#include "nmVTKRotationCenterMarkerLayer.h"

#include <QCoreApplication>
#include <QThread>

#include <vtkActor.h>
#include <vtkCallbackCommand.h>
#include <vtkCamera.h>
#include <vtkCellArray.h>
#include <vtkCellData.h>
#include <vtkCommand.h>
#include <vtkMath.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderer.h>
#include <vtkUnsignedCharArray.h>
#include <vtkWeakPointer.h>

#include <cmath>
#include <limits>

namespace {

const double ROTATION_CENTER_HALF_LENGTH_PIXELS = 18.0;
const double ROTATION_CENTER_DEPTH_OFFSET_PIXELS = 1.5;
const double ROTATION_CENTER_HOMOGENEOUS_EPSILON =
        std::numeric_limits<double>::epsilon();

bool isRotationCenterMarkerGuiThread()
{
    QCoreApplication* pApplication = QCoreApplication::instance();
    return pApplication == nullptr ||
            pApplication->thread() == QThread::currentThread();
}

bool isFinitePoint3(const double dPoint[3])
{
    return dPoint != nullptr &&
            vtkMath::IsFinite(dPoint[0]) &&
            vtkMath::IsFinite(dPoint[1]) &&
            vtkMath::IsFinite(dPoint[2]);
}

bool worldToDisplay(vtkRenderer* pRenderer,
                    const double dWorld[3],
                    double dDisplay[3])
{
    if(pRenderer == nullptr || dWorld == nullptr || dDisplay == nullptr) {
        return false;
    }

    pRenderer->SetWorldPoint(dWorld[0], dWorld[1], dWorld[2], 1.0);
    pRenderer->WorldToDisplay();
    const double* pDisplay = pRenderer->GetDisplayPoint();
    if(!isFinitePoint3(pDisplay)) {
        return false;
    }

    dDisplay[0] = pDisplay[0];
    dDisplay[1] = pDisplay[1];
    dDisplay[2] = pDisplay[2];
    return true;
}

bool displayToWorld(vtkRenderer* pRenderer,
                    const double dDisplay[3],
                    double dWorld[3])
{
    if(pRenderer == nullptr || dDisplay == nullptr || dWorld == nullptr ||
       !isFinitePoint3(dDisplay)) {
        return false;
    }

    pRenderer->SetDisplayPoint(
                dDisplay[0], dDisplay[1], dDisplay[2]);
    pRenderer->DisplayToWorld();
    const double* pHomogeneousWorld = pRenderer->GetWorldPoint();
    if(pHomogeneousWorld == nullptr ||
       !vtkMath::IsFinite(pHomogeneousWorld[0]) ||
       !vtkMath::IsFinite(pHomogeneousWorld[1]) ||
       !vtkMath::IsFinite(pHomogeneousWorld[2]) ||
       !vtkMath::IsFinite(pHomogeneousWorld[3]) ||
       std::fabs(pHomogeneousWorld[3]) <=
           ROTATION_CENTER_HOMOGENEOUS_EPSILON) {
        return false;
    }

    const double dInverseW = 1.0 / pHomogeneousWorld[3];
    dWorld[0] = pHomogeneousWorld[0] * dInverseW;
    dWorld[1] = pHomogeneousWorld[1] * dInverseW;
    dWorld[2] = pHomogeneousWorld[2] * dInverseW;
    return isFinitePoint3(dWorld);
}

}

class nmVTKRotationCenterMarkerLayerPrivate
{
public:
    nmVTKRotationCenterMarkerLayerPrivate()
        : m_pPoints(vtkSmartPointer<vtkPoints>::New()),
          m_pLines(vtkSmartPointer<vtkCellArray>::New()),
          m_pColors(vtkSmartPointer<vtkUnsignedCharArray>::New()),
          m_pPolyData(vtkSmartPointer<vtkPolyData>::New()),
          m_pMapper(vtkSmartPointer<vtkPolyDataMapper>::New()),
          m_pActor(vtkSmartPointer<vtkActor>::New()),
          m_pRendererCallback(vtkSmartPointer<vtkCallbackCommand>::New()),
          m_pCameraCallback(vtkSmartPointer<vtkCallbackCommand>::New()),
          m_pRenderer(nullptr),
          m_pCamera(nullptr),
          m_nRendererObserverTag(0),
          m_nCameraObserverTag(0),
          m_bHasWorldCenter(false)
    {
        // 必须通过 vtkActor::New() 的对象工厂路径获得实际 OpenGL Actor。
        initializeGeometry();

