#include <errno.h>

#include <mutex>

#include <stddef.h>

#include <string.h>

#include "grids.hpp"

#include "proj_internal.h"

PROJ_HEAD(hgridshift, "Horizontal grid shift");

static std::mutex gMutexHGridShift{};

static std::set<std::string> gKnownGridsHGridShift{};

using namespace NS_PROJ;

namespace { // anonymous namespace

struct hgridshiftData {

    double t_final = 0;

    double t_epoch = 0;

    ListOfHGrids grids{};

    bool defer_grid_opening = false;

    int error_code_in_defer_grid_opening = 0;

};

} // anonymous namespace

static PJ_XYZ pj_hgridshift_forward_3d(PJ_LPZ lpz, PJ *P) {

    auto Q = static_cast<hgridshiftData *>(P->opaque);

    PJ_COORD point = {{0, 0, 0, 0}};

    point.lpz = lpz;

    if (Q->defer_grid_opening) {

        Q->defer_grid_opening = false;

        Q->grids = pj_hgrid_init(P, "grids");

        Q->error_code_in_defer_grid_opening = proj_errno(P);

    }

    if (Q->error_code_in_defer_grid_opening) {

        proj_errno_set(P, Q->error_code_in_defer_grid_opening);

        return proj_coord_error().xyz;

    }

    if (!Q->grids.empty()) {

        /* Only try the gridshift if at least one grid is loaded,

         * otherwise just pass the coordinate through unchanged. */

        point.lp = pj_hgrid_apply(P->ctx, Q->grids, point.lp, PJ_FWD);

    }

    return point.xyz;

}

static PJ_LPZ pj_hgridshift_reverse_3d(PJ_XYZ xyz, PJ *P) {

    auto Q = static_cast<hgridshiftData *>(P->opaque);

    PJ_COORD point = {{0, 0, 0, 0}};

    point.xyz = xyz;

    if (Q->defer_grid_opening) {

        Q->defer_grid_opening = false;

        Q->grids = pj_hgrid_init(P, "grids");

        Q->error_code_in_defer_grid_opening = proj_errno(P);

    }

    if (Q->error_code_in_defer_grid_opening) {

        proj_errno_set(P, Q->error_code_in_defer_grid_opening);

        return proj_coord_error().lpz;

    }

    if (!Q->grids.empty()) {

        /* Only try the gridshift if at least one grid is loaded,

         * otherwise just pass the coordinate through unchanged. */

        point.lp = pj_hgrid_apply(P->ctx, Q->grids, point.lp, PJ_INV);

    }

    return point.lpz;

}

static void pj_hgridshift_forward_4d(PJ_COORD &coo, PJ *P) {

    struct hgridshiftData *Q = (struct hgridshiftData *)P->opaque;

    /* If transformation is not time restricted, we always call it */

    if (Q->t_final == 0 || Q->t_epoch == 0) {

        // Assigning in 2 steps avoids cppcheck warning

        // "Overlapping read/write of union is undefined behavior"

        // Cf

        // https://github.com/OSGeo/PROJ/pull/3527#pullrequestreview-1233332710

        const auto xyz = pj_hgridshift_forward_3d(coo.lpz, P);

        coo.xyz = xyz;

        return;

    }

    /* Time restricted - only apply transform if within time bracket */

    if (coo.lpzt.t < Q->t_epoch && Q->t_final > Q->t_epoch) {

        // Assigning in 2 steps avoids cppcheck warning

        // "Overlapping read/write of union is undefined behavior"

        // Cf

        // https://github.com/OSGeo/PROJ/pull/3527#pullrequestreview-1233332710

        const auto xyz = pj_hgridshift_forward_3d(coo.lpz, P);

        coo.xyz = xyz;

    }

}

static void pj_hgridshift_reverse_4d(PJ_COORD &coo, PJ *P) {

    struct hgridshiftData *Q = (struct hgridshiftData *)P->opaque;

    /* If transformation is not time restricted, we always call it */

    if (Q->t_final == 0 || Q->t_epoch == 0) {

        // Assigning in 2 steps avoids cppcheck warning

        // "Overlapping read/write of union is undefined behavior"

        // Cf

        // https://github.com/OSGeo/PROJ/pull/3527#pullrequestreview-1233332710

        const auto lpz = pj_hgridshift_reverse_3d(coo.xyz, P);

        coo.lpz = lpz;

        return;

    }

    /* Time restricted - only apply transform if within time bracket */

    if (coo.lpzt.t < Q->t_epoch && Q->t_final > Q->t_epoch) {

        // Assigning in 2 steps avoids cppcheck warning

        // "Overlapping read/write of union is undefined behavior"

        // Cf

        // https://github.com/OSGeo/PROJ/pull/3527#pullrequestreview-1233332710

        const auto lpz = pj_hgridshift_reverse_3d(coo.xyz, P);

        coo.lpz = lpz;

    }

}

static PJ *pj_hgridshift_destructor(PJ *P, int errlev) {

    if (nullptr == P)

        return nullptr;

    delete static_cast<struct hgridshiftData *>(P->opaque);

    P->opaque = nullptr;

    return pj_default_destructor(P, errlev);

}

static void pj_hgridshift_reassign_context(PJ *P, PJ_CONTEXT *ctx) {

    auto Q = (struct hgridshiftData *)P->opaque;

    for (auto &grid : Q->grids) {

        grid->reassign_context(ctx);

    }

}

PJ *PJ_TRANSFORMATION(hgridshift, 0) {

    auto Q = new hgridshiftData;

    P->opaque = (void *)Q;

    P->destructor = pj_hgridshift_destructor;

    P->reassign_context = pj_hgridshift_reassign_context;

    P->fwd4d = pj_hgridshift_forward_4d;

    P->inv4d = pj_hgridshift_reverse_4d;

    P->fwd3d = pj_hgridshift_forward_3d;

    P->inv3d = pj_hgridshift_reverse_3d;

    P->fwd = nullptr;

    P->inv = nullptr;

    P->left = PJ_IO_UNITS_RADIANS;

    P->right = PJ_IO_UNITS_RADIANS;

    if (0 == pj_param(P->ctx, P->params, "tgrids").i) {

        proj_log_error(P, _("+grids parameter missing."));

        return pj_hgridshift_destructor(P, PROJ_ERR_INVALID_OP_MISSING_ARG);

    }

    Q->t_final = pj_parse_t_final(P);

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

        Q->t_epoch = pj_param(P->ctx, P->params, "dt_epoch").f;

    if (P->ctx->defer_grid_opening) {

        Q->defer_grid_opening = true;

    } else {

        const char *gridnames = pj_param(P->ctx, P->params, "sgrids").s;

        gMutexHGridShift.lock();

        const bool isKnownGrid = gKnownGridsHGridShift.find(gridnames) !=

                                 gKnownGridsHGridShift.end();

        gMutexHGridShift.unlock();

        if (isKnownGrid) {

            Q->defer_grid_opening = true;

        } else {

            Q->grids = pj_hgrid_init(P, "grids");

            /* Was gridlist compiled properly? */

            if (proj_errno(P)) {

                proj_log_error(P, _("could not find required grid(s)."));

                return pj_hgridshift_destructor(

                    P, PROJ_ERR_INVALID_OP_FILE_NOT_FOUND_OR_INVALID);

            }

            gMutexHGridShift.lock();

            gKnownGridsHGridShift.insert(gridnames);

            gMutexHGridShift.unlock();

        }

    }

    return P;

}

void pj_clear_hgridshift_knowngrids_cache() {

    std::lock_guard<std::mutex> lock(gMutexHGridShift);

    gKnownGridsHGridShift.clear();

}