#include "nmVolumeDataImporter.h"
#include "nmVolumeDataBuilder.h"

#include <QCoreApplication>
#include <QDir>
#include <QFile>
#include <QFileInfo>
#include <QTemporaryFile>
#include <new>
#include <vtkAlgorithm.h>
#include <vtkCallbackCommand.h>
#include <vtkCommand.h>
#include <vtkErrorCode.h>
#include <vtkUnstructuredGrid.h>
#include <vtkUnstructuredGridReader.h>
#include <vtkXMLUnstructuredGridReader.h>

namespace {
// 固定文本标记供 Qt 4 lupdate 提取；运行期通过统一上下文翻译。
static const char* const s_pVolumeTranslationMarkers[] = {
    QT_TRANSLATE_NOOP("nmVolumeData", "Not enough memory to import the volume mesh."),
    QT_TRANSLATE_NOOP("nmVolumeData", "Select a .vtk or .vtu volume mesh file."),
    QT_TRANSLATE_NOOP("nmVolumeData", "The temporary directory path cannot be read by VTK."),
    QT_TRANSLATE_NOOP("nmVolumeData", "The volume mesh file is empty or cannot be opened."),
    QT_TRANSLATE_NOOP("nmVolumeData", "Unable to create a temporary file for this path."),
    QT_TRANSLATE_NOOP("nmVolumeData", "Unable to read the volume mesh file."),
    QT_TRANSLATE_NOOP("nmVolumeData", "VTK could not read the volume mesh: %1"),
    QT_TRANSLATE_NOOP("nmVolumeData", "Volume import canceled.")
};

QString importText(const char* pText)
{
    Q_UNUSED(s_pVolumeTranslationMarkers);
    return QCoreApplication::translate("nmVolumeData", pText);
}
struct ReaderState
{
    nmVolumeImportFeedback* m_pFeedback; ///< 非所有权反馈接口，生命周期覆盖 Reader。
    bool m_bFailed; ///< 任一 ErrorEvent 都使本次候选永久失败。
    QString m_sDetail; ///< VTK 原始诊断，仅用作错误详情显示。
};
/** @brief 在读取线程内处理 VTK 错误和进度；回调绝不访问 GUI。 */
void handleReaderEvent(vtkObject* pCaller, unsigned long nEvent,
                       void* pClientData, void* pCallData)
{
    ReaderState* pState = static_cast<ReaderState*>(pClientData);
    if(nEvent == vtkCommand::ErrorEvent) {
        pState->m_bFailed = true;
        if(pCallData != nullptr) pState->m_sDetail = QString::fromLocal8Bit(static_cast<const char*>(pCallData)).trimmed();
    }
    vtkAlgorithm* pAlgorithm = vtkAlgorithm::SafeDownCast(pCaller);
    if(pAlgorithm != nullptr && pState->m_pFeedback != nullptr) {
        if(pState->m_pFeedback->isCanceled()) pAlgorithm->AbortExecuteOn();
        if(nEvent == vtkCommand::ProgressEvent) {
            pState->m_pFeedback->reportProgress(10 + qBound(0, int(pAlgorithm->GetProgress() * 45.0), 45));
        }
    }
}
}

QSharedPointer<const nmVolumeData> nmVolumeDataImporter::loadFile(
        const QString& sFilePath, QString* pError, nmVolumeImportFeedback* pFeedback)
{
    if(pError != nullptr) pError->clear();
    QString sError;
    try {
        do {
            const QFileInfo oFileInfo(sFilePath);
            const QString sSuffix = oFileInfo.suffix().toLower();
            if(sSuffix != QLatin1String("vtk") && sSuffix != QLatin1String("vtu")) {
                sError = importText("Select a .vtk or .vtu volume mesh file.");
                break;
            }
            QFile oSource(sFilePath);
            if(!oSource.open(QIODevice::ReadOnly) || oSource.size() == 0) {
                sError = importText("The volume mesh file is empty or cannot be opened.");
                break;
            }

