/******************************************************************************
 * Project:  OGR
 * Purpose:  OGRGMLASDriver implementation
 * Author:   Even Rouault, <even dot rouault at spatialys dot com>
 *
 * Initial development funded by the European Earth observation programme
 * Copernicus
 *
 ******************************************************************************
 * Copyright (c) 2016, Even Rouault, <even dot rouault at spatialys dot 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.
 ****************************************************************************/

// Must be first for DEBUG_BOOL case
#include "ogr_gmlas.h"

#define CONSTANT_DEFINITION
#undef OGR_GMLAS_CONSTS_INCLUDED_REDEFINABLE
#include "ogr_gmlas_consts.h"

#include "cpl_minixml.h"

#include <algorithm>

CPL_CVSID("$Id: ogrgmlasconf.cpp 7e07230bbff24eb333608de4dbd460b7312839d0 2017-12-11 19:08:47Z Even Rouault $")

/************************************************************************/
/*                          GMLASConfiguration()                        */
/************************************************************************/

GMLASConfiguration::GMLASConfiguration()
    : m_bAllowRemoteSchemaDownload(ALLOW_REMOTE_SCHEMA_DOWNLOAD_DEFAULT)
    , m_bAlwaysGenerateOGRId(ALWAYS_GENERATE_OGR_ID_DEFAULT)
    , m_bRemoveUnusedLayers(REMOVE_UNUSED_LAYERS_DEFAULT)
    , m_bRemoveUnusedFields(REMOVE_UNUSED_FIELDS_DEFAULT)
    , m_bUseArrays(USE_ARRAYS_DEFAULT)
    , m_bUseNullState(USE_NULL_STATE_DEFAULT)
    , m_bIncludeGeometryXML(INCLUDE_GEOMETRY_XML_DEFAULT)
    , m_bInstantiateGMLFeaturesOnly(INSTANTIATE_GML_FEATURES_ONLY_DEFAULT)
    , m_nIdentifierMaxLength(0)
    , m_bCaseInsensitiveIdentifier(CASE_INSENSITIVE_IDENTIFIER_DEFAULT)
    , m_bPGIdentifierLaundering(PG_IDENTIFIER_LAUNDERING_DEFAULT)
    , m_nMaximumFieldsForFlattening(MAXIMUM_FIELDS_FLATTENING_DEFAULT)
    , m_bAllowXSDCache(ALLOW_XSD_CACHE_DEFAULT)
    , m_bSchemaFullChecking(SCHEMA_FULL_CHECKING_DEFAULT)
    , m_bHandleMultipleImports(HANDLE_MULTIPLE_IMPORTS_DEFAULT)
    , m_bValidate(VALIDATE_DEFAULT)
    , m_bFailIfValidationError(FAIL_IF_VALIDATION_ERROR_DEFAULT)
    , m_bExposeMetadataLayers(WARN_IF_EXCLUDED_XPATH_FOUND_DEFAULT)
    , m_eSWEActivationMode(SWE_ACTIVATE_IF_NAMESPACE_FOUND)
    , m_bSWEProcessDataRecord(SWE_PROCESS_DATA_RECORD_DEFAULT)
    , m_bSWEProcessDataArray(SWE_PROCESS_DATA_ARRAY_DEFAULT)
    , m_nIndentSize(INDENT_SIZE_DEFAULT)
    , m_osSRSNameFormat(szSRSNAME_DEFAULT)
    , m_osWrapping(szWFS2_FEATURECOLLECTION)
    , m_osWFS20SchemaLocation(szWFS20_SCHEMALOCATION)
{
}

/************************************************************************/
/*                         ~GMLASConfiguration()                        */
/************************************************************************/

GMLASConfiguration::~GMLASConfiguration()
{
}

/************************************************************************/
/*                        GetBaseCacheDirectory()                       */
/************************************************************************/

