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#include "../shared/examplefw.h"

// Compute shader example with image load/store. The texture sampled in the
// fragment shader is generated by the compute shader.

struct {
    QVector<QRhiResource *> releasePool;

    QRhiTexture *texIn = nullptr;
    QRhiTexture *texOut = nullptr;
    QRhiBuffer *computeUBuf = nullptr;
    QRhiShaderResourceBindings *computeBindings = nullptr;
    QRhiComputePipeline *computePipeline = nullptr;

    QRhiBuffer *vbuf = nullptr;
    QRhiBuffer *ibuf = nullptr;
    QRhiBuffer *ubuf = nullptr;
    QRhiSampler *sampler = nullptr;
    QRhiShaderResourceBindings *srb = nullptr;
    QRhiGraphicsPipeline *ps = nullptr;

    QRhiResourceUpdateBatch *initialUpdates = nullptr;
    QSize imageSize;
    QMatrix4x4 winProj;
    float factor = 1.0f;
} d;

static float quadVertexData[] =
{ // Y up, CCW
  -0.5f,   0.5f,   0.0f, 0.0f,
  -0.5f,  -0.5f,   0.0f, 1.0f,
  0.5f,   -0.5f,   1.0f, 1.0f,
  0.5f,   0.5f,    1.0f, 0.0f
};

static quint16 quadIndexData[] =
{
    0, 1, 2, 0, 2, 3
};

void Window::customInit()
{
    if (!m_r->isFeatureSupported(QRhi::Compute))
        qFatal("Compute is not supported");

    d.initialUpdates = m_r->nextResourceUpdateBatch();

    // compute pass

    const QImage image = QImage(QLatin1String(":/qt256.png")).convertToFormat(QImage::Format_RGBA8888);
    d.imageSize = image.size();
    d.texIn = m_r->newTexture(QRhiTexture::RGBA8, d.imageSize, 1, QRhiTexture::UsedWithLoadStore);
    d.texIn->build();
    d.releasePool << d.texIn;

    d.texOut = m_r->newTexture(QRhiTexture::RGBA8, d.imageSize, 1, QRhiTexture::UsedWithLoadStore);
    d.texOut->build();
    d.releasePool << d.texOut;

    d.initialUpdates->uploadTexture(d.texIn, image);

    d.computeUBuf = m_r->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::UniformBuffer, 4);
    d.computeUBuf->build();
    d.releasePool << d.computeUBuf;

    d.computeBindings = m_r->newShaderResourceBindings();
    d.computeBindings->setBindings({
                                       QRhiShaderResourceBinding::uniformBuffer(0, QRhiShaderResourceBinding::ComputeStage, d.computeUBuf),
                                       QRhiShaderResourceBinding::imageLoad(1, QRhiShaderResourceBinding::ComputeStage, d.texIn, 0),
                                       QRhiShaderResourceBinding::imageStore(2, QRhiShaderResourceBinding::ComputeStage, d.texOut, 0)
                                   });
    d.computeBindings->build();
    d.releasePool << d.computeBindings;

    d.computePipeline = m_r->newComputePipeline();
    d.computePipeline->setShaderResourceBindings(d.computeBindings);
    d.computePipeline->setShaderStage({ QRhiShaderStage::Compute, getShader(QLatin1String(":/image.comp.qsb")) });
    d.computePipeline->build();
    d.releasePool << d.computePipeline;

