view.hpp

/*
 Copyright (c) 2026 ETIB Corporation
 
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 this software and associated documentation files (the "Software"), to deal in
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 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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 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
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 */
 
#pragma once
 
#include <cmath>
#include <numbers>
#include <ostream>
#include <stdexcept>
#include <type_traits>
#include <utility>
#include <ostream>
 
#include "utility/graphic/field_of_view.hpp"
#include "utility/graphic/pose.hpp"
#include "utility/graphic/ray.hpp"
 
namespace utility::graphic
{
 
    template<typename ViewComponentType>
    concept CanBeViewComponent = CanBeFieldOfViewComponent<ViewComponentType>
        && CanBePoseComponent<ViewComponentType>
        && CanBeRayComponent<ViewComponentType>;
 
    template<CanBeViewComponent ViewComponentType> class View
    {
        private:
        Pose<ViewComponentType> _pose;    //< View position and orientation
 
        FieldOfView<ViewComponentType>
            _fieldOfView;    
 
        math::Vector<ViewComponentType, 2>
            _viewportSize;    
 
        ViewComponentType _nearPlane;    
        ViewComponentType _farPlane;     
 
        bool _flipY = true;    
 
        static void validatePerspective(ViewComponentType verticalFovRadians,
                                        ViewComponentType aspectRatio)
        {
            if (verticalFovRadians <= ViewComponentType {}
                || verticalFovRadians
                    >= std::numbers::pi_v<ViewComponentType>) {
                throw std::invalid_argument(
                    "View vertical FOV must be in range (0, pi) radians");
            }
 
            if (aspectRatio <= ViewComponentType {}) {
                throw std::invalid_argument(
                    "View aspect ratio must be positive");
            }
        }
 
        static FieldOfView<ViewComponentType>
            makeSymmetricFieldOfView(ViewComponentType verticalFovRadians,
                                     ViewComponentType aspectRatio)
        {
            const ViewComponentType halfVertical =
                verticalFovRadians / ViewComponentType { 2 };
 
            const ViewComponentType halfHorizontal =
                std::atan(std::tan(halfVertical) * aspectRatio);
 
            return FieldOfView<ViewComponentType>(
                halfVertical, -halfVertical, -halfHorizontal, halfHorizontal);
        }
 
        static void validateOrientation(
            const math::Vector<ViewComponentType, 3> &forward,
            const math::Vector<ViewComponentType, 3> &up)
        {
            if (math::dot(forward, forward) == ViewComponentType {}) {
                throw std::invalid_argument(
                    "View forward vector must be non-zero");
            }
            if (math::dot(up, up) == ViewComponentType {}) {
                throw std::invalid_argument("View up vector must be non-zero");
            }
            if (math::dot(math::cross(forward, up), math::cross(forward, up))
                == ViewComponentType {}) {
                throw std::invalid_argument(
                    "View forward and up vectors must not be collinear");
            }
        }
 
        math::Vector<ViewComponentType, 4> normalizedRotationComponents() const
        {
            const auto normalized = _pose.getOrientation().normalized();
            return math::Vector<ViewComponentType, 4> {
                static_cast<ViewComponentType>(normalized.x),
                static_cast<ViewComponentType>(normalized.y),
                static_cast<ViewComponentType>(normalized.z),
                static_cast<ViewComponentType>(normalized.w)
            };
        }
 
        math::Vector<ViewComponentType, 3> rotateVectorByRotation(
            const math::Vector<ViewComponentType, 3> &vector) const
        {
            const auto q = normalizedRotationComponents();
            const math::Vector<ViewComponentType, 3> u { q[0], q[1], q[2] };
            const ViewComponentType s = q[3];
 
            return u * (ViewComponentType { 2 } * math::dot(u, vector))
                + vector.operator*(s * s - math::dot(u, u))
                + math::cross(u, vector) * (ViewComponentType { 2 } * s);
        }
 
        public:
        View(void)
            : _pose()
            , _fieldOfView()
            , _viewportSize()
            , _nearPlane(ViewComponentType { 1.0 })
            , _farPlane(ViewComponentType { 1000.0 })
        {
        }
 
        View(Pose<ViewComponentType> pose,
             utility::graphic::FieldOfView<ViewComponentType> fov,
             math::Vector<ViewComponentType, 2> viewportSize,
             ViewComponentType nearPlane, ViewComponentType farPlane)
            : _pose(std::move(pose))
            , _fieldOfView(std::move(fov))
            , _viewportSize(std::move(viewportSize))
            , _nearPlane(nearPlane)
            , _farPlane(farPlane)
        {
        }
 
        View(const View &other) = default;
 
        View(View &&other) noexcept = default;
 
        View &operator=(const View &other) = default;
 
        View &operator=(View &&other) noexcept = default;
 
        ~View(void) = default;
 
        void setPose(const Pose<ViewComponentType> &pose)
        {
            _pose = pose;
        }
 