CPLString GMLASConfiguration::GetBaseCacheDirectory()
{
#ifdef WIN32
    const char* pszHome = CPLGetConfigOption("USERPROFILE", nullptr);
#else
    const char* pszHome = CPLGetConfigOption("HOME", nullptr);
#endif
    if( pszHome != nullptr )
    {
        return CPLFormFilename( pszHome, ".gdal", nullptr) ;
    }
    else
    {
        const char *pszDir = CPLGetConfigOption( "CPL_TMPDIR", nullptr );

        if( pszDir == nullptr )
            pszDir = CPLGetConfigOption( "TMPDIR", nullptr );

        if( pszDir == nullptr )
            pszDir = CPLGetConfigOption( "TEMP", nullptr );

        const char* pszUsername = CPLGetConfigOption("USERNAME", nullptr);
        if( pszUsername == nullptr )
            pszUsername = CPLGetConfigOption("USER", nullptr);

        if( pszDir != nullptr && pszUsername != nullptr )
        {
            return CPLFormFilename( pszDir,
                    CPLSPrintf(".gdal_%s", pszUsername), nullptr) ;
        }
    }
    return CPLString();
}

/************************************************************************/
/*                              Finalize()                              */
/************************************************************************/

void GMLASConfiguration::Finalize()
{
    if( m_bAllowXSDCache && m_osXSDCacheDirectory.empty() )
    {
        m_osXSDCacheDirectory = GetBaseCacheDirectory();
        if( m_osXSDCacheDirectory.empty() )
        {
            CPLError(CE_Warning, CPLE_AppDefined,
                    "Could not determine a directory for GMLAS XSD cache");
        }
        else
        {
            m_osXSDCacheDirectory = CPLFormFilename( m_osXSDCacheDirectory,
                                                  "gmlas_xsd_cache", nullptr) ;
            CPLDebug("GMLAS", "XSD cache directory: %s",
                     m_osXSDCacheDirectory.c_str());
        }
    }
}

/************************************************************************/
/*                          CPLGetXMLBoolValue()                        */
/************************************************************************/

static bool CPLGetXMLBoolValue(CPLXMLNode* psNode,
                               const char* pszKey,
                               bool bDefault)
{
    const char* pszVal = CPLGetXMLValue(psNode, pszKey, nullptr);
    if( pszVal )
        return CPLTestBool(pszVal);
    else
        return bDefault;
}

/************************************************************************/
/*                            IsValidXPath()                            */
/************************************************************************/

static bool IsValidXPath(const CPLString& osXPath )
{
    // Check that the XPath syntax belongs to the subset we
    // understand
    bool bOK = !osXPath.empty();
    for(size_t i = 0; i < osXPath.size(); ++i )
    {
        const char chCur = osXPath[i];
        if( chCur == '/' )
        {
            // OK
        }
        else if( chCur == '@' &&
                 (i == 0 || osXPath[i-1] == '/') &&
                 i < osXPath.size()-1 &&
                 isalpha( static_cast<int>(osXPath[i+1]) ) )
        {
            // OK
        }
        else if( chCur == '_' ||
                    isalpha( static_cast<int>(chCur) ) )
        {
            // OK
        }
        else if( isdigit( static_cast<int>(chCur) ) &&
                    i > 0 &&
                    (isalnum( static_cast<int>(osXPath[i-1]) ) ||
                    osXPath[i-1] == '_') )
        {
            // OK
        }
        else if( chCur == ':' &&
                 i > 0 &&
                 (isalnum( static_cast<int>(osXPath[i-1]) ) ||
                  osXPath[i-1] == '_') &&
                 i < osXPath.size()-1 &&
                 isalpha( static_cast<int>(osXPath[i+1]) ) )
        {
            // OK
        }
        else
        {
            bOK = false;
            break;
        }
    }
    return bOK;
}

/************************************************************************/
/*                    GMLASConfigurationErrorHandler()                  */
/************************************************************************/

static void CPL_STDCALL GMLASConfigurationErrorHandler(CPLErr /*eErr*/,
                                                       CPLErrorNum /*nType*/,
                                                       const char* pszMsg)
{
    std::vector<CPLString>* paosErrors =
            (std::vector<CPLString>* )CPLGetErrorHandlerUserData();
    paosErrors->push_back(pszMsg);
}

