/******************************************************************************
 * QSkinny - Copyright (C) 2016 Uwe Rathmann
 * This file may be used under the terms of the QSkinny License, Version 1.0
 *****************************************************************************/

#ifndef QSK_BOX_RENDERER_COLOR_MAP_H
#define QSK_BOX_RENDERER_COLOR_MAP_H

#include <QskGlobal.h>
#include <QskVertex.h>
#include <QskGradient.h>
#include <cassert>

class QskBoxShapeMetrics;

namespace QskVertex
{
    class ColorMapNone
    {
    public:
        constexpr inline Color colorAt( qreal ) const
        {
            return Color();
        }
    };

    class ColorMapSolid
    {
    public:
        constexpr inline ColorMapSolid( Color color ):
            m_color( color )
        {
        }

        inline Color colorAt( qreal ) const
        {
            return m_color;
        }

    private:
        const Color m_color;
    };

    class ColorMapGradient
    {
    public:
        inline ColorMapGradient( Color color1, Color color2 ):
            m_color1( color1 ),
            m_color2( color2 )
        {
        }

        inline Color colorAt( qreal value ) const
        {
            return m_color1.interpolatedTo( m_color2, value );
        }

    private:
        const Color m_color1;
        const Color m_color2;
    };

    class ColorIterator
    {
    public:
        static inline bool advance()
        {
            return false;
        }

        inline qreal value() const
        {
            assert( false );
            return 0.0;
        }

        inline Color color() const
        {
            assert( false );
            return Color();
        }

        static inline bool isDone()
        {
            return true;
        }
    };

    class SolidColorIterator : public ColorIterator
    {
    public:
        inline SolidColorIterator( const QColor& color ):
            m_color( color )
        {   
        }
        
        inline Color colorAt( qreal ) const
        {
            return m_color;
        }   
        
    private:
        const Color m_color;
    };  

    class TwoColorIterator01 : public ColorIterator
    {
    public:
        inline TwoColorIterator01( const QColor& color1, const QColor& color2 ):
            m_color1( color1 ),
            m_color2( color2 )
        {   
        }   
        
        inline Color colorAt( qreal value ) const
        {
            return m_color1.interpolatedTo( m_color2, value );
        }   
        
    private:
        const Color m_color1, m_color2;
    };  

    class TwoColorIterator : public ColorIterator
    {
    public:
        inline TwoColorIterator( qreal value1, qreal value2,
                const QColor& color1, const QColor& color2 ):
            m_value1( value1 ),
            m_range( value2 - value1 ),
            m_color1( color1 ),
            m_color2( color2 )
        {   
        }   
        
        inline Color colorAt( qreal value ) const
        {
            const qreal r = ( value - m_value1 ) / m_range;
            return m_color1.interpolatedTo( m_color2, r );
        }   
        
    private:
        const qreal m_value1, m_range;
        const Color m_color1, m_color2;
    };  

    class GradientColorIterator : public ColorIterator
    {
    public:
        inline GradientColorIterator( qreal value1, qreal value2,
            const QVector< QskGradientStop > stops ):
            m_value1( value1 ),
            m_value2( value2 ),
            m_stops( stops ) 
        {   
            Q_ASSERT( stops.size() > 2 );
            
            m_color1 = stops[0].color();
            m_color2 = stops[1].color();
            
            m_valueStep1 = value1;
            m_valueStep2 = valueAt( stops[1].position() );
            m_stepSize = m_valueStep2 - m_valueStep1;
            
            m_index = 1;
        }   
        
        inline qreal value() const
        {
            return m_valueStep2;
        }   
        
        inline Color color() const
        {
            return m_color2;
        }   
        
        inline Color colorAt( qreal value ) const
        {
            const qreal r = ( value - m_valueStep1 ) / m_stepSize;
            return m_color1.interpolatedTo( m_color2, r );
        }   

        inline bool advance()
        {
            const auto& stop = m_stops[ ++m_index ];
            
            m_color1 = m_color2;
            m_color2 = stop.color();
            
            m_valueStep1 = m_valueStep2;
            m_valueStep2 = valueAt( stop.position() );
            m_stepSize = m_valueStep2 - m_valueStep1;
            
            return !isDone();
        }   
        
        inline bool isDone() const
        {
            return m_index >= m_stops.count() - 1;
        }   
        
    private:
        inline qreal valueAt( qreal pos ) const
        {
            return m_value1 + pos * ( ( m_value2 - m_value1 ) );
        }   
        
        const qreal m_value1, m_value2;
        QVector< QskGradientStop > m_stops;
        
        int m_index;
        qreal m_valueStep1, m_valueStep2, m_stepSize;
        Color m_color1, m_color2;
    };  

    template< class ContourIterator, class ColorIterator >
    ColoredLine* fillOrdered( ContourIterator& contourIt,
        ColorIterator& colorIt, ColoredLine* line  )
    {
        do
        {
            while ( !colorIt.isDone() && ( colorIt.value() < contourIt.value() ) )
            {
                contourIt.setGradientLine( colorIt, line++ );
                colorIt.advance();
            }

            contourIt.setContourLine( colorIt, line++ );

        } while ( contourIt.advance() );

        return line;
    }

    template< class ContourIterator >
    ColoredLine* fillOrdered( ContourIterator& contourIt,
        qreal value1, qreal value2, const QskGradient& gradient, ColoredLine* line )
    {
        if ( gradient.stops().size() == 2 )
        {
            if ( value2 == 1.0 && value1 == 0.0 )
            {
                TwoColorIterator01 colorIt( gradient.startColor(), gradient.endColor() );
                line = fillOrdered( contourIt, colorIt, line );
            }
            else
            {
                TwoColorIterator colorIt( value1, value2,
                    gradient.startColor(), gradient.endColor() );

                line = fillOrdered( contourIt, colorIt, line );
            }
        }
        else
        {
            GradientColorIterator colorIt( value1, value2, gradient.stops() );
            line = fillOrdered( contourIt, colorIt, line );
        }

        return line;
    }
}

#endif