        m_dWorldCenter[0] = 0.0;
        m_dWorldCenter[1] = 0.0;
        m_dWorldCenter[2] = 0.0;

        m_pRendererCallback->SetClientData(this);
        m_pRendererCallback->SetCallback(
                    nmVTKRotationCenterMarkerLayerPrivate::rendererStarted);
        m_pCameraCallback->SetClientData(this);
        m_pCameraCallback->SetCallback(
                    nmVTKRotationCenterMarkerLayerPrivate::cameraModified);
    }

    ~nmVTKRotationCenterMarkerLayerPrivate()
    {
        // 先移除 Renderer 和 Camera Observer，再阻断裸回调目标。
        unbindRenderer();
        m_pRendererCallback->SetClientData(nullptr);
        m_pRendererCallback->SetCallback(nullptr);
        m_pCameraCallback->SetClientData(nullptr);
        m_pCameraCallback->SetCallback(nullptr);
    }

    vtkActor* getActor() const
    {
        return m_pActor;
    }

    bool bindRenderer(vtkRenderer* pRenderer)
    {
        if(pRenderer == nullptr) {
            return false;
        }

        if(m_pRenderer.GetPointer() != pRenderer) {
            unbindRenderer();
            m_pRenderer = pRenderer;
        }

        if(!ensureRendererObserver(pRenderer) ||
           !ensureCameraObserver(pRenderer->GetActiveCamera())) {
            unbindRenderer();
            return false;
        }
        return true;
    }

    void unbindRenderer()
    {
        removeCameraObserver();
        removeRendererObserver();
        m_pRenderer = nullptr;
    }

    bool synchronize()
    {
        return synchronizeForRenderer(m_pRenderer.GetPointer());
    }

    bool synchronizeForRenderer(vtkRenderer* pRenderer)
    {
        if(pRenderer == nullptr || m_pRenderer.GetPointer() != pRenderer ||
           !m_bHasWorldCenter) {
            return false;
        }

        vtkCamera* pCamera = pRenderer->GetActiveCamera();
        if(pCamera == nullptr || !ensureCameraObserver(pCamera)) {
            return false;
        }

        int* pViewportSize = pRenderer->GetSize();
        if(pViewportSize == nullptr || pViewportSize[0] <= 0 ||
           pViewportSize[1] <= 0) {
            return false;
        }

        const double dLogicalCenter[3] = {
            m_dWorldCenter[0], m_dWorldCenter[1], m_dWorldCenter[2]
        };
        double dCameraPosition[3];
        pCamera->GetPosition(dCameraPosition);
        if(!isFinitePoint3(dLogicalCenter) ||
           !isFinitePoint3(dCameraPosition)) {
            return false;
        }

        double dCenterDisplay[3];
        if(!worldToDisplay(pRenderer, dLogicalCenter, dCenterDisplay)) {
            return false;
        }

        double dOffsetDisplay[3] = {
            dCenterDisplay[0],
            dCenterDisplay[1] + ROTATION_CENTER_HALF_LENGTH_PIXELS,
            dCenterDisplay[2]
        };
        double dCenterAtDepth[3];
        double dOffsetAtDepth[3];
        if(!displayToWorld(pRenderer, dCenterDisplay, dCenterAtDepth) ||
           !displayToWorld(pRenderer, dOffsetDisplay, dOffsetAtDepth)) {
            return false;
        }

