// Copyright (C) 2017 Klaralvdalens Datakonsult AB (KDAB).
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

#include "basegeometryloader_p.h"

#include <Qt3DCore/qattribute.h>
#include <Qt3DCore/qbuffer.h>
#include <Qt3DCore/qgeometry.h>

#include <Qt3DRender/private/qaxisalignedboundingbox_p.h>
#include <Qt3DRender/private/renderlogging_p.h>

QT_BEGIN_NAMESPACE

using namespace Qt3DCore;

namespace Qt3DRender {

Q_LOGGING_CATEGORY(BaseGeometryLoaderLog, "Qt3D.BaseGeometryLoader", QtWarningMsg)

BaseGeometryLoader::BaseGeometryLoader()
    : m_loadTextureCoords(true)
    , m_generateTangents(true)
    , m_centerMesh(false)
    , m_geometry(nullptr)
{
}

Qt3DCore::QGeometry *BaseGeometryLoader::geometry() const
{
    return m_geometry;
}

bool BaseGeometryLoader::load(QIODevice *ioDev, const QString &subMesh)
{
    if (!doLoad(ioDev, subMesh))
        return false;

    if (m_normals.empty())
        generateAveragedNormals(m_points, m_normals, m_indices);

    if (m_generateTangents && !m_texCoords.empty())
        generateTangents(m_points, m_normals, m_indices, m_texCoords, m_tangents);

    if (m_centerMesh)
        center(m_points);

    qCDebug(BaseGeometryLoaderLog) << "Loaded mesh:";
    qCDebug(BaseGeometryLoaderLog) << " " << m_points.size() << "points";
    qCDebug(BaseGeometryLoaderLog) << " " << m_indices.size() / 3 << "triangles.";
    qCDebug(BaseGeometryLoaderLog) << " " << m_normals.size() << "normals";
    qCDebug(BaseGeometryLoaderLog) << " " << m_tangents.size() << "tangents ";
    qCDebug(BaseGeometryLoaderLog) << " " << m_texCoords.size() << "texture coordinates.";

    generateGeometry();

    return true;
}

void BaseGeometryLoader::generateAveragedNormals(const std::vector<QVector3D> &points,
                                                 std::vector<QVector3D> &normals,
                                                 const std::vector<unsigned int> &faces) const
{
    for (size_t i = 0; i < points.size(); ++i)
        normals.push_back(QVector3D());

    for (size_t i = 0; i < faces.size(); i += 3) {
        const QVector3D &p1 = points[ faces[i]   ];
        const QVector3D &p2 = points[ faces[i+1] ];
        const QVector3D &p3 = points[ faces[i+2] ];

        const QVector3D a = p2 - p1;
        const QVector3D b = p3 - p1;
        const QVector3D n = QVector3D::crossProduct(a, b).normalized();

        normals[ faces[i]   ] += n;
        normals[ faces[i+1] ] += n;
        normals[ faces[i+2] ] += n;
    }

    for (size_t i = 0; i < normals.size(); ++i)
        normals[i].normalize();
}

void BaseGeometryLoader::generateGeometry()
{
    QByteArray bufferBytes;
    const uint count = uint(m_points.size());
    const quint32 elementSize = 3 + (hasTextureCoordinates() ? 2 : 0)
        + (hasNormals() ? 3 : 0)
        + (hasTangents() ? 4 : 0);
    const quint32 stride = elementSize * sizeof(float);
    bufferBytes.resize(stride * count);
    float *fptr = reinterpret_cast<float*>(bufferBytes.data());

    for (size_t index = 0; index < count; ++index) {
        *fptr++ = m_points.at(index).x();
        *fptr++ = m_points.at(index).y();
        *fptr++ = m_points.at(index).z();

        if (hasTextureCoordinates()) {
            *fptr++ = m_texCoords.at(index).x();
            *fptr++ = m_texCoords.at(index).y();
        }

        if (hasNormals()) {
            *fptr++ = m_normals.at(index).x();
            *fptr++ = m_normals.at(index).y();
            *fptr++ = m_normals.at(index).z();
        }

        if (hasTangents()) {
            *fptr++ = m_tangents.at(index).x();
            *fptr++ = m_tangents.at(index).y();
            *fptr++ = m_tangents.at(index).z();
            *fptr++ = m_tangents.at(index).w();
        }
    } // of buffer filling loop

    auto *buf = new Qt3DCore::QBuffer();
    buf->setData(bufferBytes);

    if (m_geometry)
        qDebug(BaseGeometryLoaderLog, "Existing geometry instance getting overridden.");
    m_geometry = new QGeometry();