        Pose<ViewComponentType> getPose(void) const
        {
            return _pose;
        }
 
        math::Vector<ViewComponentType, 3> getForward(void) const
        {
            return math::normalize(
                rotateVectorByRotation(math::Vector<ViewComponentType, 3> {
                    ViewComponentType {}, ViewComponentType {},
                    ViewComponentType { -1 } }));
        }
 
        math::Vector<ViewComponentType, 3> getUp(void) const
        {
            return math::normalize(rotateVectorByRotation(
                math::Vector<ViewComponentType, 3> { ViewComponentType {},
                                                     ViewComponentType { 1 },
                                                     ViewComponentType {} }));
        }
 
        void setPerspective(ViewComponentType verticalFovRadians,
                            ViewComponentType aspectRatio)
        {
            validatePerspective(verticalFovRadians, aspectRatio);
            _fieldOfView =
                makeSymmetricFieldOfView(verticalFovRadians, aspectRatio);
        }
 
        ViewComponentType getAspectRatio() const
        {
            const ViewComponentType vertical = std::tan(_fieldOfView.getUp())
                - std::tan(_fieldOfView.getDown());
            const ViewComponentType horizontal =
                std::tan(_fieldOfView.getRight())
                - std::tan(_fieldOfView.getLeft());
            if (vertical == ViewComponentType {}) {
                return ViewComponentType {};
            }
            return horizontal / vertical;
        }
 
        void setFieldOfView(const FieldOfView<ViewComponentType> &fieldOfView)
        {
            _fieldOfView = fieldOfView;
        }
 
        FieldOfView<ViewComponentType> getFieldOfView(void) const
        {
            return _fieldOfView;
        }
 
        math::Vector<ViewComponentType, 3> getRight(void) const
        {
            return math::normalize(rotateVectorByRotation(
                math::Vector<ViewComponentType, 3> { ViewComponentType { 1 },
                                                     ViewComponentType {},
                                                     ViewComponentType {} }));
        }
 
        void setClippingPlanes(ViewComponentType nearDistance,
                               ViewComponentType farDistance)
        {
            if (nearDistance <= ViewComponentType { 0 }) {
                throw std::invalid_argument("Near plane must be > 0");
            }
            if (farDistance <= nearDistance) {
                throw std::invalid_argument("Far plane must be > near plane");
            }
 
            _nearPlane = nearDistance;
            _farPlane  = farDistance;
        }
 
        ViewComponentType getNearPlane() const noexcept
        {
            return _nearPlane;
        }
 
        ViewComponentType getFarPlane() const noexcept
        {
            return _farPlane;
        }
 
        void move(const math::Vector<ViewComponentType, 3> &offset)
        {
            _pose.translate(Position<ViewComponentType>(offset));
        }
 
        View moved(const math::Vector<ViewComponentType, 3> &offset) const
        {
            View result(*this);
            result.move(offset);
            return result;
        }
 
        Ray<ViewComponentType> viewRay(ViewComponentType ndcX,
                                       ViewComponentType ndcY) const
        {
            const auto tx0 = std::tan(_fieldOfView.getLeft());
            const auto tx1 = std::tan(_fieldOfView.getRight());
            const auto ty0 = std::tan(_fieldOfView.getDown());
            const auto ty1 = std::tan(_fieldOfView.getUp());
 
            const ViewComponentType horizontalOffset =
                ((ndcX + ViewComponentType { 1 }) * ViewComponentType { 0.5 })
                    * (tx1 - tx0)
                + tx0;
 
            const ViewComponentType verticalOffset =
                ((ndcY + ViewComponentType { 1 }) * ViewComponentType { 0.5 })
                    * (ty1 - ty0)
                + ty0;
 
            const auto rayDirection = getForward()
                + getRight() * horizontalOffset + getUp() * verticalOffset;
 
            return Ray<ViewComponentType>(_pose.getPosition(),
                                          math::normalize(rayDirection));
        }
 
        Ray<ViewComponentType> viewPointToRay(
            const math::Vector<ViewComponentType, 2> &point) const
        {
            if (point.x < 0 || point.y < 0 || point.x >= _viewportSize.x
                || point.y >= _viewportSize.y) {
                throw std::out_of_range(
                    "View point is outside of viewport bounds");
            }
 
            const ViewComponentType ndcX =
                (static_cast<ViewComponentType>(point.x) / _viewportSize.x)
                    * ViewComponentType { 2 }
                - ViewComponentType { 1 };
 
            const ViewComponentType ndcY = ViewComponentType { 1 }
                - (static_cast<ViewComponentType>(point.y) / _viewportSize.y)
                    * ViewComponentType { 2 };
 
            return viewRay(ndcX, ndcY);
        }
 
        ViewComponentType getVerticalFovRadians() const noexcept
        {
            return _fieldOfView.getUp() - _fieldOfView.getDown();
        }
 
        ViewComponentType getHorizontalFovRadians() const noexcept
        {
            return _fieldOfView.getRight() - _fieldOfView.getLeft();
        }
        bool isFieldOfViewSymmetric(
            ViewComponentType epsilon = ViewComponentType {
                1e-6 }) const noexcept
        {
            return _fieldOfView.isSymmetric(epsilon);
        }
 