/************************************************************************/
/*                           ParseNamespaces()                          */
/************************************************************************/

static void ParseNamespaces(CPLXMLNode* psContainerNode,
                            std::map<CPLString, CPLString>& oMap)
{
    CPLXMLNode* psNamespaces = CPLGetXMLNode(psContainerNode, "Namespaces");
    if( psNamespaces != nullptr )
    {
        for( CPLXMLNode* psIter = psNamespaces->psChild;
                            psIter != nullptr;
                            psIter = psIter->psNext )
        {
            if( psIter->eType == CXT_Element &&
                EQUAL(psIter->pszValue, "Namespace") )
            {
                CPLString osPrefix = CPLGetXMLValue(psIter, "prefix", "");
                CPLString osURI = CPLGetXMLValue(psIter, "uri", "");
                if( !osPrefix.empty() && !osURI.empty() )
                {
                    if( oMap.find(osPrefix) ==
                        oMap.end() )
                    {
                        oMap[osPrefix] = osURI;
                    }
                    else
                    {
                        CPLError(CE_Warning, CPLE_AppDefined,
                                    "Prefix %s was already mapped to %s. "
                                    "Attempt to map it to %s ignored",
                                    osPrefix.c_str(),
                                    oMap[osPrefix].
                                                                    c_str(),
                                    osURI.c_str());
                    }
                }
            }
        }
    }
}

/************************************************************************/
/*                                 Load()                               */
/************************************************************************/

bool GMLASConfiguration::Load(const char* pszFilename)
{
    // Allow configuration to be inlined
    CPLXMLNode* psRoot = STARTS_WITH(pszFilename, "<Configuration") ?
                                CPLParseXMLString(pszFilename) :
                                CPLParseXMLFile(pszFilename);
    if( psRoot == nullptr )
    {
        Finalize();
        return false;
    }
    CPLXMLTreeCloser oCloser(psRoot);

    // Validate the configuration file
    if( CPLTestBool(CPLGetConfigOption("GDAL_XML_VALIDATION", "YES")) )
    {
        const char* pszXSD = CPLFindFile( "gdal", "gmlasconf.xsd" );
        if( pszXSD != nullptr )
        {
            std::vector<CPLString> aosErrors;
            const CPLErr eErrClass = CPLGetLastErrorType();
            const CPLErrorNum nErrNum = CPLGetLastErrorNo();
            const CPLString osErrMsg = CPLGetLastErrorMsg();
            CPLPushErrorHandlerEx(GMLASConfigurationErrorHandler, &aosErrors);
            int bRet = CPLValidateXML(pszFilename, pszXSD, nullptr);
            CPLPopErrorHandler();
            if( !bRet && !aosErrors.empty() &&
                strstr(aosErrors[0].c_str(), "missing libxml2 support") == nullptr )
            {
                for(size_t i = 0; i < aosErrors.size(); i++)
                {
                    CPLError(CE_Warning, CPLE_AppDefined,
                             "%s", aosErrors[i].c_str());
                }
            }
            else
            {
                CPLErrorSetState(eErrClass, nErrNum, osErrMsg);
            }
        }
    }

    m_bAllowRemoteSchemaDownload = CPLGetXMLBoolValue(psRoot,
                                "=Configuration.AllowRemoteSchemaDownload",
                                ALLOW_REMOTE_SCHEMA_DOWNLOAD_DEFAULT );

    m_bAllowXSDCache = CPLGetXMLBoolValue( psRoot,
                                           "=Configuration.SchemaCache.enabled",
                                           ALLOW_XSD_CACHE_DEFAULT );
    if( m_bAllowXSDCache )
    {
        m_osXSDCacheDirectory =
            CPLGetXMLValue(psRoot, "=Configuration.SchemaCache.Directory",
                           "");
    }

    m_bSchemaFullChecking = CPLGetXMLBoolValue( psRoot,
                    "=Configuration.SchemaAnalysisOptions.SchemaFullChecking",
                    SCHEMA_FULL_CHECKING_DEFAULT);

    m_bHandleMultipleImports = CPLGetXMLBoolValue( psRoot,
                    "=Configuration.SchemaAnalysisOptions.HandleMultipleImports",
                    HANDLE_MULTIPLE_IMPORTS_DEFAULT);

