#include <errno.h>

#include <math.h>

#include "proj.h"

#include "proj_internal.h"

PROJ_HEAD(wag3, "Wagner III") "\n\tPCyl, Sph\n\tlat_ts=";

#define TWOTHIRD 0.6666666666666666666667

namespace { // anonymous namespace

struct pj_wag3 {

    double C_x;

};

} // anonymous namespace

static PJ_XY wag3_s_forward(PJ_LP lp, PJ *P) { /* Spheroidal, forward */

    PJ_XY xy = {0.0, 0.0};

    xy.x = static_cast<struct pj_wag3 *>(P->opaque)->C_x * lp.lam *

           cos(TWOTHIRD * lp.phi);

    xy.y = lp.phi;

    return xy;

}

static PJ_LP wag3_s_inverse(PJ_XY xy, PJ *P) { /* Spheroidal, inverse */

    PJ_LP lp = {0.0, 0.0};

    lp.phi = xy.y;

    lp.lam = xy.x / (static_cast<struct pj_wag3 *>(P->opaque)->C_x *

                     cos(TWOTHIRD * lp.phi));

    return lp;

}

PJ *PJ_PROJECTION(wag3) {

    double ts;

    struct pj_wag3 *Q =

        static_cast<struct pj_wag3 *>(calloc(1, sizeof(struct pj_wag3)));

    if (nullptr == Q)

        return pj_default_destructor(P, PROJ_ERR_OTHER /*ENOMEM*/);

    P->opaque = Q;

    ts = pj_param(P->ctx, P->params, "rlat_ts").f;

    static_cast<struct pj_wag3 *>(P->opaque)->C_x = cos(ts) / cos(2. * ts / 3.);

    P->es = 0.;

    P->inv = wag3_s_inverse;

    P->fwd = wag3_s_forward;

    return P;

}

#undef TWOTHIRD