        const double dScaleX = dOffsetAtDepth[0] - dCenterAtDepth[0];
        const double dScaleY = dOffsetAtDepth[1] - dCenterAtDepth[1];
        const double dScaleZ = dOffsetAtDepth[2] - dCenterAtDepth[2];
        const double dHalfLength = std::sqrt(
                    dScaleX * dScaleX +
                    dScaleY * dScaleY +
                    dScaleZ * dScaleZ);
        if(!vtkMath::IsFinite(dHalfLength) || dHalfLength <= 0.0) {
            return false;
        }

        double dTowardCamera[3];
        if(pCamera->GetParallelProjection() != 0) {
            const double* pDirectionOfProjection =
                    pCamera->GetDirectionOfProjection();
            if(!isFinitePoint3(pDirectionOfProjection)) {
                return false;
            }
            dTowardCamera[0] = -pDirectionOfProjection[0];
            dTowardCamera[1] = -pDirectionOfProjection[1];
            dTowardCamera[2] = -pDirectionOfProjection[2];
        } else {
            dTowardCamera[0] = dCameraPosition[0] - dLogicalCenter[0];
            dTowardCamera[1] = dCameraPosition[1] - dLogicalCenter[1];
            dTowardCamera[2] = dCameraPosition[2] - dLogicalCenter[2];
        }
        if(vtkMath::Normalize(dTowardCamera) <= 0.0) {
            return false;
        }

        const double dWorldPerPixel =
                dHalfLength / ROTATION_CENTER_HALF_LENGTH_PIXELS;
        const double dDepthOffset =
                dWorldPerPixel * ROTATION_CENTER_DEPTH_OFFSET_PIXELS;
        const double dDisplayCenter[3] = {
            dLogicalCenter[0] + dTowardCamera[0] * dDepthOffset,
            dLogicalCenter[1] + dTowardCamera[1] * dDepthOffset,
            dLogicalCenter[2] + dTowardCamera[2] * dDepthOffset
        };

        const double dAxisPoints[6][3] = {
            { dDisplayCenter[0] - dHalfLength,
              dDisplayCenter[1], dDisplayCenter[2] },
            { dDisplayCenter[0] + dHalfLength,
              dDisplayCenter[1], dDisplayCenter[2] },
            { dDisplayCenter[0],
              dDisplayCenter[1] - dHalfLength, dDisplayCenter[2] },
            { dDisplayCenter[0],
              dDisplayCenter[1] + dHalfLength, dDisplayCenter[2] },
            { dDisplayCenter[0], dDisplayCenter[1],
              dDisplayCenter[2] - dHalfLength },
            { dDisplayCenter[0], dDisplayCenter[1],
              dDisplayCenter[2] + dHalfLength }
        };
        for(vtkIdType nPoint = 0; nPoint < 6; ++nPoint) {
            if(!isFinitePoint3(dAxisPoints[nPoint])) {
                return false;
            }
        }
        for(vtkIdType nPoint = 0; nPoint < 6; ++nPoint) {
            m_pPoints->SetPoint(nPoint, dAxisPoints[nPoint]);
        }
        m_pPoints->Modified();
        m_pPolyData->Modified();
        return true;
    }

    bool setWorldCenter(double dX, double dY, double dZ)
    {
        const double dCenter[3] = { dX, dY, dZ };
        if(!isFinitePoint3(dCenter)) {
            return false;
        }
        m_dWorldCenter[0] = dX;
        m_dWorldCenter[1] = dY;
        m_dWorldCenter[2] = dZ;
        m_bHasWorldCenter = true;
        synchronize();
        return true;
    }

    bool hasWorldCenter() const
    {
        return m_bHasWorldCenter;
    }

private:
    static void rendererStarted(vtkObject* pCaller,
                                unsigned long,
                                void* pClientData,
                                void*)
    {
        nmVTKRotationCenterMarkerLayerPrivate* pThis =
                static_cast<nmVTKRotationCenterMarkerLayerPrivate*>(
                    pClientData);
        if(pThis != nullptr) {
            // StartEvent 位于 Prop 遍历之前，可使用最终视口尺寸覆盖 Resize 路径。
            pThis->synchronizeForRenderer(
                        vtkRenderer::SafeDownCast(pCaller));
        }
    }

