feat(cpp-object-oriented-modular-refactoring): step 19 - boundary-condition-policy

include/fesa/constraints/boundary_condition.h

@@ -0,0 +1,71 @@
+#ifndef FESA_CONSTRAINTS_BOUNDARY_CONDITION_H_
+#define FESA_CONSTRAINTS_BOUNDARY_CONDITION_H_
+
+#include <cstddef>
+#include <functional>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "fesa/core/diagnostic.h"
+#include "fesa/core/status.h"
+
+namespace fesa {
+
+class DofManager;
+class Domain;
+class SourceTargetResolver;
+
+/// @brief Describes one prescribed value in stable full-DOF order.
+struct ConstraintDefinition {
+  std::size_t source_order;
+  std::size_t full_dof_index;
+  double prescribed_value;
+};
+
+/// @brief Provides immutable semantic and equation context to a boundary.
+/// @note Every referenced object must outlive a constraint request.
+struct BoundaryConditionContext {
+  const Domain& domain;
+  const DofManager& dof_manager;
+  const SourceTargetResolver& target_resolver;
+};
+
+/// @brief Produces ordered constraint definitions without equation mutation.
+class BoundaryCondition {
+ public:
+  virtual ~BoundaryCondition() = default;
+
+  /// @brief Resolves finite full-DOF definitions in stable target order.
+  /// @param context Non-owning semantic and equation context for this call.
+  /// @return Ordered definitions or a structured model failure.
+  virtual Result<std::vector<ConstraintDefinition>> ResolveConstraints(
+      const BoundaryConditionContext& context) const = 0;
+
+  /// @brief Returns the source location used by policy diagnostics.
+  const SourceLocation& Location() const noexcept { return location_; }
+
+  /// @brief Returns the source target identity used by policy diagnostics.
+  const std::string& TargetIdentity() const noexcept {
+    return target_identity_;
+  }
+
+ protected:
+  /// @brief Creates a boundary with optional shared diagnostic provenance.
+  BoundaryCondition(std::string target_identity = {},
+                    SourceLocation location = {})
+      : target_identity_{std::move(target_identity)},
+        location_{std::move(location)} {}
+
+ private:
+  std::string target_identity_;
+  SourceLocation location_;
+};
+
+/// @brief Holds non-owning boundaries in an explicitly supplied source order.
+using BoundaryConditionView =
+    std::vector<std::reference_wrapper<const BoundaryCondition>>;
+
+}  // namespace fesa
+
+#endif  // FESA_CONSTRAINTS_BOUNDARY_CONDITION_H_