/******************************************************************************

 * Project:  PROJ.4

 * Purpose:  Implementation of the airy (Airy) projection.

 * Author:   Gerald Evenden (1995)

 *           Thomas Knudsen (2016) - revise/add regression tests

 *

 ******************************************************************************

 * Copyright (c) 1995, Gerald Evenden

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included

 * in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS

 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER

 * DEALINGS IN THE SOFTWARE.

 *****************************************************************************/

#include "proj.h"

#include "proj_internal.h"

#include <errno.h>

PROJ_HEAD(airy, "Airy") "\n\tMisc Sph, no inv\n\tno_cut lat_b=";

namespace { // anonymous namespace

enum Mode { N_POLE = 0, S_POLE = 1, EQUIT = 2, OBLIQ = 3 };

} // anonymous namespace

namespace { // anonymous namespace

struct pj_airy {

    double p_halfpi;

    double sinph0;

    double cosph0;

    double Cb;

    enum Mode mode;

    int no_cut; /* do not cut at hemisphere limit */

};

} // anonymous namespace

#define EPS 1.e-10

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

    PJ_XY xy = {0.0, 0.0};

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

    double sinlam, coslam, cosphi, sinphi, t, s, Krho, cosz;

    sinlam = sin(lp.lam);

    coslam = cos(lp.lam);

    switch (Q->mode) {

    case EQUIT:

    case OBLIQ:

        sinphi = sin(lp.phi);

        cosphi = cos(lp.phi);

        cosz = cosphi * coslam;

        if (Q->mode == OBLIQ)

            cosz = Q->sinph0 * sinphi + Q->cosph0 * cosz;

        if (!Q->no_cut && cosz < -EPS) {

            proj_errno_set(P, PROJ_ERR_COORD_TRANSFM_OUTSIDE_PROJECTION_DOMAIN);

            return xy;

        }

        s = 1. - cosz;

        if (fabs(s) > EPS) {

            t = 0.5 * (1. + cosz);

            if (t == 0) {

                proj_errno_set(

                    P, PROJ_ERR_COORD_TRANSFM_OUTSIDE_PROJECTION_DOMAIN);

                return xy;

            }

            Krho = -log(t) / s - Q->Cb / t;

        } else

            Krho = 0.5 - Q->Cb;

        xy.x = Krho * cosphi * sinlam;

        if (Q->mode == OBLIQ)

            xy.y = Krho * (Q->cosph0 * sinphi - Q->sinph0 * cosphi * coslam);

        else

            xy.y = Krho * sinphi;

        break;

    case S_POLE:

    case N_POLE:

        lp.phi = fabs(Q->p_halfpi - lp.phi);

        if (!Q->no_cut && (lp.phi - EPS) > M_HALFPI) {

            proj_errno_set(P, PROJ_ERR_COORD_TRANSFM_OUTSIDE_PROJECTION_DOMAIN);

            return xy;

        }

        lp.phi *= 0.5;

        if (lp.phi > EPS) {

            t = tan(lp.phi);

            Krho = -2. * (log(cos(lp.phi)) / t + t * Q->Cb);

            xy.x = Krho * sinlam;

            xy.y = Krho * coslam;

            if (Q->mode == N_POLE)

                xy.y = -xy.y;

        } else

            xy.x = xy.y = 0.;

    }

    return xy;

}

PJ *PJ_PROJECTION(airy) {

    double beta;

    struct pj_airy *Q =

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

    if (nullptr == Q)

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

    P->opaque = Q;

    Q->no_cut = pj_param(P->ctx, P->params, "bno_cut").i;

    beta = 0.5 * (M_HALFPI - pj_param(P->ctx, P->params, "rlat_b").f);

    if (fabs(beta) < EPS)

        Q->Cb = -0.5;

    else {

        Q->Cb = 1. / tan(beta);

        Q->Cb *= Q->Cb * log(cos(beta));

    }

    if (fabs(fabs(P->phi0) - M_HALFPI) < EPS)

        if (P->phi0 < 0.) {

            Q->p_halfpi = -M_HALFPI;

            Q->mode = S_POLE;

        } else {

            Q->p_halfpi = M_HALFPI;

            Q->mode = N_POLE;

        }

    else {

        if (fabs(P->phi0) < EPS)

            Q->mode = EQUIT;

        else {

            Q->mode = OBLIQ;

            Q->sinph0 = sin(P->phi0);

            Q->cosph0 = cos(P->phi0);

        }

    }

    P->fwd = airy_s_forward;

    P->es = 0.;

    return P;

}

#undef EPS