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#ifndef GEOMETRY_ANGLES_UTILS_H
#define GEOMETRY_ANGLES_UTILS_H

#ifndef _USE_MATH_DEFINES
    #define _USE_MATH_DEFINES
#endif

#include <algorithm>
#include <cmath>

namespace angles {

/*!
 * \brief Convert degrees to radians
 */

static inline double from_degrees(double degrees) {
    return degrees * M_PI / 180.0;
}

/*!
 * \brief Convert radians to degrees
 */
static inline double to_degrees(double radians) {
    return radians * 180.0 / M_PI;
}

/*!
 * \brief normalize_angle_positive
 *
 *        Normalizes the angle to be 0 to 2*M_PI
 *        It takes and returns radians.
 */
static inline double normalize_angle_positive(double angle) {
    const double result = fmod(angle, 2.0 * M_PI);
    if (result < 0)
        return result + 2.0 * M_PI;
    return result;
}

/*!
 * \brief normalize
 *
 * Normalizes the angle to be -M_PI circle to +M_PI circle
 * It takes and returns radians.
 *
 */
static inline double normalize_angle(double angle) {
    const double result = fmod(angle + M_PI, 2.0 * M_PI);
    if (result <= 0.0)
        return result + M_PI;
    return result - M_PI;
}

/*!
 * \function
 * \brief shortest_angular_distance
 *
 * Given 2 angles, this returns the shortest angular
 * difference.  The inputs and ouputs are of course radians.
 *
 * The result
 * would always be -pi <= result <= pi.  Adding the result
 * to "from" will always get you an equivelent angle to "to".
 */

static inline double shortest_angular_distance(double from, double to) {
    return normalize_angle(to - from);
}

/*!
 * \function
 *
 * \brief returns the angle in [-2*M_PI, 2*M_PI]  going the other way along the
 * unit circle. \param angle The angle to which you want to turn in the range
 * [-2*M_PI, 2*M_PI] E.g. two_pi_complement(-M_PI/4) returns 7_M_PI/4
 * two_pi_complement(M_PI/4) returns -7*M_PI/4
 *
 */
static inline double two_pi_complement(double angle) {
    // check input conditions
    if (angle > 2 * M_PI || angle < -2.0 * M_PI)
        angle = fmod(angle, 2.0 * M_PI);
    if (angle < 0)
        return (2 * M_PI + angle);
    else if (angle > 0)
        return (-2 * M_PI + angle);

    return (2 * M_PI);
}

/*!
 * \function
 *
 * \brief This function is only intended for internal use and not intended for
 * external use. If you do use it, read the documentation very carefully.
 * Returns the min and max amount (in radians) that can be moved from "from"
 * angle to "left_limit" and "right_limit". \return returns false if "from"
 * angle does not lie in the interval [left_limit,right_limit] \param from -
 * "from" angle - must lie in [-M_PI, M_PI) \param left_limit - left limit of
 * valid interval for angular position - must lie in [-M_PI, M_PI], left and
 * right limits are specified on the unit circle w.r.t to a reference pointing
 * inwards \param right_limit - right limit of valid interval for angular
 * position - must lie in [-M_PI, M_PI], left and right limits are specified on
 * the unit circle w.r.t to a reference pointing inwards \param result_min_delta
 * - minimum (delta) angle (in radians) that can be moved from "from" position
 * before hitting the joint stop \param result_max_delta - maximum (delta) angle
 * (in radians) that can be movedd from "from" position before hitting the joint
 * stop
 */
static bool find_min_max_delta(
    double from,
    double left_limit,
    double right_limit,
    double& result_min_delta,
    double& result_max_delta
) {
    double delta[4];

    delta[0] = shortest_angular_distance(from, left_limit);
    delta[1] = shortest_angular_distance(from, right_limit);

    delta[2] = two_pi_complement(delta[0]);
    delta[3] = two_pi_complement(delta[1]);

    if (delta[0] == 0) {
        result_min_delta = delta[0];
        result_max_delta = std::max<double>(delta[1], delta[3]);
        return true;
    }

    if (delta[1] == 0) {
        result_max_delta = delta[1];
        result_min_delta = std::min<double>(delta[0], delta[2]);
        return true;
    }

    double delta_min = delta[0];
    double delta_min_2pi = delta[2];
    if (delta[2] < delta_min) {
        delta_min = delta[2];
        delta_min_2pi = delta[0];
    }

    double delta_max = delta[1];
    double delta_max_2pi = delta[3];
    if (delta[3] > delta_max) {
        delta_max = delta[3];
        delta_max_2pi = delta[1];
    }

