From bbe8168ecd7d0817f9169faa516f3ab4b7f01b2a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20BRIOL?= <fbriol@gmail.com>
Date: Thu, 15 Feb 2024 22:06:03 +0100
Subject: [PATCH] =?UTF-8?q?=E2=99=BB=EF=B8=8F=20Refactor=20spline=20interp?=
 =?UTF-8?q?olation=20in=20Spline2D=20class?=
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---
 .../detail/interpolation/factory_1d.hpp       | 41 +++++++++++++++++
 .../include/pyinterp/detail/math/spline2d.hpp | 46 ++++---------------
 2 files changed, 51 insertions(+), 36 deletions(-)
 create mode 100644 src/pyinterp/core/include/pyinterp/detail/interpolation/factory_1d.hpp

diff --git a/src/pyinterp/core/include/pyinterp/detail/interpolation/factory_1d.hpp b/src/pyinterp/core/include/pyinterp/detail/interpolation/factory_1d.hpp
new file mode 100644
index 00000000..90da9f52
--- /dev/null
+++ b/src/pyinterp/core/include/pyinterp/detail/interpolation/factory_1d.hpp
@@ -0,0 +1,41 @@
+#pragma once
+#include <stdexcept>
+
+#include "pyinterp/detail/interpolation/akima.hpp"
+#include "pyinterp/detail/interpolation/akima_periodic.hpp"
+#include "pyinterp/detail/interpolation/cspline.hpp"
+#include "pyinterp/detail/interpolation/cspline_periodic.hpp"
+#include "pyinterp/detail/interpolation/linear.hpp"
+#include "pyinterp/detail/interpolation/polynomial.hpp"
+#include "pyinterp/detail/interpolation/steffen.hpp"
+
+namespace pyinterp::detail::interpolation {
+
+template <typename T>
+static inline auto factory_1d(const std::string &kind)
+    -> std::unique_ptr<Interpolator1D<T>> {
+  if (kind == "linear") {
+    return std::make_unique<Linear<T>>();
+  }
+  if (kind == "polynomial") {
+    return std::make_unique<Polynomial<T>>();
+  }
+  if (kind == "c_spline") {
+    return std::make_unique<CSpline<T>>();
+  }
+  if (kind == "c_spline_periodic") {
+    return std::make_unique<CSplinePeriodic<T>>();
+  }
+  if (kind == "akima") {
+    return std::make_unique<Akima<T>>();
+  }
+  if (kind == "akima_periodic") {
+    return std::make_unique<AkimaPeriodic<T>>();
+  }
+  if (kind == "steffen") {
+    return std::make_unique<Steffen<T>>();
+  }
+  throw std::invalid_argument("Invalid interpolation type: " + kind);
+}
+
+}  // namespace pyinterp::detail::interpolation
diff --git a/src/pyinterp/core/include/pyinterp/detail/math/spline2d.hpp b/src/pyinterp/core/include/pyinterp/detail/math/spline2d.hpp
index af1adf54..a2ea1eb9 100644
--- a/src/pyinterp/core/include/pyinterp/detail/math/spline2d.hpp
+++ b/src/pyinterp/core/include/pyinterp/detail/math/spline2d.hpp
@@ -8,7 +8,7 @@
 #include <Eigen/Core>
 #include <string>
 
-#include "pyinterp/detail/gsl/interpolate1d.hpp"
+#include "pyinterp/detail/interpolation/factory_1d.hpp"
 #include "pyinterp/detail/math/frame.hpp"
 
 namespace pyinterp::detail::math {
@@ -22,53 +22,27 @@ class Spline2D {
   /// @param type method of calculation
   explicit Spline2D(const Frame2D &xr, const std::string &kind)
       : column_(xr.y()->size()),
-        x_interpolator_(xr.x()->size(),
-                        gsl::Interpolate1D::parse_interp_type(kind),
-                        gsl::Accelerator()),
-        y_interpolator_(xr.y()->size(),
-                        gsl::Interpolate1D::parse_interp_type(kind),
-                        gsl::Accelerator()) {}
+        x_interpolator_(interpolation::factory_1d<double>(kind)),
+        y_interpolator_(interpolation::factory_1d<double>(kind)) {}
 
   /// Return the interpolated value of y for a given point x
   auto interpolate(const double x, const double y, const Frame2D &xr)
       -> double {
-    return evaluate(&gsl::Interpolate1D::interpolate, x, y, xr);
-  }
-
-  /// Return the derivative for a given point x
-  auto derivative(const double x, const double y, const Frame2D &xr) -> double {
-    return evaluate(&gsl::Interpolate1D::derivative, x, y, xr);
-  }
-
-  /// Return the second derivative for a given point x
-  auto second_derivative(const double x, const double y, const Frame2D &xr)
-      -> double {
-    return evaluate(&gsl::Interpolate1D::second_derivative, x, y, xr);
+    // Spline interpolation as function of X-coordinate
+    for (Eigen::Index ix = 0; ix < xr.y()->size(); ++ix) {
+      column_(ix) = (*x_interpolator_)(*(xr.x()), xr.q()->col(ix), x);
+    }
+    return (*y_interpolator_)(*(xr.y()), column_, y);
   }
 
  private:
-  using InterpolateFunction = double (gsl::Interpolate1D::*)(
-      const Eigen::VectorXd &, const Eigen::VectorXd &, const double);
   /// Column of the interpolation window (interpolation according to Y
   /// coordinates)
   Eigen::VectorXd column_;
 
   /// GSL interpolators
-  gsl::Interpolate1D x_interpolator_;
-  gsl::Interpolate1D y_interpolator_;
-
-  /// Evaluation of the GSL function performing the calculation.
-  auto evaluate(
-      const std::function<double(gsl::Interpolate1D &, const Eigen::VectorXd &,
-                                 const Eigen::VectorXd &, const double)>
-          &function,
-      const double x, const double y, const Frame2D &xr) -> double {
-    // Spline interpolation as function of X-coordinate
-    for (Eigen::Index ix = 0; ix < xr.y()->size(); ++ix) {
-      column_(ix) = function(x_interpolator_, *(xr.x()), xr.q()->col(ix), x);
-    }
-    return function(y_interpolator_, *(xr.y()), column_, y);
-  }
+  std::unique_ptr<interpolation::Interpolator1D<double>> x_interpolator_;
+  std::unique_ptr<interpolation::Interpolator1D<double>> y_interpolator_;
 };
 
 }  // namespace pyinterp::detail::math