/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
 *                                                                                       *
 * Copyright (c) 2014-2019                                                               *
 *                                                                                       *
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 * without restriction, including without limitation the rights to use, copy, modify,    *
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 * permit persons to whom the Software is furnished to do so, subject to the following   *
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 * or substantial portions of the Software.                                              *
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 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,   *
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A         *
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT    *
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 ****************************************************************************************/

#include <openspace/util/distanceconversion.h>

#include <openspace/util/distanceconstants.h>
#include <openspace/util/timeconversion.h>

#include <ghoul/glm.h>

namespace openspace {

std::pair<double, std::string> simplifyDistance(double meters, bool forceSingularForm) {
    constexpr const double GraceFactor = 0.5;

    const double metersVal = glm::abs(meters);

    if (metersVal == 0.0) {
        return { 0.0, forceSingularForm ? "meter" : "meters"};
    }
    else if (metersVal > 1e-3 && metersVal < 1e3) {
        return { meters, (meters == 1.0 || forceSingularForm) ? "meter" : "meters" };
    }

    if (metersVal < 1e-9) {
        const double val = meters / 1e-9;
        return { val, (val == 1.0 || forceSingularForm) ? "nanometer" : "nanometers" };
    }
    else if (metersVal < 1e-6) {
        const double val = meters / 1e-6;
        return { val, (val == 1.0 || forceSingularForm) ? "micrometer" : "micrometers" };
    }
    else if (metersVal < 1e-3) {
        const double val = meters / 1e-3;
        return { val, (val == 1.0 || forceSingularForm) ? "millimeter" : "millimeters" };
    }

    if (metersVal > (1e9 * GraceFactor * distanceconstants::Parsec)) {
        const double val = meters / (1e9 * distanceconstants::Parsec);
        return { val, (val == 1.0 || forceSingularForm) ? "Gigaparsec" : "Gigaparsecs" };
    }
    else if (metersVal > (1e6 * GraceFactor * distanceconstants::Parsec)) {
        const double val = meters / (1e6 * distanceconstants::Parsec);
        return { val, (val == 1.0 || forceSingularForm) ? "Megaparsec" : "Megaparsecs" };
    }
    else if (metersVal > (1e3 * GraceFactor * distanceconstants::Parsec)) {
        const double val = meters / (1e3 * distanceconstants::Parsec);
        return { val, (val == 1.0 || forceSingularForm) ? "Kiloparsec" : "Kiloparsecs" };
    }
    else if (metersVal > GraceFactor * distanceconstants::Parsec) {
        const double val = meters / distanceconstants::Parsec;
        return { val, (val == 1.0 || forceSingularForm) ? "Parsec" : "Parsecs" };
    }
    else if (metersVal > GraceFactor * distanceconstants::LightYear) {
        const double val = meters / distanceconstants::LightYear;
        return { val, (val == 1.0 || forceSingularForm) ? "Lightyear" : "Lightyears" };
    }
    else if (metersVal > GraceFactor * distanceconstants::LightMonth) {
        const double val = meters / distanceconstants::LightMonth;
        return { val, (val == 1.0 || forceSingularForm) ? "Lightmonth" : "Lightmonths" };
    }
    else if (metersVal > GraceFactor * distanceconstants::LightDay) {
        const double val = meters / distanceconstants::LightDay;
        return { val, (val == 1.0 || forceSingularForm) ? "Lightday" : "Lightdays" };
    }
    else if (metersVal > GraceFactor * distanceconstants::LightHour) {
        const double val = meters / distanceconstants::LightHour;
        return { val, (val == 1.0 || forceSingularForm) ? "Lighthour" : "Lighthours" };
    }
    else if (metersVal > GraceFactor * distanceconstants::AstronomicalUnit) {
        return { meters / distanceconstants::AstronomicalUnit, "AU" };
    }
    else {
        return { meters / 1000.0, "km" };
    }
}

float convertMasPerYearToMeterPerSecond(float masPerYear, float parallax) {
    double degreeFromMas = 1.0 / 3600000.0;
    double radiusInMeter = (distanceconstants::Parsec * 1000.0) / parallax;
    double perYearToPerSecond = 1.0 / SecondsPerYear;
    double meterPerSecond = masPerYear * degreeFromMas * radiusInMeter *
                            perYearToPerSecond;
    return static_cast<float>(meterPerSecond);
}

} // namespace openspace