#ifndef FESA_ANALYSIS_HHT_FIELD_CONVERGENCE_H_
#define FESA_ANALYSIS_HHT_FIELD_CONVERGENCE_H_

#include <array>
#include <cstddef>
#include <cstdint>
#include <optional>
#include <vector>

#include "fesa/core/status.h"

namespace fesa::hht_field_convergence {
inline constexpr const char* kPolicyId = "abaqus2025-field-on-fesa-v1";
// Ordered element rows first, then external source entries (including explicit zero).
// External entries use internal=value, inertia=0. No assembled cancellation here.
struct FluxOccurrence { double internal = 0.0; double inertia = 0.0; };
struct History {
  double nonzero_sum = 0.0;
  std::uint64_t nonzero_count = 0;
  double maximum_sum = 0.0;
  std::uint64_t maximum_count = 0;
};
struct FieldInput {
  bool active = false;  // At least one free full DOF of this field.
  std::vector<FluxOccurrence> flux;
  double residual = 0.0;  // max |I+fint-F| on full free endpoint DOFs, fi=1.
  double increment = 0.0; // max |q_trial-q_last_accepted| in fixed full u/phi chart.
  std::optional<double> correction; // max |q_trial-q_previous_selected|, i>=1.
  std::optional<double> previous_residual;
  std::optional<double> older_residual;
};
enum class Branch { kNotEvaluated, kLinear, kZeroFlux, kNonquadratic, kNormal };
struct FieldResult {
  std::optional<double> spatial_flux, maximum_flux, time_average_flux, residual_scale;
  std::optional<double> estimated_correction, residual_threshold, correction_threshold;
  std::optional<bool> residual_pass, correction_pass, field_pass;
  Branch branch = Branch::kNotEvaluated;
};
struct Evaluation {
  Status status = Status::Failure(FailureCategory::kSolver, {});
  bool field_pass = false;
  std::array<FieldResult, 2> fields;
  // Pure pending snapshot: procedure owns exactly-once commit after every gate/output.
  std::array<History, 2> pending;
};
// Index 0: force/translation; index 1: generalized moment/total rotation phi.
Evaluation Evaluate(const std::array<FieldInput, 2>& fields,
                    const std::array<History, 2>& committed,
                    std::size_t iteration, double reference_length);
}  // namespace fesa::hht_field_convergence

#endif  // FESA_ANALYSIS_HHT_FIELD_CONVERGENCE_H_