/**
 ******************************************************************************
 *
 * @file       WMMInternal.h
 * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
 * @brief      Include file of the WorldMagModel internal functionality.
 *
 * @see        The GNU Public License (GPL) Version 3
 *
 *****************************************************************************/
/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#ifndef WMMINTERNAL_H_
#define WMMINTERNAL_H_

	// internal constants
	#define TRUE            ((uint16_t)1)
	#define FALSE           ((uint16_t)0)
	#define WMM_MAX_MODEL_DEGREES	12
	#define WMM_MAX_SECULAR_VARIATION_MODEL_DEGREES	12
	#define	NUMTERMS 91 // ((WMM_MAX_MODEL_DEGREES+1)*(WMM_MAX_MODEL_DEGREES+2)/2);
	#define NUMPCUP 92  // NUMTERMS +1
	#define NUMPCUPS 13 // WMM_MAX_MODEL_DEGREES +1
	#define RAD2DEG(rad)    ((rad)*(180.0L/M_PI))
	#define DEG2RAD(deg)    ((deg)*(M_PI/180.0L))


	// internal structure definitions
	typedef struct {
		float EditionDate;
		float epoch;						  //Base time of Geomagnetic model epoch (yrs)
		char  ModelName[20];
		float Main_Field_Coeff_G[NUMTERMS];  // C - Gauss coefficients of main geomagnetic model (nT)
		float Main_Field_Coeff_H[NUMTERMS];  // C - Gauss coefficients of main geomagnetic model (nT)
		float Secular_Var_Coeff_G[NUMTERMS]; // CD - Gauss coefficients of secular geomagnetic model (nT/yr)
		float Secular_Var_Coeff_H[NUMTERMS]; // CD - Gauss coefficients of secular geomagnetic model (nT/yr)
		uint16_t nMax;                             // Maximum degree of spherical harmonic model
		uint16_t nMaxSecVar;                       // Maxumum degree of spherical harmonic secular model
		uint16_t SecularVariationUsed;             // Whether or not the magnetic secular variation vector will be needed by program
	} WMMtype_MagneticModel;

	typedef struct {
		float a;     // semi-major axis of the ellipsoid
		float b;     // semi-minor axis of the ellipsoid
		float fla;   // flattening
		float epssq; // first eccentricity squared
		float eps;   // first eccentricity 
		float re;    // mean radius of  ellipsoid
	} WMMtype_Ellipsoid;

	typedef struct {
		float lambda; // longitude
		float phi;    // geodetic latitude
		float HeightAboveEllipsoid; // height above the ellipsoid (HaE)
	} WMMtype_CoordGeodetic;

	typedef struct {
		float lambda; // longitude
		float phig;   // geocentric latitude
		float r;      // distance from the center of the ellipsoid
	} WMMtype_CoordSpherical;

	typedef struct {
				uint16_t	Year;
				uint16_t	Month;
				uint16_t	Day;
				float DecimalYear;
	} WMMtype_Date;

	typedef struct {
				float Pcup[NUMPCUP];  // Legendre Function 
				float dPcup[NUMPCUP]; // Derivative of Lagendre fn 
	} WMMtype_LegendreFunction;

	typedef struct {
				float Bx;    // North
				float By;	 // East
				float Bz;    // Down 
	} WMMtype_MagneticResults;

	typedef struct {

				float RelativeRadiusPower[WMM_MAX_MODEL_DEGREES+1];  // [earth_reference_radius_km / sph. radius ]^n
				float cos_mlambda[WMM_MAX_MODEL_DEGREES+1]; // cp(m)  - cosine of (m*spherical coord. longitude
				float sin_mlambda[WMM_MAX_MODEL_DEGREES+1]; // sp(m)  - sine of (m*spherical coord. longitude)
	} WMMtype_SphericalHarmonicVariables;

