#ifndef FESA_ANALYSIS_NEWTON_ITERATION_LOG_H_
#define FESA_ANALYSIS_NEWTON_ITERATION_LOG_H_

#include <array>
#include <cstdint>
#include <filesystem>
#include <fstream>
#include <string>

#include "fesa/analysis/nonlinear_static_control.h"
#include "fesa/core/status.h"

namespace fesa {

/// @brief Identifies the latest Newton procedure stage reached by a record.
enum class NewtonIterationStage {
  kEntered,
  kKinematicsEvaluated,
  kInternalAssembled,
  kExternalAssembled,
  kSolvedCorrection,
  kConvergenceEvaluated,
  kAccepted,
  kFailed,
};

/// @brief Carries the controlled failure that ended one Newton iteration.
struct NewtonIterationFailure {
  bool present;
  NewtonIterationStage stage;
  std::string diagnostic_code;
  std::string reason;
};

/// @brief Carries one fixed-schema Newton iteration diagnostic record.
struct NewtonIterationLogRecord {
  std::string step_name;
  std::uint32_t increment_index;
  double load_factor;
  std::uint32_t iteration;
  NewtonIterationStage last_completed_stage;
  NewtonIterationFailure failure;
  std::string transition;
  std::string outcome;
  std::string diagnostic_code;
  NewtonChannelDecision force_residual;
  NewtonChannelDecision moment_residual;
  NewtonChannelDecision translation_correction;
  NewtonChannelDecision rotation_correction;
  bool combined_passed;
};

/// @brief Carries two-channel HHT endpoint convergence evidence.
/// @note Array entries are translation and rotation channels, respectively.
/// Corrections are dimensionless N2 metrics; rate corrections already include
/// h or h squared. Residual numerator and scale retain force/moment units.
struct DynamicNewtonIterationLogRecord {
  std::uint32_t increment_index = 0U;
  std::uint32_t iteration_index = 0U;
  double time = 0.0;
  std::string stage;
  std::string outcome;
  std::string failure_code;
  std::array<double, 2U> residual_numerator{};
  std::array<double, 2U> residual_scale{};
  std::array<double, 2U> coordinate_correction{};
  std::array<double, 2U> velocity_correction{};
  std::array<double, 2U> acceleration_correction{};
  std::array<double, 2U> algorithmic_correction{};
  bool residual_pass = false;
  bool correction_pass = false;
};

/// @brief Writes deterministic, line-oriented Newton iteration diagnostics.
/// @note A write, flush, or close failure permanently prevents a successful
/// log lifecycle for this writer instance.
class NewtonIterationLogWriter {
 public:
  /// @brief Opens and truncates the diagnostic log before Newton execution.
  /// @param log_path Derived application-owned diagnostic-log path.
  /// @return Success when the writer owns an empty binary log, otherwise an
  /// output failure with code `log-output-failure`.
  Status Open(const std::filesystem::path& log_path);

  /// @brief Writes one complete LF-terminated Newton iteration record.
  /// @param record Explicit stage, outcome, and typed convergence decision.
  /// @return Success after writing a complete record, otherwise an output
  /// failure with code `log-output-failure`.
  Status Write(const NewtonIterationLogRecord& record);

  /// @brief Writes one complete HHT record using schema `hht-log-v1`.
  /// @return Success after the complete line is written; invalid numeric
  /// evidence or stream failure permanently fails this writer instance.
  Status Write(const DynamicNewtonIterationLogRecord& record);

  /// @brief Flushes every complete record written so far to the log.
  /// @return Success after the stream flush, otherwise an output failure with
  /// code `log-output-failure`.
  Status Flush();

  /// @brief Closes the log before authoritative result finalization.
  /// @return Success after close, otherwise an output failure with code
  /// `log-output-failure`.
  Status Close();

 private:
  enum class State { kReady, kOpen, kClosed, kFailed };

  std::ofstream stream_;
  std::filesystem::path log_path_;
  State state_{State::kReady};
};

}  // namespace fesa

#endif  // FESA_ANALYSIS_NEWTON_ITERATION_LOG_H_