#ifndef THIRD_PARTY_MILOTIC_EXTERNAL_CC_TLBMC_THERMAL_PID_CONTROLLER_H_
#define THIRD_PARTY_MILOTIC_EXTERNAL_CC_TLBMC_THERMAL_PID_CONTROLLER_H_

#include <algorithm>
#include <limits>
#include <memory>
#include <optional>
#include <string>
#include <utility>
#include <vector>

#include "absl/base/attributes.h"
#include "absl/base/nullability.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/str_format.h"
#include "absl/strings/string_view.h"
#include <nlohmann/json_fwd.hpp>
#include "thermal_config.pb.h"
#include "thermal_controller_specification.pb.h"
#include "tlbmc/thermal/controller/algorithm/pid.h"
#include "tlbmc/thermal/controller/controller.h"
#include "tlbmc/thermal/controller/optimizer/pid/pid_optimizer.h"
#include "tlbmc/thermal/zone_manager.h"

namespace milotic_tlbmc {
namespace thermal {

constexpr double kDefaultPidSetpointValue = 0.0;

struct PidOptimizerInfo {
  optimizer::PidOptimizerStates states;
  std::unique_ptr<optimizer::PidOptimizer> optimizer = nullptr;
};

struct PidControllerParameters {
  std::string id;
  ZoneManager* absl_nonnull zone_manager ABSL_REQUIRE_EXPLICIT_INIT;
  std::unique_ptr<PidThermalLoop> absl_nonnull pid_loop
      ABSL_REQUIRE_EXPLICIT_INIT;
  double setpoint = kDefaultPidSetpointValue;
  PidControllerInputProcessType input_process_type;
  std::vector<PidControllerSensorInfo> input_sensors;
  std::optional<PidOptimizerInfo> pid_optimizer_info = std::nullopt;
};

/**
 * `PidController` provides a connection between the thermal zone manager and
 * the PID (i.e., proportional, integral, and derivative) thermal loop. It will
 * handle the sensor reading & fan output process, and the PID thermal loop
 * calculations.
 *
 * There will be, and should be, exactly one configured PID thermal loop
 * assigned to each PID controller object, which may be shared, however, by
 * multiple controllers.
 *
 * This class is not thread-safe.
 *
 * This class is created based on `pidcontroller.*` and
 * `thermalcontroller.*` files at
 * https://source.corp.google.com/piper///depot/google3/third_party/openbmc_phosphor_pid_control/pid/
 */
class PidController : public ThermalController {
 public:
  // These are the coefficients that are allowed to be tuned for PID
  // Controllers.
  struct PidControllerCoefficients {
    std::optional<double> coeff_proportional;
    std::optional<double> coeff_integral;
    std::optional<double> coeff_derivative;
    std::optional<double> feed_forward_offset;
    std::optional<double> feed_forward_gain;
    std::optional<double> setpoint;

    bool operator==(const PidControllerCoefficients& other) const = default;
  };

  ~PidController() final = default;

  static absl::StatusOr<std::unique_ptr<PidController>> Create(
      PidControllerParameters params);

  void ProcessThermalLoop() final;
  double ProcessInput() final;
  void ProcessOutput(double output) final;

  std::string GetId() const final { return id_; }
  bool IsFanController() const final { return false; }
  bool IsSupportiveController() const final { return false; }
  const std::vector<std::string>& GetAffectedControllerIds() const final {
    return empty_affected_controller_ids_;
  }
  void AdjustSetpoint(double offset) final { setpoint_ += offset; }

  double GetSetpoint() const { return setpoint_; }

  ZoneManager* GetZoneManager() const { return zone_owner_; }

  PidThermalLoop* GetPidLoop() const { return pid_loop_.get(); }

  static bool IsPidThermalType(PidControllerInputProcessType type) {
    return type == PidControllerInputProcessType::MARGIN_PID ||
           type == PidControllerInputProcessType::TEMP_PID ||
           type == PidControllerInputProcessType::POWER_PID ||
           type == PidControllerInputProcessType::POWERSUM_PID;
  }
  absl::Status SetInputProcessType(PidControllerInputProcessType type) {
    if (!IsPidThermalType(type)) {
      return absl::InvalidArgumentError(absl::StrFormat(
          "Invalid PID thermal type for PID controller `%s`!", id_));
    }

    if (type == PidControllerInputProcessType::MARGIN_PID) {
      input_process_type_ = PidThermalType::MARGIN;
    }
    if ((type == PidControllerInputProcessType::TEMP_PID) ||
        (type == PidControllerInputProcessType::POWER_PID)) {
      input_process_type_ = PidThermalType::ABSOLUTE;
    }
    if (type == PidControllerInputProcessType::POWERSUM_PID) {
      input_process_type_ = PidThermalType::SUMMATION;
    }
    return absl::OkStatus();
  }
  PidThermalType GetInputProcessType() const { return input_process_type_; }

