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#include "qsgshadereffectmesh_p.h"
#include "qsggeometry.h"
#include "qsgshadereffectitem_p.h"

QT_BEGIN_NAMESPACE

QSGShaderEffectMesh::QSGShaderEffectMesh(QObject *parent)
    : QObject(parent)
{
}

/*!
    \qmlclass GridMesh QSGGridMesh
    \since 5.0
    \ingroup qml-utility-elements
    \brief GridMesh defines a mesh to be used with \l ShaderEffectItem.

    GridMesh defines a rectangular mesh consisting of vertices arranged in an
    evenly spaced grid. It can be assigned to the \l ShaderEffectItem's mesh
    property. The grid resolution is specified with the \l resolution property.
    
    \row
    \o \image declarative-gridmesh.png
    \o \qml
        import QtQuick 2.0

        ShaderEffectItem {
            width: 200
            height: 200
            mesh: GridMesh { resolution: Qt.size(20, 20) }
            property variant source: Image {
                source: "qt-logo.png"
                sourceSize {width: 200; height: 200 }
                smooth: true
            }
            vertexShader: "
                uniform highp mat4 qt_ModelViewProjectionMatrix;
                attribute highp vec4 qt_Vertex;
                attribute highp vec2 qt_MultiTexCoord0;
                varying highp vec2 qt_TexCoord0;
                uniform highp float width;
                void main() {
                    highp vec4 pos = qt_Vertex;
                    highp float d = .5 * smoothstep(0., 1., qt_MultiTexCoord0.y);
                    pos.x = width * mix(d, 1.0 - d, qt_MultiTexCoord0.x);
                    gl_Position = qt_ModelViewProjectionMatrix * pos;
                    qt_TexCoord0 = qt_MultiTexCoord0;
                }"
        }
        \endqml
    \endrow

*/

QSGGridMesh::QSGGridMesh(QObject *parent)
    : QSGShaderEffectMesh(parent)
    , m_resolution(1, 1)
{
    connect(this, SIGNAL(resolutionChanged()), this, SIGNAL(geometryChanged()));
}

QSGGeometry *QSGGridMesh::updateGeometry(QSGGeometry *geometry, const QVector<QByteArray> &attributes, const QRectF &dstRect) const
{
    int vmesh = m_resolution.height();
    int hmesh = m_resolution.width();
    int attrCount = attributes.count();

    if (!geometry) {
        bool error = true;
        switch (attrCount) {
        case 0:
            qWarning("QSGGridMesh:: No attributes specified.");
            break;
        case 1:
            if (attributes.at(0) == qtPositionAttributeName()) {
                error = false;
                break;
            }
            qWarning("QSGGridMesh:: Missing \'%s\' attribute.",
                     qtPositionAttributeName());
            break;
        case 2:
            if (attributes.contains(qtPositionAttributeName())
                && attributes.contains(qtTexCoordAttributeName()))
            {
                error = false;
                break;
            }
            qWarning("QSGGridMesh:: Missing \'%s\' or \'%s\' attribute.",
                     qtPositionAttributeName(), qtTexCoordAttributeName());
            break;
        default:
            qWarning("QSGGridMesh:: Too many attributes specified.");
            break;
        }

        geometry = new QSGGeometry(attrCount == 1
                                   ? QSGGeometry::defaultAttributes_Point2D()
                                   : QSGGeometry::defaultAttributes_TexturedPoint2D(),
                                   (vmesh + 1) * (hmesh + 1), vmesh * 2 * (hmesh + 2),
                                   GL_UNSIGNED_SHORT);

    } else {
        geometry->allocate((vmesh + 1) * (hmesh + 1), vmesh * 2 * (hmesh + 2));
    }

    QSGGeometry::Point2D *vdata = static_cast<QSGGeometry::Point2D *>(geometry->vertexData());

    bool positionFirst = attributes.at(0) == qtPositionAttributeName();

    QRectF srcRect(0, 0, 1, 1);
    for (int iy = 0; iy <= vmesh; ++iy) {
        float fy = iy / float(vmesh);
        float y = float(dstRect.top()) + fy * float(dstRect.height());
        float ty = float(srcRect.top()) + fy * float(srcRect.height());
        for (int ix = 0; ix <= hmesh; ++ix) {
            float fx = ix / float(hmesh);
            for (int ia = 0; ia < attrCount; ++ia) {
                if (positionFirst == (ia == 0)) {
                    vdata->x = float(dstRect.left()) + fx * float(dstRect.width());
                    vdata->y = y;
                    ++vdata;
                } else {
                    vdata->x = float(srcRect.left()) + fx * float(srcRect.width());
                    vdata->y = ty;
                    ++vdata;
                }
            }
        }
    }

    quint16 *indices = (quint16 *)geometry->indexDataAsUShort();
    int i = 0;
    for (int iy = 0; iy < vmesh; ++iy) {
        *(indices++) = i + hmesh + 1;
        for (int ix = 0; ix <= hmesh; ++ix, ++i) {
            *(indices++) = i + hmesh + 1;
            *(indices++) = i;
        }
        *(indices++) = i - 1;
    }

    return geometry;
}

/*!
    \qmlproperty size GridMesh::resolution

    This property holds the grid resolution. The resolution's width and height
    specify the number of cells or spacings between vertices horizontally and
    vertically respectively. The minimum and default is 1x1, which corresponds
    to four vertices in total, one in each corner.
*/

void QSGGridMesh::setResolution(const QSize &res)
{
    if (res == m_resolution)
        return;
    if (res.width() < 1 || res.height() < 1) {
        return;
    }
    m_resolution = res;
    emit resolutionChanged();
}

QSize QSGGridMesh::resolution() const
{
    return m_resolution;
}

QT_END_NAMESPACE