/******************************************************************************
 *
 * Project:  GML Translator
 * Purpose:  Code to translate OGRGeometry to GML string representation.
 * Author:   Frank Warmerdam, warmerdam@pobox.com
 *
 ******************************************************************************
 * Copyright (c) 2002, Frank Warmerdam <warmerdam@pobox.com>
 * Copyright (c) 2009-2013, Even Rouault <even dot rouault at spatialys.com>
 *
 * 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.
 *****************************************************************************
 *
 * Independent Security Audit 2003/04/17 Andrey Kiselev:
 *   Completed audit of this module. All functions may be used without buffer
 *   overflows and stack corruptions if caller could be trusted.
 *
 * Security Audit 2003/03/28 warmerda:
 *   Completed security audit.  I believe that this module may be safely used
 *   to generate GML from arbitrary but well formed OGRGeomety objects that
 *   come from a potentially hostile source, but through a trusted OGR importer
 *   without compromising the system.
 *
 */

#include "cpl_port.h"
#include "ogr_api.h"

#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>

#include "cpl_conv.h"
#include "cpl_error.h"
#include "cpl_minixml.h"
#include "cpl_string.h"
#include "ogr_core.h"
#include "ogr_geometry.h"
#include "ogr_p.h"
#include "ogr_spatialref.h"

constexpr int SRSDIM_LOC_GEOMETRY = 1 << 0;
constexpr int SRSDIM_LOC_POSLIST = 1 << 1;

enum GMLSRSNameFormat
{
    SRSNAME_SHORT,
    SRSNAME_OGC_URN,
    SRSNAME_OGC_URL
};

/************************************************************************/
/*                        MakeGMLCoordinate()                           */
/************************************************************************/

static void MakeGMLCoordinate(char *pszTarget, double x, double y, double z,
                              bool b3D)

{
    OGRMakeWktCoordinate(pszTarget, x, y, z, b3D ? 3 : 2);
    while (*pszTarget != '\0')
    {
        if (*pszTarget == ' ')
            *pszTarget = ',';
        pszTarget++;
    }
}

/************************************************************************/
/*                            _GrowBuffer()                             */
/************************************************************************/

static void _GrowBuffer(size_t nNeeded, char **ppszText, size_t *pnMaxLength)

{
    if (nNeeded + 1 >= *pnMaxLength)
    {
        *pnMaxLength = std::max(*pnMaxLength * 2, nNeeded + 1);
        *ppszText = static_cast<char *>(CPLRealloc(*ppszText, *pnMaxLength));
    }
}

/************************************************************************/
/*                            AppendString()                            */
/************************************************************************/

static void AppendString(char **ppszText, size_t *pnLength, size_t *pnMaxLength,
                         const char *pszTextToAppend)

{
    _GrowBuffer(*pnLength + strlen(pszTextToAppend) + 1, ppszText, pnMaxLength);

    strcat(*ppszText + *pnLength, pszTextToAppend);
    *pnLength += strlen(*ppszText + *pnLength);
}

/************************************************************************/
/*                        AppendCoordinateList()                        */
/************************************************************************/

static void AppendCoordinateList(const OGRLineString *poLine, char **ppszText,
                                 size_t *pnLength, size_t *pnMaxLength)

{
    const bool b3D = wkbHasZ(poLine->getGeometryType()) != FALSE;

    *pnLength += strlen(*ppszText + *pnLength);
    _GrowBuffer(*pnLength + 20, ppszText, pnMaxLength);

    strcat(*ppszText + *pnLength, "<gml:coordinates>");
    *pnLength += strlen(*ppszText + *pnLength);

    char szCoordinate[256] = {};
    for (int iPoint = 0; iPoint < poLine->getNumPoints(); iPoint++)
    {
        MakeGMLCoordinate(szCoordinate, poLine->getX(iPoint),
                          poLine->getY(iPoint), poLine->getZ(iPoint), b3D);
        _GrowBuffer(*pnLength + strlen(szCoordinate) + 1, ppszText,
                    pnMaxLength);

        if (iPoint != 0)
            strcat(*ppszText + *pnLength, " ");

        strcat(*ppszText + *pnLength, szCoordinate);
        *pnLength += strlen(*ppszText + *pnLength);
    }

    _GrowBuffer(*pnLength + 20, ppszText, pnMaxLength);
    strcat(*ppszText + *pnLength, "</gml:coordinates>");
    *pnLength += strlen(*ppszText + *pnLength);
}

/************************************************************************/
/*                       OGR2GMLGeometryAppend()                        */
/************************************************************************/

static bool OGR2GMLGeometryAppend(const OGRGeometry *poGeometry,
                                  char **ppszText, size_t *pnLength,
                                  size_t *pnMaxLength, bool bIsSubGeometry,
                                  const char *pszNamespaceDecl)

{
    /* -------------------------------------------------------------------- */
    /*      Check for Spatial Reference System attached to given geometry   */
    /* -------------------------------------------------------------------- */

    // Buffer for xmlns:gml and srsName attributes (srsName="...")
    char szAttributes[128] = {};
    size_t nAttrsLength = 0;

    szAttributes[0] = 0;

    const OGRSpatialReference *poSRS = poGeometry->getSpatialReference();

    if (pszNamespaceDecl != nullptr)
    {
        snprintf(szAttributes + nAttrsLength,
                 sizeof(szAttributes) - nAttrsLength, " xmlns:gml=\"%s\"",
                 pszNamespaceDecl);
        nAttrsLength += strlen(szAttributes + nAttrsLength);
        pszNamespaceDecl = nullptr;
    }

    if (nullptr != poSRS && !bIsSubGeometry)
    {
        const char *pszTarget = poSRS->IsProjected() ? "PROJCS" : "GEOGCS";
        const char *pszAuthName = poSRS->GetAuthorityName(pszTarget);
        const char *pszAuthCode = poSRS->GetAuthorityCode(pszTarget);
        if (nullptr != pszAuthName && strlen(pszAuthName) < 10 &&
            nullptr != pszAuthCode && strlen(pszAuthCode) < 10)
        {
            snprintf(szAttributes + nAttrsLength,
                     sizeof(szAttributes) - nAttrsLength, " srsName=\"%s:%s\"",
                     pszAuthName, pszAuthCode);

            nAttrsLength += strlen(szAttributes + nAttrsLength);
        }
    }

    OGRwkbGeometryType eType = poGeometry->getGeometryType();
    OGRwkbGeometryType eFType = wkbFlatten(eType);

    /* -------------------------------------------------------------------- */
    /*      2D Point                                                        */
    /* -------------------------------------------------------------------- */
    if (eType == wkbPoint)
    {
        const auto poPoint = poGeometry->toPoint();

        char szCoordinate[256] = {};
        MakeGMLCoordinate(szCoordinate, poPoint->getX(), poPoint->getY(), 0.0,
                          false);