    m_bValidate = CPLGetXMLBoolValue( psRoot,
                                      "=Configuration.Validation.enabled",
                                      VALIDATE_DEFAULT );

    if( m_bValidate )
    {
        m_bFailIfValidationError = CPLGetXMLBoolValue(psRoot,
                                        "=Configuration.Validation.FailIfError",
                                        FAIL_IF_VALIDATION_ERROR_DEFAULT );
    }

    m_bExposeMetadataLayers = CPLGetXMLBoolValue( psRoot,
                                      "=Configuration.ExposeMetadataLayers",
                                      EXPOSE_METADATA_LAYERS_DEFAULT );

    m_bAlwaysGenerateOGRId = CPLGetXMLBoolValue( psRoot,
                                "=Configuration.LayerBuildingRules.AlwaysGenerateOGRId",
                                ALWAYS_GENERATE_OGR_ID_DEFAULT );

    m_bRemoveUnusedLayers = CPLGetXMLBoolValue( psRoot,
                                "=Configuration.LayerBuildingRules.RemoveUnusedLayers",
                                REMOVE_UNUSED_LAYERS_DEFAULT );

    m_bRemoveUnusedFields = CPLGetXMLBoolValue( psRoot,
                                "=Configuration.LayerBuildingRules.RemoveUnusedFields",
                                REMOVE_UNUSED_FIELDS_DEFAULT );

    m_bUseArrays = CPLGetXMLBoolValue( psRoot,
                                "=Configuration.LayerBuildingRules.UseArrays",
                                USE_ARRAYS_DEFAULT );
    m_bUseNullState = CPLGetXMLBoolValue( psRoot,
                                "=Configuration.LayerBuildingRules.UseNullState",
                                USE_NULL_STATE_DEFAULT );
    m_bIncludeGeometryXML = CPLGetXMLBoolValue( psRoot,
                       "=Configuration.LayerBuildingRules.GML.IncludeGeometryXML",
                       INCLUDE_GEOMETRY_XML_DEFAULT );
    m_bInstantiateGMLFeaturesOnly = CPLGetXMLBoolValue( psRoot,
                "=Configuration.LayerBuildingRules.GML.InstantiateGMLFeaturesOnly",
                INSTANTIATE_GML_FEATURES_ONLY_DEFAULT );
    m_nIdentifierMaxLength = atoi( CPLGetXMLValue( psRoot,
                "=Configuration.LayerBuildingRules.IdentifierMaxLength",
                "0" ) );
    m_bCaseInsensitiveIdentifier = CPLGetXMLBoolValue( psRoot,
                "=Configuration.LayerBuildingRules.CaseInsensitiveIdentifier",
                CASE_INSENSITIVE_IDENTIFIER_DEFAULT );
    m_bPGIdentifierLaundering = CPLGetXMLBoolValue( psRoot,
                "=Configuration.LayerBuildingRules.PostgreSQLIdentifierLaundering",
                PG_IDENTIFIER_LAUNDERING_DEFAULT );

    CPLXMLNode* psFlatteningRules = CPLGetXMLNode(psRoot,
                        "=Configuration.LayerBuildingRules.FlatteningRules");
    if( psFlatteningRules )
    {
        m_nMaximumFieldsForFlattening = atoi( CPLGetXMLValue( psFlatteningRules,
                "MaximumNumberOfFields",
                CPLSPrintf("%d", MAXIMUM_FIELDS_FLATTENING_DEFAULT) ) );

