#ifndef SGP4_H_
#define SGP4_H_

#include "Tle.h"
#include "OrbitalElements.h"
#include "Eci.h"
#include "SatelliteException.h"

class SGP4 {
public:
    SGP4(const Tle& tle);
    virtual ~SGP4(void);

    void SetTle(const Tle& tle);
    void FindPosition(Eci* eci, double tsince) const;
    void FindPosition(Eci* eci, const Julian& date) const;

    struct CommonConstants {

        CommonConstants()
        : cosio(0.0), sinio(0.0), eta(0.0), t2cof(0.0), a3ovk2(0.0),
        x1mth2(0.0), x3thm1(0.0), x7thm1(0.0), aycof(0.0), xlcof(0.0),
        xnodcf(0.0), c1(0.0), c4(0.0), omgdot(0.0), xnodot(0.0), xmdot(0.0) {
        }

        double cosio;
        double sinio;
        double eta;
        double t2cof;
        double a3ovk2;
        double x1mth2;
        double x3thm1;
        double x7thm1;
        double aycof;
        double xlcof;
        double xnodcf;
        double c1;
        double c4;
        double omgdot; // secular rate of omega (radians/sec)
        double xnodot; // secular rate of xnode (radians/sec)
        double xmdot; // secular rate of xmo (radians/sec)
    };

    struct NearSpaceConstants {

        NearSpaceConstants()
        : c5(0.0), omgcof(0.0), xmcof(0.0), delmo(0.0), sinmo(0.0), d2(0.0),
        d3(0.0), d4(0.0), t3cof(0.0), t4cof(0.0), t5cof(0.0) {
        }

        double c5;
        double omgcof;
        double xmcof;
        double delmo;
        double sinmo;
        double d2;
        double d3;
        double d4;
        double t3cof;
        double t4cof;
        double t5cof;
    };

    struct DeepSpaceConstants {

        DeepSpaceConstants()
        : gsto(0.0), zmol(0.0), zmos(0.0), resonance_flag(false),
        synchronous_flag(false), sse(0.0), ssi(0.0), ssl(0.0), ssg(0.0),
        ssh(0.0), se2(0.0), si2(0.0), sl2(0.0), sgh2(0.0), sh2(0.0), se3(0.0),
        si3(0.0), sl3(0.0), sgh3(0.0), sh3(0.0), sl4(0.0), sgh4(0.0), ee2(0.0),
        e3(0.0), xi2(0.0), xi3(0.0), xl2(0.0), xl3(0.0), xl4(0.0), xgh2(0.0),
        xgh3(0.0), xgh4(0.0), xh2(0.0), xh3(0.0), d2201(0.0), d2211(0.0),
        d3210(0.0), d3222(0.0), d4410(0.0), d4422(0.0), d5220(0.0), d5232(0.0),
        d5421(0.0), d5433(0.0), del1(0.0), del2(0.0), del3(0.0) {
        }

        double gsto;
        double zmol;
        double zmos;
        /*
         * whether the deep space orbit is
         * geopotential resonance for 12 hour orbits
         */
        bool resonance_flag;
        /*
         * whether the deep space orbit is
         * 24h synchronous resonance
         */
        bool synchronous_flag;
        /*
         * lunar / solar constants for epoch
         * applied during DeepSpaceSecular()
         */
        double sse;
        double ssi;
        double ssl;
        double ssg;
        double ssh;
        /*
         * lunar / solar constants
         * used during DeepSpaceCalculateLunarSolarTerms()
         */
        double se2;
        double si2;
        double sl2;
        double sgh2;
        double sh2;
        double se3;
        double si3;
        double sl3;
        double sgh3;
        double sh3;
        double sl4;
        double sgh4;
        double ee2;
        double e3;
        double xi2;
        double xi3;
        double xl2;
        double xl3;
        double xl4;
        double xgh2;
        double xgh3;
        double xgh4;
        double xh2;
        double xh3;
        /*
         * used during DeepSpaceCalcDotTerms()
         */
        double d2201;
        double d2211;
        double d3210;
        double d3222;
        double d4410;
        double d4422;
        double d5220;
        double d5232;
        double d5421;
        double d5433;
        double del1;
        double del2;
        double del3;
    };

    struct IntegratorValues {
	IntegratorValues() : xndot(0.0), xnddt(0.0), xldot(0.0) {
	}

	double xndot;
	double xnddt;
	double xldot;
    };

    struct IntegratorConstants {

        IntegratorConstants() : xfact(0.0), xlamo(0.0) {
        }

        /*
         * integrator constants
         */
        double xfact;
        double xlamo;

        /*
         * integrator values for epoch
         */
	struct IntegratorValues values_0;
    };

    struct IntegratorParams {

        IntegratorParams() : xli(0.0), xni(0.0), atime(0.0) {
        }

        /*
         * integrator values
         */
        double xli;
        double xni;
        double atime;
        /*
         * itegrator values for current d_atime_
         */
	struct IntegratorValues values_t;
    };

private:
    void Initialize();
    void DeepSpaceInitialize(const double& eosq, const double& sinio, const double& cosio, const double& betao,
            const double& theta2, const double& betao2,
            const double& xmdot, const double& omgdot, const double& xnodot);
    void DeepSpaceCalculateLunarSolarTerms(const double t, double* pe, double* pinc,
            double* pl, double* pgh, double* ph) const;
    void DeepSpacePeriodics(const double& t, double* em, double* xinc,
            double* omgasm, double* xnodes, double* xll) const;
    void DeepSpaceSecular(const double& t, double* xll, double* omgasm,
            double* xnodes, double* em, double* xinc, double* xn) const;
    void FindPositionSDP4(Eci* eci, double tsince) const;
    void FindPositionSGP4(Eci* eci, double tsince) const;
    void CalculateFinalPositionVelocity(Eci* eci, const double& tsince, const double& e,
            const double& a, const double& omega, const double& xl, const double& xnode,
            const double& xincl, const double& xlcof, const double& aycof,
            const double& x3thm1, const double& x1mth2, const double& x7thm1,
            const double& cosio, const double& sinio) const;
    void DeepSpaceCalcDotTerms(struct IntegratorValues *values) const;
    void DeepSpaceIntegrator(const double delt, const double step2,
            const struct IntegratorValues& values)const;
    void Reset();

    /*
     * flags
     */
    bool first_run_;
    bool use_simple_model_;
    bool use_deep_space_;

    /*
     * the constants used
     */
    struct CommonConstants common_consts_;
    struct NearSpaceConstants nearspace_consts_;
    struct DeepSpaceConstants deepspace_consts_;
    struct IntegratorConstants integrator_consts_;
    mutable struct IntegratorParams integrator_params_;

    /*
     * the orbit data
     */
    OrbitalElements elements_;
};

#endif