPercentiles( const std::vector<double>&         inputValues,
                                                                        const std::vector<double>&         pValPositions,
                                                                        RigStatisticsMath::PercentileStyle percentileStyle )
{
    std::vector<double> sortedValues;
    sortedValues.reserve( inputValues.size() );

    for ( size_t i = 0; i < inputValues.size(); ++i )
    {
        if ( RiaStatisticsTools::isValidNumber<double>( inputValues[i] ) )
        {
            sortedValues.push_back( inputValues[i] );
        }
    }

    std::sort( sortedValues.begin(), sortedValues.end() );

    std::vector<double> percentiles( pValPositions.size(), HUGE_VAL );
    if ( sortedValues.size() )
    {
        for ( size_t i = 0; i < pValPositions.size(); ++i )
        {
            double pVal = HUGE_VAL;

            double pValPosition = cvf::Math::abs( pValPositions[i] ) / 100;
            if ( percentileStyle == RigStatisticsMath::PercentileStyle::SWITCHED ) pValPosition = 1.0 - pValPosition;

            size_t pValIndex = static_cast<size_t>( sortedValues.size() * pValPosition );

            if ( pValIndex >= sortedValues.size() ) pValIndex = sortedValues.size() - 1;

            pVal           = sortedValues[pValIndex];
            percentiles[i] = pVal;
        }
    }

    return percentiles;
};

//--------------------------------------------------------------------------------------------------
/// Calculate the percentiles of /a inputValues at the pValPosition percentages by interpolating input values.
/// This method treats HUGE_VAL as "undefined" values, and ignores these. Will return HUGE_VAL if
/// the inputValues does not contain any valid values
//--------------------------------------------------------------------------------------------------
std::vector<double> RigStatisticsMath::calculateInterpolatedPercentiles( const std::vector<double>&         inputValues,
                                                                         const std::vector<double>&         pValPositions,
                                                                         RigStatisticsMath::PercentileStyle percentileStyle )
{
    std::vector<double> sortedValues;
    sortedValues.reserve( inputValues.size() );

    for ( size_t i = 0; i < inputValues.size(); ++i )
    {
        if ( RiaStatisticsTools::isValidNumber<double>( inputValues[i] ) )
        {
            sortedValues.push_back( inputValues[i] );
        }
    }

    std::sort( sortedValues.begin(), sortedValues.end() );

    std::vector<double> percentiles( pValPositions.size(), HUGE_VAL );
    if ( sortedValues.size() )
    {
        for ( size_t i = 0; i < pValPositions.size(); ++i )
        {
            double pVal = HUGE_VAL;

            double pValPosition = cvf::Math::abs( pValPositions[i] ) / 100.0;
            if ( percentileStyle == RigStatisticsMath::PercentileStyle::SWITCHED ) pValPosition = 1.0 - pValPosition;

            double doubleIndex = ( sortedValues.size() - 1 ) * pValPosition;

            size_t lowerValueIndex = static_cast<size_t>( floor( doubleIndex ) );
            size_t upperValueIndex = lowerValueIndex + 1;

            double upperValueWeight = doubleIndex - lowerValueIndex;
            assert( upperValueWeight < 1.0 );

            if ( upperValueIndex < sortedValues.size() )
            {
                pVal = ( 1.0 - upperValueWeight ) * sortedValues[lowerValueIndex] + upperValueWeight * sortedValues[upperValueIndex];
            }
            else
            {
                pVal = sortedValues[lowerValueIndex];
            }
            percentiles[i] = pVal;
        }
    }

    return percentiles;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
RigHistogramCalculator::RigHistogramCalculator( double min, double max, size_t nBins, std::vector<size_t>* histogram )
{
    assert( histogram );
    assert( nBins > 0 );

    if ( max == min )
    {
        nBins = 1;
    } // Avoid dividing on 0 range

    m_histogram        = histogram;
    m_min              = min;
    m_observationCount = 0;

    // Initialize bins
    m_histogram->resize( nBins );
    for ( size_t i = 0; i < m_histogram->size(); ++i )
        ( *m_histogram )[i] = 0;

    m_range    = max - min;
    m_maxIndex = nBins - 1;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
void RigHistogramCalculator::addValue( double value )
{
    if ( RiaStatisticsTools::isInvalidNumber<double>( value ) ) return;

    size_t index = 0;

    if ( m_maxIndex > 0 ) index = (size_t)( m_maxIndex * ( value - m_min ) / m_range );

    if ( index < m_histogram->size() ) // Just clip to the max min range (-index will overflow to positive )
    {
        ( *m_histogram )[index]++;
        m_observationCount++;
    }
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
void RigHistogramCalculator::addData( const std::vector<double>& data )
{
    assert( m_histogram );
    for ( size_t i = 0; i < data.size(); ++i )
    {
        addValue( data[i] );
    }
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
void RigHistogramCalculator::addData( const std::vector<float>& data )
{
    assert( m_histogram );
    for ( size_t i = 0; i < data.size(); ++i )
    {
        addValue( data[i] );
    }
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
double RigHistogramCalculator::calculatePercentil( double pVal, RigStatisticsMath::PercentileStyle percentileStyle )
{
    assert( m_histogram );
    assert( m_histogram->size() );
    auto pValClamped = cvf::Math::clamp( pVal, 0.0, 1.0 );
    assert( 0.0 <= pValClamped && pValClamped <= 1.0 );
    if ( percentileStyle == RigStatisticsMath::PercentileStyle::SWITCHED )
    {
        pValClamped = 1.0 - pValClamped;
    }

    double pValObservationCount = pValClamped * m_observationCount;
    if ( pValObservationCount == 0.0 ) return m_min;

    size_t accObsCount = 0;
    double binWidth    = m_range / m_histogram->size();
    for ( size_t binIdx = 0; binIdx < m_histogram->size(); ++binIdx )
    {
        size_t binObsCount = ( *m_histogram )[binIdx];

        accObsCount += binObsCount;
        if ( accObsCount >= pValObservationCount )
        {
            double domainValueAtEndOfBin   = m_min + ( binIdx + 1 ) * binWidth;
            double unusedFractionOfLastBin = (double)( accObsCount - pValObservationCount ) / binObsCount;

            double histogramBasedEstimate = domainValueAtEndOfBin - unusedFractionOfLastBin * binWidth;

            // See https://resinsight.org/docs/casegroupsandstatistics/#percentile-methods for details

            return histogramBasedEstimate;
        }
    }
    assert( false );

    return HUGE_VAL;
}