// Unnamed CAD Software
//
// License: GPLv3, see LICENSE.txt
// Language: C++17
// Notes:
//     - use a right-handed, Z-up coordinate system to match OpenCASCADE

#include "Snapping.h"

#include "ViewportWidget.h"
#include "Camera.h"
#include "Document.h"
#include "SketchFeature.h"
#include "SketchLine.h"
#include "SketchRectangle.h"
#include "SketchObject.h"
#include "ApplicationController.h"

#include <QOpenGLShaderProgram>
#include <QVector>
#include <QtMath>

Snapping::Snapping(ViewportWidget* viewport) : m_viewport(viewport)
{
}

bool Snapping::update(const QPoint& mousePos)
{
    bool oldIsSnappingOrigin = m_isSnappingOrigin;
    bool oldIsSnappingVertex = m_isSnappingVertex;

    bool shouldSnap = false;
    if (m_viewport->currentPlane() != ViewportWidget::SketchPlane::NONE && m_viewport->activeTool() != static_cast<int>(ApplicationController::ToolType::None)) {
        QVector3D worldPos = m_viewport->unproject(mousePos, m_viewport->currentPlane());
        const float snapRectHalfSize = 0.0075f * -m_viewport->camera()->zoom();

        switch (m_viewport->currentPlane()) {
            case ViewportWidget::SketchPlane::XY:
                shouldSnap = qAbs(worldPos.x()) < snapRectHalfSize && qAbs(worldPos.y()) < snapRectHalfSize;
                break;
            case ViewportWidget::SketchPlane::XZ:
                shouldSnap = qAbs(worldPos.x()) < snapRectHalfSize && qAbs(worldPos.z()) < snapRectHalfSize;
                break;
            case ViewportWidget::SketchPlane::YZ:
                shouldSnap = qAbs(worldPos.y()) < snapRectHalfSize && qAbs(worldPos.z()) < snapRectHalfSize;
                break;
            case ViewportWidget::SketchPlane::NONE:
                break;
        }
    }

    m_isSnappingOrigin = shouldSnap;
    if (m_isSnappingOrigin) {
        m_isSnappingVertex = false;
    }

    m_isSnappingVertex = false;
    if (!m_isSnappingOrigin && m_viewport->document() && m_viewport->currentPlane() != ViewportWidget::SketchPlane::NONE && m_viewport->activeTool() != static_cast<int>(ApplicationController::ToolType::None)) {
        QVector3D worldPos = m_viewport->unproject(mousePos, m_viewport->currentPlane());
        const float snapRectHalfSize = 0.0075f * -m_viewport->camera()->zoom();

        for (Feature* feature : m_viewport->document()->features()) {
            if (auto sketch = dynamic_cast<SketchFeature*>(feature)) {
                for (const auto& obj : sketch->objects()) {
                    if (obj->type() == SketchObject::ObjectType::Line) {
                        auto line = static_cast<const SketchLine*>(obj);
                        const gp_Pnt vertices[] = {line->startPoint(), line->endPoint()};
                        for (const auto& vertex : vertices) {
                            bool isClose = false;
                            switch (m_viewport->currentPlane()) {
                            case ViewportWidget::SketchPlane::XY:
                                isClose = qAbs(worldPos.x() - vertex.X()) < snapRectHalfSize && qAbs(worldPos.y() - vertex.Y()) < snapRectHalfSize;
                                break;
                            case ViewportWidget::SketchPlane::XZ:
                                isClose = qAbs(worldPos.x() - vertex.X()) < snapRectHalfSize && qAbs(worldPos.z() - vertex.Z()) < snapRectHalfSize;
                                break;
                            case ViewportWidget::SketchPlane::YZ:
                                isClose = qAbs(worldPos.y() - vertex.Y()) < snapRectHalfSize && qAbs(worldPos.z() - vertex.Z()) < snapRectHalfSize;
                                break;
                            case ViewportWidget::SketchPlane::NONE:
                                break;
                            }

                            if (isClose) {
                                m_isSnappingVertex = true;
                                m_snapVertex = vertex;
                                goto end_snap_check;
                            }
                        }
                    } else if (obj->type() == SketchObject::ObjectType::Rectangle) {
                        auto rect = static_cast<const SketchRectangle*>(obj);
                        const auto& p1 = rect->corner1();
                        const auto& p3 = rect->corner2();
                        gp_Pnt p2, p4;

                        if (sketch->plane() == SketchFeature::SketchPlane::XY) {
                            p2.SetCoord(p3.X(), p1.Y(), p1.Z());
                            p4.SetCoord(p1.X(), p3.Y(), p1.Z());
                        } else if (sketch->plane() == SketchFeature::SketchPlane::XZ) {
                            p2.SetCoord(p3.X(), p1.Y(), p1.Z());
                            p4.SetCoord(p1.X(), p1.Y(), p3.Z());
                        } else if (sketch->plane() == SketchFeature::SketchPlane::YZ) {
                            p2.SetCoord(p1.X(), p3.Y(), p1.Z());
                            p4.SetCoord(p1.X(), p1.Y(), p3.Z());
                        }