        _GrowBuffer(*pnLength + strlen(szCoordinate) + 60 + nAttrsLength,
                    ppszText, pnMaxLength);

        snprintf(
            *ppszText + *pnLength, *pnMaxLength - *pnLength,
            "<gml:Point%s><gml:coordinates>%s</gml:coordinates></gml:Point>",
            szAttributes, szCoordinate);

        *pnLength += strlen(*ppszText + *pnLength);
    }
    /* -------------------------------------------------------------------- */
    /*      3D Point                                                        */
    /* -------------------------------------------------------------------- */
    else if (eType == wkbPoint25D)
    {
        const auto poPoint = poGeometry->toPoint();

        char szCoordinate[256] = {};
        MakeGMLCoordinate(szCoordinate, poPoint->getX(), poPoint->getY(),
                          poPoint->getZ(), true);

        _GrowBuffer(*pnLength + strlen(szCoordinate) + 70 + nAttrsLength,
                    ppszText, pnMaxLength);

        snprintf(
            *ppszText + *pnLength, *pnMaxLength - *pnLength,
            "<gml:Point%s><gml:coordinates>%s</gml:coordinates></gml:Point>",
            szAttributes, szCoordinate);

        *pnLength += strlen(*ppszText + *pnLength);
    }

    /* -------------------------------------------------------------------- */
    /*      LineString and LinearRing                                       */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbLineString)
    {
        bool bRing = EQUAL(poGeometry->getGeometryName(), "LINEARRING");

        // Buffer for tag name + srsName attribute if set
        const size_t nLineTagLength = 16;
        const size_t nLineTagNameBufLen = nLineTagLength + nAttrsLength + 1;
        char *pszLineTagName =
            static_cast<char *>(CPLMalloc(nLineTagNameBufLen));

        if (bRing)
        {
            snprintf(pszLineTagName, nLineTagNameBufLen, "<gml:LinearRing%s>",
                     szAttributes);

            AppendString(ppszText, pnLength, pnMaxLength, pszLineTagName);
        }
        else
        {
            snprintf(pszLineTagName, nLineTagNameBufLen, "<gml:LineString%s>",
                     szAttributes);

            AppendString(ppszText, pnLength, pnMaxLength, pszLineTagName);
        }

        // Free tag buffer.
        CPLFree(pszLineTagName);

        const auto poLineString = poGeometry->toLineString();
        AppendCoordinateList(poLineString, ppszText, pnLength, pnMaxLength);

        if (bRing)
            AppendString(ppszText, pnLength, pnMaxLength, "</gml:LinearRing>");
        else
            AppendString(ppszText, pnLength, pnMaxLength, "</gml:LineString>");
    }

    /* -------------------------------------------------------------------- */
    /*      Polygon                                                         */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbPolygon)
    {
        const auto poPolygon = poGeometry->toPolygon();

        // Buffer for polygon tag name + srsName attribute if set.
        const size_t nPolyTagLength = 13;
        const size_t nPolyTagNameBufLen = nPolyTagLength + nAttrsLength + 1;
        char *pszPolyTagName =
            static_cast<char *>(CPLMalloc(nPolyTagNameBufLen));

        // Compose Polygon tag with or without srsName attribute.
        snprintf(pszPolyTagName, nPolyTagNameBufLen, "<gml:Polygon%s>",
                 szAttributes);

        AppendString(ppszText, pnLength, pnMaxLength, pszPolyTagName);

        // Free tag buffer.
        CPLFree(pszPolyTagName);

        // Don't add srsName to polygon rings.
        if (poPolygon->getExteriorRing() != nullptr)
        {
            AppendString(ppszText, pnLength, pnMaxLength,
                         "<gml:outerBoundaryIs>");

            CPL_IGNORE_RET_VAL(
                OGR2GMLGeometryAppend(poPolygon->getExteriorRing(), ppszText,
                                      pnLength, pnMaxLength, true, nullptr));

            AppendString(ppszText, pnLength, pnMaxLength,
                         "</gml:outerBoundaryIs>");
        }

        for (int iRing = 0; iRing < poPolygon->getNumInteriorRings(); iRing++)
        {
            const OGRLinearRing *poRing = poPolygon->getInteriorRing(iRing);

            AppendString(ppszText, pnLength, pnMaxLength,
                         "<gml:innerBoundaryIs>");

            CPL_IGNORE_RET_VAL(OGR2GMLGeometryAppend(
                poRing, ppszText, pnLength, pnMaxLength, true, nullptr));
            AppendString(ppszText, pnLength, pnMaxLength,
                         "</gml:innerBoundaryIs>");
        }

        AppendString(ppszText, pnLength, pnMaxLength, "</gml:Polygon>");
    }

    /* -------------------------------------------------------------------- */
    /*      MultiPolygon, MultiLineString, MultiPoint, MultiGeometry        */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbMultiPolygon || eFType == wkbMultiLineString ||
             eFType == wkbMultiPoint || eFType == wkbGeometryCollection)
    {
        const auto poGC = poGeometry->toGeometryCollection();
        const char *pszElemClose = nullptr;
        const char *pszMemberElem = nullptr;

        // Buffer for opening tag + srsName attribute.
        char *pszElemOpen = nullptr;

        if (eFType == wkbMultiPolygon)
        {
            const size_t nBufLen = 13 + nAttrsLength + 1;
            pszElemOpen = static_cast<char *>(CPLMalloc(nBufLen));
            snprintf(pszElemOpen, nBufLen, "MultiPolygon%s>", szAttributes);

            pszElemClose = "MultiPolygon>";
            pszMemberElem = "polygonMember>";
        }
        else if (eFType == wkbMultiLineString)
        {
            const size_t nBufLen = 16 + nAttrsLength + 1;
            pszElemOpen = static_cast<char *>(CPLMalloc(nBufLen));
            snprintf(pszElemOpen, nBufLen, "MultiLineString%s>", szAttributes);

            pszElemClose = "MultiLineString>";
            pszMemberElem = "lineStringMember>";
        }
        else if (eFType == wkbMultiPoint)
        {
            const size_t nBufLen = 11 + nAttrsLength + 1;
            pszElemOpen = static_cast<char *>(CPLMalloc(nBufLen));
            snprintf(pszElemOpen, nBufLen, "MultiPoint%s>", szAttributes);

            pszElemClose = "MultiPoint>";
            pszMemberElem = "pointMember>";
        }
        else
        {
            const size_t nBufLen = 19 + nAttrsLength + 1;
            pszElemOpen = static_cast<char *>(CPLMalloc(nBufLen));
            snprintf(pszElemOpen, nBufLen, "MultiGeometry%s>", szAttributes);

            pszElemClose = "MultiGeometry>";
            pszMemberElem = "geometryMember>";
        }