    QAttribute *positionAttribute = new QAttribute(buf, QAttribute::defaultPositionAttributeName(), QAttribute::Float, 3, count, 0, stride);
    m_geometry->addAttribute(positionAttribute);
    quint32 offset = sizeof(float) * 3;

    if (hasTextureCoordinates()) {
        QAttribute *texCoordAttribute = new QAttribute(buf, QAttribute::defaultTextureCoordinateAttributeName(),  QAttribute::Float, 2, count, offset, stride);
        m_geometry->addAttribute(texCoordAttribute);
        offset += sizeof(float) * 2;
    }

    if (hasNormals()) {
        QAttribute *normalAttribute = new QAttribute(buf, QAttribute::defaultNormalAttributeName(), QAttribute::Float, 3, count, offset, stride);
        m_geometry->addAttribute(normalAttribute);
        offset += sizeof(float) * 3;
    }

    if (hasTangents()) {
        QAttribute *tangentAttribute = new QAttribute(buf, QAttribute::defaultTangentAttributeName(),QAttribute::Float, 4, count, offset, stride);
        m_geometry->addAttribute(tangentAttribute);
        offset += sizeof(float) * 4;
    }

    QByteArray indexBytes;
    QAttribute::VertexBaseType ty;
    if (m_indices.size() < 65536) {
        // we can use USHORT
        ty = QAttribute::UnsignedShort;
        indexBytes.resize(m_indices.size() * sizeof(quint16));
        quint16 *usptr = reinterpret_cast<quint16*>(indexBytes.data());
        for (int i = 0; i < int(m_indices.size()); ++i)
            *usptr++ = static_cast<quint16>(m_indices.at(i));
    } else {
        // use UINT - no conversion needed, but let's ensure int is 32-bit!
        ty = QAttribute::UnsignedInt;
        Q_ASSERT(sizeof(int) == sizeof(quint32));
        indexBytes.resize(m_indices.size() * sizeof(quint32));
        memcpy(indexBytes.data(), reinterpret_cast<const char*>(m_indices.data()), indexBytes.size());
    }

    auto *indexBuffer = new Qt3DCore::QBuffer();
    indexBuffer->setData(indexBytes);
    QAttribute *indexAttribute = new QAttribute(indexBuffer, ty, 1, uint(m_indices.size()));
    indexAttribute->setAttributeType(QAttribute::IndexAttribute);
    m_geometry->addAttribute(indexAttribute);
}

void BaseGeometryLoader::generateTangents(const std::vector<QVector3D> &points,
                                          const std::vector<QVector3D> &normals,
                                          const std::vector<unsigned int> &faces,
                                          const std::vector<QVector2D> &texCoords,
                                          std::vector<QVector4D> &tangents) const
{
    tangents.clear();
    std::vector<QVector3D> tan1Accum;
    std::vector<QVector3D> tan2Accum;

    tan1Accum.resize(points.size());
    tan2Accum.resize(points.size());
    tangents.resize(points.size());

    // Compute the tangent vector
    for (size_t i = 0; i < faces.size(); i += 3) {
        const QVector3D &p1 = points[ faces[i] ];
        const QVector3D &p2 = points[ faces[i+1] ];
        const QVector3D &p3 = points[ faces[i+2] ];

        const QVector2D &tc1 = texCoords[ faces[i] ];
        const QVector2D &tc2 = texCoords[ faces[i+1] ];
        const QVector2D &tc3 = texCoords[ faces[i+2] ];

        const QVector3D q1 = p2 - p1;
        const QVector3D q2 = p3 - p1;
        const float s1 = tc2.x() - tc1.x(), s2 = tc3.x() - tc1.x();
        const float t1 = tc2.y() - tc1.y(), t2 = tc3.y() - tc1.y();
        const float r = 1.0f / (s1 * t2 - s2 * t1);
        const QVector3D tan1((t2 * q1.x() - t1 * q2.x()) * r,
                             (t2 * q1.y() - t1 * q2.y()) * r,
                             (t2 * q1.z() - t1 * q2.z()) * r);
        const QVector3D tan2((s1 * q2.x() - s2 * q1.x()) * r,
                             (s1 * q2.y() - s2 * q1.y()) * r,
                             (s1 * q2.z() - s2 * q1.z()) * r);
        tan1Accum[ faces[i]   ] += tan1;
        tan1Accum[ faces[i+1] ] += tan1;
        tan1Accum[ faces[i+2] ] += tan1;
        tan2Accum[ faces[i]   ] += tan2;
        tan2Accum[ faces[i+1] ] += tan2;
        tan2Accum[ faces[i+2] ] += tan2;
    }

    for (size_t i = 0; i < points.size(); ++i) {
        const QVector3D &n = normals[i];
        const QVector3D &t1 = tan1Accum[i];
        const QVector3D &t2 = tan2Accum[i];

        // Gram-Schmidt orthogonalize
        tangents[i] = QVector4D(QVector3D(t1 - QVector3D::dotProduct(n, t1) * n).normalized(), 0.0f);

        // Store handedness in w
        tangents[i].setW((QVector3D::dotProduct(QVector3D::crossProduct(n, t1), t2) < 0.0f) ? -1.0f : 1.0f);
    }
}

void BaseGeometryLoader::center(std::vector<QVector3D> &points)
{
    if (points.empty())
        return;

    const QAxisAlignedBoundingBox bb(points);
    const QVector3D center = bb.center();

    // Translate center of the AABB to the origin
    for (size_t i = 0; i < points.size(); ++i) {
        QVector3D &point = points[i];
        point = point - center;
    }
}

} // namespace Qt3DRender

QT_END_NAMESPACE

#include "moc_basegeometryloader_p.cpp"
