#ifndef THIRD_PARTY_MILOTIC_EXTERNAL_CC_TLBMC_THERMAL_CONTROLLER_DFF_H_
#define THIRD_PARTY_MILOTIC_EXTERNAL_CC_TLBMC_THERMAL_CONTROLLER_DFF_H_

#include "thermal_config.pb.h"

namespace milotic_tlbmc {
namespace thermal {

/*
 * `DffThermalLoop` is the Dynamic Feedforward thermal loop, which is usually
 * used as an additional term to stablize the PID thermal loop: go/dff-neutron
 *
 * This feedforward controller will take signals that are causatively related
 * with temperature increment, and derive a supportive setpoint, to provide a
 * compensation to the feedback controllers (e.g., PID) to help the system
 * converge to a stable setpoint more swiftly.
 *
 * This class is not thread-safe.
 *
 * More materials can be found at:
 *   https://control.com/textbook/basic-process-control-strategies/feedforward-with-dynamic-compensation/
 */
class DffThermalLoop {
 public:
  DffThermalLoop() = default;

  explicit DffThermalLoop(const DffLoopConfig& dff_params)
      : dff_params_(dff_params) {
    // If no valid sample time is provided, set it to 1 by default.
    if (dff_params.sample_time_sec() <= 0) {
      dff_params_.set_sample_time_sec(1.0);
    }
  }

  /*
   * `ExecuteDffLoop` performs exactly one iteration of a DFF loop with the
   * current input.
   */
  double ExecuteDffLoop(double disturbance,
                        bool enable_calculation_log = false);

  void SetLastDisturbance(double last_disturbance) {
    last_disturbance_ = last_disturbance;
  }
  void SetLastFilteredDisturbance(double last_filtered_disturbance) {
    last_filtered_disturbance_ = last_filtered_disturbance;
  }
  void SetLastDffValue(double last_dff_value) {
    last_dff_value_ = last_dff_value;
  }
  void SetLastOutput(double last_dff_output) { last_output_ = last_dff_output; }

  double GetLastDisturbance() const { return last_disturbance_; }
  double GetLastFilteredDisturbance() const {
    return last_filtered_disturbance_;
  }
  double GetLastDffValue() const { return last_dff_value_; }
  double GetLastOutput() const { return last_output_; }

  double GetSampleTime() const { return dff_params_.sample_time_sec(); }
  void SetCoeffH1(double coeff_h1) { dff_params_.set_coeff_h1(coeff_h1); }
  double GetCoeffH1() const { return dff_params_.coeff_h1(); }
  void SetCoeffH2(double coeff_h2) { dff_params_.set_coeff_h2(coeff_h2); }
  double GetCoeffH2() const { return dff_params_.coeff_h2(); }
  void SetCoeffH3(double coeff_h3) { dff_params_.set_coeff_h3(coeff_h3); }
  double GetCoeffH3() const { return dff_params_.coeff_h3(); }
  void SetCoeffF1(double coeff_f1) { dff_params_.set_coeff_f1(coeff_f1); }
  double GetCoeffF1() const { return dff_params_.coeff_f1(); }
  void SetCoeffF2(double coeff_f2) { dff_params_.set_coeff_f2(coeff_f2); }
  double GetCoeffF2() const { return dff_params_.coeff_f2(); }
  void SetCoeffF3(double coeff_f3) { dff_params_.set_coeff_f3(coeff_f3); }
  double GetCoeffF3() const { return dff_params_.coeff_f3(); }
  void SetReferencePower(double reference_power) {
    dff_params_.set_reference_power(reference_power);
  }
  double GetReferencePower() const { return dff_params_.reference_power(); }
  double GetOutputLimitMax() const { return dff_params_.output_limit_max(); }
  double GetOutputLimitMin() const { return dff_params_.output_limit_min(); }
  double GetSlewNeg() const { return dff_params_.slew_neg(); }
  double GetSlewPos() const { return dff_params_.slew_pos(); }

 protected:
  /*
   * `ApplyLowPassFilterToDisturbance` applies a low pass filter to the
   * disturbance signal, in order to mitigate the effects of high-frequency
   * noise in the disturbance signal. This will help prevent noise amplification
   * and reduce the risk of instability.
   *
   * This is usually done before the DFF calculation.
   *
   * Reference:
   *   https://web.mit.edu/6.055/notes/r09-abstraction-low-pass.pdf
   */
  double ApplyLowPassFilterToDisturbance(
      double disturbance, bool enable_calculation_log = false) const;

 private:
  double last_disturbance_ = 0.0;  // The last disturbance value.
  double last_filtered_disturbance_ =
      0.0;                       // The last filtered disturbance value.
  double last_dff_value_ = 0.0;  // The last DFF calculated value.
  double last_output_ = 0.0;     // The last output (e.g., DFF value affected by
                                 // slew rate clamping).

  DffLoopConfig dff_params_;  // The parameters for this DFF thermal loop.
};

}  // namespace thermal
}  // namespace milotic_tlbmc

#endif  // THIRD_PARTY_MILOTIC_EXTERNAL_CC_TLBMC_THERMAL_CONTROLLER_DFF_H_