        AppendString(ppszText, pnLength, pnMaxLength, "<gml:");
        AppendString(ppszText, pnLength, pnMaxLength, pszElemOpen);

        for (int iMember = 0; iMember < poGC->getNumGeometries(); iMember++)
        {
            const auto poMember = poGC->getGeometryRef(iMember);

            AppendString(ppszText, pnLength, pnMaxLength, "<gml:");
            AppendString(ppszText, pnLength, pnMaxLength, pszMemberElem);

            if (!OGR2GMLGeometryAppend(poMember, ppszText, pnLength,
                                       pnMaxLength, true, nullptr))
            {
                CPLFree(pszElemOpen);
                return false;
            }

            AppendString(ppszText, pnLength, pnMaxLength, "</gml:");
            AppendString(ppszText, pnLength, pnMaxLength, pszMemberElem);
        }

        AppendString(ppszText, pnLength, pnMaxLength, "</gml:");
        AppendString(ppszText, pnLength, pnMaxLength, pszElemClose);

        // Free tag buffer.
        CPLFree(pszElemOpen);
    }
    else
    {
        CPLError(CE_Failure, CPLE_NotSupported, "Unsupported geometry type %s",
                 OGRGeometryTypeToName(eType));
        return false;
    }

    return true;
}

/************************************************************************/
/*                   OGR_G_ExportEnvelopeToGMLTree()                    */
/************************************************************************/

/** Export the envelope of a geometry as a gml:Box. */
CPLXMLNode *OGR_G_ExportEnvelopeToGMLTree(OGRGeometryH hGeometry)

{
    OGREnvelope sEnvelope;

    OGRGeometry::FromHandle(hGeometry)->getEnvelope(&sEnvelope);

    if (!sEnvelope.IsInit())
    {
        // TODO: There is apparently a special way of representing a null box
        // geometry. Should use it here eventually.
        return nullptr;
    }

    CPLXMLNode *psBox = CPLCreateXMLNode(nullptr, CXT_Element, "gml:Box");

    /* -------------------------------------------------------------------- */
    /*      Add minxy coordinate.                                           */
    /* -------------------------------------------------------------------- */
    CPLXMLNode *psCoord = CPLCreateXMLNode(psBox, CXT_Element, "gml:coord");

    char szCoordinate[256] = {};
    MakeGMLCoordinate(szCoordinate, sEnvelope.MinX, sEnvelope.MinY, 0.0, false);
    char *pszY = strstr(szCoordinate, ",");
    // There must be more after the comma or we have an internal consistency
    // bug in MakeGMLCoordinate.
    if (pszY == nullptr || strlen(pszY) < 2)
    {
        CPLError(CE_Failure, CPLE_AssertionFailed, "MakeGMLCoordinate failed.");
        return nullptr;
    }
    *pszY = '\0';
    pszY++;

    CPLCreateXMLElementAndValue(psCoord, "gml:X", szCoordinate);
    CPLCreateXMLElementAndValue(psCoord, "gml:Y", pszY);

    /* -------------------------------------------------------------------- */
    /*      Add maxxy coordinate.                                           */
    /* -------------------------------------------------------------------- */
    psCoord = CPLCreateXMLNode(psBox, CXT_Element, "gml:coord");

    MakeGMLCoordinate(szCoordinate, sEnvelope.MaxX, sEnvelope.MaxY, 0.0, false);
    pszY = strstr(szCoordinate, ",") + 1;
    pszY[-1] = '\0';

    CPLCreateXMLElementAndValue(psCoord, "gml:X", szCoordinate);
    CPLCreateXMLElementAndValue(psCoord, "gml:Y", pszY);

    return psBox;
}

/************************************************************************/
/*                     AppendGML3CoordinateList()                       */
/************************************************************************/

static void AppendGML3CoordinateList(const OGRSimpleCurve *poLine,
                                     bool bCoordSwap, char **ppszText,
                                     size_t *pnLength, size_t *pnMaxLength,
                                     int nSRSDimensionLocFlags)

{
    bool b3D = wkbHasZ(poLine->getGeometryType());

    *pnLength += strlen(*ppszText + *pnLength);
    _GrowBuffer(*pnLength + 40, ppszText, pnMaxLength);

    if (b3D && (nSRSDimensionLocFlags & SRSDIM_LOC_POSLIST) != 0)
        strcat(*ppszText + *pnLength, "<gml:posList srsDimension=\"3\">");
    else
        strcat(*ppszText + *pnLength, "<gml:posList>");
    *pnLength += strlen(*ppszText + *pnLength);

    char szCoordinate[256] = {};

    for (int iPoint = 0; iPoint < poLine->getNumPoints(); iPoint++)
    {
        if (bCoordSwap)
            OGRMakeWktCoordinate(szCoordinate, poLine->getY(iPoint),
                                 poLine->getX(iPoint), poLine->getZ(iPoint),
                                 b3D ? 3 : 2);
        else
            OGRMakeWktCoordinate(szCoordinate, poLine->getX(iPoint),
                                 poLine->getY(iPoint), poLine->getZ(iPoint),
                                 b3D ? 3 : 2);
        _GrowBuffer(*pnLength + strlen(szCoordinate) + 1, ppszText,
                    pnMaxLength);

        if (iPoint != 0)
            strcat(*ppszText + *pnLength, " ");

        strcat(*ppszText + *pnLength, szCoordinate);
        *pnLength += strlen(*ppszText + *pnLength);
    }

    _GrowBuffer(*pnLength + 20, ppszText, pnMaxLength);
    strcat(*ppszText + *pnLength, "</gml:posList>");
    *pnLength += strlen(*ppszText + *pnLength);
}

/************************************************************************/
/*                      OGR2GML3GeometryAppend()                        */
/************************************************************************/

static bool OGR2GML3GeometryAppend(
    const OGRGeometry *poGeometry, const OGRSpatialReference *poParentSRS,
    char **ppszText, size_t *pnLength, size_t *pnMaxLength, bool bIsSubGeometry,
    GMLSRSNameFormat eSRSNameFormat, bool bCoordSwap, bool bLineStringAsCurve,
    const char *pszGMLId, int nSRSDimensionLocFlags,
    bool bForceLineStringAsLinearRing, const char *pszNamespaceDecl,
    const char *pszOverriddenElementName)

{

    /* -------------------------------------------------------------------- */
    /*      Check for Spatial Reference System attached to given geometry   */
    /* -------------------------------------------------------------------- */

    // Buffer for srsName, xmlns:gml, srsDimension and gml:id attributes
    // (srsName="..." gml:id="...").