    // graphics pass

    d.vbuf = m_r->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::VertexBuffer, sizeof(quadVertexData));
    d.vbuf->build();
    d.releasePool << d.vbuf;

    d.initialUpdates->uploadStaticBuffer(d.vbuf, quadVertexData);

    d.ibuf = m_r->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::IndexBuffer, sizeof(quadIndexData));
    d.ibuf->build();
    d.releasePool << d.ibuf;

    d.initialUpdates->uploadStaticBuffer(d.ibuf, quadIndexData);

    d.ubuf = m_r->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::UniformBuffer, 68);
    d.ubuf->build();
    d.releasePool << d.ubuf;

    qint32 flip = 0; // regardless of isYUpInFramebuffer() since the input is not flipped so the end result is good for GL too
    d.initialUpdates->updateDynamicBuffer(d.ubuf, 64, 4, &flip);

    d.sampler = m_r->newSampler(QRhiSampler::Linear, QRhiSampler::Linear, QRhiSampler::None,
                                QRhiSampler::ClampToEdge, QRhiSampler::ClampToEdge);
    d.releasePool << d.sampler;
    d.sampler->build();

    d.srb = m_r->newShaderResourceBindings();
    d.releasePool << d.srb;
    d.srb->setBindings({
        QRhiShaderResourceBinding::uniformBuffer(0, QRhiShaderResourceBinding::VertexStage | QRhiShaderResourceBinding::FragmentStage, d.ubuf),
        QRhiShaderResourceBinding::sampledTexture(1, QRhiShaderResourceBinding::FragmentStage, d.texOut, d.sampler)
    });
    d.srb->build();

    d.ps = m_r->newGraphicsPipeline();
    d.releasePool << d.ps;
    d.ps->setShaderStages({
        { QRhiShaderStage::Vertex, getShader(QLatin1String(":/texture.vert.qsb")) },
        { QRhiShaderStage::Fragment, getShader(QLatin1String(":/texture.frag.qsb")) }
    });
    QRhiVertexInputLayout inputLayout;
    inputLayout.setBindings({
        { 4 * sizeof(float) }
    });
    inputLayout.setAttributes({
        { 0, 0, QRhiVertexInputAttribute::Float2, 0 },
        { 0, 1, QRhiVertexInputAttribute::Float2, 2 * sizeof(float) }
    });
    d.ps->setVertexInputLayout(inputLayout);
    d.ps->setShaderResourceBindings(d.srb);
    d.ps->setRenderPassDescriptor(m_rp);
    d.ps->build();
}

void Window::customRelease()
{
    qDeleteAll(d.releasePool);
    d.releasePool.clear();
}

void Window::customRender()
{
    const QSize outputSizeInPixels = m_sc->currentPixelSize();
    QRhiCommandBuffer *cb = m_sc->currentFrameCommandBuffer();
    QRhiResourceUpdateBatch *u = m_r->nextResourceUpdateBatch();
    if (d.initialUpdates) {
        u->merge(d.initialUpdates);
        d.initialUpdates->release();
        d.initialUpdates = nullptr;
    }

    if (d.winProj != m_proj) {
        d.winProj = m_proj;
        QMatrix4x4 mvp = m_proj;
        mvp.scale(2.5f);
        u->updateDynamicBuffer(d.ubuf, 0, 64, mvp.constData());
    }

    u->updateDynamicBuffer(d.computeUBuf, 0, 4, &d.factor);
    d.factor += 0.1f;
    if (d.factor >= 50.0f)
        d.factor = 1.0f;

    cb->beginComputePass(u);
    cb->setComputePipeline(d.computePipeline);
    cb->setShaderResources();
    cb->dispatch(d.imageSize.width() / 16, d.imageSize.height() / 16, 1);
    cb->endComputePass();

    cb->beginPass(m_sc->currentFrameRenderTarget(), m_clearColor, { 1.0f, 0 });
    cb->setGraphicsPipeline(d.ps);
    cb->setViewport({ 0, 0, float(outputSizeInPixels.width()), float(outputSizeInPixels.height()) });
    cb->setShaderResources();
    QRhiCommandBuffer::VertexInput vbufBinding(d.vbuf, 0);
    cb->setVertexInput(0, 1, &vbufBinding, d.ibuf, 0, QRhiCommandBuffer::IndexUInt16);
    cb->drawIndexed(6);
    cb->endPass();
}