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 // This file is part of the ACTS project.
 //
 // Copyright (C) 2016 CERN for the benefit of the ACTS project
 //
 // This Source Code Form is subject to the terms of the Mozilla Public
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
 #pragma once
 
 #include "Acts/Definitions/Algebra.hpp"
 #include "Acts/Utilities/AxisDefinitions.hpp"
 #include "Acts/Utilities/Delegate.hpp"
 #include "Acts/Utilities/VectorHelpers.hpp"
 
 #include <array>
 
 namespace Acts {
 
 namespace GridAccessHelpers {
 
 /// Unroll the cast loop
 ///
 /// @tparam cast_container is the container type of cast objects
 /// @tparam Array is the array type to be filled
 ///
 /// @param position is the position of the update call
 /// @param globalCasts is the cast value vector from global to grid position
 /// @param ra is the array to be filled
 template <typename cast_container, typename Array, std::size_t... idx>
 void fillCasts(const Vector3& position, const cast_container& globalCasts,
                Array& ra, std::index_sequence<idx...> /*indices*/) {
   ((ra[idx] = VectorHelpers::cast(position, globalCasts[idx])), ...);
 }
 /// Cast into a lookup position
 ///
 /// This method allows to transform a global position into a grid position
 /// that is specified by binning values. It casts the global position info
 /// into a format suitable for the grid.
 ///
 /// @tparam cast_container is the container type of cast objects
 /// @tparam Array is the array type to be filled
 ///
 /// @param position is the position of the update call
 /// @param globalCasts is the cast value vector from global to grid position
 ///
 /// @return a grid point in an appropriate format
 template <typename grid_type, typename cast_container>
 typename grid_type::point_t castPosition(const Vector3& position,
                                          const cast_container& globalCasts) {
   // Fill the grid point from global
   typename grid_type::point_t casted{};
   fillCasts(position, globalCasts, casted,
             std::make_integer_sequence<std::size_t, grid_type::DIM>{});
   return casted;
 }
 
 /// Unroll the local position loop
 ///
 /// @param lposition is the local position
 /// @param laccess the local accessors
 /// @param ra is the array to be filled
 ///
 /// @note void function that fills the provided array
 template <typename Array, typename local_indices, std::size_t... idx>
 void fillLocal(const Vector2& lposition, const local_indices& laccess,
                Array& ra, std::index_sequence<idx...> /*indices*/) {
   ((ra[idx] = lposition[laccess[idx]]), ...);
 }
 
 /// Access local parameters for a propriate lookup position
 ///
 /// This method allows to transform a local position into a
 /// grid position, it only works for 1-D and 2-D grids.
 ///
 /// @param lposition is the position of the update call
 /// @param laccess the local accessors
 ///
 /// @return an array suitable for the grid
 template <typename grid_type, typename local_indices>
 typename grid_type::point_t accessLocal(const Vector2& lposition,
                                         const local_indices& laccess) {
   if constexpr (grid_type::DIM > 2u) {
     throw std::invalid_argument(
         "GridAccessHelper: only 1-D and 2-D grids are possible for local "
         "access.");
   }
   // Fill the grid point from local according to the accessors
   typename grid_type::point_t accessed{};
   fillLocal(lposition, laccess, accessed,
             std::make_integer_sequence<std::size_t, grid_type::DIM>{});
   return accessed;
 }
 
 }  // namespace GridAccessHelpers
 
 namespace GridAccess {
 
 /// Interface class for owning delegate
 class IGlobalToGridLocal {
  public:
   virtual ~IGlobalToGridLocal() = default;
 };
 
 /// Interface class for owning delegate
 class IBoundToGridLocal {
  public:
   virtual ~IBoundToGridLocal() = default;
 };
 
 /// Adapter that applies an affine transform before grid-local conversion.
 template <typename global_to_grid_local_t>
 class Affine3Transformed : public IGlobalToGridLocal {
  public:
   /// Grid-local coordinate type.
   using grid_local_t = typename global_to_grid_local_t::grid_local_t;
 
   /// The global to local transformation
   global_to_grid_local_t globalToGridLocal;
 
   /// The transformation matrix
   Transform3 transform;
 
   /// Constructor
   ///
   /// @param g2gl is the global to grid local transformation
   /// @param t is the transformation matrix
   Affine3Transformed(global_to_grid_local_t g2gl, const Transform3& t)
       : globalToGridLocal(std::move(g2gl)), transform(t) {}
 
   /// Transform in to the local frame, then the grid local position
   ///
   /// @param position is the global position
   ///
   /// @return the grid position
   typename global_to_grid_local_t::grid_local_t toGridLocal(
       const Vector3& position) const {
     return globalToGridLocal.toGridLocal(transform * position);
   }
 };
 
