// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only

#include "qquick3dparticlemodelparticle_p.h"

QT_BEGIN_NAMESPACE

/*!
    \qmltype ModelParticle3D
    \inherits Particle3D
    \inqmlmodule QtQuick3D.Particles3D
    \brief Particle using a Qt Quick 3D Model.
    \since 6.2

    The ModelParticle3D is a logical particle element that creates particles
    from a Qt Quick 3D \l Model component.
*/

QQuick3DParticleModelParticle::QQuick3DParticleModelParticle(QQuick3DNode *parent)
    : QQuick3DParticle(parent)
    , m_initialScale(1.0f, 1.0f, 1.0f)
{
    QObject::connect(this, &QQuick3DParticle::maxAmountChanged, this, [this]() {
        handleMaxAmountChanged(m_maxAmount);
    });
    QObject::connect(this, &QQuick3DParticle::sortModeChanged, this, [this]() {
        handleSortModeChanged(sortMode());
    });
}

void QQuick3DParticleModelParticle::handleMaxAmountChanged(int amount)
{
    if (m_particleData.size() == amount)
        return;

    m_particleData.resize(amount);
    m_particleData.fill({});
}

/*!
    \qmlproperty Component ModelParticle3D::delegate

    The delegate provides a template defining each object instantiated by the particle.

    For example, to allocate 200 red cube particles:

    \qml
    Component {
        id: particleComponent
        Model {
            source: "#Cube"
            scale: Qt.vector3d(0.2, 0.2, 0.2)
            materials: DefaultMaterial { }
        }
    }

    ModelParticle3D {
        id: particleRed
        delegate: particleComponent
        maxAmount: 200
        color: "#ff0000"
    }
    \endqml
*/
QQmlComponent *QQuick3DParticleModelParticle::delegate() const
{
    return m_delegate.data();
}

void QQuick3DParticleModelParticle::setDelegate(QQmlComponent *delegate)
{
    if (delegate == m_delegate)
        return;
    m_delegate = delegate;

    regenerate();
    Q_EMIT delegateChanged();
}

class QQuick3DParticleInstanceTable : public QQuick3DInstancing
{
    struct SortData
    {
        float age;
        int index;
    };

public:
    QQuick3DParticleInstanceTable() {}
    void clear() { m_instances.clear(); m_sortData.clear(); }
    void commit() { sort(); markDirty(); }
    void addInstance(const QVector3D &position,
                     const QVector3D &scale,
                     const QVector3D &eulerRotation,
                     const QColor &color,
                     float age) {
        auto entry = calculateTableEntry(position, scale, eulerRotation, color);
        m_instances.append(reinterpret_cast<char *>(&entry), sizeof(InstanceTableEntry));
        if (m_ageSorting)
            m_sortData.append({age, int(m_instances.size() / sizeof(InstanceTableEntry))});
    }
    void setSorting(bool enable, bool inverted = false)
    {
        m_ageSorting = enable;
        m_inverted = inverted;
    }
protected:
    QByteArray getInstanceBuffer(int *instanceCount) override
    {
        if (instanceCount)
            *instanceCount = int(m_instances.size() / sizeof(InstanceTableEntry));

        if (!m_ageSorting)
            return m_instances;
        return m_sortedInstances;
    }
    void sort()
    {
        if (!m_ageSorting)
            return;

        if (m_inverted) {
            std::sort(m_sortData.begin(), m_sortData.end(), [&](const SortData &a, const SortData &b) {
                return a.age < b.age;
            });
        } else {
            std::sort(m_sortData.begin(), m_sortData.end(), [&](const SortData &a, const SortData &b) {
                return a.age > b.age;
            });
        }
        m_sortedInstances.resize(m_instances.size());
        const InstanceTableEntry *src = reinterpret_cast<InstanceTableEntry *>(m_instances.data());
        InstanceTableEntry *dst = reinterpret_cast<InstanceTableEntry *>(m_sortedInstances.data());
        for (auto &e : m_sortData)
            *dst++ = src[e.index];
    }

private:
    QList<SortData> m_sortData;
    QByteArray m_instances;
    QByteArray m_sortedInstances;
    bool m_ageSorting = false;
    bool m_inverted = false;
};

void QQuick3DParticleModelParticle::handleSortModeChanged(QQuick3DParticle::SortMode mode)
{
    if (m_instanceTable) {
        if (mode == QQuick3DParticle::SortNewest || mode == QQuick3DParticle::SortOldest)
            m_instanceTable->setSorting(true, mode == QQuick3DParticle::SortNewest);
        else
            m_instanceTable->setSorting(false);
        m_instanceTable->setDepthSortingEnabled(mode == QQuick3DParticle::SortDistance);
    }
}

/*!
    \qmlproperty Instancing ModelParticle3D::instanceTable

    The instanceTable provides access to the \l Instancing table of the model particle.
    ModelParticle3D uses an internal instance table to implement efficient rendering.
    This table can be applied to the \l{Model::instancing}{instancing} property of models
    that are not part of the particle system.