        Ray<ViewComponentType> centerRay(void) const
        {
            return viewRay(0, 0);
        }
 
        bool operator==(const View &other) const noexcept
        {
            return _pose == other._pose
                && _fieldOfView.getUp() == other._fieldOfView.getUp()
                && _fieldOfView.getDown() == other._fieldOfView.getDown()
                && _fieldOfView.getLeft() == other._fieldOfView.getLeft()
                && _fieldOfView.getRight() == other._fieldOfView.getRight();
        }
 
        bool operator!=(const View &other) const noexcept
        {
            return !(*this == other);
        }
 
        void setViewportSize(
            const math::Vector<ViewComponentType, 2> &viewportSize)
        {
            _viewportSize = viewportSize;
        }
 
        math::Vector<ViewComponentType, 2> getViewportSize(void) const
        {
            return _viewportSize;
        }
 
        utility::math::Matrix<ViewComponentType, 4, 4> toViewMatrix(void) const
        {
            const auto orientation = _pose.getOrientation();
            const auto position    = _pose.getPosition();
 
            utility::math::Matrix<ViewComponentType, 4, 4> view { glm::inverse(
                glm::translate(glm::identity<glm::mat4>(),
                               glm::vec3(position.x, position.y, position.z))
                * glm::mat4_cast(glm::quat(orientation.w, orientation.x,
                                           orientation.y, orientation.z))) };
 
            // GLM is column-major: view[col][row]
            // view[0][0] = static_cast<ViewComponentType>(right[0]);
            // view[0][1] = static_cast<ViewComponentType>(up[0]);
            // view[0][2] = static_cast<ViewComponentType>(-forward[0]);
            // view[0][3] = static_cast<ViewComponentType>(0);
 
            // view[1][0] = static_cast<ViewComponentType>(right[1]);
            // view[1][1] = static_cast<ViewComponentType>(up[1]);
            // view[1][2] = static_cast<ViewComponentType>(-forward[1]);
            // view[1][3] = static_cast<ViewComponentType>(0);
 
            // view[2][0] = static_cast<ViewComponentType>(right[2]);
            // view[2][1] = static_cast<ViewComponentType>(up[2]);
            // view[2][2] = static_cast<ViewComponentType>(-forward[2]);
            // view[2][3] = static_cast<ViewComponentType>(0);
 
            // view[3][0] =
            //  -static_cast<ViewComponentType>(math::dot(right, position));
            // view[3][1] =
            //  -static_cast<ViewComponentType>(math::dot(up, position));
            // view[3][2] =
            //  static_cast<ViewComponentType>(math::dot(forward, position));
            // view[3][3] = static_cast<ViewComponentType>(1);
 
            return view;
        }
 
        utility::math::Matrix<ViewComponentType, 4, 4>
            getProjectionMatrix() const
        {
            const ViewComponentType tanLeft = std::tan(_fieldOfView.getLeft());
            const ViewComponentType tanRight =
                std::tan(_fieldOfView.getRight());
            const ViewComponentType tanUp   = std::tan(_fieldOfView.getUp());
            const ViewComponentType tanDown = std::tan(_fieldOfView.getDown());
 
            const ViewComponentType width  = tanRight - tanLeft;
            const ViewComponentType height = tanUp - tanDown;
 
            if (width <= ViewComponentType { 0 }
                || height <= ViewComponentType { 0 }) {
                throw std::invalid_argument(
                    "View frustum width and height must be positive");
            }
 
            if (_farPlane <= _nearPlane) {
                throw std::invalid_argument(
                    "View far plane must be greater than near plane");
            }
 
            utility::math::Matrix<ViewComponentType, 4, 4> projection = {};
 
            projection[0][0] = static_cast<ViewComponentType>(2) / width;
            projection[1][1] = static_cast<ViewComponentType>(2) / height;
            projection[2][0] = (tanRight + tanLeft) / width;
            projection[2][1] = (tanUp + tanDown) / height;
            projection[2][2] = -_farPlane / (_farPlane - _nearPlane);
            projection[2][3] = -static_cast<ViewComponentType>(1);
            projection[3][2] =
                -(_farPlane * _nearPlane) / (_farPlane - _nearPlane);
            projection[3][3] = static_cast<ViewComponentType>(0);
 
            if (_flipY) {
                // Invert Y for Vulkan-style NDC (Y pointing down).
                projection[1][1] *= static_cast<ViewComponentType>(-1);
                projection[2][1] *= static_cast<ViewComponentType>(-1);
            }
 
            return projection;
        }
 
        void setFlipY(bool flip) noexcept
        {
            _flipY = flip;
        }
 
        bool isFlipY(void) const noexcept
        {
            return _flipY;
        }
    };
 
    using ViewF = View<float>;
 
    using ViewD = View<double>;
 
    std::ostream &operator<<(std::ostream &stream, const ViewF &view);
 
    std::ostream &operator<<(std::ostream &stream, const ViewD &view);
 
}    // namespace utility::graphic