/*
 * Copyright (C) 2017-2021 Apple Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions
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 *
 * 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 APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 */

#pragma once

#include "ColorTypes.h"

namespace WebCore {

// All color types, other than XYZA or those inheriting from RGBType, must implement
// the following conversions to and from their "Reference" color.
//
//    template<> struct ColorConversion<`ColorType`<float>::Reference, `ColorType`<float>> {
//        WEBCORE_EXPORT static `ColorType`<float>::Reference convert(const `ColorType`<float>&);
//    };
//    
//    template<> struct ColorConversion<`ColorType`<float>, `ColorType`<float>::Reference> {
//        WEBCORE_EXPORT static `ColorType`<float> convert(const `ColorType`<float>::Reference&);
//    };
//

template<typename Output, typename Input, typename = void> struct ColorConversion;

template<typename Output, typename Input> inline Output convertColor(const Input& color)
{
    return ColorConversion<Output, Input>::convert(color);
}


// MARK: Chromatic Adaptation conversions.

// http://www.brucelindbloom.com/index.html?Eqn_ChromAdapt.html
template<WhitePoint From, WhitePoint To> struct ChromaticAdapation;

template<> struct ChromaticAdapation<WhitePoint::D65, WhitePoint::D50> {
    static constexpr ColorMatrix<3, 3> matrix {
         1.0478112f, 0.0228866f, -0.0501270f,
         0.0295424f, 0.9904844f, -0.0170491f,
        -0.0092345f, 0.0150436f,  0.7521316f
    };
};

template<> struct ChromaticAdapation<WhitePoint::D50, WhitePoint::D65> {
    static constexpr ColorMatrix<3, 3> matrix {
         0.9555766f, -0.0230393f, 0.0631636f,
        -0.0282895f,  1.0099416f, 0.0210077f,
         0.0122982f, -0.0204830f, 1.3299098f
    };
};

// MARK: HSLA
template<> struct ColorConversion<SRGBA<float>, HSLA<float>> {
    WEBCORE_EXPORT static SRGBA<float> convert(const HSLA<float>&);
};
template<> struct ColorConversion<HSLA<float>, SRGBA<float>> {
    WEBCORE_EXPORT static HSLA<float> convert(const SRGBA<float>&);
};

// MARK: HWBA
template<> struct ColorConversion<SRGBA<float>, HWBA<float>> {
    WEBCORE_EXPORT static SRGBA<float> convert(const HWBA<float>&);
};
template<> struct ColorConversion<HWBA<float>, SRGBA<float>> {
    WEBCORE_EXPORT static HWBA<float> convert(const SRGBA<float>&);
};

// MARK: LCHA
template<> struct ColorConversion<Lab<float>, LCHA<float>> {
    WEBCORE_EXPORT static Lab<float> convert(const LCHA<float>&);
};
template<> struct ColorConversion<LCHA<float>, Lab<float>> {
    WEBCORE_EXPORT static LCHA<float> convert(const Lab<float>&);
};

// MARK: Lab
template<> struct ColorConversion<XYZA<float, WhitePoint::D50>, Lab<float>> {
    WEBCORE_EXPORT static XYZA<float, WhitePoint::D50> convert(const Lab<float>&);
};
template<> struct ColorConversion<Lab<float>, XYZA<float, WhitePoint::D50>> {
    WEBCORE_EXPORT static Lab<float> convert(const XYZA<float, WhitePoint::D50>&);
};

// MARK: SRGBA<uint8_t>
// Only sRGB supports non-floating point component types.
template<> struct ColorConversion<SRGBA<float>, SRGBA<uint8_t>> {
    WEBCORE_EXPORT static SRGBA<float> convert(const SRGBA<uint8_t>&);
};
template<> struct ColorConversion<SRGBA<uint8_t>, SRGBA<float>> {
    WEBCORE_EXPORT static SRGBA<uint8_t> convert(const SRGBA<float>&);
};


// Identity conversion.

template<typename ColorType> struct ColorConversion<ColorType, ColorType> {
    static ColorType convert(const ColorType& color)
    {
        return color;
    }
};


// Main conversion.

