#include <math.h>

#include "proj.h"

#include "proj_internal.h"

PROJ_HEAD(crast, "Craster Parabolic (Putnins P4)") "\n\tPCyl, Sph";

#define XM 0.97720502380583984317

#define RXM 1.02332670794648848847

#define YM 3.06998012383946546542

#define RYM 0.32573500793527994772

#define THIRD 0.333333333333333333

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

    PJ_XY xy = {0.0, 0.0};

    (void)P;

    lp.phi *= THIRD;

    xy.x = XM * lp.lam * (2. * cos(lp.phi + lp.phi) - 1.);

    xy.y = YM * sin(lp.phi);

    return xy;

}

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

    PJ_LP lp = {0.0, 0.0};

    (void)P;

    lp.phi = 3. * asin(xy.y * RYM);

    lp.lam = xy.x * RXM / (2. * cos((lp.phi + lp.phi) * THIRD) - 1);

    return lp;

}

PJ *PJ_PROJECTION(crast) {

    P->es = 0.0;

    P->inv = crast_s_inverse;

    P->fwd = crast_s_forward;

    return P;

}