  void AddInputSensor(const PidControllerSensorInfo& input_sensor) {
    input_sensors_.push_back(input_sensor);
  }
  const std::vector<PidControllerSensorInfo>& GetInputSensors() const {
    return input_sensors_;
  }

  double InitializeInputBasedOnPidThermalType() const {
    switch (GetInputProcessType()) {
      case PidThermalType::MARGIN:
        // If the input process type is `MARGIN`, we will use the minimal value
        // of all input sensors. Therefore, return the maximum double value as
        // the initial value.
        return std::numeric_limits<double>::max();
      case PidThermalType::ABSOLUTE:
        // If the input process type is `ABSOLUTE`, we will use the maximum
        // value of all input sensors. Therefore, return the minimum double
        // value as the initial value.
        return std::numeric_limits<double>::lowest();
      default:
        // The type is `SUMMATION`; so return 0.0 as the initial value for the
        // later sum.
        return 0.0;
    }
  }
  double ProcessSensorReadingForMarginPid(
      double sensor_value, const PidControllerSensorInfo& sensor) const {
    if (GetInputProcessType() != PidThermalType::MARGIN ||
        !sensor.convert_temperature_to_margin()) {
      return sensor_value;
    }

    // Return the margin value.
    return sensor.max_junction_temperature() - sensor_value;
  }
  double IntegrateSensorReadingBasedOnPidThermalType(
      double current_input, double sensor_value) const {
    switch (GetInputProcessType()) {
      case PidThermalType::MARGIN:
        return std::min(current_input, sensor_value);
      case PidThermalType::ABSOLUTE:
        return std::max(current_input, sensor_value);
      default:
        // The type is `PidThermalType::SUMMATION`.
        return current_input + sensor_value;
    }
  }

  nlohmann::json ToJson() const;

  // Setters of PID coefficients for tuning purposes.
  void SetCoefficients(const PidControllerCoefficients& coefficients);

 protected:
  explicit PidController(absl::string_view id, ZoneManager* zone_manager,
                         std::unique_ptr<PidThermalLoop> absl_nonnull pid_loop,
                         double setpoint,
                         std::vector<PidControllerSensorInfo> input_sensors)
      : ThermalController(),
        id_(id),
        zone_owner_(zone_manager),
        pid_loop_(std::move(pid_loop)),
        setpoint_(setpoint),
        input_sensors_(std::move(input_sensors)) {}

  explicit PidController(absl::string_view id, ZoneManager* zone_manager,
                         std::unique_ptr<PidThermalLoop> absl_nonnull pid_loop,
                         double setpoint,
                         std::vector<PidControllerSensorInfo> input_sensors,
                         PidOptimizerInfo pid_optimizer_info)
      : ThermalController(),
        id_(id),
        zone_owner_(zone_manager),
        pid_loop_(std::move(pid_loop)),
        setpoint_(setpoint),
        input_sensors_(std::move(input_sensors)) {
    if (pid_optimizer_info.optimizer != nullptr) {
      pid_optimizer_info_ = std::move(pid_optimizer_info);
      PreparePidOptimizer();
    }
  }

  // `PreparePidOptimizer` sets up the controller environment for PID optimizer.
  // It should only be called when `pid_optimizer_info_` is present.
  void PreparePidOptimizer();

 private:
  const std::string id_;
  // Use a simple pointer here to avoid circular dependency, as `ZoneManager`
  // depends on `PidController` with `std::unique_ptr`.
  // Every `ZoneManager` will be owned by the thermal control collector of
  // tlBMC, and will live as long as the thermal control service is on.
  ZoneManager* zone_owner_ = nullptr;

  // Every `PidThermalLoop` will be owned by its thermal controller, and will
  // live as long as the thermal control service is on.
  std::unique_ptr<PidThermalLoop> pid_loop_;
  double setpoint_ = kDefaultPidSetpointValue;
  PidThermalType input_process_type_;
  std::vector<PidControllerSensorInfo> input_sensors_;
  // An empty vector to return by reference for `GetAffectedControllerIds`.
  const std::vector<std::string> empty_affected_controller_ids_;

  PidOptimizerInfo pid_optimizer_info_;
};

}  // namespace thermal
}  // namespace milotic_tlbmc

#endif  // THIRD_PARTY_MILOTIC_EXTERNAL_CC_TLBMC_THERMAL_PID_CONTROLLER_H_