#include "nmVTKRotationCenterPicker.h"

#include <QCoreApplication>
#include <QEvent>
#include <QKeyEvent>
#include <QMouseEvent>
#include <QThread>
#include <QVTKWidget.h>

#include <vtkCellPicker.h>
#include <vtkMath.h>
#include <vtkProp.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkSmartPointer.h>

namespace {

// Qt 控件状态和 VTK Picker 均只允许在 GUI 线程中修改。
bool isRotationCenterPickerGuiThread()
{
    QCoreApplication* pApplication = QCoreApplication::instance();
    return pApplication == nullptr ||
            pApplication->thread() == QThread::currentThread();
}

int scalePixelCoordinate(int nPosition,
                         int nWidgetExtent,
                         int nRenderExtent)
{
    const double dScaled =
            (static_cast<double>(nPosition) + 0.5) *
            static_cast<double>(nRenderExtent) /
            static_cast<double>(nWidgetExtent) - 0.5;
    int nResult = static_cast<int>(dScaled + 0.5);
    if(nResult < 0) {
        nResult = 0;
    } else if(nResult >= nRenderExtent) {
        nResult = nRenderExtent - 1;
    }
    return nResult;
}

}

nmVTKRotationCenterPicker::nmVTKRotationCenterPicker()
    : m_pPickTarget(nullptr),
      m_pWidget(nullptr),
      m_pRenderer(nullptr),
      m_oPreviousCursor(),
      m_nPendingReleaseButton(static_cast<int>(Qt::NoButton)),
      m_bHadExplicitCursor(false),
      m_bCursorOverridden(false),
      m_bActive(false),
      m_bHasPickedPosition(false)
{
    Q_ASSERT(isRotationCenterPickerGuiThread());
    m_dPickedPosition[0] = 0.0;
    m_dPickedPosition[1] = 0.0;
    m_dPickedPosition[2] = 0.0;
}

nmVTKRotationCenterPicker::~nmVTKRotationCenterPicker()
{
    Q_ASSERT(isRotationCenterPickerGuiThread());
    // 先恢复 Qt 临时状态，再解除对拾取目标的弱引用观察关系。
    reset();
    m_pPickTarget = nullptr;
}

void nmVTKRotationCenterPicker::setPickTarget(vtkProp* pTarget)
{
    Q_ASSERT(isRotationCenterPickerGuiThread());
    if(!isRotationCenterPickerGuiThread()) {
        return;
    }

    if(m_pPickTarget.GetPointer() == pTarget) {
        // 弱目标已经失效时，显式清空仍必须结束可能遗留的交互状态。
        if(pTarget == nullptr && (m_bActive || hasPendingRelease())) {
            reset();
        }
        return;
    }

    // 网格更换时旧 Press/Release 序列不再有效，必须先结束当前模式。
    reset();
    m_pPickTarget = pTarget;
}

vtkProp* nmVTKRotationCenterPicker::getPickTarget() const
{
    return m_pPickTarget.GetPointer();
}

bool nmVTKRotationCenterPicker::hasPickTarget() const
{
    return m_pPickTarget.GetPointer() != nullptr;
}

bool nmVTKRotationCenterPicker::start(
        QVTKWidget* pWidget,
        vtkRenderer* pRenderer)
{
    Q_ASSERT(isRotationCenterPickerGuiThread());
    if(!isRotationCenterPickerGuiThread() || m_bActive ||
       hasPendingRelease() || pWidget == nullptr || pRenderer == nullptr ||
       !hasPickTarget()) {
        return false;
    }

    vtkRenderWindow* pRenderWindow = pRenderer->GetRenderWindow();
    if(pRenderWindow == nullptr ||
       pWidget->GetRenderWindow() != pRenderWindow) {
        return false;
    }

    m_pWidget = pWidget;
    m_pRenderer = pRenderer;
    m_bHasPickedPosition = false;
    m_bHadExplicitCursor = pWidget->testAttribute(Qt::WA_SetCursor);
    m_oPreviousCursor = pWidget->cursor();
    pWidget->setCursor(Qt::CrossCursor);
    m_bCursorOverridden = true;
    m_bActive = true;
    pWidget->setFocus(Qt::OtherFocusReason);
    return true;
}

nmVTKRotationCenterPicker::PickEventResult
nmVTKRotationCenterPicker::cancel()
{
    const bool bWasActive = m_bActive;
    reset();
    return PickEventResult(false,
                           bWasActive ? PickOutcome_Cancelled :
                                        PickOutcome_None);
}

void nmVTKRotationCenterPicker::reset()
{
    Q_ASSERT(isRotationCenterPickerGuiThread());
    if(!isRotationCenterPickerGuiThread()) {
        return;
    }

    m_bActive = false;
    m_nPendingReleaseButton = static_cast<int>(Qt::NoButton);
    restoreCursor();
    m_pWidget = nullptr;
    m_pRenderer = nullptr;
    m_bHasPickedPosition = false;
}

bool nmVTKRotationCenterPicker::isActive() const
{
    return m_bActive;
}

bool nmVTKRotationCenterPicker::hasPendingRelease() const
{
    return m_nPendingReleaseButton != static_cast<int>(Qt::NoButton);
}

nmVTKRotationCenterPicker::PickEventResult
nmVTKRotationCenterPicker::handleEvent(QEvent* pEvent)
{
    Q_ASSERT(isRotationCenterPickerGuiThread());
    if(!isRotationCenterPickerGuiThread() || pEvent == nullptr) {
        return PickEventResult();
    }