    static void cameraModified(vtkObject*,
                               unsigned long,
                               void* pClientData,
                               void*)
    {
        nmVTKRotationCenterMarkerLayerPrivate* pThis =
                static_cast<nmVTKRotationCenterMarkerLayerPrivate*>(
                    pClientData);
        if(pThis != nullptr) {
            // 相机回调只同步几何，最终 Render 仍由交互器或容器统一提交。
            pThis->synchronize();
        }
    }

    void initializeGeometry()
    {
        m_pPoints->SetDataTypeToDouble();
        m_pPoints->SetNumberOfPoints(6);
        for(vtkIdType nPoint = 0; nPoint < 6; ++nPoint) {
            m_pPoints->SetPoint(nPoint, 0.0, 0.0, 0.0);
        }

        for(vtkIdType nAxis = 0; nAxis < 3; ++nAxis) {
            vtkIdType nPointIds[2] = {
                nAxis * 2, nAxis * 2 + 1
            };
            m_pLines->InsertNextCell(2, nPointIds);
        }

        m_pColors->SetName("RotationCenterAxisColors");
        m_pColors->SetNumberOfComponents(3);
        m_pColors->InsertNextTuple3(255.0, 0.0, 0.0);
        m_pColors->InsertNextTuple3(254.0, 255.0, 0.0);
        m_pColors->InsertNextTuple3(0.0, 255.0, 0.0);

        m_pPolyData->SetPoints(m_pPoints);
        m_pPolyData->SetLines(m_pLines);
        m_pPolyData->GetCellData()->SetScalars(m_pColors);

        m_pMapper->SetInputData(m_pPolyData);
        m_pMapper->ScalarVisibilityOn();
        m_pMapper->SetScalarModeToUseCellData();
        m_pMapper->SetColorModeToDirectScalars();

        m_pActor->SetMapper(m_pMapper);
        m_pActor->GetProperty()->SetLineWidth(1.0f);
        m_pActor->GetProperty()->SetOpacity(1.0);
        m_pActor->GetProperty()->LightingOff();
        m_pActor->PickableOff();
        m_pActor->UseBoundsOff();
    }

    bool ensureRendererObserver(vtkRenderer* pRenderer)
    {
        if(pRenderer == nullptr || m_pRendererCallback == nullptr) {
            return false;
        }
        if(m_pRenderer.GetPointer() == pRenderer &&
           m_nRendererObserverTag != 0) {
            return true;
        }

        removeRendererObserver();
        m_nRendererObserverTag = pRenderer->AddObserver(
                    vtkCommand::StartEvent, m_pRendererCallback);
        return m_nRendererObserverTag != 0;
    }

    void removeRendererObserver()
    {
        vtkRenderer* pRenderer = m_pRenderer.GetPointer();
        if(pRenderer != nullptr && m_nRendererObserverTag != 0) {
            pRenderer->RemoveObserver(m_nRendererObserverTag);
        }
        m_nRendererObserverTag = 0;
    }

    bool ensureCameraObserver(vtkCamera* pCamera)
    {
        if(pCamera == nullptr || m_pCameraCallback == nullptr) {
            return false;
        }
        if(m_pCamera.GetPointer() == pCamera &&
           m_nCameraObserverTag != 0) {
            return true;
        }

        removeCameraObserver();
        m_pCamera = pCamera;
        m_nCameraObserverTag = pCamera->AddObserver(
                    vtkCommand::ModifiedEvent, m_pCameraCallback);
        if(m_nCameraObserverTag == 0) {
            m_pCamera = nullptr;
            return false;
        }
        return true;
    }

    void removeCameraObserver()
    {
        vtkCamera* pCamera = m_pCamera.GetPointer();
        if(pCamera != nullptr && m_nCameraObserverTag != 0) {
            pCamera->RemoveObserver(m_nCameraObserverTag);
        }
        m_nCameraObserverTag = 0;
        m_pCamera = nullptr;
    }

