#include <errno.h>

#include <math.h>

#include "proj.h"

#include "proj_internal.h"

PROJ_HEAD(urm5, "Urmaev V") "\n\tPCyl, Sph, no inv\n\tn= q= alpha=";

namespace { // anonymous namespace

struct pj_urm5 {

    double m, rmn, q3, n;

};

} // anonymous namespace

static PJ_XY urm5_s_forward(PJ_LP lp, PJ *P) { /* Spheroidal, forward */

    PJ_XY xy = {0.0, 0.0};

    struct pj_urm5 *Q = static_cast<struct pj_urm5 *>(P->opaque);

    double t;

    t = lp.phi = aasin(P->ctx, Q->n * sin(lp.phi));

    xy.x = Q->m * lp.lam * cos(lp.phi);

    t *= t;

    xy.y = lp.phi * (1. + t * Q->q3) * Q->rmn;

    return xy;

}

PJ *PJ_PROJECTION(urm5) {

    double alpha, t;

    struct pj_urm5 *Q =

        static_cast<struct pj_urm5 *>(calloc(1, sizeof(struct pj_urm5)));

    if (nullptr == Q)

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

    P->opaque = Q;

    if (!pj_param(P->ctx, P->params, "tn").i) {

        proj_log_error(P, _("Missing parameter n."));

        return pj_default_destructor(P, PROJ_ERR_INVALID_OP_MISSING_ARG);

    }

    Q->n = pj_param(P->ctx, P->params, "dn").f;

    if (Q->n <= 0. || Q->n > 1.) {

        proj_log_error(P,

                       _("Invalid value for n: it should be in ]0,1] range."));

        return pj_default_destructor(P, PROJ_ERR_INVALID_OP_ILLEGAL_ARG_VALUE);

    }

    Q->q3 = pj_param(P->ctx, P->params, "dq").f / 3.;

    alpha = pj_param(P->ctx, P->params, "ralpha").f;

    t = Q->n * sin(alpha);

    const double denom = sqrt(1. - t * t);

    if (denom == 0) {

        proj_log_error(

            P,

            _("Invalid value for n / alpha: n * sin(|alpha|) should be < 1."));

        return pj_default_destructor(P, PROJ_ERR_INVALID_OP_ILLEGAL_ARG_VALUE);

    }

    Q->m = cos(alpha) / denom;

    Q->rmn = 1. / (Q->m * Q->n);

    P->es = 0.;

    P->inv = nullptr;

    P->fwd = urm5_s_forward;

    return P;

}