/*****************************************************************************************
*                                                                                       *
* OpenSpace                                                                             *
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* Copyright (c) 2014-2019                                                               *
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#include <modules/autonavigation/speedfunction.h>

#include <ghoul/logging/logmanager.h>
#include <ghoul/misc/easing.h>

namespace {
    constexpr const char* _loggerCat = "SpeedFunction";
} // namespace

namespace openspace::autonavigation {

SpeedFunction::~SpeedFunction() {}

/*
* Get speed at time value in the range [0, duration], scaled according to the constraint
* in eq. 14 in Eberly 2007
* (https://www.geometrictools.com/Documentation/MovingAlongCurveSpecifiedSpeed.pdf)
* OBS! If integrated over the duration for the path it shall match the total length.
*/
double SpeedFunction::scaledValue(double time, double duration, double pathLength) const {
    ghoul_assert(time >= 0 && time <= duration, "Time out of range [0, duration]");
    double t = std::clamp(time / duration, 0.0, 1.0);
    return (pathLength * this->value(t)) / (duration * _integratedSum);
}

void SpeedFunction::initIntegratedSum() {
    // apply duration constraint (eq. 14 in Eberly)
    double speedSum = 0.0;
    int steps = 100;
    double h = 1.0 / steps;
    for (double t = 0.0; t <= 1.0; t += h) {
        double midpointSpeed = 0.5 * (value(t + 0.5*h) + value(t - 0.5*h));
        speedSum += h * midpointSpeed;
    }
    _integratedSum = speedSum;
}

CubicDampenedSpeed::CubicDampenedSpeed() {
    initIntegratedSum();
}

double CubicDampenedSpeed::value(double t) const {
    ghoul_assert(t >= 0.0 && t <= 1.0, "Variable t out of range [0,1]");

    const double tPeak = 0.5;
    double speed = 1.0;

    // accelerate
    if (t <= tPeak) {
        double tScaled = t / tPeak;
        speed = ghoul::cubicEaseInOut(tScaled);
    }
    // deaccelerate
    else if (t < 1.0) {
        double tScaled = (t - tPeak) / (1.0 - tPeak);
        speed = 1.0 - ghoul::cubicEaseInOut(tScaled);
    }

    // avoid zero speed
    speed += 0.001;
    return speed;
}

} // namespace openspace::autonavigation