 /// @brief A global (potentially casted) sub space of a global
 /// position
 /// @tparam ...Args
 template <AxisDirection... Args>
 class GlobalSubspace : public IGlobalToGridLocal {
  public:
   /// Type alias for grid-local coordinate array
   using grid_local_t = std::array<double, sizeof...(Args)>;
 
   /// Assert that size has to be bigger than 0
   static_assert(sizeof...(Args) > 0,
                 "GlobalSubspace: cannot have an empty binning value list.");
 
   /// Assert that size has to be smaller than 4
   static_assert(sizeof...(Args) <= 3,
                 "GlobalSubspace: cannot have more than 3 binning values.");
 
   // Constructor
   GlobalSubspace() = default;
 
   /// The axis directions of the subspace
   static constexpr std::array<AxisDirection, sizeof...(Args)> axisDirs = {
       Args...};
 
   /// Transform in to the local frame, then the grid local position
   ///
   /// @param position is the global position
   ///
   /// @return the grid position
   grid_local_t toGridLocal(const Vector3& position) const {
     // Fill the grid point from global
     grid_local_t glocal{};
     GridAccessHelpers::fillCasts(
         position, axisDirs, glocal,
         std::make_integer_sequence<std::size_t, sizeof...(Args)>{});
     return glocal;
   }
 };
 
 // The bound to grid local transformation, if only access of a subspace
 // is requested
 /// Access a local coordinate subspace for bound parameter grids.
 template <std::size_t... Args>
 class LocalSubspace : public IBoundToGridLocal {
  public:
   /// Grid local coordinate type
   using grid_local_t = std::array<double, sizeof...(Args)>;
 
   /// Assert that the accessors are unique
   static_assert(sizeof...(Args) == 1 || sizeof...(Args) == 2,
                 "LocalSubspace: only 1 or 2 accessors are allowed.");
 
   /// Only 0 or 1 are allowed
   static_assert(((Args < 2) && ...),
                 "LocalSubspace: local access needs to be 0u or 1u");
 
   // Constructor
   LocalSubspace() = default;
 
   /// Accessor indices
   static constexpr std::array<std::size_t, sizeof...(Args)> accessors = {
       Args...};
 
   /// Access the local entries
   ///
   /// @param lposition is the local position
   ///
   /// @return the grid position
   grid_local_t toGridLocal(const Vector2& lposition) const {
     // Fill the grid point from local according to the accessors
     grid_local_t accessed{};
     GridAccessHelpers::fillLocal(
         lposition, accessors, accessed,
         std::make_integer_sequence<std::size_t, sizeof...(Args)>{});
     return accessed;
   }
 };
 
 /// Convert bound cylinder local coordinates to Z-Phi grid coordinates.
 class BoundCylinderToZPhi : public IBoundToGridLocal {
  public:
   /// Cylinder radius
   double radius = 1.;
   /// Z-coordinate shift
   double shift = 0.;
 
   /// Constructor with arguments
   /// @param r the radius
   /// @param z the shift
   BoundCylinderToZPhi(double r, double z) : radius(r), shift(z) {}
 
   /// Convert local coordinates to grid coordinates
   /// @param local Local coordinates
   /// @return Grid coordinates
   std::array<double, 2u> toGridLocal(const Vector2& local) const {
     return {local[1u] + shift, local[0u] / radius};
   }
 
   /// Type alias for disc-to-RPhi transformation
   using BoundDiscToRPhi = LocalSubspace<0u, 1u>;
 };
 
 // Definition of bound (on surface) to grid local representation delegate
 // 1 dimensional local grid
 using BoundToGridLocal1DimDelegate =
     OwningDelegate<std::array<double, 1u>(const Vector2&),
                    GridAccess::IBoundToGridLocal>;
 
 // Definition of global to grid local representation delegate
 // 1 dimensional local grid
 using GlobalToGridLocal1DimDelegate =
     OwningDelegate<std::array<double, 1u>(const Vector3&),
                    GridAccess::IGlobalToGridLocal>;
 
 // Definition of bound (on surface) to grid local representation delegate
 // 2 dimensional local grid
 using BoundToGridLocal2DimDelegate =
     OwningDelegate<std::array<double, 2u>(const Vector2&),
                    GridAccess::IBoundToGridLocal>;
 
 // Definition of global to grid local representation delegate
 // 2 dimensional local grid
 using GlobalToGridLocal2DimDelegate =
     OwningDelegate<std::array<double, 2u>(const Vector3&),
                    GridAccess::IGlobalToGridLocal>;
 
 }  // namespace GridAccess
 }  // namespace Acts

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