#include <errno.h>

#include <math.h>

#include "proj.h"

#include "proj_internal.h"

namespace { // anonymous namespace

struct pj_cea_data {

    double qp;

    double *apa;

};

} // anonymous namespace

PROJ_HEAD(cea, "Equal Area Cylindrical") "\n\tCyl, Sph&Ell\n\tlat_ts=";

#define EPS 1e-10

static PJ_XY cea_e_forward(PJ_LP lp, PJ *P) { /* Ellipsoidal, forward */

    PJ_XY xy = {0.0, 0.0};

    xy.x = P->k0 * lp.lam;

    xy.y = 0.5 * pj_authalic_lat_q(sin(lp.phi), P) / P->k0;

    return xy;

}

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

    PJ_XY xy = {0.0, 0.0};

    xy.x = P->k0 * lp.lam;

    xy.y = sin(lp.phi) / P->k0;

    return xy;

}

static PJ_LP cea_e_inverse(PJ_XY xy, PJ *P) { /* Ellipsoidal, inverse */

    PJ_LP lp = {0.0, 0.0};

    const struct pj_cea_data *Q =

        static_cast<const struct pj_cea_data *>(P->opaque);

    lp.phi = pj_authalic_lat_inverse(asin(2. * xy.y * P->k0 / Q->qp), Q->apa, P,

                                     Q->qp);

    lp.lam = xy.x / P->k0;

    return lp;

}

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

    PJ_LP lp = {0.0, 0.0};

    xy.y *= P->k0;

    const double t = fabs(xy.y);

    if (t - EPS <= 1.) {

        if (t >= 1.)

            lp.phi = xy.y < 0. ? -M_HALFPI : M_HALFPI;

        else

            lp.phi = asin(xy.y);

        lp.lam = xy.x / P->k0;

    } else {

        proj_errno_set(P, PROJ_ERR_COORD_TRANSFM_OUTSIDE_PROJECTION_DOMAIN);

        return lp;

    }

    return (lp);

}

static PJ *pj_cea_destructor(PJ *P, int errlev) { /* Destructor */

    if (nullptr == P)

        return nullptr;

    if (nullptr == P->opaque)

        return pj_default_destructor(P, errlev);

    free(static_cast<struct pj_cea_data *>(P->opaque)->apa);

    return pj_default_destructor(P, errlev);

}

PJ *PJ_PROJECTION(cea) {

    double t = 0.0;

    struct pj_cea_data *Q = static_cast<struct pj_cea_data *>(

        calloc(1, sizeof(struct pj_cea_data)));

    if (nullptr == Q)

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

    P->opaque = Q;

    P->destructor = pj_cea_destructor;

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

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

        P->k0 = cos(t);

        if (P->k0 < 0.) {

            proj_log_error(

                P, _("Invalid value for lat_ts: |lat_ts| should be <= 90°"));

            return pj_default_destructor(P,

                                         PROJ_ERR_INVALID_OP_ILLEGAL_ARG_VALUE);

        }

    }

    if (P->es != 0.0) {

        t = sin(t);

        P->k0 /= sqrt(1. - P->es * t * t);

        P->e = sqrt(P->es);

        Q->apa = pj_authalic_lat_compute_coeffs(P->n);

        if (!(Q->apa))

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

        Q->qp = pj_authalic_lat_q(1.0, P);

        P->inv = cea_e_inverse;

        P->fwd = cea_e_forward;

    } else {

        P->inv = cea_s_inverse;

        P->fwd = cea_s_forward;

    }

    return P;

}

#undef EPS