#pragma once

#include <cstdint>
#include <math.h>
#include <boost/accumulators/accumulators.hpp>
#include <boost/accumulators/statistics/stats.hpp>
#include <boost/accumulators/statistics/rolling_mean.hpp>
#include <boost/function.hpp>

namespace differential
{
  namespace bacc = boost::accumulators;

  /**
   * \brief The Odometry class handles odometry readings
   * (2D pose and velocity with related timestamp)
   */
  class Odometry
  {
  public:

    /// Integration function, used to integrate the odometry:
    typedef boost::function<void(double, double)> IntegrationFunction;

    /**
     * \brief Constructor
     * Timestamp will get the current time value
     * Value will be set to zero
     * \param velocity_rolling_window_size Rolling window size used to compute the velocity mean
     */
    Odometry(size_t velocity_rolling_window_size = 10);

    /**
     * \brief Initialize the odometry
     * \param time Current time
     */
    void init(const double &time);

    /**
     * \brief Updates the odometry class with latest wheel angular velocities
     * \param left_vel  Left  wheel angular velocity [rad/s]
     * \param right_vel Right wheel angular velocity [rad/s]
     * \param time      Current time
     * \return true if the odometry is actually updated
     */
    bool updateWheel(double left_vel, double right_vel, const double &time);

    /**
     * \brief Updates odometry from cumulative encoder tick counts
     *
     * Converts tick deltas to wheel arc lengths, then integrates pose with the
     * same exact/RK2 path as updateWheel. The first call after init() only
     * seeds the previous tick counts and returns false.
     *
     * Caller should unwrap hardware counter overflow into a monotonic int64
     * cumulative count before calling.
     *
     * \param left_ticks  Cumulative left  wheel ticks (after gearbox, wheel side)
     * \param right_ticks Cumulative right wheel ticks (after gearbox, wheel side)
     * \param time        Current time [s]
     * \return true if the odometry is actually updated
     */
    bool updateTicks(std::int64_t left_ticks, std::int64_t right_ticks, const double &time);

    /**
     * \brief Updates the odometry class with latest velocity command
     * \param linear  Linear velocity [m/s]
     * \param angular Angular velocity [rad/s]
     * \param time    Current time
     */
    void updateOdom(double linear, double angular, const double &time);

    /**
     * \brief heading getter
     * \return heading [rad]
     */
    double getHeading() const
    {
      return heading_;
    }

    /**
     * \brief x position getter
     * \return x position [m]
     */
    double getX() const
    {
      return x_;
    }

    /**
     * \brief y position getter
     * \return y position [m]
     */
    double getY() const
    {
      return y_;
    }

    /**
     * \brief linear velocity getter
     * \return linear velocity [m/s]
     */
    double getLinear() const
    {
      return linear_;
    }

    /**
     * \brief angular velocity getter
     * \return angular velocity [rad/s]
     */
    double getAngular() const
    {
      return angular_;
    }

    /**
     * \brief Sets the wheel parameters: radius and separation
     * \param wheel_separation   Separation between left and right wheels [m]
     * \param left_wheel_radius  Left wheel radius [m]
     * \param right_wheel_radius Right wheel radius [m]
     */
    void setWheelParams(double wheel_separation, double left_wheel_radius, double right_wheel_radius);

    /**
     * \brief Sets encoder resolution for both wheels (same CPR)
     * \param ticks_per_revolution Ticks per wheel revolution (wheel side)
     */
    void setEncoderParams(double ticks_per_revolution);

    /**
     * \brief Sets encoder resolution per wheel
     * \param left_ticks_per_revolution  Left  wheel ticks per revolution
     * \param right_ticks_per_revolution Right wheel ticks per revolution
     */
    void setEncoderParams(double left_ticks_per_revolution, double right_ticks_per_revolution);

    /**
     * \brief Velocity rolling window size setter
     * \param velocity_rolling_window_size Velocity rolling window size
     */
    void setVelocityRollingWindowSize(size_t velocity_rolling_window_size);

  private:

    /// Rolling mean accumulator and window:
    typedef bacc::accumulator_set<double, bacc::stats<bacc::tag::rolling_mean> > RollingMeanAcc;
    typedef bacc::tag::rolling_window RollingWindow;

    /**
     * \brief Integrates the velocities (linear and angular) using 2nd order Runge-Kutta
     * \param linear  Linear  displacement [m]
     * \param angular Angular displacement [rad]
     */
    void integrateRungeKutta2(double linear, double angular);

    /**
     * \brief Integrates the velocities (linear and angular) using exact method
     * \param linear  Linear  displacement [m]
     * \param angular Angular displacement [rad]
     */
    void integrateExact(double linear, double angular);

    /**
     *  \brief Reset linear and angular accumulators
     */
    void resetAccumulators();

    /// Current timestamp:
    double timestamp_;

    /// Current pose:
    double x_;        //   [m]
    double y_;        //   [m]
    double heading_;  // [rad]

    /// Current velocity:
    double linear_;  //   [m/s]
    double angular_; // [rad/s]

    /// Wheel kinematic parameters [m]:
    double wheel_separation_;
    double left_wheel_radius_;
    double right_wheel_radius_;

    /// Encoder resolution [ticks / wheel revolution]:
    double left_ticks_per_revolution_;
    double right_ticks_per_revolution_;

    /// Previous cumulative tick counts for delta computation:
    bool ticks_initialized_;
    std::int64_t left_ticks_prev_;
    std::int64_t right_ticks_prev_;

    /// Rolling mean accumulators for the linear and angular velocities:
    size_t velocity_rolling_window_size_;
    RollingMeanAcc linear_acc_;
    RollingMeanAcc angular_acc_;

    /// Integration function, used to integrate the odometry:
    IntegrationFunction integrate_fun_;
  };
}