                        const gp_Pnt vertices[] = {p1, p2, p3, p4};
                        for (const auto& vertex : vertices) {
                            bool isClose = false;
                            switch (m_viewport->currentPlane()) {
                            case ViewportWidget::SketchPlane::XY:
                                isClose = qAbs(worldPos.x() - vertex.X()) < snapRectHalfSize && qAbs(worldPos.y() - vertex.Y()) < snapRectHalfSize;
                                break;
                            case ViewportWidget::SketchPlane::XZ:
                                isClose = qAbs(worldPos.x() - vertex.X()) < snapRectHalfSize && qAbs(worldPos.z() - vertex.Z()) < snapRectHalfSize;
                                break;
                            case ViewportWidget::SketchPlane::YZ:
                                isClose = qAbs(worldPos.y() - vertex.Y()) < snapRectHalfSize && qAbs(worldPos.z() - vertex.Z()) < snapRectHalfSize;
                                break;
                            case ViewportWidget::SketchPlane::NONE:
                                break;
                            }

                            if (isClose) {
                                m_isSnappingVertex = true;
                                m_snapVertex = vertex;
                                goto end_snap_check;
                            }
                        }
                    }
                }
            }
        }
    end_snap_check:;
    }

    return (oldIsSnappingOrigin != m_isSnappingOrigin) || (oldIsSnappingVertex != m_isSnappingVertex);
}

void Snapping::paintGL() const
{
    if (!m_isSnappingOrigin && !m_isSnappingVertex) {
        return;
    }

    QVector<GLfloat> vertices;
    if (m_isSnappingOrigin) {
        const float rectSize = 0.0075f * -m_viewport->camera()->zoom();
        if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::XY) {
            vertices << -rectSize << -rectSize << 0 << rectSize << -rectSize << 0;
            vertices << rectSize << -rectSize << 0 << rectSize << rectSize << 0;
            vertices << rectSize << rectSize << 0 << -rectSize << rectSize << 0;
            vertices << -rectSize << rectSize << 0 << -rectSize << -rectSize << 0;
        } else if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::XZ) {
            vertices << -rectSize << 0 << -rectSize << rectSize << 0 << -rectSize;
            vertices << rectSize << 0 << -rectSize << rectSize << 0 << rectSize;
            vertices << rectSize << 0 << rectSize << -rectSize << 0 << rectSize;
            vertices << -rectSize << 0 << rectSize << -rectSize << 0 << -rectSize;
        } else if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::YZ) {
            vertices << 0 << -rectSize << -rectSize << 0 << rectSize << -rectSize;
            vertices << 0 << rectSize << -rectSize << 0 << rectSize << rectSize;
            vertices << 0 << rectSize << rectSize << 0 << -rectSize << rectSize;
            vertices << 0 << -rectSize << rectSize << 0 << -rectSize << -rectSize;
        }
    } else if (m_isSnappingVertex) {
        const float rectSize = 0.0075f * -m_viewport->camera()->zoom();
        const auto& v = m_snapVertex;
        if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::XY) {
            vertices << v.X() - rectSize << v.Y() - rectSize << v.Z() << v.X() + rectSize << v.Y() - rectSize << v.Z();
            vertices << v.X() + rectSize << v.Y() - rectSize << v.Z() << v.X() + rectSize << v.Y() + rectSize << v.Z();
            vertices << v.X() + rectSize << v.Y() + rectSize << v.Z() << v.X() - rectSize << v.Y() + rectSize << v.Z();
            vertices << v.X() - rectSize << v.Y() + rectSize << v.Z() << v.X() - rectSize << v.Y() - rectSize << v.Z();
        } else if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::XZ) {
            vertices << v.X() - rectSize << v.Y() << v.Z() - rectSize << v.X() + rectSize << v.Y() << v.Z() - rectSize;
            vertices << v.X() + rectSize << v.Y() << v.Z() - rectSize << v.X() + rectSize << v.Y() << v.Z() + rectSize;
            vertices << v.X() + rectSize << v.Y() << v.Z() + rectSize << v.X() - rectSize << v.Y() << v.Z() + rectSize;
            vertices << v.X() - rectSize << v.Y() << v.Z() + rectSize << v.X() - rectSize << v.Y() << v.Z() - rectSize;
        } else if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::YZ) {
            vertices << v.X() << v.Y() - rectSize << v.Z() - rectSize << v.X() << v.Y() + rectSize << v.Z() - rectSize;
            vertices << v.X() << v.Y() + rectSize << v.Z() - rectSize << v.X() << v.Y() + rectSize << v.Z() + rectSize;
            vertices << v.X() << v.Y() + rectSize << v.Z() + rectSize << v.X() << v.Y() - rectSize << v.Z() + rectSize;
            vertices << v.X() << v.Y() - rectSize << v.Z() + rectSize << v.X() << v.Y() - rectSize << v.Z() - rectSize;
        }
    }
    m_viewport->shaderProgram()->setUniformValue(m_viewport->colorLoc(), QVector4D(1.0f, 1.0f, 0.0f, 0.5f));
    m_viewport->vbo().bind();
    m_viewport->vbo().allocate(vertices.constData(), vertices.size() * sizeof(GLfloat));
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glDrawArrays(GL_LINES, 0, vertices.size() / 3);
    glDisable(GL_BLEND);
}