	typedef struct {
				float Decl; 	/* 1. Angle between the magnetic field vector and true north, positive east*/
				float Incl; 	/*2. Angle between the magnetic field vector and the horizontal plane, positive down*/
				float F; 		/*3. Magnetic Field Strength*/
				float H; 		/*4. Horizontal Magnetic Field Strength*/
				float X; 		/*5. Northern component of the magnetic field vector*/
				float Y; 		/*6. Eastern component of the magnetic field vector*/
				float Z; 		/*7. Downward component of the magnetic field vector*/
				float GV; 		/*8. The Grid Variation*/
				float Decldot; /*9. Yearly Rate of change in declination*/
				float Incldot; /*10. Yearly Rate of change in inclination*/
				float Fdot; 	/*11. Yearly rate of change in Magnetic field strength*/
				float Hdot; 	/*12. Yearly rate of change in horizontal field strength*/
				float Xdot; 	/*13. Yearly rate of change in the northern component*/
				float Ydot; 	/*14. Yearly rate of change in the eastern component*/
				float Zdot; 	/*15. Yearly rate of change in the downward component*/
				float GVdot;	/*16. Yearly rate of chnage in grid variation*/
	} WMMtype_GeoMagneticElements;

	// Internal Function Prototypes
	void WMM_Set_Coeff_Array();
	void WMM_GeodeticToSpherical(WMMtype_CoordGeodetic * CoordGeodetic, WMMtype_CoordSpherical *CoordSpherical);
	uint16_t WMM_DateToYear (WMMtype_Date *CalendarDate, char *Error);
  void WMM_TimelyModifyMagneticModel(WMMtype_Date * UserDate);
	uint16_t WMM_Geomag(WMMtype_CoordSpherical * CoordSpherical,
					WMMtype_CoordGeodetic * CoordGeodetic,
					WMMtype_GeoMagneticElements  *GeoMagneticElements);

	uint16_t WMM_AssociatedLegendreFunction(	WMMtype_CoordSpherical * CoordSpherical, uint16_t nMax, WMMtype_LegendreFunction *LegendreFunction);

	uint16_t WMM_CalculateGeoMagneticElements(WMMtype_MagneticResults *MagneticResultsGeo, WMMtype_GeoMagneticElements *GeoMagneticElements);

	uint16_t WMM_CalculateSecularVariation(WMMtype_MagneticResults *MagneticVariation, WMMtype_GeoMagneticElements *MagneticElements);

	uint16_t WMM_ComputeSphericalHarmonicVariables(	WMMtype_CoordSpherical  *CoordSpherical,
							uint16_t nMax,
							WMMtype_SphericalHarmonicVariables * SphVariables);

	uint16_t WMM_PcupLow( float *Pcup, float *dPcup, float x, uint16_t nMax);

	uint16_t WMM_PcupHigh( float *Pcup, float *dPcup, float x, uint16_t nMax);

	uint16_t WMM_RotateMagneticVector(WMMtype_CoordSpherical * ,
								 WMMtype_CoordGeodetic * CoordGeodetic,
								 WMMtype_MagneticResults * MagneticResultsSph,
								 WMMtype_MagneticResults *MagneticResultsGeo);

	uint16_t WMM_SecVarSummation(WMMtype_LegendreFunction *LegendreFunction,
							WMMtype_SphericalHarmonicVariables * SphVariables,
							WMMtype_CoordSpherical * CoordSpherical,
							WMMtype_MagneticResults *MagneticResults);

	uint16_t WMM_SecVarSummationSpecial(WMMtype_SphericalHarmonicVariables * SphVariables,
								WMMtype_CoordSpherical * CoordSpherical,
								WMMtype_MagneticResults *MagneticResults);

	uint16_t WMM_Summation(	WMMtype_LegendreFunction *LegendreFunction,
						WMMtype_SphericalHarmonicVariables * SphVariables,
						WMMtype_CoordSpherical * CoordSpherical,
						WMMtype_MagneticResults *MagneticResults);

	uint16_t WMM_SummationSpecial(WMMtype_SphericalHarmonicVariables * SphVariables,
						WMMtype_CoordSpherical * CoordSpherical,
						WMMtype_MagneticResults *MagneticResults);


#endif /* WMMINTERNAL_H_ */