    It is also possible to use this feature to provide an instancing table without showing any
    particles. This is done by omitting the \l delegate property. For example:

    \qml
    ParticleSystem3D {
        id: psystem
        ModelParticle3D {
            id: particleRed
            maxAmount: 200
            color: "#ff0000"
            colorVariation: Qt.vector4d(0.5,0.5,0.5,0.5)
        }

        ParticleEmitter3D {
            particle: particleRed
            velocity: VectorDirection3D {
                direction: Qt.vector3d(-20, 200, 0)
                directionVariation: Qt.vector3d(20, 20, 20)
            }
            particleScale: 0.2
            emitRate: 20
            lifeSpan: 2000
        }
    }

    Model {
        source: "#Sphere"
        instancing: particleRed.instanceTable
        materials: PrincipledMaterial {
            baseColor: "yellow"
        }
    }
    \endqml
*/

QQuick3DInstancing *QQuick3DParticleModelParticle::instanceTable() const
{
    return m_instanceTable;
}

void QQuick3DParticleModelParticle::clearInstanceTable()
{
    if (m_instanceTable)
        m_instanceTable->clear();
}

void QQuick3DParticleModelParticle::addInstance(const QVector3D &position, const QVector3D &scale, const QVector3D &eulerRotation, const QColor &color, float age)
{
    if (m_instanceTable)
        m_instanceTable->addInstance(position, scale, eulerRotation, color, age);
}

void QQuick3DParticleModelParticle::commitInstance()
{
    if (m_instanceTable) {
        m_instanceTable->setHasTransparency(hasTransparency());
        m_instanceTable->commit();
    }
}

static void setInstancing(QQuick3DNode *node, QQuick3DInstancing *instanceTable, float bias)
{
    auto *asModel = qobject_cast<QQuick3DModel *>(node);
    if (asModel) {
        asModel->setInstancing(instanceTable);
        asModel->setDepthBias(bias);
    }
    const auto children = node->childItems();
    for (auto *child : children) {
        auto *childNode = qobject_cast<QQuick3DNode *>(child);
        if (childNode)
            setInstancing(childNode, instanceTable, bias);
    }
}

void QQuick3DParticleModelParticle::updateDepthBias(float bias)
{
    setInstancing(m_node, m_instanceTable, bias);
}

void QQuick3DParticleModelParticle::regenerate()
{
    delete m_node;
    m_node = nullptr;

    if (!isComponentComplete())
        return;

    if (!m_instanceTable) {
        m_instanceTable = new QQuick3DParticleInstanceTable();
        m_instanceTable->setParent(this);
        m_instanceTable->setParentItem(this);
        emit instanceTableChanged();
    } else {
        m_instanceTable->clear();
    }

    if (m_delegate.isNull())
        return;

    auto *obj = m_delegate->create(m_delegate->creationContext());

    m_node = qobject_cast<QQuick3DNode *>(obj);
    if (m_node) {
        setInstancing(m_node, m_instanceTable, depthBias());
        auto *particleSystem = system();
        m_node->setParent(particleSystem);
        m_node->setParentItem(particleSystem);
    } else {
        delete obj;
    }
}

void QQuick3DParticleModelParticle::componentComplete()
{
    if (!system() && qobject_cast<QQuick3DParticleSystem *>(parentItem()))
        setSystem(qobject_cast<QQuick3DParticleSystem *>(parentItem()));

    QQuick3DParticle::componentComplete();
    regenerate();
}

void QQuick3DParticleModelParticle::itemChange(QQuick3DObject::ItemChange change, const QQuick3DObject::ItemChangeData &value)
{
    QQuick3DObject::itemChange(change, value);
    if (change == ItemParentHasChanged)
        regenerate();
}

QT_END_NAMESPACE
