DNF_DEV/source/math/Interpolator.h

// Copyright (c) 2016-2018 Ember - Nomango
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#pragma once
#include <core/Function.h>
#include <math/Vec2.hpp>
#include <math/Rect.hpp>
#include <math/Transform.hpp>

namespace ember
{
    namespace math
    {

        template <typename _Method = void>
        struct InterpolateMethod;

        template <>
        struct InterpolateMethod<void>
        {
            inline float operator()(float frac) const noexcept
            {
                return frac;
            }
        };

        template <>
        struct InterpolateMethod<float (*)(float)>
        {
            float (*method)(float);

            InterpolateMethod(float (*method)(float)) noexcept
                : method(method)
            {
            }

            inline float operator()(float frac) const noexcept
            {
                if (method)
                    return method(frac);
                return frac;
            }
        };

        template <>
        struct InterpolateMethod<Function<float(float)>>
        {
            Function<float(float)> method;

            InterpolateMethod(const Function<float(float)> &method) noexcept
                : method(method)
            {
            }

            inline float operator()(float frac) const noexcept
            {
                if (method)
                    return method(frac);
                return frac;
            }
        };

        template <typename _Ty>
        class Interpolator;

        template <typename _Ty>
        class Interpolator
        {
        public:
            template <typename _Method = void>
            inline _Ty Interpolate(_Ty start, _Ty end, float frac, const InterpolateMethod<_Method> &method = {})
            {
                if (frac >= 1)
                    return end;
                return start + static_cast<_Ty>(static_cast<float>(end - start) * method(frac));
            }
        };

        template <typename _Ty>
        class Interpolator<Vec2T<_Ty>>
        {
        public:
            template <typename _Method = void>
            inline Vec2T<_Ty> Interpolate(const Vec2T<_Ty> &start, const Vec2T<_Ty> &end, float frac,
                                          const InterpolateMethod<_Method> &method = {})
            {
                if (frac >= 1)
                    return end;

                Interpolator<_Ty> fi;
                return Vec2T<_Ty>{fi.Interpolate(start.x, end.x, frac, method), fi.Interpolate(start.y, end.y, frac, method)};
            }
        };

        template <typename _Ty>
        class Interpolator<RectT<_Ty>>
        {
        public:
            template <typename _Method = void>
            inline RectT<_Ty> Interpolate(const RectT<_Ty> &start, const RectT<_Ty> &end, float frac,
                                          const InterpolateMethod<_Method> &method = {})
            {
                if (frac >= 1)
                    return end;

                Interpolator<Vec2T<_Ty>> vi;
                return RectT<_Ty>{vi.Interpolate(start.left_top, end.left_top, frac, method),
                                  vi.Interpolate(start.right_bottom, end.right_bottom, frac, method)};
            }
        };

        template <typename _Ty>
        class Interpolator<TransformT<_Ty>>
        {
        public:
            template <typename _Method = void>
            inline TransformT<_Ty> Interpolate(const TransformT<_Ty> &start, const TransformT<_Ty> &end, float frac,
                                               const InterpolateMethod<_Method> &method = {})
            {
                if (frac >= 1)
                    return end;

                Interpolator<_Ty> fi;
                Interpolator<Vec2T<_Ty>> vi;

                TransformT<_Ty> transform;
                transform.rotation = fi.Interpolate(start.rotation, end.rotation, frac, method);
                transform.position = vi.Interpolate(start.position, end.position, frac, method);
                transform.scale = vi.Interpolate(start.scale, end.scale, frac, method);
                transform.skew = vi.Interpolate(start.skew, end.skew, frac, method);
                return transform;
            }
        };

    } // namespace math
} // namespace ember