/////////////////////////////////////////////////////////////////////////////////
//
//  Copyright (C) 2025-     Equinor ASA
//
//  ResInsight is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  ResInsight is distributed in the hope that it will be useful, but WITHOUT ANY
//  WARRANTY; without even the implied warranty of MERCHANTABILITY or
//  FITNESS FOR A PARTICULAR PURPOSE.
//
//  See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
//  for more details.
//
/////////////////////////////////////////////////////////////////////////////////

#include "RifVtkImportUtil.h"

#include "RiaStdStringTools.h"

#include "fast_float/fast_float.h"

#include <cstring>
#include <filesystem>
#include <string>
#include <vector>
#include <version>

// std::ispanstream is C++23.  libc++ on Homebrew llvm@19 does not ship
// <spanstream>; fall back to std::istringstream when unavailable.  Only
// difference: the fallback copies the string_view into an owning string.
// Use the feature-test macro from <version> rather than __has_include,
// since the header may be present without a usable implementation.
// See #14045.
#if defined( __cpp_lib_spanstream ) && __cpp_lib_spanstream >= 202106L
#include <spanstream>
#define RIA_HAS_STD_SPANSTREAM 1
#else
#include <sstream>
#define RIA_HAS_STD_SPANSTREAM 0
#endif

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
std::vector<cvf::Vec3d> RifVtkImportUtil::readPoints( const pugi::xml_node& piece )
{
    auto points = piece.child( "Points" );
    if ( !points ) return {};

    auto coords = points.child( "DataArray" );
    if ( !coords || std::string( coords.attribute( "Name" ).value() ) != "Coordinates" ) return {};

    std::string_view        text     = coords.text().get();
    std::vector<cvf::Vec3d> vertices = parseVec3ds( text );

    // Update to internal z direction
    for ( cvf::Vec3d& v : vertices )
        v.z() = -v.z();

    return vertices;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
std::vector<cvf::Vec3f> RifVtkImportUtil::readDisplacements( const pugi::xml_node& piece )
{
    auto pointData = piece.child( "PointData" );
    if ( !pointData ) return {};

    auto dataArray = pointData.child( "DataArray" );
    if ( !dataArray || std::string( dataArray.attribute( "Name" ).value() ) != "disp" ) return {};

    std::string_view        text          = dataArray.text().get();
    std::vector<cvf::Vec3f> displacements = parseVec3fs( text );

    for ( cvf::Vec3f& d : displacements )
        d.z() = -d.z();

    return displacements;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
std::vector<unsigned> RifVtkImportUtil::readConnectivity( const pugi::xml_node& piece )
{
    auto cells = piece.child( "Cells" );
    if ( !cells ) return {};

    std::vector<unsigned> connectivity;
    auto                  connectivityArray = cells.child( "DataArray" );

    while ( connectivityArray )
    {
        if ( std::string( connectivityArray.attribute( "Name" ).value() ) == "connectivity" )
        {
            std::string        connectivityText = connectivityArray.text().get();
            std::istringstream iss( connectivityText );

            unsigned index;
            while ( iss >> index )
            {
                connectivity.push_back( index );
            }
            break;
        }
        connectivityArray = connectivityArray.next_sibling( "DataArray" );
    }

    return connectivity;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
std::map<std::string, std::vector<float>> RifVtkImportUtil::readProperties( const pugi::xml_node& piece )
{
    auto cellData = piece.child( "CellData" );
    if ( !cellData ) return {};

    std::map<std::string, std::vector<float>> properties;

    for ( const auto& dataArray : cellData.children( "DataArray" ) )
    {
        const char* name = dataArray.attribute( "Name" ).value();
        if ( name && *name )
        {
            std::vector<float> values;
            const char*        text    = dataArray.text().get();
            const char*        ptr     = text;
            const char*        textEnd = text + std::strlen( text );

            while ( *ptr != '\0' )
            {
                // Skip whitespace
                while ( *ptr == ' ' || *ptr == '\t' || *ptr == '\n' || *ptr == '\r' )
                    ++ptr;

                if ( *ptr == '\0' ) break;