            // VTK 7.1 的文件流使用本地窄字符串。不可往返的路径通过 Qt 复制到临时
            // 文件，保持二进制内容不变，并以流式复制避免额外占用整文件内存。
            QString sReaderPath = oFileInfo.absoluteFilePath();
            QTemporaryFile oTemporary(QDir::tempPath() + QLatin1String("/nm_volume_XXXXXX.") + sSuffix);
            QByteArray aReaderPath = QFile::encodeName(sReaderPath);
            if(QFile::decodeName(aReaderPath) != sReaderPath) {
                if(!oTemporary.open()) {
                    sError = importText("Unable to create a temporary file for this path.");
                    break;
                }
                while(!oSource.atEnd() && !(pFeedback != nullptr && pFeedback->isCanceled())) {
                    const QByteArray aChunk = oSource.read(1024 * 1024);
                    if(aChunk.isEmpty() || oTemporary.write(aChunk) != aChunk.size()) {
                        sError = importText("Unable to read the volume mesh file.");
                        break;
                    }
                }
                if(!oTemporary.flush()) sError = importText("Unable to read the volume mesh file.");
                sReaderPath = oTemporary.fileName();
                oTemporary.close();
                aReaderPath = QFile::encodeName(sReaderPath);
                if(QFile::decodeName(aReaderPath) != sReaderPath) sError = importText("The temporary directory path cannot be read by VTK.");
            }
            if(!sError.isEmpty() || (pFeedback != nullptr && pFeedback->isCanceled())) break;
            ReaderState oState;
            oState.m_pFeedback = pFeedback;
            oState.m_bFailed = false;
            vtkSmartPointer<vtkCallbackCommand> pObserver = vtkSmartPointer<vtkCallbackCommand>::New();
            pObserver->SetClientData(&oState);
            pObserver->SetCallback(handleReaderEvent);
            vtkSmartPointer<vtkAlgorithm> pReader;
            vtkSmartPointer<vtkUnstructuredGrid> pGrid;
            if(sSuffix == QLatin1String("vtk")) {
                vtkSmartPointer<vtkUnstructuredGridReader> pLegacy = vtkSmartPointer<vtkUnstructuredGridReader>::New();
                pReader = pLegacy;
                pLegacy->SetFileName(aReaderPath.constData());
                pLegacy->ReadAllScalarsOn();
                pLegacy->ReadAllFieldsOn();
            } else {
                vtkSmartPointer<vtkXMLUnstructuredGridReader> pXml = vtkSmartPointer<vtkXMLUnstructuredGridReader>::New();
                pReader = pXml;
                pXml->SetFileName(aReaderPath.constData());
            }
            pReader->AddObserver(vtkCommand::ErrorEvent, pObserver);
            pReader->AddObserver(vtkCommand::ProgressEvent, pObserver);
            pReader->UpdateInformation();
            vtkXMLUnstructuredGridReader* pXml = vtkXMLUnstructuredGridReader::SafeDownCast(pReader);
            if(pXml != nullptr && !oState.m_bFailed) {
                for(int nIndex = 0; nIndex < pXml->GetNumberOfPointArrays(); ++nIndex) pXml->SetPointArrayStatus(pXml->GetPointArrayName(nIndex), 1);
                for(int nIndex = 0; nIndex < pXml->GetNumberOfCellArrays(); ++nIndex) pXml->SetCellArrayStatus(pXml->GetCellArrayName(nIndex), 1);
            }
            if(!oState.m_bFailed && !(pFeedback != nullptr && pFeedback->isCanceled())) pReader->Update();
            // 观察者引用的是栈状态；必须在状态离开作用域前解除回调。
            pReader->RemoveObservers(vtkCommand::ErrorEvent, pObserver);
            pReader->RemoveObservers(vtkCommand::ProgressEvent, pObserver);
            pObserver->SetClientData(nullptr);
            if(pFeedback != nullptr && pFeedback->isCanceled()) break;
            if(oState.m_bFailed || pReader->GetErrorCode() != vtkErrorCode::NoError) {
                sError = importText("VTK could not read the volume mesh: %1").arg(oState.m_sDetail);
                break;
            }
            pGrid = vtkUnstructuredGrid::SafeDownCast(pReader->GetOutputDataObject(0));
            return nmVolumeDataBuilder::buildFromGrid(pGrid, oFileInfo.fileName(), pError, pFeedback);
        } while(false);
    } catch(const std::bad_alloc&) {
        sError = importText("Not enough memory to import the volume mesh.");
    }
    if(pError != nullptr) {
        *pError = pFeedback != nullptr && pFeedback->isCanceled()
                ? importText("Volume import canceled.") : sError;
    }
    return QSharedPointer<const nmVolumeData>();
}