    //    printf("%f %f %f %f\n",delta_min,delta_min_2pi,delta_max,delta_max_2pi);
    if ((delta_min <= delta_max_2pi) || (delta_max >= delta_min_2pi)) {
        result_min_delta = delta_max_2pi;
        result_max_delta = delta_min_2pi;
        if (left_limit == -M_PI && right_limit == M_PI)
            return true;
        else
            return false;
    }
    result_min_delta = delta_min;
    result_max_delta = delta_max;
    return true;
}

/*!
 * \function
 *
 * \brief Returns the delta from `from_angle` to `to_angle`, making sure it does
 * not violate limits specified by `left_limit` and `right_limit`. This function
 * is similar to `shortest_angular_distance_with_limits()`, with the main
 * difference that it accepts limits outside the `[-M_PI, M_PI]` range. Even if
 * this is quite uncommon, one could indeed consider revolute joints with large
 * rotation limits, e.g., in the range `[-2*M_PI, 2*M_PI]`.
 *
 * In this case, a strict requirement is to have `left_limit` smaller than
 * `right_limit`. Note also that `from` must lie inside the valid range, while
 * `to` does not need to. In fact, this function will evaluate the shortest
 * (valid) angle `shortest_angle` so that `from+shortest_angle` equals `to` up
 * to an integer multiple of `2*M_PI`. As an example, a call to
 * `shortest_angular_distance_with_large_limits(0, 10.5*M_PI, -2*M_PI, 2*M_PI,
 * shortest_angle)` will return `true`, with `shortest_angle=0.5*M_PI`. This is
 * because `from` and `from+shortest_angle` are both inside the limits, and
 * `fmod(to+shortest_angle, 2*M_PI)` equals `fmod(to, 2*M_PI)`. On the other
 * hand, `shortest_angular_distance_with_large_limits(10.5*M_PI, 0, -2*M_PI,
 * 2*M_PI, shortest_angle)` will return false, since `from` is not in the valid
 * range. Finally, note that the call
 * `shortest_angular_distance_with_large_limits(0, 10.5*M_PI, -2*M_PI, 0.1*M_PI,
 * shortest_angle)` will also return `true`. However, `shortest_angle` in this
 * case will be `-1.5*M_PI`.
 *
 * \return true if `left_limit < right_limit` and if "from" and
 * "from+shortest_angle" positions are within the valid interval, false
 * otherwise. \param from - "from" angle. \param to - "to" angle. \param
 * left_limit - left limit of valid interval, must be smaller than right_limit.
 * \param right_limit - right limit of valid interval, must be greater than
 * left_limit. \param shortest_angle - result of the shortest angle calculation.
 */
static inline bool shortest_angular_distance_with_large_limits(
    double from,
    double to,
    double left_limit,
    double right_limit,
    double& shortest_angle
) {
    // Shortest steps in the two directions
    double delta = shortest_angular_distance(from, to);
    double delta_2pi = two_pi_complement(delta);

    // "sort" distances so that delta is shorter than delta_2pi
    if (std::fabs(delta) > std::fabs(delta_2pi))
        std::swap(delta, delta_2pi);

    if (left_limit > right_limit) {
        // If limits are something like [PI/2 , -PI/2] it actually means that we
        // want rotations to be in the interval [-PI,PI/2] U [PI/2,PI], ie, the
        // half unit circle not containing the 0. This is already gracefully
        // handled by shortest_angular_distance_with_limits, and therefore this
        // function should not be called at all. However, if one has limits that
        // are larger than PI, the same rationale behind
        // shortest_angular_distance_with_limits does not hold, ie, M_PI+x should
        // not be directly equal to -M_PI+x. In this case, the correct way of
        // getting the shortest solution is to properly set the limits, eg, by
        // saying that the interval is either [PI/2, 3*PI/2] or [-3*M_PI/2,
        // -M_PI/2]. For this reason, here we return false by default.
        shortest_angle = delta;
        return false;
    }

    // Check in which direction we should turn (clockwise or counter-clockwise).