    vtkSmartPointer<vtkPoints> m_pPoints;
    vtkSmartPointer<vtkCellArray> m_pLines;
    vtkSmartPointer<vtkUnsignedCharArray> m_pColors;
    vtkSmartPointer<vtkPolyData> m_pPolyData;
    vtkSmartPointer<vtkPolyDataMapper> m_pMapper;
    vtkSmartPointer<vtkActor> m_pActor;
    vtkSmartPointer<vtkCallbackCommand> m_pRendererCallback;
    vtkSmartPointer<vtkCallbackCommand> m_pCameraCallback;
    vtkWeakPointer<vtkRenderer> m_pRenderer; ///< 非所有权引用。
    vtkWeakPointer<vtkCamera> m_pCamera; ///< 非所有权引用。
    unsigned long m_nRendererObserverTag; ///< 为零表示尚未注册观察者。
    unsigned long m_nCameraObserverTag; ///< 为零表示尚未注册观察者。
    double m_dWorldCenter[3]; ///< 独立于相机焦点的逻辑中心。
    bool m_bHasWorldCenter;
};

nmVTKRotationCenterMarkerLayer::nmVTKRotationCenterMarkerLayer(
        const QString& sLayerId)
    : nmVTKRenderLayer(sLayerId),
      m_pPrivate(new nmVTKRotationCenterMarkerLayerPrivate)
{
    Q_ASSERT(isRotationCenterMarkerGuiThread());
    setRenderProp(m_pPrivate->getActor());
    setVisible(false);
}

nmVTKRotationCenterMarkerLayer::~nmVTKRotationCenterMarkerLayer()
{
    Q_ASSERT(isRotationCenterMarkerGuiThread());
    if(m_pPrivate != nullptr) {
        // Renderer/Camera Observer 必须在 Renderer 和回调目标释放前解除。
        m_pPrivate->unbindRenderer();
        detach();
        delete m_pPrivate;
        m_pPrivate = nullptr;
    }
}

bool nmVTKRotationCenterMarkerLayer::bindRenderer(vtkRenderer* pRenderer)
{
    Q_ASSERT(isRotationCenterMarkerGuiThread());
    if(!isRotationCenterMarkerGuiThread() || m_pPrivate == nullptr ||
       pRenderer == nullptr || getAttachedRenderer() != pRenderer) {
        return false;
    }
    return m_pPrivate->bindRenderer(pRenderer);
}

void nmVTKRotationCenterMarkerLayer::unbindRenderer()
{
    Q_ASSERT(isRotationCenterMarkerGuiThread());
    if(isRotationCenterMarkerGuiThread() && m_pPrivate != nullptr) {
        m_pPrivate->unbindRenderer();
    }
}

bool nmVTKRotationCenterMarkerLayer::synchronize()
{
    Q_ASSERT(isRotationCenterMarkerGuiThread());
    return isRotationCenterMarkerGuiThread() && m_pPrivate != nullptr &&
            m_pPrivate->synchronize();
}

bool nmVTKRotationCenterMarkerLayer::setWorldCenter(
        double dX,
        double dY,
        double dZ)
{
    Q_ASSERT(isRotationCenterMarkerGuiThread());
    return isRotationCenterMarkerGuiThread() && m_pPrivate != nullptr &&
            m_pPrivate->setWorldCenter(dX, dY, dZ);
}

bool nmVTKRotationCenterMarkerLayer::hasWorldCenter() const
{
    return m_pPrivate != nullptr && m_pPrivate->hasWorldCenter();
}

void nmVTKRotationCenterMarkerLayer::setMarkerVisible(bool bVisible)
{
    Q_ASSERT(isRotationCenterMarkerGuiThread());
    if(!isRotationCenterMarkerGuiThread()) {
        return;
    }

    const bool bCanShow = bVisible && m_pPrivate != nullptr &&
            m_pPrivate->hasWorldCenter();
    setVisible(bCanShow);
    if(bCanShow) {
        // 首次显示先准备几何；视口尚未建立时由绘制前同步再次补齐。
        m_pPrivate->synchronize();
    }
}

bool nmVTKRotationCenterMarkerLayer::isMarkerVisible() const
{
    return isVisible();
}