    const OGRSpatialReference *poSRS =
        poParentSRS ? poParentSRS : poGeometry->getSpatialReference();

    char szAttributes[256] = {};
    size_t nAttrsLength = 0;

    if (pszNamespaceDecl != nullptr)
    {
        snprintf(szAttributes + nAttrsLength,
                 sizeof(szAttributes) - nAttrsLength, " xmlns:gml=\"%s\"",
                 pszNamespaceDecl);
        pszNamespaceDecl = nullptr;
        nAttrsLength += strlen(szAttributes + nAttrsLength);
    }

    if (nullptr != poSRS)
    {
        const char *pszTarget = poSRS->IsProjected() ? "PROJCS" : "GEOGCS";
        const char *pszAuthName = poSRS->GetAuthorityName(pszTarget);
        const char *pszAuthCode = poSRS->GetAuthorityCode(pszTarget);
        if (nullptr != pszAuthName && strlen(pszAuthName) < 10 &&
            nullptr != pszAuthCode && strlen(pszAuthCode) < 10)
        {
            if (!bIsSubGeometry)
            {
                if (eSRSNameFormat == SRSNAME_OGC_URN)
                {
                    snprintf(szAttributes + nAttrsLength,
                             sizeof(szAttributes) - nAttrsLength,
                             " srsName=\"urn:ogc:def:crs:%s::%s\"", pszAuthName,
                             pszAuthCode);
                }
                else if (eSRSNameFormat == SRSNAME_SHORT)
                {
                    snprintf(szAttributes + nAttrsLength,
                             sizeof(szAttributes) - nAttrsLength,
                             " srsName=\"%s:%s\"", pszAuthName, pszAuthCode);
                }
                else if (eSRSNameFormat == SRSNAME_OGC_URL)
                {
                    snprintf(
                        szAttributes + nAttrsLength,
                        sizeof(szAttributes) - nAttrsLength,
                        " srsName=\"http://www.opengis.net/def/crs/%s/0/%s\"",
                        pszAuthName, pszAuthCode);
                }
                nAttrsLength += strlen(szAttributes + nAttrsLength);
            }
        }
    }

    if ((nSRSDimensionLocFlags & SRSDIM_LOC_GEOMETRY) != 0 &&
        wkbHasZ(poGeometry->getGeometryType()))
    {
        snprintf(szAttributes + nAttrsLength,
                 sizeof(szAttributes) - nAttrsLength, " srsDimension=\"3\"");
        nAttrsLength += strlen(szAttributes + nAttrsLength);

        nSRSDimensionLocFlags &= ~SRSDIM_LOC_GEOMETRY;
    }

    if (pszGMLId != nullptr &&
        nAttrsLength + 9 + strlen(pszGMLId) + 1 < sizeof(szAttributes))
    {
        snprintf(szAttributes + nAttrsLength,
                 sizeof(szAttributes) - nAttrsLength, " gml:id=\"%s\"",
                 pszGMLId);
        nAttrsLength += strlen(szAttributes + nAttrsLength);
    }

    const OGRwkbGeometryType eType = poGeometry->getGeometryType();
    const OGRwkbGeometryType eFType = wkbFlatten(eType);

    /* -------------------------------------------------------------------- */
    /*      2D Point                                                        */
    /* -------------------------------------------------------------------- */
    if (eType == wkbPoint)
    {
        const auto poPoint = poGeometry->toPoint();

        char szCoordinate[256] = {};
        if (bCoordSwap)
            OGRMakeWktCoordinate(szCoordinate, poPoint->getY(), poPoint->getX(),
                                 0.0, 2);
        else
            OGRMakeWktCoordinate(szCoordinate, poPoint->getX(), poPoint->getY(),
                                 0.0, 2);

        _GrowBuffer(*pnLength + strlen(szCoordinate) + 60 + nAttrsLength,
                    ppszText, pnMaxLength);

        snprintf(*ppszText + *pnLength, *pnMaxLength - *pnLength,
                 "<gml:Point%s><gml:pos>%s</gml:pos></gml:Point>", szAttributes,
                 szCoordinate);

        *pnLength += strlen(*ppszText + *pnLength);
    }
    /* -------------------------------------------------------------------- */
    /*      3D Point                                                        */
    /* -------------------------------------------------------------------- */
    else if (eType == wkbPoint25D)
    {
        const auto poPoint = poGeometry->toPoint();

        char szCoordinate[256] = {};
        if (bCoordSwap)
            OGRMakeWktCoordinate(szCoordinate, poPoint->getY(), poPoint->getX(),
                                 poPoint->getZ(), 3);
        else
            OGRMakeWktCoordinate(szCoordinate, poPoint->getX(), poPoint->getY(),
                                 poPoint->getZ(), 3);

        _GrowBuffer(*pnLength + strlen(szCoordinate) + 70 + nAttrsLength,
                    ppszText, pnMaxLength);

        snprintf(*ppszText + *pnLength, *pnMaxLength - *pnLength,
                 "<gml:Point%s><gml:pos>%s</gml:pos></gml:Point>", szAttributes,
                 szCoordinate);

        *pnLength += strlen(*ppszText + *pnLength);
    }

    /* -------------------------------------------------------------------- */
    /*      LineString and LinearRing                                       */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbLineString)
    {
        const bool bRing = EQUAL(poGeometry->getGeometryName(), "LINEARRING") ||
                           bForceLineStringAsLinearRing;
        if (!bRing && bLineStringAsCurve)
        {
            AppendString(ppszText, pnLength, pnMaxLength, "<gml:Curve");
            AppendString(ppszText, pnLength, pnMaxLength, szAttributes);
            AppendString(ppszText, pnLength, pnMaxLength,
                         "><gml:segments><gml:LineStringSegment>");
            const auto poLineString = poGeometry->toLineString();
            AppendGML3CoordinateList(poLineString, bCoordSwap, ppszText,
                                     pnLength, pnMaxLength,
                                     nSRSDimensionLocFlags);
            AppendString(ppszText, pnLength, pnMaxLength,
                         "</gml:LineStringSegment></gml:segments></gml:Curve>");
        }
        else
        {
            // Buffer for tag name + srsName attribute if set.
            const size_t nLineTagLength = 16;
            const size_t nLineTagNameBufLen = nLineTagLength + nAttrsLength + 1;
            char *pszLineTagName =
                static_cast<char *>(CPLMalloc(nLineTagNameBufLen));

            if (bRing)
            {
                // LinearRing isn't supposed to have srsName attribute according
                // to GML3 SF-0.
                AppendString(ppszText, pnLength, pnMaxLength,
                             "<gml:LinearRing>");
            }
            else
            {
                snprintf(pszLineTagName, nLineTagNameBufLen,
                         "<gml:LineString%s>", szAttributes);

                AppendString(ppszText, pnLength, pnMaxLength, pszLineTagName);
            }

            // Free tag buffer.
            CPLFree(pszLineTagName);

            const auto poLineString = poGeometry->toLineString();