//                ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┼ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
//                 Matrix Conversions    ┌───────────┐│┌───────────┐
//                │                      │ XYZ (D50) │││ XYZ (D65) │                                                                                                                      │
//                                       └─────▲─────┘│└─────▲─────┘
//                │                            │      │      │                                                                                                                            │
//       ┌─────────────────────────┬───────────┘      │      └───────────┬───────────────────────────────┬───────────────────────────────┬───────────────────────────────┐
//       │        │                │                  │                  │                               │                               │                               │                │
//       │                         │                  │                  │                               │                               │                               │
//       │        │                │                  │                  │                               │                               │                               │                │
//       │          ProPhotoRGB───────────────────┐   │   SRGB──────────────────────────┐ DisplayP3─────────────────────┐ A98RGB────────────────────────┐ Rec2020───────────────────────┐
//       │        │ │┌────────┐ ┌────────────────┐│   │   │┌────────┐ ┌────────────────┐│ │┌────────┐ ┌────────────────┐│ │┌────────┐ ┌────────────────┐│ │┌────────┐ ┌────────────────┐│ │
//       │          ││ Linear │ │ LinearExtended ││   │   ││ Linear │ │ LinearExtended ││ ││ Linear │ │ LinearExtended ││ ││ Linear │ │ LinearExtended ││ ││ Linear │ │ LinearExtended ││
//       │        │ │└────────┘ └────────────────┘│   │   │└────────┘ └────────────────┘│ │└────────┘ └────────────────┘│ │└────────┘ └────────────────┘│ │└────────┘ └────────────────┘│ │
//       │         ─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─ ─│─ ─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─
// ┌───────────┐    │┌────────┐ ┌────────────────┐│   │   │┌────────┐ ┌────────────────┐│ │┌────────┐ ┌────────────────┐│ │┌────────┐ ┌────────────────┐│ │┌────────┐ ┌────────────────┐│
// │    Lab    │    ││ Gamma  │ │ GammaExtended  ││   │   ││ Gamma  │ │ GammaExtended  ││ ││ Gamma  │ │ GammaExtended  ││ ││ Gamma  │ │ GammaExtended  ││ ││ Gamma  │ │ GammaExtended  ││
// └─────▲─────┘    │└────────┘ └────────────────┘│   │   │└────▲───┘ └────────────────┘│ │└────────┘ └────────────────┘│ │└────────┘ └────────────────┘│ │└────────┘ └────────────────┘│
//       │          └─────────────────────────────┘   │   └─────┼───────────────────────┘ └─────────────────────────────┘ └─────────────────────────────┘ └─────────────────────────────┘
//       │                                            │      ┌──┴──────────┬─────────────┐
//       │                                            │      │             │             │
// ┌───────────┐                                      │┌───────────┐ ┌───────────┐┌─────────────┐
// │    LCH    │                                      ││    HSL    │ │    HWB    ││SRGB<uint8_t>│
// └───────────┘                                      │└───────────┘ └───────────┘└─────────────┘

template<typename Output, typename Input, typename> struct ColorConversion {
public:
    static constexpr Output convert(const Input& color)
    {
        // 1. Handle the special case SRGBA<uint8_t> for Input and Output.
        if constexpr (std::is_same_v<Input, SRGBA<uint8_t>> || std::is_same_v<Output, SRGBA<uint8_t>>)
            return convertColor<Output>(convertColor<SRGBA<float>>(color));

        // 2. Handle all color types that are not IsRGBType<T> or IsXYZA<T> for Input and Output. For all
        //    these other color types, we can uncondtionally convert them to their "reference" color, as
        //    either they have already been handled by a ColorConversion specialization or this will
        //    get us closer to the final conversion.
        else if constexpr (!IsRGBType<Input> && !IsXYZA<Input>)
            return convertColor<Output>(convertColor<typename Input::Reference>(color));
        else if constexpr (!IsRGBType<Output> && !IsXYZA<Output>)
            return convertColor<Output>(convertColor<typename Output::Reference>(color));

        // 3. Handle conversions within a RGBFamily (e.g. all have the same descriptor).
        else if constexpr (IsSameRGBTypeFamily<Output, Input>)
            return handleRGBFamilyConversion(color);

        // 4. Handle any gamma conversions for the Input and Output.
        else if constexpr (IsRGBGammaEncodedType<Input>)
            return convertColor<Output>(convertColor<typename Input::LinearCounterpart>(color));
        else if constexpr (IsRGBGammaEncodedType<Output>)
            return convertColor<Output>(convertColor<typename Output::LinearCounterpart>(color));

        // 5. At this point, Input and Output are each either Linear-RGB types (of different familes) or XYZA
        //    and therefore all additional conversion can happen via matrix transformation.
        else
            return handleMatrixConversion(color);
    }

private:
    template<typename ColorType> static inline constexpr auto toLinearEncoded(const ColorType& color) -> typename ColorType::LinearCounterpart
    {
        auto [c1, c2, c3, alpha] = color;
        return { ColorType::TransferFunction::toLinear(c1), ColorType::TransferFunction::toLinear(c2), ColorType::TransferFunction::toLinear(c3), alpha };
    }

    template<typename ColorType> static inline constexpr auto toGammaEncoded(const ColorType& color) -> typename ColorType::GammaEncodedCounterpart
    {
        auto [c1, c2, c3, alpha] = color;
        return { ColorType::TransferFunction::toGammaEncoded(c1), ColorType::TransferFunction::toGammaEncoded(c2), ColorType::TransferFunction::toGammaEncoded(c3), alpha };
    }

    template<typename ColorType> static inline constexpr auto toExtended(const ColorType& color) -> typename ColorType::ExtendedCounterpart
    {
        return makeFromComponents<typename ColorType::ExtendedCounterpart>(asColorComponents(color));
    }

    template<typename ColorType> static inline constexpr auto toBounded(const ColorType& color) -> typename ColorType::BoundedCounterpart
    {
        return makeFromComponentsClampingExceptAlpha<typename ColorType::BoundedCounterpart>(asColorComponents(color));
    }

    static inline constexpr Output handleRGBFamilyConversion(const Input& color)
    {
        static_assert(IsSameRGBTypeFamily<Output, Input>);

