From ecef2fe4f3bc83cc1aacc2b7bb3ecba502947a77 Mon Sep 17 00:00:00 2001
From: Caromel <132669192+UCaromel@users.noreply.github.com>
Date: Sat, 21 Sep 2024 15:11:19 +0200
Subject: [PATCH] field initialization refactor (#890)

---
 src/core/data/field/field.hpp                 |  2 +-
 .../initializers/field_user_initializer.hpp   | 36 +++++++++++++++++++
 .../data/vecfield/vecfield_initializer.hpp    | 28 +++------------
 3 files changed, 41 insertions(+), 25 deletions(-)
 create mode 100644 src/core/data/field/initializers/field_user_initializer.hpp

diff --git a/src/core/data/field/field.hpp b/src/core/data/field/field.hpp
index 542e1c191..100b967c0 100644
--- a/src/core/data/field/field.hpp
+++ b/src/core/data/field/field.hpp
@@ -71,7 +71,7 @@ class Field : public NdArrayView<dim, Data_t>
 
     bool isUsable() const { return Super::data() != nullptr; }
     bool isSettable() const { return !isUsable(); }
-
+    
 
     template<typename... Args>
     NO_DISCARD auto& operator()(Args&&... args)
diff --git a/src/core/data/field/initializers/field_user_initializer.hpp b/src/core/data/field/initializers/field_user_initializer.hpp
new file mode 100644
index 000000000..d9c74275a
--- /dev/null
+++ b/src/core/data/field/initializers/field_user_initializer.hpp
@@ -0,0 +1,36 @@
+#ifndef _PHARE_CORE_DATA_FIELD_INITIAZILIZERS_FIELD_USER_INITIALIZER_HPP_
+#define _PHARE_CORE_DATA_FIELD_INITIAZILIZERS_FIELD_USER_INITIALIZER_HPP_
+
+#include "core/utilities/span.hpp"
+#include "initializer/data_provider.hpp"
+
+#include <tuple>
+#include <memory>
+
+namespace PHARE::core
+{
+class FieldUserFunctionInitializer
+{
+public:
+    template<typename Field, typename GridLayout>
+    void static initialize(Field& field, GridLayout const& layout,
+                           initializer::InitFunction<GridLayout::dimension> const& init)
+    {
+        auto const indices = layout.ghostStartToEndIndices(field, /*includeEnd=*/true);
+        auto const coords  = layout.template indexesToCoordVectors</*WithField=*/true>(
+            indices, field, [](auto& gridLayout, auto& field_, auto const&... args) {
+                return gridLayout.fieldNodeCoordinates(field_, gridLayout.origin(), args...);
+            });
+
+        std::shared_ptr<Span<double>> gridPtr // keep grid data alive
+            = std::apply([&](auto&... args) { return init(args...); }, coords);
+        Span<double>& grid = *gridPtr;
+
+        for (std::size_t cell_idx = 0; cell_idx < indices.size(); cell_idx++)
+            std::apply([&](auto&... args) { field(args...) = grid[cell_idx]; }, indices[cell_idx]);
+    }
+};
+
+} // namespace PHARE::core
+
+#endif
diff --git a/src/core/data/vecfield/vecfield_initializer.hpp b/src/core/data/vecfield/vecfield_initializer.hpp
index b73b37bb9..edeb83bc6 100644
--- a/src/core/data/vecfield/vecfield_initializer.hpp
+++ b/src/core/data/vecfield/vecfield_initializer.hpp
@@ -4,6 +4,7 @@
 #include "core/data/grid/gridlayoutdefs.hpp"
 #include "core/data/vecfield/vecfield_component.hpp"
 #include "initializer/data_provider.hpp"
+#include "core/data/field/initializers/field_user_initializer.hpp"
 
 #include <array>
 
@@ -31,33 +32,12 @@ namespace core
             static_assert(GridLayout::dimension == VecField::dimension,
                           "dimension mismatch between vecfield and gridlayout");
 
-            initializeComponent_(v.getComponent(Component::X), layout, x_);
-            initializeComponent_(v.getComponent(Component::Y), layout, y_);
-            initializeComponent_(v.getComponent(Component::Z), layout, z_);
+            FieldUserFunctionInitializer::initialize(v.getComponent(Component::X), layout, x_);
+            FieldUserFunctionInitializer::initialize(v.getComponent(Component::Y), layout, y_);
+            FieldUserFunctionInitializer::initialize(v.getComponent(Component::Z), layout, z_);
         }
 
     private:
-        template<typename Field, typename GridLayout>
-        void initializeComponent_(Field& field, GridLayout const& layout,
-                                  initializer::InitFunction<dimension> const& init)
-        {
-            auto const indices = layout.ghostStartToEndIndices(field, /*includeEnd=*/true);
-            auto const coords  = layout.template indexesToCoordVectors</*WithField=*/true>(
-                indices, field, [](auto& gridLayout, auto& field_, auto const&... args) {
-                    return gridLayout.fieldNodeCoordinates(field_, gridLayout.origin(), args...);
-                });
-
-            std::shared_ptr<Span<double>> gridPtr // keep grid data alive
-                = std::apply([&](auto&... args) { return init(args...); }, coords);
-            Span<double>& grid = *gridPtr;
-
-            for (std::size_t cell_idx = 0; cell_idx < indices.size(); cell_idx++)
-                std::apply([&](auto&... args) { field(args...) = grid[cell_idx]; },
-                           indices[cell_idx]);
-        }
-
-
-
         initializer::InitFunction<dimension> x_;
         initializer::InitFunction<dimension> y_;
         initializer::InitFunction<dimension> z_;