#include "nmVTKImageExporter.h"

#include <QApplication>
#include <QClipboard>
#include <QCoreApplication>
#include <QDialog>
#include <QPainter>
#include <QPrintDialog>
#include <QPrintPreviewDialog>
#include <QPrinter>
#include <QThread>
#include <QWidget>

#include <vtkImageData.h>
#include <vtkImageFlip.h>
#include <vtkPointData.h>
#include <vtkRenderWindow.h>
#include <vtkSmartPointer.h>
#include <vtkUnsignedCharArray.h>
#include <vtkWindowToImageFilter.h>

namespace {

// 剪贴板、打印对话框和 RenderWindow 均要求在 Qt GUI 线程访问。
bool isImageExporterGuiThread()
{
    QCoreApplication* pApplication = QCoreApplication::instance();
    return pApplication == nullptr ||
            pApplication->thread() == QThread::currentThread();
}

}

nmVTKImageExporter::nmVTKImageExporter(QObject* pParent)
    : QObject(pParent),
      m_pRenderWindow(nullptr)
{
    Q_ASSERT(isImageExporterGuiThread());
}

nmVTKImageExporter::~nmVTKImageExporter()
{
    Q_ASSERT(isImageExporterGuiThread());
    // RenderWindow 由容器中的 QVTKWidget 持有，本服务只解除非所有权引用。
    m_pRenderWindow = nullptr;
}

void nmVTKImageExporter::setRenderWindow(vtkRenderWindow* pRenderWindow)
{
    Q_ASSERT(isImageExporterGuiThread());
    // 不增加 VTK 引用计数，容器销毁时必须先传入 nullptr 解除关系。
    if(isImageExporterGuiThread()) {
        m_pRenderWindow = pRenderWindow;
    }
}

vtkRenderWindow* nmVTKImageExporter::getRenderWindow() const
{
    return m_pRenderWindow;
}

QImage nmVTKImageExporter::captureImage() const
{
    Q_ASSERT(isImageExporterGuiThread());
    if(!isImageExporterGuiThread() || m_pRenderWindow == nullptr) {
        return QImage();
    }

    // 捕获前提交最新场景，随后从后台缓冲读取，避免交换缓冲产生黑图。
    m_pRenderWindow->Render();
    vtkSmartPointer<vtkWindowToImageFilter> pCapture =
            vtkSmartPointer<vtkWindowToImageFilter>::New();
    pCapture->SetInput(m_pRenderWindow);
    pCapture->SetInputBufferTypeToRGB();
    // Render 已完成后读取后台缓冲，避免前台缓冲在窗口交换时得到黑图。
    pCapture->ReadFrontBufferOff();
    pCapture->Update();

    // VTK 原点位于左下角，统一翻转为 QImage 使用的左上角原点。
    vtkSmartPointer<vtkImageFlip> pFlip =
            vtkSmartPointer<vtkImageFlip>::New();
    pFlip->SetInputData(pCapture->GetOutput());
    pFlip->SetFilteredAxis(1);
    pFlip->Update();
    return createQImage(pFlip->GetOutput());
}

bool nmVTKImageExporter::saveImage(const QString& sFileName) const
{
    Q_ASSERT(isImageExporterGuiThread());
    if(!isImageExporterGuiThread() || sFileName.isEmpty()) {
        return false;
    }
    const QImage oImage = captureImage();
    // QImage::save 在 Qt 4.8 中可按扩展名选择已部署的图片插件。
    return !oImage.isNull() && oImage.save(sFileName);
}

bool nmVTKImageExporter::copyImageToClipboard() const
{
    Q_ASSERT(isImageExporterGuiThread());
    if(!isImageExporterGuiThread()) {
        return false;
    }
    const QImage oImage = captureImage();
    if(oImage.isNull() || QApplication::clipboard() == nullptr) {
        return false;
    }
    QApplication::clipboard()->setImage(oImage);
    return true;
}

bool nmVTKImageExporter::printImage(QWidget* pParent)
{
    Q_ASSERT(isImageExporterGuiThread());
    if(!isImageExporterGuiThread() || m_pRenderWindow == nullptr) {
        return false;
    }