            AppendGML3CoordinateList(poLineString, bCoordSwap, ppszText,
                                     pnLength, pnMaxLength,
                                     nSRSDimensionLocFlags);

            if (bRing)
                AppendString(ppszText, pnLength, pnMaxLength,
                             "</gml:LinearRing>");
            else
                AppendString(ppszText, pnLength, pnMaxLength,
                             "</gml:LineString>");
        }
    }

    /* -------------------------------------------------------------------- */
    /*      ArcString or Circle                                             */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbCircularString)
    {
        AppendString(ppszText, pnLength, pnMaxLength, "<gml:Curve");
        AppendString(ppszText, pnLength, pnMaxLength, szAttributes);
        const auto poSC = poGeometry->toCircularString();

        // SQL MM has a unique type for arc and circle, GML does not.
        if (poSC->getNumPoints() == 3 && poSC->getX(0) == poSC->getX(2) &&
            poSC->getY(0) == poSC->getY(2))
        {
            const double dfMidX = (poSC->getX(0) + poSC->getX(1)) / 2.0;
            const double dfMidY = (poSC->getY(0) + poSC->getY(1)) / 2.0;
            const double dfDirX = (poSC->getX(1) - poSC->getX(0)) / 2.0;
            const double dfDirY = (poSC->getY(1) - poSC->getY(0)) / 2.0;
            const double dfNormX = -dfDirY;
            const double dfNormY = dfDirX;
            const double dfNewX = dfMidX + dfNormX;
            const double dfNewY = dfMidY + dfNormY;
            OGRLineString *poLS = new OGRLineString();
            OGRPoint p;
            poSC->getPoint(0, &p);
            poLS->addPoint(&p);
            poSC->getPoint(1, &p);
            if (poSC->getCoordinateDimension() == 3)
                poLS->addPoint(dfNewX, dfNewY, p.getZ());
            else
                poLS->addPoint(dfNewX, dfNewY);
            poLS->addPoint(&p);
            AppendString(ppszText, pnLength, pnMaxLength,
                         "><gml:segments><gml:Circle>");
            AppendGML3CoordinateList(poLS, bCoordSwap, ppszText, pnLength,
                                     pnMaxLength, nSRSDimensionLocFlags);
            AppendString(ppszText, pnLength, pnMaxLength,
                         "</gml:Circle></gml:segments></gml:Curve>");
            delete poLS;
        }
        else
        {
            AppendString(ppszText, pnLength, pnMaxLength,
                         "><gml:segments><gml:ArcString>");
            AppendGML3CoordinateList(poSC, bCoordSwap, ppszText, pnLength,
                                     pnMaxLength, nSRSDimensionLocFlags);
            AppendString(ppszText, pnLength, pnMaxLength,
                         "</gml:ArcString></gml:segments></gml:Curve>");
        }
    }

    /* -------------------------------------------------------------------- */
    /*      CompositeCurve                                                  */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbCompoundCurve)
    {
        AppendString(ppszText, pnLength, pnMaxLength, "<gml:CompositeCurve");
        AppendString(ppszText, pnLength, pnMaxLength, szAttributes);
        AppendString(ppszText, pnLength, pnMaxLength, ">");

        const auto poCC = poGeometry->toCompoundCurve();
        for (int i = 0; i < poCC->getNumCurves(); i++)
        {
            AppendString(ppszText, pnLength, pnMaxLength, "<gml:curveMember>");

            char *pszGMLIdSub = nullptr;
            if (pszGMLId != nullptr)
                pszGMLIdSub = CPLStrdup(CPLSPrintf("%s.%d", pszGMLId, i));

            CPL_IGNORE_RET_VAL(OGR2GML3GeometryAppend(
                poCC->getCurve(i), poSRS, ppszText, pnLength, pnMaxLength, true,
                eSRSNameFormat, bCoordSwap, bLineStringAsCurve, pszGMLIdSub,
                nSRSDimensionLocFlags, false, nullptr, nullptr));

            CPLFree(pszGMLIdSub);

            AppendString(ppszText, pnLength, pnMaxLength, "</gml:curveMember>");
        }
        AppendString(ppszText, pnLength, pnMaxLength, "</gml:CompositeCurve>");
    }

    /* -------------------------------------------------------------------- */
    /*      Polygon                                                         */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbPolygon || eFType == wkbCurvePolygon)
    {
        const auto poCP = poGeometry->toCurvePolygon();

        // Buffer for polygon tag name + srsName attribute if set.
        const char *pszElemName =
            pszOverriddenElementName ? pszOverriddenElementName : "Polygon";
        const size_t nPolyTagLength = 7 + strlen(pszElemName);
        const size_t nPolyTagNameBufLen = nPolyTagLength + nAttrsLength + 1;
        char *pszPolyTagName =
            static_cast<char *>(CPLMalloc(nPolyTagNameBufLen));

        // Compose Polygon tag with or without srsName attribute.
        snprintf(pszPolyTagName, nPolyTagNameBufLen, "<gml:%s%s>", pszElemName,
                 szAttributes);

        AppendString(ppszText, pnLength, pnMaxLength, pszPolyTagName);

        // Free tag buffer.
        CPLFree(pszPolyTagName);

        const auto AppendCompoundCurveMembers =
            [&](const OGRGeometry *poRing, const char *pszGMLIdRing)
        {
            const auto eRingType = wkbFlatten(poRing->getGeometryType());
            if (eRingType == wkbCompoundCurve)
            {
                AppendString(ppszText, pnLength, pnMaxLength, "<gml:Ring>");
                const auto poCC = poRing->toCompoundCurve();
                const int nNumCurves = poCC->getNumCurves();
                for (int i = 0; i < nNumCurves; i++)
                {
                    AppendString(ppszText, pnLength, pnMaxLength,
                                 "<gml:curveMember>");

                    char *pszGMLIdSub = nullptr;
                    if (pszGMLIdRing != nullptr)
                        pszGMLIdSub =
                            CPLStrdup(CPLSPrintf("%s.%d", pszGMLIdRing, i));

                    CPL_IGNORE_RET_VAL(OGR2GML3GeometryAppend(
                        poCC->getCurve(i), poSRS, ppszText, pnLength,
                        pnMaxLength, true, eSRSNameFormat, bCoordSwap,
                        bLineStringAsCurve, pszGMLIdSub, nSRSDimensionLocFlags,
                        false, nullptr, nullptr));

                    CPLFree(pszGMLIdSub);

                    AppendString(ppszText, pnLength, pnMaxLength,
                                 "</gml:curveMember>");
                }
                AppendString(ppszText, pnLength, pnMaxLength, "</gml:Ring>");
            }
            else
            {
                if (eRingType != wkbLineString)
                {
                    AppendString(ppszText, pnLength, pnMaxLength,
                                 "<gml:Ring><gml:curveMember>");
                }