                // Check for NaN (case-insensitive). ptr[3] is safe because text is null-terminated,
                // so if ptr points to the last three chars "nan", ptr[3] == '\0' which matches the condition.
                if ( ( *ptr == 'n' || *ptr == 'N' ) && ( ptr[1] == 'a' || ptr[1] == 'A' ) && ( ptr[2] == 'n' || ptr[2] == 'N' ) &&
                     ( ptr[3] == '\0' || ptr[3] == ' ' || ptr[3] == '\t' || ptr[3] == '\n' || ptr[3] == '\r' ) )
                {
                    values.push_back( std::numeric_limits<float>::quiet_NaN() );
                    ptr += 3;
                    continue;
                }

                // Parse float directly using fast_float
                float fValue       = 0.0f;
                auto  result       = fast_float::from_chars( ptr, textEnd, fValue );
                auto* parsedEndPtr = result.ptr;

                if ( result.ec != std::errc() || parsedEndPtr == ptr )
                {
                    // Failed to parse
                    return {};
                }

                values.push_back( fValue );
                ptr = parsedEndPtr;
            }

            if ( !values.empty() )
            {
                properties[name] = std::move( values );
            }
        }
    }

    return properties;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
std::vector<RifVtkImportUtil::PvdDataset> RifVtkImportUtil::parsePvdDatasets( const std::filesystem::path& filepath )
{
    pugi::xml_document     doc;
    pugi::xml_parse_result result = doc.load_file( filepath.string().c_str() );
    if ( !result ) return {};

    auto root = doc.child( "VTKFile" );
    if ( !root ) return {};

    auto collection = root.child( "Collection" );
    if ( !collection ) return {};

    std::filesystem::path baseDir = filepath.parent_path();

    std::vector<PvdDataset> datasets;

    for ( const auto& datasetElem : collection.children( "DataSet" ) )
    {
        const char* file        = datasetElem.attribute( "file" ).value();
        const char* timestepStr = datasetElem.attribute( "timestep" ).value();

        if ( file && timestepStr )
        {
            double                timestep = std::stod( timestepStr );
            std::filesystem::path fullPath = std::filesystem::absolute( baseDir / file );

            datasets.push_back( { timestep, fullPath } );
        }
    }

    return datasets;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
std::vector<cvf::Vec3d> RifVtkImportUtil::parseVec3ds( std::string_view text )
{
#if RIA_HAS_STD_SPANSTREAM
    std::ispanstream iss( text );
#else
    std::istringstream iss{ std::string{ text } };
#endif

    std::vector<cvf::Vec3d> vecs;

    std::string xStr, yStr, zStr;
    while ( iss >> xStr >> yStr >> zStr )
    {
        double x, y, z;
        if ( !RiaStdStringTools::toDouble( xStr, x ) || !RiaStdStringTools::toDouble( yStr, y ) || !RiaStdStringTools::toDouble( zStr, z ) )
        {
            return {};
        }

        vecs.emplace_back( x, y, z );
    }

    return vecs;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
std::vector<cvf::Vec3f> RifVtkImportUtil::parseVec3fs( std::string_view text )
{
#if RIA_HAS_STD_SPANSTREAM
    std::ispanstream iss( text );
#else
    std::istringstream iss{ std::string{ text } };
#endif

    std::vector<cvf::Vec3f> vecs;

    std::string xStr, yStr, zStr;
    while ( iss >> xStr >> yStr >> zStr )
    {
        double x, y, z;
        if ( !RiaStdStringTools::toDouble( xStr, x ) || !RiaStdStringTools::toDouble( yStr, y ) || !RiaStdStringTools::toDouble( zStr, z ) )
        {
            return {};
        }

        vecs.emplace_back( static_cast<float>( x ), static_cast<float>( y ), static_cast<float>( z ) );
    }

    return vecs;
}