#ifndef FESA_LOADS_LOAD_H_
#define FESA_LOADS_LOAD_H_

#include <cstddef>
#include <functional>
#include <vector>

#include "fesa/core/status.h"

namespace fesa {

class DofManager;
class Domain;
class SourceTargetResolver;

/// @brief Describes one ordered contribution to the full load vector.
struct LoadContribution {
  std::size_t source_order;
  std::size_t full_dof_index;
  double value;
};

/// @brief Provides immutable semantic and equation context to a Load.
/// @note Every referenced object must outlive a contribution request.
struct LoadContext {
  const Domain& domain;
  const DofManager& dof_manager;
  const SourceTargetResolver& target_resolver;
};

/// @brief Produces local ordered load contributions without global mutation.
class Load {
 public:
  virtual ~Load() = default;

  /// @brief Computes finite full-DOF contributions in stable target order.
  /// @param context Non-owning semantic and equation context for this call.
  /// @return Ordered contributions or a structured model failure.
  virtual Result<std::vector<LoadContribution>> ComputeContributions(
      const LoadContext& context) const = 0;
};

/// @brief Holds non-owning loads in an explicitly supplied source order.
using LoadView = std::vector<std::reference_wrapper<const Load>>;

}  // namespace fesa

#endif  // FESA_LOADS_LOAD_H_