                CPL_IGNORE_RET_VAL(OGR2GML3GeometryAppend(
                    poRing, poSRS, ppszText, pnLength, pnMaxLength, true,
                    eSRSNameFormat, bCoordSwap, bLineStringAsCurve,
                    pszGMLIdRing, nSRSDimensionLocFlags, true, nullptr,
                    nullptr));

                if (eRingType != wkbLineString)
                {
                    AppendString(ppszText, pnLength, pnMaxLength,
                                 "</gml:curveMember></gml:Ring>");
                }
            }
        };

        // Don't add srsName to polygon rings.

        const auto poExteriorRing = poCP->getExteriorRingCurve();
        if (poExteriorRing != nullptr)
        {
            AppendString(ppszText, pnLength, pnMaxLength, "<gml:exterior>");

            AppendCompoundCurveMembers(
                poExteriorRing,
                pszGMLId ? (std::string(pszGMLId) + ".exterior").c_str()
                         : nullptr);

            AppendString(ppszText, pnLength, pnMaxLength, "</gml:exterior>");

            for (int iRing = 0; iRing < poCP->getNumInteriorRings(); iRing++)
            {
                const OGRCurve *poRing = poCP->getInteriorRingCurve(iRing);

                AppendString(ppszText, pnLength, pnMaxLength, "<gml:interior>");

                AppendCompoundCurveMembers(
                    poRing, pszGMLId ? (std::string(pszGMLId) + ".interior." +
                                        std::to_string(iRing))
                                           .c_str()
                                     : nullptr);

                AppendString(ppszText, pnLength, pnMaxLength,
                             "</gml:interior>");
            }
        }

        AppendString(ppszText, pnLength, pnMaxLength, "</gml:");
        AppendString(ppszText, pnLength, pnMaxLength, pszElemName);
        AppendString(ppszText, pnLength, pnMaxLength, ">");
    }

    /* -------------------------------------------------------------------- */
    /*     Triangle                                                         */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbTriangle)
    {
        const auto poTri = poGeometry->toPolygon();

        AppendString(ppszText, pnLength, pnMaxLength, "<gml:Triangle>");

        if (poTri->getExteriorRingCurve() != nullptr)
        {
            AppendString(ppszText, pnLength, pnMaxLength, "<gml:exterior>");

            CPL_IGNORE_RET_VAL(OGR2GML3GeometryAppend(
                poTri->getExteriorRingCurve(), poSRS, ppszText, pnLength,
                pnMaxLength, true, eSRSNameFormat, bCoordSwap,
                bLineStringAsCurve, nullptr, nSRSDimensionLocFlags, true,
                nullptr, nullptr));

            AppendString(ppszText, pnLength, pnMaxLength, "</gml:exterior>");
        }

        AppendString(ppszText, pnLength, pnMaxLength, "</gml:Triangle>");
    }

    /* -------------------------------------------------------------------- */
    /*      MultiSurface, MultiCurve, MultiPoint, MultiGeometry             */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbMultiPolygon || eFType == wkbMultiSurface ||
             eFType == wkbMultiLineString || eFType == wkbMultiCurve ||
             eFType == wkbMultiPoint || eFType == wkbGeometryCollection)
    {
        const auto poGC = poGeometry->toGeometryCollection();
        const char *pszElemClose = nullptr;
        const char *pszMemberElem = nullptr;

        // Buffer for opening tag + srsName attribute.
        char *pszElemOpen = nullptr;

        if (eFType == wkbMultiPolygon || eFType == wkbMultiSurface)
        {
            const size_t nBufLen = 13 + nAttrsLength + 1;
            pszElemOpen = static_cast<char *>(CPLMalloc(nBufLen));
            snprintf(pszElemOpen, nBufLen, "MultiSurface%s>", szAttributes);

            pszElemClose = "MultiSurface>";
            pszMemberElem = "surfaceMember>";
        }
        else if (eFType == wkbMultiLineString || eFType == wkbMultiCurve)
        {
            const size_t nBufLen = 16 + nAttrsLength + 1;
            pszElemOpen = static_cast<char *>(CPLMalloc(nBufLen));
            snprintf(pszElemOpen, nBufLen, "MultiCurve%s>", szAttributes);

            pszElemClose = "MultiCurve>";
            pszMemberElem = "curveMember>";
        }
        else if (eFType == wkbMultiPoint)
        {
            const size_t nBufLen = 11 + nAttrsLength + 1;
            pszElemOpen = static_cast<char *>(CPLMalloc(nBufLen));
            snprintf(pszElemOpen, nBufLen, "MultiPoint%s>", szAttributes);

            pszElemClose = "MultiPoint>";
            pszMemberElem = "pointMember>";
        }
        else
        {
            const size_t nBufLen = 19 + nAttrsLength + 1;
            pszElemOpen = static_cast<char *>(CPLMalloc(nBufLen));
            snprintf(pszElemOpen, nBufLen, "MultiGeometry%s>", szAttributes);

            pszElemClose = "MultiGeometry>";
            pszMemberElem = "geometryMember>";
        }

        AppendString(ppszText, pnLength, pnMaxLength, "<gml:");
        AppendString(ppszText, pnLength, pnMaxLength, pszElemOpen);

        // Free tag buffer.
        CPLFree(pszElemOpen);

        for (int iMember = 0; iMember < poGC->getNumGeometries(); iMember++)
        {
            const OGRGeometry *poMember = poGC->getGeometryRef(iMember);

            AppendString(ppszText, pnLength, pnMaxLength, "<gml:");
            AppendString(ppszText, pnLength, pnMaxLength, pszMemberElem);

            char *pszGMLIdSub = nullptr;
            if (pszGMLId != nullptr)
                pszGMLIdSub = CPLStrdup(CPLSPrintf("%s.%d", pszGMLId, iMember));

            if (!OGR2GML3GeometryAppend(
                    poMember, poSRS, ppszText, pnLength, pnMaxLength, true,
                    eSRSNameFormat, bCoordSwap, bLineStringAsCurve, pszGMLIdSub,
                    nSRSDimensionLocFlags, false, nullptr, nullptr))
            {
                CPLFree(pszGMLIdSub);
                return false;
            }

            CPLFree(pszGMLIdSub);

            AppendString(ppszText, pnLength, pnMaxLength, "</gml:");
            AppendString(ppszText, pnLength, pnMaxLength, pszMemberElem);
        }

        AppendString(ppszText, pnLength, pnMaxLength, "</gml:");
        AppendString(ppszText, pnLength, pnMaxLength, pszElemClose);
    }

    /* -------------------------------------------------------------------- */
    /*      Polyhedral Surface                                              */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbPolyhedralSurface)
    {
        // The patches enclosed in a single <gml:polygonPatches> tag need to be
        // co-planar.
        // TODO - enforce the condition within this implementation
        const auto poPS = poGeometry->toPolyhedralSurface();