        ParseNamespaces(psFlatteningRules, m_oMapPrefixToURIFlatteningRules);

        for( CPLXMLNode* psIter = psFlatteningRules->psChild;
                         psIter != nullptr;
                         psIter = psIter->psNext )
        {
            if( psIter->eType == CXT_Element &&
                EQUAL(psIter->pszValue, "ForceFlatteningXPath") )
            {
                m_osForcedFlattenedXPath.push_back(
                    CPLGetXMLValue(psIter, "", "") );
            }
            else if( psIter->eType == CXT_Element &&
                     EQUAL(psIter->pszValue, "DisableFlatteningXPath") )
            {
                m_osDisabledFlattenedXPath.push_back(
                    CPLGetXMLValue(psIter, "", "") );
            }
        }
    }

    const char* pszSWEProcessingActivation = CPLGetXMLValue( psRoot,
        "=Configuration.LayerBuildingRules.SWEProcessing.Activation",
        "ifSWENamespaceFoundInTopElement" );
    if( EQUAL(pszSWEProcessingActivation, "ifSWENamespaceFoundInTopElement") )
        m_eSWEActivationMode = SWE_ACTIVATE_IF_NAMESPACE_FOUND;
    else if( CPLTestBool(pszSWEProcessingActivation) )
        m_eSWEActivationMode = SWE_ACTIVATE_TRUE;
    else
        m_eSWEActivationMode = SWE_ACTIVATE_FALSE;
    m_bSWEProcessDataRecord = CPLTestBool(CPLGetXMLValue( psRoot,
        "=Configuration.LayerBuildingRules.SWEProcessing.ProcessDataRecord",
        "true" ));
    m_bSWEProcessDataArray = CPLTestBool(CPLGetXMLValue( psRoot,
        "=Configuration.LayerBuildingRules.SWEProcessing.ProcessDataArray",
        "true" ));

    CPLXMLNode* psTypingConstraints = CPLGetXMLNode(psRoot,
                                            "=Configuration.TypingConstraints");
    if( psTypingConstraints )
    {
        ParseNamespaces(psTypingConstraints, m_oMapPrefixToURITypeConstraints);

        for( CPLXMLNode* psIter = psTypingConstraints->psChild;
                         psIter != nullptr;
                         psIter = psIter->psNext )
        {
            if( psIter->eType == CXT_Element &&
                EQUAL(psIter->pszValue, "ChildConstraint") )
            {
                const CPLString& osXPath( CPLGetXMLValue(psIter, "ContainerXPath", "") );
                CPLXMLNode* psChildrenTypes = CPLGetXMLNode(psIter, "ChildrenElements");
                if( IsValidXPath(osXPath) )
                {
                    for( CPLXMLNode* psIter2 =
                            psChildrenTypes ? psChildrenTypes->psChild : nullptr;
                                     psIter2 != nullptr;
                                     psIter2 = psIter2->psNext )
                    {
                        if( psIter2->eType == CXT_Element &&
                            EQUAL(psIter2->pszValue, "Element") )
                        {
                            m_oMapChildrenElementsConstraints[osXPath].push_back(
                                CPLGetXMLValue(psIter2, "", "") );
                        }
                    }
                }
                else
                {
                    CPLError(CE_Warning, CPLE_AppDefined,
                             "XPath syntax %s not supported",
                             osXPath.c_str());
                }
            }
        }
    }

    CPLXMLNode* psIgnoredXPaths = CPLGetXMLNode(psRoot,
                                            "=Configuration.IgnoredXPaths");
    if( psIgnoredXPaths )
    {
        const bool bGlobalWarnIfIgnoredXPathFound = CPLGetXMLBoolValue(
                       psIgnoredXPaths,
                       "WarnIfIgnoredXPathFoundInDocInstance",
                       WARN_IF_EXCLUDED_XPATH_FOUND_DEFAULT );

        ParseNamespaces(psIgnoredXPaths, m_oMapPrefixToURIIgnoredXPaths);

        for( CPLXMLNode* psIter = psIgnoredXPaths->psChild;
                         psIter != nullptr;
                         psIter = psIter->psNext )
        {
            if( psIter->eType == CXT_Element &&
                EQUAL(psIter->pszValue, "XPath") )
            {
                const CPLString& osXPath( CPLGetXMLValue(psIter, "", "") );
                if( IsValidXPath(osXPath) )
                {
                    m_aosIgnoredXPaths.push_back( osXPath );

                    const bool bWarnIfIgnoredXPathFound = CPLGetXMLBoolValue(
                                psIter,
                                "warnIfIgnoredXPathFoundInDocInstance",
                                bGlobalWarnIfIgnoredXPathFound );
                    m_oMapIgnoredXPathToWarn[ osXPath ] = bWarnIfIgnoredXPathFound;
                }
                else
                {
                    CPLError(CE_Warning, CPLE_AppDefined,
                             "XPath syntax %s not supported",
                             osXPath.c_str());
                }
            }
        }
    }

