/*
 * (C) Copyright 2020 UCAR
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 */

#include "CubedSphereEquiDistProjection.h"

#include <cmath>
#include <iostream>

#include "eckit/config/Parametrisation.h"
#include "eckit/types/FloatCompare.h"
#include "eckit/utils/Hash.h"

#include "atlas/projection/detail/ProjectionFactory.h"
#include "atlas/projection/detail/ProjectionUtilities.h"
#include "atlas/runtime/Exception.h"
#include "atlas/runtime/Log.h"
#include "atlas/util/Config.h"
#include "atlas/util/Constants.h"
#include "atlas/util/CoordinateEnums.h"

namespace atlas {
namespace projection {
namespace detail {

static constexpr bool debug = false;  // constexpr so compiler can optimize `if ( debug ) { ... }` out

// -------------------------------------------------------------------------------------------------

CubedSphereEquiDistProjection::CubedSphereEquiDistProjection(const eckit::Parametrisation& params):
    CubedSphereProjectionBase(params) {}

// -------------------------------------------------------------------------------------------------

void CubedSphereEquiDistProjection::lonlat2xy(double crd[]) const {
    if (debug) {
        Log::info() << "equidist lonlat2xy start : lonlat = " << crd[LON] << " " << crd[LAT] << std::endl;
    }
    idx_t t;
    double ab[2];   // alpha-beta coordinate
    double xyz[3];  // on Cartesian grid

    CubedSphereProjectionBase::lonlat2xy_pre(crd, t, xyz);

    //now should be tile 0 - now calculate (alpha, beta) in radians.
    // should be between - 45.0 and 45.0
    ab[0] = 45.0 * xyz[YY] / xyz[XX];
    ab[1] = -45.0 * xyz[ZZ] / xyz[XX];

    if (debug) {
        Log::info() << "equidist lonlat2xy xyz ab : " << xyz[0] << " " << xyz[1] << " " << xyz[2] << " " << ab[0] << " "
                    << ab[1] << std::endl;
    }

    CubedSphereProjectionBase::alphabetat2xy(t, ab, crd);

    if (debug) {
        Log::info() << "equidist lonlat2xy end : xy = " << crd[LON] << " " << crd[LAT] << std::endl;
    }
}


// -------------------------------------------------------------------------------------------------

void CubedSphereEquiDistProjection::xy2lonlat(double crd[]) const {
    static const double rsq3 = 1.0 / sqrt(3.0);
    double xyz[3];
    double ab[2];  // alpha-beta coordinate
    idx_t t;       // tile index

    // calculate xy (in degrees) to alpha beta (in radians) and t - tile index.
    CubedSphereProjectionBase::xy2alphabetat(crd, t, ab);

    if (debug) {
        Log::info() << "equidist xy2lonlat:: crd t ab  : " << crd[LON] << " " << crd[1] << " " << t << " " << ab[0]
                    << " " << ab[1] << std::endl;
    }

    xyz[0] = -rsq3;
    xyz[1] = -rsq3 * ab[0] / 45.;
    xyz[2] = -rsq3 * ab[1] / 45.;

    CubedSphereProjectionBase::xy2lonlat_post(xyz, t, crd);

    if (debug) {
        Log::info() << "end of equidistant xy2lonlat lonlat = " << crd[LON] << " " << crd[LAT] << std::endl;
    }
}


// -------------------------------------------------------------------------------------------------

ProjectionImpl::Jacobian CubedSphereEquiDistProjection::jacobian(const PointLonLat&) const {
    ATLAS_NOTIMPLEMENTED;
}

// -------------------------------------------------------------------------------------------------

// -------------------------------------------------------------------------------------------------

CubedSphereEquiDistProjection::Spec CubedSphereEquiDistProjection::spec() const {
    // Fill projection specification
    Spec proj;
    proj.set("type", static_type());
    return proj;
}

// -------------------------------------------------------------------------------------------------

void CubedSphereEquiDistProjection::hash(eckit::Hash& h) const {
    // Add to hash
    h.add(static_type());
    CubedSphereProjectionBase::hash(h);
}

// -------------------------------------------------------------------------------------------------

namespace {
static ProjectionBuilder<CubedSphereEquiDistProjection> register_1(CubedSphereEquiDistProjection::static_type());
}

}  // namespace detail
}  // namespace projection
}  // namespace atlas