        AppendString(ppszText, pnLength, pnMaxLength, "<gml:PolyhedralSurface");
        AppendString(ppszText, pnLength, pnMaxLength, szAttributes);
        AppendString(ppszText, pnLength, pnMaxLength, "><gml:polygonPatches>");

        for (int iMember = 0; iMember < poPS->getNumGeometries(); iMember++)
        {
            const OGRGeometry *poMember = poPS->getGeometryRef(iMember);
            char *pszGMLIdSub = nullptr;
            if (pszGMLId != nullptr)
                pszGMLIdSub = CPLStrdup(CPLSPrintf("%s.%d", pszGMLId, iMember));

            if (!OGR2GML3GeometryAppend(
                    poMember, poSRS, ppszText, pnLength, pnMaxLength, true,
                    eSRSNameFormat, bCoordSwap, bLineStringAsCurve, nullptr,
                    nSRSDimensionLocFlags, false, nullptr, "PolygonPatch"))
            {
                CPLFree(pszGMLIdSub);
                return false;
            }

            CPLFree(pszGMLIdSub);
        }

        AppendString(ppszText, pnLength, pnMaxLength, "</gml:polygonPatches>");
        AppendString(ppszText, pnLength, pnMaxLength,
                     "</gml:PolyhedralSurface>");
    }

    /* -------------------------------------------------------------------- */
    /*      TIN                                                             */
    /* -------------------------------------------------------------------- */
    else if (eFType == wkbTIN)
    {
        // OGR uses the following hierarchy for TriangulatedSurface -

        // <gml:TriangulatedSurface>
        //     <gml:patches>
        //         <gml:Triangle>
        //             <gml:exterior>
        //                 <gml:LinearRing>
        //                     <gml:posList srsDimension=...>...</gml:posList>
        //                 </gml:LinearRing>
        //             </gml:exterior>
        //         </gml:Triangle>
        //     </gml:patches>
        // </gml:TriangulatedSurface>

        // <gml:trianglePatches> is deprecated, so write feature is not enabled
        // for <gml:trianglePatches>
        const auto poTIN = poGeometry->toPolyhedralSurface();

        AppendString(ppszText, pnLength, pnMaxLength,
                     "<gml:TriangulatedSurface");
        AppendString(ppszText, pnLength, pnMaxLength, szAttributes);
        AppendString(ppszText, pnLength, pnMaxLength, "><gml:patches>");

        for (int iMember = 0; iMember < poTIN->getNumGeometries(); iMember++)
        {
            const OGRGeometry *poMember = poTIN->getGeometryRef(iMember);

            char *pszGMLIdSub = nullptr;
            if (pszGMLId != nullptr)
                pszGMLIdSub = CPLStrdup(CPLSPrintf("%s.%d", pszGMLId, iMember));

            CPL_IGNORE_RET_VAL(OGR2GML3GeometryAppend(
                poMember, poSRS, ppszText, pnLength, pnMaxLength, true,
                eSRSNameFormat, bCoordSwap, bLineStringAsCurve, nullptr,
                nSRSDimensionLocFlags, false, nullptr, nullptr));

            CPLFree(pszGMLIdSub);
        }

        AppendString(ppszText, pnLength, pnMaxLength, "</gml:patches>");
        AppendString(ppszText, pnLength, pnMaxLength,
                     "</gml:TriangulatedSurface>");
    }

    else
    {
        CPLError(CE_Failure, CPLE_NotSupported, "Unsupported geometry type %s",
                 OGRGeometryTypeToName(eType));
        return false;
    }

    return true;
}

/************************************************************************/
/*                       OGR_G_ExportToGMLTree()                        */
/************************************************************************/

/** Convert a geometry into GML format. */
CPLXMLNode *OGR_G_ExportToGMLTree(OGRGeometryH hGeometry)

{
    char *pszText = OGR_G_ExportToGML(hGeometry);
    if (pszText == nullptr)
        return nullptr;

    CPLXMLNode *psTree = CPLParseXMLString(pszText);

    CPLFree(pszText);

    return psTree;
}

/************************************************************************/
/*                         OGR_G_ExportToGML()                          */
/************************************************************************/

/**
 * \brief Convert a geometry into GML format.
 *
 * The GML geometry is expressed directly in terms of GML basic data
 * types assuming the this is available in the gml namespace.  The returned
 * string should be freed with CPLFree() when no longer required.
 *
 * This method is the same as the C++ method OGRGeometry::exportToGML().
 *
 * @param hGeometry handle to the geometry.
 * @return A GML fragment or NULL in case of error.
 */

char *OGR_G_ExportToGML(OGRGeometryH hGeometry)

{
    return OGR_G_ExportToGMLEx(hGeometry, nullptr);
}

/************************************************************************/
/*                        OGR_G_ExportToGMLEx()                         */
/************************************************************************/

/**
 * \brief Convert a geometry into GML format.
 *
 * The GML geometry is expressed directly in terms of GML basic data
 * types assuming the this is available in the gml namespace.  The returned
 * string should be freed with CPLFree() when no longer required.
 *
 * The supported options are :
 * <ul>
 * <li> FORMAT=GML2/GML3/GML32 (GML2 or GML32 added in GDAL 2.1).
 *      If not set, it will default to GML 2.1.2 output.
 * <li> GML3_LINESTRING_ELEMENT=curve. (Only valid for FORMAT=GML3)
 *      To use gml:Curve element for linestrings.
 *      Otherwise gml:LineString will be used .
 * <li> GML3_LONGSRS=YES/NO. (Only valid for FORMAT=GML3, deprecated by
 *      SRSNAME_FORMAT in GDAL &gt;=2.2). Defaults to YES.
 *      If YES, SRS with EPSG authority will be written with the
 *      "urn:ogc:def:crs:EPSG::" prefix.
 *      In the case the SRS should be treated as lat/long or
 *      northing/easting, then the function will take care of coordinate order
 *      swapping if the data axis to CRS axis mapping indicates it.
 *      If set to NO, SRS with EPSG authority will be written with the "EPSG:"
 *      prefix, even if they are in lat/long order.
 * <li> SRSNAME_FORMAT=SHORT/OGC_URN/OGC_URL (Only valid for FORMAT=GML3, added
 *      in GDAL 2.2). Defaults to OGC_URN.  If SHORT, then srsName will be in
 *      the form AUTHORITY_NAME:AUTHORITY_CODE. If OGC_URN, then srsName will be
 *      in the form urn:ogc:def:crs:AUTHORITY_NAME::AUTHORITY_CODE. If OGC_URL,
 *      then srsName will be in the form
 *      http://www.opengis.net/def/crs/AUTHORITY_NAME/0/AUTHORITY_CODE. For
 *      OGC_URN and OGC_URL, in the case the SRS should be treated as lat/long
 or
 *      northing/easting, then the function will take care of coordinate order
 *      swapping if the data axis to CRS axis mapping indicates it.
 * <li> GMLID=astring. If specified, a gml:id attribute will be written in the
 *      top-level geometry element with the provided value.
 *      Required for GML 3.2 compatibility.
 * <li> SRSDIMENSION_LOC=POSLIST/GEOMETRY/GEOMETRY,POSLIST. (Only valid for
 *      FORMAT=GML3/GML32, GDAL >= 2.0) Default to POSLIST.
 *      For 2.5D geometries, define the location where to attach the
 *      srsDimension attribute.
 *      There are diverging implementations. Some put in on the
 *      &lt;gml:posList&gt; element, other on the top geometry element.