    CPLXMLNode* psXLinkResolutionNode = CPLGetXMLNode( psRoot,
                                            "=Configuration.XLinkResolution");
    if( psXLinkResolutionNode != nullptr )
        m_oXLinkResolution.LoadFromXML( psXLinkResolutionNode );

    // Parse WriterConfig
    CPLXMLNode* psWriterConfig = CPLGetXMLNode( psRoot,
                                                "=Configuration.WriterConfig");
    if( psWriterConfig != nullptr )
    {
        m_nIndentSize = atoi( CPLGetXMLValue( psWriterConfig,
                                    "IndentationSize",
                                    CPLSPrintf("%d", INDENT_SIZE_DEFAULT ) ) );
        m_nIndentSize = std::min( INDENT_SIZE_MAX,
                                  std::max( INDENT_SIZE_MIN, m_nIndentSize ) );

        m_osComment = CPLGetXMLValue( psWriterConfig, "Comment", "" );

        m_osLineFormat = CPLGetXMLValue( psWriterConfig, "LineFormat", "" );

        m_osSRSNameFormat = CPLGetXMLValue( psWriterConfig, "SRSNameFormat", "" );

        m_osWrapping = CPLGetXMLValue( psWriterConfig, "Wrapping",
                                       szWFS2_FEATURECOLLECTION );

        m_osTimestamp = CPLGetXMLValue( psWriterConfig, "Timestamp", "" );

        m_osWFS20SchemaLocation = CPLGetXMLValue( psWriterConfig,
                                                  "WFS20SchemaLocation",
                                                  szWFS20_SCHEMALOCATION );
    }

    Finalize();

    return true;
}

/************************************************************************/
/*                         GMLASXLinkResolutionConf()                   */
/************************************************************************/

GMLASXLinkResolutionConf::GMLASXLinkResolutionConf() :
    m_nTimeOut(0),
    m_nMaxFileSize(MAX_FILE_SIZE_DEFAULT),
    m_nMaxGlobalResolutionTime(0),
    m_bDefaultResolutionEnabled(DEFAULT_RESOLUTION_ENABLED_DEFAULT),
    m_bDefaultAllowRemoteDownload(ALLOW_REMOTE_DOWNLOAD_DEFAULT),
    m_eDefaultResolutionMode(RawContent),
    m_nDefaultResolutionDepth(1),
    m_bDefaultCacheResults(CACHE_RESULTS_DEFAULT),
    m_bResolveInternalXLinks(INTERNAL_XLINK_RESOLUTION_DEFAULT)
{
}

/************************************************************************/
/*                               LoadFromXML()                          */
/************************************************************************/

bool GMLASXLinkResolutionConf::LoadFromXML(CPLXMLNode* psRoot)
{
    m_nTimeOut = atoi( CPLGetXMLValue( psRoot, "Timeout", "0" ) );

    m_nMaxFileSize = atoi( CPLGetXMLValue( psRoot, "MaxFileSize",
                                CPLSPrintf("%d", MAX_FILE_SIZE_DEFAULT)) );

    m_nMaxGlobalResolutionTime = atoi(
                CPLGetXMLValue( psRoot, "MaxGlobalResolutionTime", "0" ) );

    m_osProxyServerPort = CPLGetXMLValue( psRoot, "ProxyServerPort", "" );
    m_osProxyUserPassword = CPLGetXMLValue( psRoot, "ProxyUserPassword", "" );
    m_osProxyAuth = CPLGetXMLValue( psRoot, "ProxyAuth", "" );

    m_osCacheDirectory = CPLGetXMLValue( psRoot, "CacheDirectory", "" );
    if( m_osCacheDirectory.empty() )
    {
        m_osCacheDirectory = GMLASConfiguration::GetBaseCacheDirectory();
        if( !m_osCacheDirectory.empty() )
        {
            m_osCacheDirectory = CPLFormFilename( m_osCacheDirectory,
                                                  "xlink_resolved_cache",
                                                  nullptr );
        }
    }