    QPrinter oPrinter;
    QPrintDialog oDialog(&oPrinter, pParent);
    if(oDialog.exec() != QDialog::Accepted) {
        return false;
    }
    return paintImage(&oPrinter);
}

bool nmVTKImageExporter::printPreview(QWidget* pParent)
{
    Q_ASSERT(isImageExporterGuiThread());
    if(!isImageExporterGuiThread() || m_pRenderWindow == nullptr) {
        return false;
    }

    QPrinter oPrinter(QPrinter::HighResolution);
    QPrintPreviewDialog oPreview(&oPrinter, pParent);
    oPreview.resize(800, 600);
    // Qt 4 使用字符串式信号槽；预览每次请求页面时同步重绘当前画面。
    connect(&oPreview, SIGNAL(paintRequested(QPrinter*)),
            this, SLOT(renderForPrint(QPrinter*)));
    oPreview.exec();
    return true;
}

void nmVTKImageExporter::renderForPrint(QPrinter* pPrinter)
{
    paintImage(pPrinter);
}

QImage nmVTKImageExporter::createQImage(vtkImageData* pImageData) const
{
    if(pImageData == nullptr || pImageData->GetPointData() == nullptr) {
        return QImage();
    }

    const int nWidth = pImageData->GetDimensions()[0];
    const int nHeight = pImageData->GetDimensions()[1];
    vtkUnsignedCharArray* pScalars = vtkUnsignedCharArray::SafeDownCast(
                pImageData->GetPointData()->GetScalars());
    if(nWidth <= 0 || nHeight <= 0 || pScalars == nullptr) {
        return QImage();
    }

    const int nComponents = pScalars->GetNumberOfComponents();
    unsigned char* pSource = pScalars->GetPointer(0);
    if(nComponents < 1 || nComponents > 4 || pSource == nullptr) {
        return QImage();
    }

    // QImage 使用自有 ARGB32 缓冲，不引用 VTK 过滤器的临时输出。
    // 单/双分量按灰度解释，三/四分量按 RGB/RGBA 解释。
    QImage oImage(nWidth, nHeight, QImage::Format_ARGB32);
    for(int nY = 0; nY < nHeight; ++nY) {
        QRgb* pTargetRow = reinterpret_cast<QRgb*>(oImage.scanLine(nY));
        for(int nX = 0; nX < nWidth; ++nX) {
            const vtkIdType nTuple =
                    static_cast<vtkIdType>(nY) * nWidth + nX;
            unsigned char* pTuple = pSource + nTuple * nComponents;
            const int nRed = pTuple[0];
            const int nGreen = nComponents >= 3 ? pTuple[1] : pTuple[0];
            const int nBlue = nComponents >= 3 ? pTuple[2] : pTuple[0];
            const int nAlpha = (nComponents == 2 || nComponents == 4)
                    ? pTuple[nComponents - 1] : 255;
            pTargetRow[nX] = qRgba(nRed, nGreen, nBlue, nAlpha);
        }
    }
    return oImage;
}

bool nmVTKImageExporter::paintImage(QPrinter* pPrinter) const
{
    if(pPrinter == nullptr) {
        return false;
    }
    const QImage oImage = captureImage();
    if(oImage.isNull()) {
        return false;
    }

    // 使用较小缩放比完整适配可打印区域，并将剩余留白平均分配。
    const QRect oPageRect = pPrinter->pageRect();
    const double dScale = qMin(
                static_cast<double>(oPageRect.width()) / oImage.width(),
                static_cast<double>(oPageRect.height()) / oImage.height());
    const double dWidth = oImage.width() * dScale;
    const double dHeight = oImage.height() * dScale;
    const QRectF oTarget(
                oPageRect.left() + (oPageRect.width() - dWidth) * 0.5,
                oPageRect.top() + (oPageRect.height() - dHeight) * 0.5,
                dWidth,
                dHeight);

    QPainter oPainter(pPrinter);
    // QPainter 构造时绑定打印设备，离开作用域后自动结束打印页面。
    oPainter.drawImage(oTarget, oImage);
    return true;
}