    // start by trying with the shortest angle (delta).
    double to2 = from + delta;
    if (left_limit <= to2 && to2 <= right_limit) {
        // we can move in this direction: return success if the "from" angle is
        // inside limits
        shortest_angle = delta;
        return left_limit <= from && from <= right_limit;
    }

    // delta is not ok, try to move in the other direction (using its complement)
    to2 = from + delta_2pi;
    if (left_limit <= to2 && to2 <= right_limit) {
        // we can move in this direction: return success if the "from" angle is
        // inside limits
        shortest_angle = delta_2pi;
        return left_limit <= from && from <= right_limit;
    }

    // nothing works: we always go outside limits
    shortest_angle = delta; // at least give some "coherent" result
    return false;
}

/*!
 * \function
 *
 * \brief Returns the delta from "from_angle" to "to_angle" making sure it does
 * not violate limits specified by left_limit and right_limit. The valid
 * interval of angular positions is [left_limit,right_limit]. E.g., [-0.25,0.25]
 * is a 0.5 radians wide interval that contains 0. But [0.25,-0.25] is a
 * 2*M_PI-0.5 wide interval that contains M_PI (but not 0). The value of
 * shortest_angle is the angular difference between "from" and "to" that lies
 * within the defined valid interval. E.g.
 * shortest_angular_distance_with_limits(-0.5,0.5,0.25,-0.25,ss) evaluates ss to
 * 2*M_PI-1.0 and returns true while
 * shortest_angular_distance_with_limits(-0.5,0.5,-0.25,0.25,ss) returns false
 * since -0.5 and 0.5 do not lie in the interval [-0.25,0.25]
 *
 * \return true if "from" and "to" positions are within the limit interval,
 * false otherwise \param from - "from" angle \param to - "to" angle \param
 * left_limit - left limit of valid interval for angular position, left and
 * right limits are specified on the unit circle w.r.t to a reference pointing
 * inwards \param right_limit - right limit of valid interval for angular
 * position, left and right limits are specified on the unit circle w.r.t to a
 * reference pointing inwards \param shortest_angle - result of the shortest
 * angle calculation
 */
static inline bool shortest_angular_distance_with_limits(
    double from,
    double to,
    double left_limit,
    double right_limit,
    double& shortest_angle
) {
    double min_delta = -2 * M_PI;
    double max_delta = 2 * M_PI;
    double min_delta_to = -2 * M_PI;
    double max_delta_to = 2 * M_PI;
    bool flag = find_min_max_delta(from, left_limit, right_limit, min_delta, max_delta);
    double delta = shortest_angular_distance(from, to);
    double delta_mod_2pi = two_pi_complement(delta);

    if (flag) // from position is within the limits
    {
        if (delta >= min_delta && delta <= max_delta) {
            shortest_angle = delta;
            return true;
        } else if (delta_mod_2pi >= min_delta && delta_mod_2pi <= max_delta) {
            shortest_angle = delta_mod_2pi;
            return true;
        } else // to position is outside the limits
        {
            find_min_max_delta(to, left_limit, right_limit, min_delta_to, max_delta_to);
            if (fabs(min_delta_to) < fabs(max_delta_to))
                shortest_angle = std::max<double>(delta, delta_mod_2pi);
            else if (fabs(min_delta_to) > fabs(max_delta_to))
                shortest_angle = std::min<double>(delta, delta_mod_2pi);
            else {
                if (fabs(delta) < fabs(delta_mod_2pi))
                    shortest_angle = delta;
                else
                    shortest_angle = delta_mod_2pi;
            }
            return false;
        }
    } else // from position is outside the limits
    {
        find_min_max_delta(to, left_limit, right_limit, min_delta_to, max_delta_to);

        if (fabs(min_delta) < fabs(max_delta))
            shortest_angle = std::min<double>(delta, delta_mod_2pi);
        else if (fabs(min_delta) > fabs(max_delta))
            shortest_angle = std::max<double>(delta, delta_mod_2pi);
        else {
            if (fabs(delta) < fabs(delta_mod_2pi))
                shortest_angle = delta;
            else
                shortest_angle = delta_mod_2pi;
        }
        return false;
    }

    shortest_angle = delta;
    return false;
}
} // namespace angles

#endif