    m_bDefaultResolutionEnabled = CPLGetXMLBoolValue( psRoot,
                                        "DefaultResolution.enabled",
                                        DEFAULT_RESOLUTION_ENABLED_DEFAULT);

    m_bDefaultAllowRemoteDownload = CPLGetXMLBoolValue( psRoot,
                                "DefaultResolution.AllowRemoteDownload",
                                ALLOW_REMOTE_DOWNLOAD_DEFAULT);

    // TODO when we support other modes
    // m_eDefaultResolutionMode =

    m_nDefaultResolutionDepth = atoi( CPLGetXMLValue( psRoot,
                                "DefaultResolution.ResolutionDepth", "1") );

    m_bDefaultCacheResults = CPLGetXMLBoolValue( psRoot,
                                    "DefaultResolution.CacheResults",
                                    CACHE_RESULTS_DEFAULT);

    CPLXMLNode* psIterURL = psRoot->psChild;
    for( ; psIterURL != nullptr; psIterURL = psIterURL->psNext )
    {
        if( psIterURL->eType == CXT_Element &&
            strcmp(psIterURL->pszValue, "URLSpecificResolution") == 0 )
        {
            GMLASXLinkResolutionConf::URLSpecificResolution oItem;
            oItem.m_osURLPrefix = CPLGetXMLValue(psIterURL, "URLPrefix", "");

            oItem.m_bAllowRemoteDownload = CPLGetXMLBoolValue( psIterURL,
                                                "AllowRemoteDownload",
                                                ALLOW_REMOTE_DOWNLOAD_DEFAULT);

            const char* pszResolutionModel = CPLGetXMLValue(psIterURL,
                                                "ResolutionMode", "RawContent");
            if( EQUAL(pszResolutionModel, "RawContent") )
                oItem.m_eResolutionMode = RawContent;
            else
                oItem.m_eResolutionMode = FieldsFromXPath;

            oItem.m_nResolutionDepth = atoi( CPLGetXMLValue( psIterURL,
                                        "ResolutionDepth", "1") );

            oItem.m_bCacheResults = CPLGetXMLBoolValue( psIterURL,
                                                        "CacheResults",
                                                        CACHE_RESULTS_DEFAULT);

            CPLXMLNode* psIter = psIterURL->psChild;
            for( ; psIter != nullptr; psIter = psIter->psNext )
            {
                if( psIter->eType == CXT_Element &&
                    strcmp(psIter->pszValue, "HTTPHeader") == 0 )
                {
                    CPLString osName( CPLGetXMLValue(psIter, "Name", "") );
                    CPLString osValue( CPLGetXMLValue(psIter, "Value", "") );
                    oItem.m_aosNameValueHTTPHeaders.push_back(
                            std::pair<CPLString, CPLString>(osName, osValue));
                }
                else if( psIter->eType == CXT_Element &&
                         strcmp(psIter->pszValue, "Field") == 0 )
                {
                    URLSpecificResolution::XPathDerivedField oField;
                    oField.m_osName = CPLGetXMLValue(psIter, "Name", "");
                    oField.m_osType = CPLGetXMLValue(psIter, "Type", "");
                    oField.m_osXPath = CPLGetXMLValue(psIter, "XPath", "");
                    oItem.m_aoFields.push_back( oField );
                }
            }

            m_aoURLSpecificRules.push_back( oItem );
        }
    }

    m_bResolveInternalXLinks = CPLGetXMLBoolValue( psRoot,
                                    "ResolveInternalXLinks",
                                    INTERNAL_XLINK_RESOLUTION_DEFAULT);

    return true;
}

/************************************************************************/
/*                          URLSpecificResolution()                     */
/************************************************************************/

GMLASXLinkResolutionConf::URLSpecificResolution::URLSpecificResolution() :
    m_bAllowRemoteDownload(false),
    m_eResolutionMode(RawContent),
    m_nResolutionDepth(1),
    m_bCacheResults(false)
{
}