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/* HelmholtzCoils - demonstrating separation of analysis and toolkit interface in NDIToolbox by creating a
simple magnetic field calculator

Chris Coughlin (TRI/Austin, Inc.)
*/

#ifndef HELMHOLTZCOILS_H_
#define HELMHOLTZCOILS_H_

#define _USE_MATH_DEFINES // Required on some platforms to get mathematical constants
#include <cmath>
#include <cfloat>

static const double mu_0 = 4*M_PI*1e-7;

class HelmholtzCoils {
public:
    HelmholtzCoils(int turns_per_coil, double current_per_coil, double coil_radius):
        N(turns_per_coil), I(current_per_coil), a(coil_radius), lhcoil_position(-a/2), rhcoil_position(a/2) { }

    const double H(const double position) const; // Magnetic field at position (m) in A/m
    const double centerH(void) const { return H(0); } // Magnetic field at dead center of coils
    const double B(const double position) const { return mu_0*H(position)*1000; } // Flux density at position (m) in mT
    const double centerB(void) const { return B(0); } // Flux density at dead center of coils
    const double B_mG(const double position) const { return B(position) * 1e4; } // Flux density at position (m) in mG

    const double wirelength(void) const; // Length of wire (m) to make N turns of radius a
    const double awg_recommendation(void) const; // Lookup table to make AWG recommendations based on current I

private:
    int N; // Turns per coil
    double I; // Current (A) per coil
    double a; // Common radius (m) of coils
    double lhcoil_position; // Position of left coil (m), defined as -a/2
    double rhcoil_position; // Position of right coil (m), defined as a/2
    // Geometry correction for magnetic field calcs
    const double geometry_correction(const double coil_position, const double position) const;
};

#endif // HELMHOLTZCOILS_H_