 * <li> NAMESPACE_DECL=YES/NO. If set to YES,
 *      xmlns:gml="http://www.opengis.net/gml" will be added to the root node
 *      for GML < 3.2 or xmlns:gml="http://www.opengis.net/gml/3.2" for GML 3.2
 * </ul>
 *
 * Note that curve geometries like CIRCULARSTRING, COMPOUNDCURVE, CURVEPOLYGON,
 * MULTICURVE or MULTISURFACE are not supported in GML 2.
 *
 * This method is the same as the C++ method OGRGeometry::exportToGML().
 *
 * @param hGeometry handle to the geometry.
 * @param papszOptions NULL-terminated list of options.
 * @return A GML fragment or NULL in case of error.
 *
 * @since OGR 1.8.0
 */

char *OGR_G_ExportToGMLEx(OGRGeometryH hGeometry, char **papszOptions)

{
    if (hGeometry == nullptr)
        return CPLStrdup("");

    // Do not use hGeometry after here.
    OGRGeometry *poGeometry = OGRGeometry::FromHandle(hGeometry);

    size_t nLength = 0;
    size_t nMaxLength = 1;

    char *pszText = static_cast<char *>(CPLMalloc(nMaxLength));
    pszText[0] = '\0';

    const char *pszFormat = CSLFetchNameValue(papszOptions, "FORMAT");
    const bool bNamespaceDecl =
        CPLTestBool(CSLFetchNameValueDef(papszOptions, "NAMESPACE_DECL",
                                         "NO")) != FALSE;
    if (pszFormat && (EQUAL(pszFormat, "GML3") || EQUAL(pszFormat, "GML32")))
    {
        const char *pszLineStringElement =
            CSLFetchNameValue(papszOptions, "GML3_LINESTRING_ELEMENT");
        const bool bLineStringAsCurve =
            pszLineStringElement && EQUAL(pszLineStringElement, "curve");
        const char *pszLongSRS =
            CSLFetchNameValue(papszOptions, "GML3_LONGSRS");
        const char *pszSRSNameFormat =
            CSLFetchNameValue(papszOptions, "SRSNAME_FORMAT");
        GMLSRSNameFormat eSRSNameFormat = SRSNAME_OGC_URN;
        if (pszSRSNameFormat)
        {
            if (pszLongSRS)
            {
                CPLError(CE_Warning, CPLE_NotSupported,
                         "Both GML3_LONGSRS and SRSNAME_FORMAT specified. "
                         "Ignoring GML3_LONGSRS");
            }
            if (EQUAL(pszSRSNameFormat, "SHORT"))
                eSRSNameFormat = SRSNAME_SHORT;
            else if (EQUAL(pszSRSNameFormat, "OGC_URN"))
                eSRSNameFormat = SRSNAME_OGC_URN;
            else if (EQUAL(pszSRSNameFormat, "OGC_URL"))
                eSRSNameFormat = SRSNAME_OGC_URL;
            else
            {
                CPLError(CE_Warning, CPLE_NotSupported,
                         "Invalid value for SRSNAME_FORMAT. "
                         "Using SRSNAME_OGC_URN");
            }
        }
        else if (pszLongSRS && !CPLTestBool(pszLongSRS))
            eSRSNameFormat = SRSNAME_SHORT;

        const char *pszGMLId = CSLFetchNameValue(papszOptions, "GMLID");
        if (pszGMLId == nullptr && EQUAL(pszFormat, "GML32"))
            CPLError(CE_Warning, CPLE_AppDefined,
                     "FORMAT=GML32 specified but not GMLID set");
        const char *pszSRSDimensionLoc =
            CSLFetchNameValueDef(papszOptions, "SRSDIMENSION_LOC", "POSLIST");
        char **papszSRSDimensionLoc =
            CSLTokenizeString2(pszSRSDimensionLoc, ",", 0);
        int nSRSDimensionLocFlags = 0;
        for (int i = 0; papszSRSDimensionLoc[i] != nullptr; i++)
        {
            if (EQUAL(papszSRSDimensionLoc[i], "POSLIST"))
                nSRSDimensionLocFlags |= SRSDIM_LOC_POSLIST;
            else if (EQUAL(papszSRSDimensionLoc[i], "GEOMETRY"))
                nSRSDimensionLocFlags |= SRSDIM_LOC_GEOMETRY;
            else
                CPLDebug("OGR", "Unrecognized location for srsDimension : %s",
                         papszSRSDimensionLoc[i]);
        }
        CSLDestroy(papszSRSDimensionLoc);
        const char *pszNamespaceDecl = nullptr;
        if (bNamespaceDecl && EQUAL(pszFormat, "GML32"))
            pszNamespaceDecl = "http://www.opengis.net/gml/3.2";
        else if (bNamespaceDecl)
            pszNamespaceDecl = "http://www.opengis.net/gml";

        bool bCoordSwap = false;
        const char *pszCoordSwap =
            CSLFetchNameValue(papszOptions, "COORD_SWAP");
        if (pszCoordSwap)
        {
            bCoordSwap = CPLTestBool(pszCoordSwap);
        }
        else
        {
            const OGRSpatialReference *poSRS =
                poGeometry->getSpatialReference();
            if (poSRS != nullptr && eSRSNameFormat != SRSNAME_SHORT)
            {
                const auto &map = poSRS->GetDataAxisToSRSAxisMapping();
                if (map.size() >= 2 && map[0] == 2 && map[1] == 1)
                {
                    bCoordSwap = true;
                }
            }
        }

        if (!OGR2GML3GeometryAppend(
                poGeometry, nullptr, &pszText, &nLength, &nMaxLength, false,
                eSRSNameFormat, bCoordSwap, bLineStringAsCurve, pszGMLId,
                nSRSDimensionLocFlags, false, pszNamespaceDecl, nullptr))
        {
            CPLFree(pszText);
            return nullptr;
        }

        return pszText;
    }

    const char *pszNamespaceDecl = nullptr;
    if (bNamespaceDecl)
        pszNamespaceDecl = "http://www.opengis.net/gml";
    if (!OGR2GMLGeometryAppend(poGeometry, &pszText, &nLength, &nMaxLength,
                               false, pszNamespaceDecl))
    {
        CPLFree(pszText);
        return nullptr;
    }

    return pszText;
}