    if(pEvent->type() == QEvent::MouseButtonRelease &&
       hasPendingRelease()) {
        QMouseEvent* pMouseEvent = static_cast<QMouseEvent*>(pEvent);
        if(static_cast<int>(pMouseEvent->button()) ==
           m_nPendingReleaseButton) {
            m_nPendingReleaseButton = static_cast<int>(Qt::NoButton);
            return PickEventResult(true, PickOutcome_None);
        }
        return PickEventResult();
    }

    if(!m_bActive) {
        return PickEventResult();
    }

    if(pEvent->type() == QEvent::ShortcutOverride ||
       pEvent->type() == QEvent::KeyPress) {
        QKeyEvent* pKeyEvent = static_cast<QKeyEvent*>(pEvent);
        if(pKeyEvent->key() == Qt::Key_Escape) {
            if(pEvent->type() == QEvent::ShortcutOverride) {
                pEvent->accept();
                return PickEventResult(true, PickOutcome_None);
            }
            finishActiveMode();
            return PickEventResult(true, PickOutcome_Cancelled);
        }
    }

    if(pEvent->type() != QEvent::MouseButtonPress) {
        return PickEventResult();
    }

    QMouseEvent* pMouseEvent = static_cast<QMouseEvent*>(pEvent);
    if(pMouseEvent->button() != Qt::LeftButton &&
       pMouseEvent->button() != Qt::RightButton) {
        return PickEventResult();
    }

    m_nPendingReleaseButton = static_cast<int>(pMouseEvent->button());
    if(pMouseEvent->button() == Qt::RightButton) {
        finishActiveMode();
        return PickEventResult(true, PickOutcome_Cancelled);
    }

    const bool bHit = pickAt(pMouseEvent);
    finishActiveMode();
    return PickEventResult(true,
                           bHit ? PickOutcome_Hit : PickOutcome_Miss);
}

bool nmVTKRotationCenterPicker::getPickedPosition(
        double dPosition[3]) const
{
    if(dPosition == nullptr || !m_bHasPickedPosition) {
        return false;
    }
    dPosition[0] = m_dPickedPosition[0];
    dPosition[1] = m_dPickedPosition[1];
    dPosition[2] = m_dPickedPosition[2];
    return true;
}

bool nmVTKRotationCenterPicker::pickAt(
        const QMouseEvent* pMouseEvent)
{
    m_bHasPickedPosition = false;
    if(pMouseEvent == nullptr || m_pWidget == nullptr ||
       m_pRenderer == nullptr) {
        return false;
    }

    vtkProp* pTarget = m_pPickTarget.GetPointer();
    vtkRenderWindow* pRenderWindow = m_pRenderer->GetRenderWindow();
    if(pTarget == nullptr || pRenderWindow == nullptr ||
       m_pWidget->GetRenderWindow() != pRenderWindow) {
        return false;
    }

    const int nWidgetWidth = m_pWidget->width();
    const int nWidgetHeight = m_pWidget->height();
    int* pRenderSize = pRenderWindow->GetActualSize();
    if(nWidgetWidth <= 0 || nWidgetHeight <= 0 || pRenderSize == nullptr ||
       pRenderSize[0] <= 0 || pRenderSize[1] <= 0 ||
       pMouseEvent->x() < 0 || pMouseEvent->x() >= nWidgetWidth ||
       pMouseEvent->y() < 0 || pMouseEvent->y() >= nWidgetHeight) {
        return false;
    }

    const int nRenderX = scalePixelCoordinate(
                pMouseEvent->x(), nWidgetWidth, pRenderSize[0]);
    const int nRenderYFromTop = scalePixelCoordinate(
                pMouseEvent->y(), nWidgetHeight, pRenderSize[1]);
    const int nRenderY = pRenderSize[1] - 1 - nRenderYFromTop;

    // Picker 也限定在本次调用内，避免命中结果缓存延长 Mesh Actor 生命周期。
    vtkSmartPointer<vtkCellPicker> pCellPicker =
            vtkSmartPointer<vtkCellPicker>::New();
    if(pCellPicker == nullptr) {
        return false;
    }
    pCellPicker->PickFromListOn();
    pCellPicker->InitializePickList();
    pCellPicker->AddPickList(pTarget);
    const int nPicked = pCellPicker->Pick(
                nRenderX, nRenderY, 0.0, m_pRenderer);
    const vtkIdType nCellId = pCellPicker->GetCellId();
    double* pPosition = pCellPicker->GetPickPosition();
    const bool bValid = nPicked != 0 && nCellId >= 0 &&
            pPosition != nullptr &&
            vtkMath::IsFinite(pPosition[0]) &&
            vtkMath::IsFinite(pPosition[1]) &&
            vtkMath::IsFinite(pPosition[2]);
    if(bValid) {
        m_dPickedPosition[0] = pPosition[0];
        m_dPickedPosition[1] = pPosition[1];
        m_dPickedPosition[2] = pPosition[2];
        m_bHasPickedPosition = true;
    }
    pCellPicker->InitializePickList();
    return bValid;
}

void nmVTKRotationCenterPicker::finishActiveMode()
{
    m_bActive = false;
    restoreCursor();
    m_pWidget = nullptr;
    m_pRenderer = nullptr;
}

void nmVTKRotationCenterPicker::restoreCursor()
{
    if(!m_bCursorOverridden || m_pWidget == nullptr) {
        m_bCursorOverridden = false;
        return;
    }

    if(m_bHadExplicitCursor) {
        m_pWidget->setCursor(m_oPreviousCursor);
    } else {
        m_pWidget->unsetCursor();
    }
    m_bCursorOverridden = false;
}