        //  RGB Family────────────────────┐
        //  │┌────────┐ ┌────────────────┐│
        //  ││ Linear │ │ LinearExtended ││
        //  │└────────┘ └────────────────┘│
        //  │┌────────┐ ┌────────────────┐│
        //  ││ Gamma  │ │ GammaExtended  ││
        //  │└────────┘ └────────────────┘│
        //  └─────────────────────────────┘

        // This handles conversions between any two of these within the same family, so SRGBLinear -> SRGB, but not
        // SRGBLinear -> A98RGB.

        auto boundsConversion = [](auto color) {
            if constexpr (IsRGBExtendedType<Output> && IsRGBBoundedType<Input>)
                return toExtended(color);
            else if constexpr (IsRGBBoundedType<Output> && IsRGBExtendedType<Input>)
                return toBounded(color);
            else
                return color;
        };

        auto gammaConversion = [](auto color) {
            if constexpr (IsRGBGammaEncodedType<Output> && IsRGBLinearEncodedType<Input>)
                return toGammaEncoded(color);
            else if constexpr (IsRGBLinearEncodedType<Output> && IsRGBGammaEncodedType<Input>)
                return toLinearEncoded(color);
            else
                return color;
        };

        return boundsConversion(gammaConversion(color));
    }

    static inline constexpr Output handleMatrixConversion(const Input& color)
    {
        static_assert(IsRGBLinearEncodedType<Input> || IsXYZA<Input>);
        static_assert(IsRGBLinearEncodedType<Output> || IsXYZA<Output>);

        //  ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┼ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
        //   Matrix Conversions    ┌───────────┐│┌───────────┐
        //  │                      │ XYZ (D50) │││ XYZ (D65) │                                                                                                                      │
        //                         └─────▲─────┘│└─────▲─────┘
        //  │                            │      │      │                                                                                                                            │
        //                   ┌───────────┘      │      └───────────┬───────────────────────────────┬───────────────────────────────┬───────────────────────────────┐
        //  │                │                  │                  │                               │                               │                               │                │
        //                   │                  │                  │                               │                               │                               │
        //  │                │                  │                  │                               │                               │                               │                │
        //    ProPhotoRGB───────────────────┐   │   SRGB──────────────────────────┐ DisplayP3─────────────────────┐ A98RGB────────────────────────┐ Rec2020───────────────────────┐
        //  │ │┌────────┐ ┌────────────────┐│   │   │┌────────┐ ┌────────────────┐│ │┌────────┐ ┌────────────────┐│ │┌────────┐ ┌────────────────┐│ │┌────────┐ ┌────────────────┐│ │
        //    ││ Linear │ │ LinearExtended ││   │   ││ Linear │ │ LinearExtended ││ ││ Linear │ │ LinearExtended ││ ││ Linear │ │ LinearExtended ││ ││ Linear │ │ LinearExtended ││
        //  │ │└────────┘ └────────────────┘│   │   │└────────┘ └────────────────┘│ │└────────┘ └────────────────┘│ │└────────┘ └────────────────┘│ │└────────┘ └────────────────┘│ │
        //   ─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─ ─│─ ─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─│─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─

        // This handles conversions between linear color types that can be converted using pre-defined
        // 3x3 matrices.
        
        // FIXME: Pre-compute (using constexpr) the concatenation of the matrices prior to applying them
        // to reduce number of matrix multiplications to a minimum. This will likely give subtly different
        // results (due to floating point effects) so if this optimization is considered we should ensure we
        // have sufficient testing coverage to notice any adverse effects.

        auto applyMatrices = [](const Input& color, auto... matrices) {
            return makeFromComponentsClampingExceptAlpha<Output>(applyMatricesToColorComponents(asColorComponents(color), matrices...));
        };

        if constexpr (Input::whitePoint == Output::whitePoint) {
            if constexpr (IsXYZA<Input>)
                return applyMatrices(color, Output::xyzToLinear);
            else if constexpr (IsXYZA<Output>)
                return applyMatrices(color, Input::linearToXYZ);
            else
                return applyMatrices(color, Input::linearToXYZ, Output::xyzToLinear);
        } else {
            if constexpr (IsXYZA<Input> && IsXYZA<Output>)
                return applyMatrices(color, ChromaticAdapation<Input::whitePoint, Output::whitePoint>::matrix);
            else if constexpr (IsXYZA<Input>)
                return applyMatrices(color, ChromaticAdapation<Input::whitePoint, Output::whitePoint>::matrix, Output::xyzToLinear);
            else if constexpr (IsXYZA<Output>)
                return applyMatrices(color, Input::linearToXYZ, ChromaticAdapation<Input::whitePoint, Output::whitePoint>::matrix);
            else
                return applyMatrices(color, Input::linearToXYZ, ChromaticAdapation<Input::whitePoint, Output::whitePoint>::matrix, Output::xyzToLinear);
        }
    }
};

} // namespace WebCore
